AERONAUTICS

SEVENTEENTH ANNUAL REPORT

OF THE NATIONALADVISORY COMMITTEE FOR AERONAUTICS

1931

INCLUDING TECHNICAL REPORTS ~OS. 365 to 400

lJNI.~ STATES GOVERNMENTPRIN~G OFFIOE WASHINGTON: 1S82

Forde bytheSuperintendentof Documents,Waehlugton.D.C.------...... Pricewxl(-sw2kram)

LETTER OF SUBMITTAL .— To the Congress of the United Stutes: In compliance with the provisions of the act of March 3, 1915, establishing the National Advieory Committee for Aeronautics, I submit herewith the seventeenth annual report of the committee for the fiscal year ended June 30, 1931. It is noted from the committee’s report that the progress in aerodynamic development has been gratifying and that with recent notable additions to equipment the committee now has excellent facilities for the conduct of fuH-scale research on airphmes, propellers, and seaphme floats and hulls. Attention is invited to Part TTof the report presenting a summary of progress in the technical development of aircraft. With the steady improvement in the performance of aircraft, the relative importance of aviation increases as an agency of transportation and of natiomd defense. I cmcur in the committee’s opinion that the continuous prosecution of scientific research will provide the best assurance of further progress in the develop- ment of aircraft for aUpurposes. HERBERTHOOVER. THE TVHITEHOUSE, December 11, 1931. 111

LETTER OF TRANSMITTAL

NATIONALADVISORYCOMMITTEEFOEAEROIiAKiTICS, Ta~hin@on, D. C., Nocember 17, 1931. hf E. PRESIDENT: In comphnce with the provisions of the act of Congress approved March 3, 1915 (U. S. C., title 50, sec. 163), I have the honor to transmit herewith the Seventeenth Annual Report of the National Advisory Committee for Aeronautics for the ikal year ended June 30, 1931. Gratifying progress has been made during the past year in the conduct of fundamental invdgations in aeronautics at the committee’s laboratories. Some of the new scientific data produced during the year have already found application in the development of nditary and commercial airplanes of improved performance. The research programs of the committee cover comprehensively the whole field of aircraft research, with con- tinuing emphasis upon the major problems of increasing the safety, the reliability, and the efficiency of aiqknes. .— The new fuU-scale wind tunnel recently placed in operation miUmake it possible to investigate the aero- ...— dynamic characteristics and behavior of full-sized airplanes. The new N. A. C. A. Tank will make it possible for the fit time to investigate the hydrodynamic characteristics of full-scale seaplane floats and hulk These unique pieces of equipment, in conjunction with the pmpeuer rese~ch t~el~ @~e tile cofittce e~cflent _ laboratory facditks for the conduct of full-scale research ~d VKUenable it better to meet the rese~ch ne~ . _ of military and of commercial aviation. Attention is invited to Part Trof the report presenting a summary of technical progressfin aeronautics. Respectfully submitted. JOSEPHS. AMES,Chairman. THE PFLESIDEIIT, Z%.eWMfe Ho-use, TVashington,D. C. v CONTENTS. _

lkga Letterof subtittd ------III Lettwof transmittal------v Seventeenthannualrepoti------..-----__--— 1 —. —

PART I. ORGANIZATION Functiomof thecomittie ------—------..--.-— ------3 Organizationofthecomittie------_-*------z Deathof Dr. SamuellV.Stratton------_.----.----.--.-----..— 4 -.. . Meetingsof theentiiecommithc------4 Theexecutivecomtithe ------__------_------—------.------.-----_--.-- 4 SutiommithM------5 . Quartersfor committee------6 TheLangleyMemorialAeronauticalLaborntery------6 — TheOfficeof AeronauticalIntelligence------7 Financialreport------.--.---..-.--- 8

P.4RTH. GENERAL ACTIVITIES Studyofeircraft actidenti------13 — Considerationofaeronauticalin\'entions------14 Relationstiththe tircraftindustry------14 Cooperationof Armyand Na\'y------16 Investigationundertakenfor theArmyandthe Navy-_--_-----_-----.:i ------..- 10 CooperationwithStateDepartmentabroti------17 Revisionof nomenclaturefor aero~utics------17

PART HI. REPORTS OF TECHNICAL COMMITTEES ~l)otiof committeeon urodynatics ------_-_------.__-.-- 19 Reportof committeeon powerplantsfor aircrtift--_----.------.-...—------29 Reportof committeeon materialsfor tircraft------36 . . Reportof committee.o!! problemsof airna;tigation------43

PARTIV. TECHNICAL PUBLICATION$3 OF THE COMMITTEE Summariesof technicalreporta------46 .— Listof technicalnotesissuedduringthepastyear------55 Lkt of technicalmemorrmdurnsissued(luringthepmtycar------5(3 L~tof aircraftcircularsissuedduringthep=tyear ------58 Bibliographyof aeronautics------59

PART V. SUMMARY OF PROGRESSIN AERONAUTICAL RESEARCH Aerodpwics------.------—.= ------_ .00 ——. -— Airutit en@nw------03 Structuralmaterials------...... -. ------. --__— ------. . . ---.------. . ----a- -.-_- M Aimhips------__-__-_-_------.--_---__------..------.------m 65 _—. . Sugary ------.. .-— . . . .------—----=-. -----.-- ---_------4---=_--_.. 66 . — VI

. TECHNICAL REPORTS ‘“-

Page No.365. AerodynamicCharacteristicsof Circular-hoAirfoilsat HighSpeeds. By L. J. Briggsand H. L. Dryden------67 ._- No. 366. Dynamicand FlightTestson Rubber-Cordand O1eo-Rubber-DiskLandingGearsfor an F6C+ Airplane. By — WilliamC. Peck------79 No. 367. PressureDistributionOrera Thick,TaperedandTwistedMonoplane‘Wing3fodel—N.A. C. .&81-J. By Carl J. Kemh@r ------97 . No. 36S.A h’ewChartfor Estimatingthe AbsoIuteCeilingof an Airplane. By WalterS. DieN------111 No. 369. ManeuverabilityInvadigationof the F6C-3 AirpIanewithSpeciaIFIightInstruments.By C. H. Deartmrnand .— H. W. fiwWau ------117 No. 37o. EfTectof Variationof ChordandSpanof Aileronson HingeJfomentsatSeveralAnglesof Pitch. By B.H. 310nish- 137 No. 371. Present.Statusof AircraftInstruments.By Subcommitteeon Imtrmenti ------153 No.372. The GaseousExplosiveReaction-The Effectof Pressureon the Rateof Propagationof the ReactionZoneand uponthe Rateof XIolecuhwTransformation.By F. W. Stevm ------175 No. 373. CkmiTicientsof Dischargeof FuelIn@tion Nozalesfor Compression-IgnitionEngines. By A. G. Gelal.Ies------193 No. 374. The AutomotiveIgnitionCoiL By T. H. D-en ------211 No. 375. Full-ScaIeTeds of MetalPropellersat HighTip Speeds.” By DonaldH. ~md______237 ..— No. 376. SomeApproximateEquationsfor theStandardAtmosphere.By WalterS. DieN------257 No. 377. A hfethodof FlightXfemurementof Spins. By HartleyA. Smdeand Nathan F. Scudded------267 No. 378. Comparisonof Full-scalePropellersHatingR. A. F.-6 and CIark1“AirfoilSections. By HughB. Freeman---- 83 No. 379. RolIingXomenti Due to RoIiingand Yaw for Four Vihg liodeb in Rotation. By MontgomeryKnightand CarlJ. Wetigw ------m No. 380. PresureDistributionOvertheFuselageof a P’W-9PursuitAirplaneinFlight. By RichardV. RhodeandEugene E. Lmdqtid ------327 No. 381. Static,Drop,andFlightTestson MussebnanType Ah-wheels.By W311iamC. PeckandAlbertP. Beard------355 —- No. 382. EIasticInstabilityof MembersHavingsectionsCommonin AircraftConstruction. By George‘T. Trayerand .— H. W. hfmch------873 No. 383. OntheTheoryof WingSectionswithParticularReferenceto theLiftDistribution. By TheodoreTheodorsen-- 411 No. 38*. The ComparativePerformanceof Superchargers.By OscarVi. Schey------425 No. 385. ‘WindTunnelTestson AirfoiIBoundaryLayerControIUsinga Backward-OpeningSlot. By IlillqrdJ. Bamber- 439 .— No. 3S6. hlaneuverability Irwestigationof an F6C-4 FightingAirplane. By C. H. DearbornandH. W. Kirschbaum--- 475 No. 387. The VerticalWind Tunnelof the h-ationd AdvisoryCommitteefor Aeronautics. By Carl J. ‘iVenzingerand .— ThomasA. =fi------499 .— No. 388. Investigationof the Diaphragm-TypePressureC&IL By TheodoreThmdo=~------507 No. 3s9. TheEffectof SmalIAnglesof Yawm“dPitchontheCharacteristicsof AirplanePropelIem. By HughB. FreeroarI- 523 No. 390. TheEffectof TaIveTti-ng uponthe Performanceof a SuperchargedEngineat Altitudeandan Unsupercharged —~ Engineat SeaLevel. 13yOscar’iI’.ScheyandArnoldE. Biemann------533 No. 391. The .kerodynamicCharacteristicsof EightVeryThickAirfoilsfromTestsin theVariableDensityWindTunneL —— By EastmanN. Jacob ------545 No. 392. Reductionof Turbulencein ‘i’i%dTunnels. By HughL. D~den ------557 No. 393. Span-I.aadDistributionasa Factorin Stabilityin RolI. By lIontgomeryKnightandRichard‘T. A-eyes------567 No. 394. AiIshipModeITestsin the T’ariableDensityWindTunneL By Ira H. Abhtt ------5s3 No. 395. A NewPrincipleof SoundFrequencyAnalysis. By TheodoreThmdomen------605 hro.396. Hydraulicsof FuelInjectionPumpsfor Comption-Ignition Engines. By A. M. httick---___------__ 621 No. 397. The DragCharacteristicsof SeveralAirshipsDeterminedby DecelerationTeds. By F. L. ThompsonandH. W. tihbam ------665 No. 398. Investigationof DampingLiquidsfor AircraftInstrument&II. By hi. IL Housemanand G. H. Keulegan---- 679 —.— No. 399. tie Movementand PressureDevelopmentin an EngineCylinder. By CharlesF. Yhm-in,jr., and Robert D. Bat----__--_____ ------_-__-_--_------>--- 697 No. 400. The AerodynamicCharacteristicsof a SlottedClarkY Wiig as Affectedby the AusiIiaryAirfoilPosition. By CarlJ. WenzingerandJoseph.$.Shofia1------707 m NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 8S41NAVYBUILDING,WASHINGTON,D.C.

JOSEPHS.AMES,Ph. D., Chairman, President,JohnsHopkinsUniversity,Baltimore,Md. DAVIDW. TAYLOR,D. Eng., ViceChairman, Washington,D. C. CHARLESG. ABBOT,Se.D., Searetary,SmithsonianInstitution,Washingtm,D. C. G~ORGEK. BURGESS,i%.D., Director,Bureauof Standards,Washington,D. C. ARTHURB. COOK,Captain,UnitedStatesNavy, AssistantChief,Bureauof Aeronautics,Navy Department,Washington,D. C. WILLIAMF. DURAND,Ph. D., ProfessorEmeritusof MechanicalEntineerimz,StanfordUniversitv,. . California. JAMESE. FECHET,MajorGeneral,UnitedS&tesAI%Y, Chiefof AirCorps,WarDepartment,Washin@u, D. C. HARRYF. Gu~c+EN=I~,M. A., TheAmerioanAmbassador,Habana,Cuba. CHARLESA. LINDBEE~H,LL. D. NewYorkCity. WILLIAMP. MCCRACKEN,Jr.,Ph. B., Washington,D. C. CHARLES F. MAEVIN,M. E., Chief,UnitedStateaWeatherBureau,Washington.D. C. WILLIAMA. MOFFETT,RearAdmird,UnitedStateaNavy, Chief,Bureauof Aeronautic,NavyDepartment,Washington,D. C. HF.NRYC. PRATT,BrigadierGeneral,Uniti StatesArmy, Chief,Mat6rie1Division,AirCorps,‘WrightField,Dayton,Ohio. EDWARDP. WARNER,M. S., IMitor,AVIATION,NewYorkcity. — ORVILLEWRXaHT,Ss.D., Dayton,Ohio.

. G~oRoEW. LEWKADirectorof AeronauticalRwurch JOENF. VICTORY,8ecrsiaW HENRYJ. E. REID,En@neer-in-Charge,LanglegMemorialAeronauticaltia~org, LanglegField, Va. JOHNJ. IDE,TechnicalA8tiiant in Europe,Patia,France.

EXECUTIVECOMMITTEE J08EPE& Amm, Chairman. - W: TAYLOR,Vice Chairman. CHARLESG. ABBOT. CH~S F. MARVIN, GEORGEK BU~GESS. WILLIAMA. MOFFETT. ARTEURB. COOK, HENBYC. PRATT, JAMESE. FECHET. EDWARDP. WARNEIL CEARUIS A. LINDBERGH. ORVILIEWRIGHT. WILLIAMP. MCCRACKEN. JOEINF. VICPORY,Secretiry. Vm SEVENTEENTH ANNUAL REPORT OF THE NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

WASHDWTOX,D. C., Novendwr 10, 1931. that ordy further research wiU p~ovide in order to To tlw Con9rew of the United fitates: make possible further improved performance, as, for — In accordance with the act of Congress approved example, through the reduction of interference drag March 3, 1915, establishing the National Advisory or the general aerodynamic improvement of airplan~-. .- Committee for Aeronautics, the committee submits In the investigation of problems of this character, it herewith its seventeenth annuaI report for the fiscal is necessary in order to obtain satisfactory ~ts to rear 1931. conduct tests under full-scale conditions. Satisfac- During the past year there has been continued prog- tory tests involtig the study of drag can not be made r- in the development of aircraft and in the ex- in tlight. tension of their USC. There has been a gratifying in- During the past year the committee completed and crease in air-passger transportation and in the placed in operation a fuIl~cale wind tunnel at its ._ scheduled miks flown by the air lines. This indicates laboratory at Langley Field, Va. (See &g. 1 and 2.) that the pubfic is in fact accepting atiation as a means This is the only wind tunnel in existence large enough . of transportation and that as the traveling public be- to test full-size airplanes. The committee aIso placed comes acquainted thro~~h experience -with the air- in operation during the past year a new towing tank transport service offered by the air lines on regdar for the in~estigation of the hydrodynamic character- .“.:. schedules and at attractive rates, the ~=e of air trans- istics of seaphme floats and hulIs. (See fig. 3.) portation by the people -will, in all probabihty, con- These two new major pieces of scientific equipment in tinue to increase. conjunct ion with the prope~er research tunnel (see The principal factor in the increasing use of air fig. 4) for the fnll-sade testing of aircraft propellers, travel is, of course, speed. During the past year, there and with the equipment of the fight research labora- hm been marked improvement in the speed of both tory for determining such aerodynamic characteristics military and commercial airplanes of new types. of airplanes as can be determined in flight, give the Where a masimum cruising speed of air transports a committee excellent facilities for the full-scale testing year ago was cbse to 120 miles per hour, it has been of airplanes. Aeronautics is greatly indebted to the increased on single-engine transports on a few routes farsighted support of the President and of the Con- during the past year to 170 miles per hour. AIthough gress in providing necessary funds for the equipment such high cruising speeds are exceptional at this time of the committee’s laboratory and for the conduct of in air transports, such speciaI performance or special its scientific in-instigations. service may -wsIIbe regarded as a forerunner of nor- The facilities of the committee are used for the con- maI demand and of normrd service in the future. duct of researches requested by the Army and Navy Increase in cruising speed has been accomplished air organizations and also to meet the needs of c.om- primarily through improvement in aerodynamic de- mercial aviation. To determine the needs of commer- sign by reduction in the drag of airplanes. The com- cial aviation the committee holds an annual conference mittee in continuing its investigation of the cowling with representatives of the aircraft industry and the and cooling of air-cooled engines determined during suggestions received are considered by the various the past year that the Iocation of the engines in the technical subcommittees in formulating research pro- . wing of a multienginedmonoplane is better than lo- grams. These programs are comprehensive in scope cating them either above or be~ow the wing as is the and embrace problems of military, naval, commercial, generar custom. and privateIy owned airplanes, and of airships. With each improvement in performance there is Special emphasis has for years been placed on the created a demand for further scienttic information development of means to obtain greater control of-an . 2 REPORTN.4TIONALADVISORYCOMM17XEEFORAERONAUTICS

airplane at low speeds incident to taking off and land- the maximum of results for both types from a given ing, vvith a view to increasing safety and reliability. investigation. k the design of military airplanes, speed and high This annual report is submitted in five ptirts. Part performance, especially in military maneuvers in I describes the organization’ of the committee, states which great strains are imposed on the structure, are its functions, outlines the facilities available under the of the greatest importance, while in the design of com- committee’s direction for the conduct- of scientific re- mercial and privately owned airplanes, safety and search in aeronautics, explains the activities and reliability are of greater relative importance. growt.h_of the Office of Aeronautical Intelligence in , From the standpoint of the development of the the collection, analysis, and dissemination of scientific aircraft industry, the most difficult problem is the and technical data, and presents a financial report of development of a satisfactory airplane for private expenditures during the fiscal year ended June 30, use. Such an airplane should not ordy be safe and 1931. reliable, bulmlso economical in first cost and in cost In I%rt II of this report the commit&e describes its of maintenance and operation. The committee, while miscellaneous activities, including the study of air- devoting much attention b this general problem, has craft accidents, the consideration of aeronautical in- also recognized the desirable features of certain types, ventions and designs, its relations with the aircraft — notably the autogiro and airplanes fitted with slots industry, and its cooperation with other governmental and flaps. Examples of these types have been ob- agencies. tained by the committee for the conduct of inve&i- In Part III the committee presents reports on the gations in this field. Intensive study has also been major results of its fundamental work in the form of made of the conventional type of airplane with con- reports of its standing technical subcommittees on trols and landing gear so modified as to simplify the aerodynamics, power plants for aircraft, materials for problem of taking off and landing, and of maneuver- aircraft, and problems of air navigation, which in- ing incid~t thereto. clude statementsof the organization and the functions Progress as made determines largely the trend of of each and of the progress of investigation conducted design and of the demand for further information under their general cognizance in governmenttil and along the same line. The new equipment of the com- private laboratories. mittee for full-scale research is especially adapted to In Part IV the committee presents summaries of the solve the fundamental problem of safety in aeronau- technical reports published during the past year, and tics. Although the specific problems of military and enumerates by title the technical notes, technical of commercial aircraft are different, the solution for memorandums, and aircraft circu~ars isued. one is usually helpful for the other, and the research In Part V the committee presents a summary of progrmns of the committee are so arranged as to yield pogress in aircraft development, 1

PART I ORGANIZATION

— FUhrCTIONSOF THE COMMITTEE and other branches of the Government and such as is The ~ational ~ritvisory committee for ~eronautics not confidential is immediately released to university was established by act of Congress approved March laboratories and aircraft manufacturers interested in 3, 1915 (U. S. C., title 50, sec. 151). The organic act the study of specific problems, and also to the public. charged the committee with the supervision and direc- .Shrth. The committee holds itself at the service of tion of the scientific study of the problems of flight the President} the Congress, and the executive depart- .._ with a view to their practical solution, the determina- ments of the Government for the consideration of tion of problems .which should be experimentally special problems which may be referred to it. attacked, and their investigation and application to By act of Congresi appro~ed July 2, 1926, and practical questions of aeronautics. The act also mnended March 3, 1927 (U. S. C., Supp. IV, title 10, — authorized the committee to direct and conduct sec. 310r), the committee was given an additional func- research arid experimentation in aeronautics in such tion. This Iebgislationcreated and specified the func- laboratory or laboratories, in whole or in part, as may tions of an aeronautical patents and design board, con- be placed under its direction. sist~~ of an Assistant Secretary of War, an titant Supplementing the prescribed duties of the com- Secretary of the Navy, and an Aa&tant Secretary of mittee under its organic act, its broad general func- Commerce, and provided that upon favorable recom- tions may be stated as fo~ows: mendation of the h’ational Advisory Committee for FirsL Under the law the committee hokls itself at Aeronautics the patents and desi=gnboard &all deter- the service of any department or agency of the Gov- mine questions as to the use and value to the Govern- ernment interested in aeronautics for the furnishing ment of aeronautical in-rentions submitted to any of information or assistance in regard to scientific or branch of the Government. The legislation provided technical matters relating to aeronautics, and in par- that designs submitted to the board should be referred ticular for the investigation and study of fundamental to the NationaI Advisory Committee for Aeronautics probkms submitted by the War and h’avy Depart- for its recommendation, and this has served to impose ments with a vie-w to their practical solution. upon the committee the additional duty of consider~m Second. The committee may also e~cise its fuuc- on behalf of the Go~ernment all aeronautical inven- tions for any individual, firm, association, or corpora- tions and designs submitted. tion within the United States, provided that such individual, tlrxr+association, or corporation defray ORGANIZATIONOF THE COMMITTEE the actual cost involved. In accordance tith the provisions of the act of Third. The committee institutes research, investi- Clonggesswtabliehin~ the committee, as amended by .- gation, and study of problems which, in the j~dggment act approved March 2, M29 (U. S. C., Supp. IV, titLe of its members or of the members of its various sub- 50, see 151a), the h’atiomd Advisory Committee for committee+ are needful and timely for the advance Aeronautics consists of 15 members appointed by the . . of the science and art of aeronautics in its various Pr&dent, as follows: Two members from the War branches. Department, from the ofice in charge of military Fourth, The committee keeps itself advised of the aeronautics; two members from the Navy Depart- progress made in research and experimental work in ment, from the office in charge of navaJ aeronautics; a aeronautics in alI parts of the world, particularly in representative each of the Smithsonian Institution, England, France, Italy, Germany, and Canada. the United States ‘Weather Bureau, and the United Fifth. The information thus gathered is brought to States Bureau of Standards; and not more than eight the attention of the various subcommittees for con- additional persons acquainted with the needs of aero- sideration in connection with the preparation of pro- nautical science, either civil or military, or skilled in grams for research and experimental work in this aeronautical engineering or its allied sciencss, ‘I’he country. This information is also made available law further provides that all members as such shall promptly to the military and naval air organizations serve without compensation. a 4 REPORTNATIONALADVISORY00MMIIIl!EEFORAERONAUTICS

On May 21, 1931, Capt. John H. Towers, United Dl?.ATHOF DR. SMMUEL IV. STRATTON States Navy, submitted his resignation as a member of In the death of Dr. Samuel W. Stratton in Boston the committee because of his relief from duty as assist- on October 18, 1931, the committee lost one of the ant-chief of the Bureau of Ae&mautics of the Navy original 12 members appointed by President Wilson Department and assignment to- duty with the fleet. in 1915. In cooperation with the late Dr. Charles D. LTnderdate of May 23, 1931, the President--appointed Walcott, Doctor Stratton was instrumental in bring- CapL Arthur B. Cook, United States Navy, to suc- ing about the enactment by Congress of legislation ceed Captain Towers as a member of-the committee. which created the committee in 1916 and exerted a Captain Cook is also Captain Tower’s successor as as- marked influence on the development of the commit- sistant chief of the Bureau of Aeronautics. He exe- tee’s organization. For 15 years he was chairman of cuted the oath of office as a member on June 3, 1931. the important subcommittee on power plants for air” On October 18, 1931, the committee lost one of its craft, and for seven years, from 1916 tcr1923, he was original members through the death of Dr. Samuel W. secretary of the National Advisory Committee for Stratton, and under date of-November 6, 1931, the Aeronautics. At- the annual meeting of the entire President appointed as his successor on the committee committee held on October 22, 1931, the committee Col. Charles A. Liidbergh. Colonel Lindbergh will expressed its sense of loss in a resolution which was also serve as a member of the executive committee. spread upon its minutes and copies of which were The entire committee meets twice a year, the annual sent to the family oEDoctor Stratton. meeting being held in October and the semiannual meeting in April. The present report includes the MEETINGSOF THE ENTIRE COMMITTEE activities of the committee between the annual meet- The semiannual meeting of the entire committm ing held on October 23, 1930, and that held on October was held on April 23, 1931, at the committee’s head- 22, 1931. quarters in Washington, and the annual meeting on The organization of the committee is as follows: October 22, 1931, also at the committee’s hctidquar- Joseph S. Ames, Ph. D., chairman, president of ters. At these meetings the recent progress in aero- Johns Hopkins University, Baltimore, Md. nautical research was reviewed and some of the prin- David TT7.Taylor, D. Eng., vice chairman, Wash- cipal problems of aeronautics were discussed. Ad- ington, D. C. ministrative reports of the secretary, Mr. John l?. Charles G. Abbot, Sc. D., Secretary of the Smith- Victory, and of the director of the 05ce of Aeronau- sonian Institution. tical Intelligence, Dr. Joseph S. Ames, were also sub- George K. Burgess, Sc. D., Director of the Bureau mitted. of Standards. At both the annual and semiannual meetings de- Capt. Arthur B. Cook, United States Navy, tailed reports of the research work being conducted Assistant Chief of the Bureau of Aeronautics, by the committee at the Langley Memorial Aeronau- Navy Department, tical Laboratory, Langley Field, Hampton, 17a.,were William l?. Durancl, Ph. D., professor emeritus presented, and charts and photographs were exhibited of mechanical engineering, Stanford Univer- showing the methods used and the results obtained in sity, Calif. the more important investigations. Maj. Gen. James E. Fechet, United States Army, The election of officers was the concluding feature Chief of the Air Corps. of the annual meeting. The officers of the committee Harry F. Guggenheim, M. A., American ambassa- were reelected for the ensuing year, as follows: dor to Cuba, Chairman, Dr. Joseph S. Ames; vice chnirman, Dr. CO].CharlesA, Lindbergh, LL. D., New York City. David W. Taylor; chairman executive committoe, Dr. William P. McCracken, jr., Ph. B., Washington, Joseph S. Ames; vice chairman executive committee, D. C, Dr. David W. Taylor. Charles l?. Marvin, M. E., Chief of the weather THE EXECUTIVE COMM1’ITEE Bureau. RermAdmiral William A. Moffett, United States For the purpose of carrying out the work of the Navy, Chief of the Bureau of Aeronautics, advisory committee the regulations provide for the Navy Department. election annually of- an executive committee, to con- Brig. Gem IIenry C. Pratt, United States Army, sist of seven members and to include in addition any chief of the matkriel division, Air Corps. member of the advisory committee not otherwise a Edward P. Warner, M. S., editor of ‘~Aviation.” lnember of the executive committ-e but resident-in or near Washington and giving his time wholly or chiefly Orville Wright, Sc. D., Dayton, Ohio. .. REPORTNATIONALADVISOBY(30M3HTTEEFOBAEROHAUTICIS 5 to the special work of the committee. The present on aerodynamics -was discontinued because it vas — organization of the executive committee is as foIIows: bdie-red that the continuation of its work was being Joseph S. &rMs, Ph. D., chairman.” provided for by other agencies; the subcommittee on David W. Taylor, D. E@., vice chairman. woods and glues and the subcommittee on coverings, Charles G. Abbot, SC. D. dopes, and protective coatings of the committee on George K. Burgess, Sc. D. materials for aircraft were discharged and in their Capt. Arthur B. Cook, United States Navy. stead a new subcommittee on miscellaneous materials llaj. Gen. James E. Fechet, United States Army. wcs established; and the subcommittee on problems of CO1.Charles A. Lindbergh. communication of the committee on problems of air William P. McCracken, jr. navigation was discontinued because of the overlap- Charles F. Marvin, M. E. ping of its functions with the -work of a committee Rear Admiral William A. Moffett, United States of the aeronautics branch of the Department of Navy. Commerce. Brig. Gen. Henry C. Pratt, United States &my. In addition, a temporary subcommittee on research program on monocoque design has been established Edward P. Warner, 3L S. .— Orville Wright, Sc. D. under the subcommittee on aircraft structures. The The executive committee, in accordance with gen- executive committee has recently authorized” aIso the eral instructions of the advisory committee, performs organization of a standing subcommittee on methods the functions pr=cribed by law for the -whole com- and devices for testing aircraft materials and struc- mittee, administers the affairs of the committee, and tures as an additional subcommittee of the committee exercises general supervision over all its activitiw. on materials for aircraft. The executi~e committee has organized the neces- The standing committees of the executive commit- sary clerical and technical staffs for handling the -work tee, with their subcommittees, are at present as of the committee proper. The total paid personnel folIows : of the committee numbered 306 employees on June Aerod~amics- 30, 1931, comprising 44 in Washington, 259 at the Subcommittee on airships. Langley Memorial Aeronautical Laboratory, Langley Power plants for aircrafi. Field, Vs., and 3 at the office of the technical assist- Materials for aircraft- ant in Europe, Paris, France. GeneraI responsibility Subcommittee on metaLs. for the execution of the policies and the direction of Subcommittee on aircraft struct~ the activities approved by the executive committee Temporary subcommittee on research is vested in the directcmof aeronautical research, Mr. program on monocoque design. George W. Lewis. He has immediate charge of the Subcommittee on miscellaneous materials. scientific and tecticd work of the committee, being Subcommittee on methods and devices for directly responsible to the chairman of the executive testing aircraft materials and structures. committee, Dr. Joseph S. knee. The secretary, Mr. Problems of air navigation— John F. Victory, is ex officio secretary of the execu- Subcommittee on instruments. tive committee, directs the administrative work of the Subcommittee on meteorological problems. organizatio~ and exerci..s general supervision over Aircraft accidents. the expenditures of funds and the employment of Aeronautical inventions and designs. personnel. Publications and intelligence. Personnel, buildings, and equipment. suBco31MrrTEEs The organization and work of the technical commit- h order to facilitate the conduct of its work, the tees on aerodpmrnics, power pkmta for aircraft, mate- executive committee has organized a number of stand- rials for aircraft, and problems of air nmigation are ing committees, with subcommittees in some instances covered in the reports of those committees in Part 111 ...— to cover the general field more effectively. During the of this report, while the activities of the committee on past year the executive committee, believing that aircraft accidents and the committee on aeronautical changes in its needs had occurred which should be inventions and designs are included in Part II under ...— met by changes in its subcommittees, effected a reor- the subjects of the study of aircraft accidents and the ganization. consideration of aeronautical inventions, respectively. In this reorganization the committee on govern- Statements of the organization and functions of the mental relations w-asdischarged; the subcommittee on administrative committees on publications and intelli- aeronautical research in universities of the committee gence, and personneI, buildings, and equipment follow: .- ...— 6 REPORTNxrIoN’fi ADVISORYCOMMITTEEFORA3R0NAtTTICS

COMMITTEE ON PUBLICATIONS AND INTELLIGENCE Hampton, Va,, and the office of-the technical assistant FUNCTIONS in Europe, located at the American Embassy in Paris. The scientific investigations authorized by the com- 1. The collection, cksification, and diffusion of mittee are not all conducted at the Langley Memorial technical knowledge on the subject of aeronautics, in- Aeronautical Laboratory, but the f acititi- of other cluding the resulti-of research and experimental work governmental laboratories are utilized, as well as the done in all parts of the world. laboratories connected with institutions of learning 2. The encouragement of the study of the subject of whose cooperation in the scientific study of speeific aeronautic in institutions of learning, problems in aeronautics has been secureil. 8. Supervision of the Office of Aeronautical Intelli- gence. THE LANGLEY MEMORIALAERONAUTICAL 4. Supervision of the““committee’s foreign office in LABORATORY Paris. The “Langley ImmemorialAeronautical Laboratory is 5. The collection and preparation for publication of cperated under the direct control of the committee. the technical reports, technical notes, technical memo- It is located at Langley Field, Vs., on a plot of grouncl randums, and aircraft circulars of the committee. set aside by the War Department for the cotnmittee’s ORGANIZATION use, The Laboratory was started in 1916 coincident Dr. Joseph S. Ames, chairman. with the establishment of Langley Field. Prof. Charles F. Marvin, vice chairman, The laboratory is organized with seven divisions, Miss M. M. Muller, secretary. as follows: Aaodynamics division, power plants divi- sioy, h~drodynamics division, physical research divi- COMMITTEE ON PERSONNEL BUILDINGS AND sion, technical service division, flight operations EQUIPMENT divison, and property ancI clerical division. The FUNCI!IONS laboratory is under the immediate direction 01-an 1. To handle all matters relating to personnel, in- engine~ in charge, Mr. Henry J. E. Reid, subject tu cluding the employment, promotion, discharge, and the general supervision of-the officemof the committee. duties of all employees. During the past year the construction of t~le full- 2. To consider questions referred to it and niake scale wind tunnel and of the seaplane channel were recommendations regarding the initiation of projects completed. The new wind tunnel has an oval-shaped concerning the erection or alteration of laboratories throat, 60 by 30 feet, which permits the testing of and offices. full-size airplanes. This tunnel was placcd in opera- 3, To meet from time to time on call of the chair- tion during _the sixth annual aircraft engineering man and reportits actions and recommendations to the research conference on May 27, 19S1. Since then studies have been made of the flow conditions and executive committee. 4. To supervise such construction and equipment several tests on full-size airplanes have been rnacle. work as may be authorized by the executive committee. The tests made thus far have indicated that the opera- tion of the tunnel will be satisfactory and that it will ORGANIZATION prove to be a valuable tool for studying the character- Dr. Joseph S. Ames, chairman, istics off ull-size airplanes. Dr. David W. Taylor, vice chairman, During the same conference the new seaplane chan- John F. Victory, secretary. nel, or N, A. C. A. Tank, as it is nom officially desig- nated, was placed in operation. This tank has a QUARTERSFOR (!CMIIITTEE channel length of 2,020 feet and a width of 24 feet, The headquarters of the National Advisory Com- and the carriage and test equipment are capable of mittee for Aeronautics are located at the rear of the towing Iarge models of seaphme floats at speeds up eighth wing, third floor of the Navy Building, Con- to about 60 miles per hour. Up to the present time stitution Avenue and Eighteenth Str~t NW., Wash- the -work with this tank has been mainly confined to ington, D. C., in close proximity” to the Army and calibration and assembly of instrumental equipment Navy air organizations. This space, totaling 8,914 for towing models. The preliminary tests of seaplanc square feet, has been officially assigned for use of the floats have indicated that this tank, which in- committee by the Public Buildings Commission. The cludes several novel features, will operate entirely administrative ofice is also the headquarters of the satisfactorily. various subcommittees and of the OtEce of Aero- In accordance with the Army’s program for making nautical Intelligence. miIita@” improvements at Langley Field, it will be Field stations of the committee are the Langley necessary to remove the committee’s present hangar, Memorial Aeronautical Laboratory, Langley Field, and therefore the construction of a new permanent REPORTNATIONALADVISORYCOMMITTEEFOEAERONAUTICS 7 brick hangar was started during the past summer. 6. A ser-rice building containing an instrument This hangar will contain, in addition to the repair Laboratory, drafting room, machine shoP, WoOd~Ork- shop and facilities for taking care of airplanes used ing shop, and storeroom. in flight, offices for the flight research staff. 7. A propeller research tunnel, in which tests may Other less extensive additions to the equipment of be made in a 20-foot air stream at 100 miles per the laboratory have included: A new spray-combus- hour. This equipment permits the full-scale testing — tion apparatus, with which it is possible to photograph of propellers, fuselages, and landing gears. the spray and its combustion in a compression- 8. An airplane hangar -with a repair shop and fa- .— ignition-engine cylinder; equipment for studying the ciliti= for taking care of airplanes used in flight ....— cooliqg of finned cylinders, such as are used in aircraft research. This will be replaced by a new hangar! as e.msjnes; a sound amdyzer by which it is possible to stated above. measure the sound intensities at. various frequencies 9. A combination heating plant, storehouse, and in connection tith the study of aircraft noises. Two garage. aircraft have also been added, namely, the McDonnell 10. A new full-scale wind tunnel, described above. .— airplanel which is being used for the study of the 11. A new N. -A. C. A. tank, described above. etl?ectof slots and flaps on the control at large angles items 1, 2, 3, 4, 5, 6, and 9 are located on plot 16. of attack ancl on the performance of the a.irplan~ and Items 7, 10, and 11 are located within two blocks of the autogiro, which was recentiy purchased in order the laboratory headquarters, and item 8 is located an to study the po.&bilities of this form of aircraft. b flying &ld9 There are at present 11 structures comprising the 13ecognition by tie Government of the necessity Langley Memorial &ronauticaI Laboratory, as fol- of satisfying the increasing demand for new and lows : accurate knowledge on the fundamental problems of 1. A research laboratory building containing admin- @ht has made possible the development of the lLa~- istrati~e offices, technical library, physics laboratory, ley ~emorial Aeronautical Laboratory as an efficient photographic laboratory, and headquarters of the vari- research organization numbering 259 emplo~ees at ous divisions. the close of the flscal year 1931. The work of the 2. b atmospheric wind-tunnel building, in which laboratory is conducted without interference with the 5-foot wind tunnel of a standard closed-throat military operations at the field. In fact, there is a . . .— type has been replaced by more modern equipment. splendid spirit of cooperation on the part of the In the space formerly required by the 5-foot tunnel miIitary authorities, who by their helpfulness in many has been built a modern clcswl-return tunnel with mn -ways ha~e aided the committee materially in its open rectangular throat 7 by 10 feet and a vertical work tunnel with closed return and an open throat 5 feet in THE OFFICE OF -AERONAUTICALWI!ELLIGEN’CE diameter. These two pieces of equipment are to be The Office of Aeronautical Intelligence was estab- uss in a comprehensive study of the problems of con- .-. — trol and spinning characteristics of an airplane. In lished in the early part of 1918 as an integral branch addition to the above equipment the buikling now of the committee’s activities. Its functions are the houses a 6-inch open-throat wind tunnel for instru- collection, classMcation, and diffusion of technical ment and wind-tunnel studies and a 6-inch refriger- knowledge on the .wbject of aeronautics, including the ated tunnel for the study of ice formation on aircraft. resdts of research and experimental work conducted . . More efficient use of space has akmprovided room for iR all parts of the world, to the rditary and navaI air a worlmhop and ofiice for the staff operating the organizations, aircraft manufacturers, educational in- tunnels. stitutions, and others interested. It is the officially 3. A variable-density wind-tumd building, housing designated Go~ernment depository for scientific and the variable-density wind tunnel and a jet-type high- technicaI reports and data on aeronaut.i.x+. speed wind tunnel which utilizes the waste air from Promptly upon receipt, all reports are analyzed, the variable-density wind tmmel. classified, and brought to the special attention of the 4 ancl 5. Two engine dynamometer laboratories of subcommittees having cognizance and to the attention a semip+xmanent type equipped to carry on investi- of other interested parties through the medium of gations in connection with power plants for aircraft. pubIic and confidential bulletins. Reports are dupli- In addition to the usual dynamometer equipment and cated where practicable and distributed upon request. single-cylinder test engines for studying both carbu- Confidential bulletins and reports are not circulated ..— reted and Diesel-oil engines, there is equipment suited outside of Government channels. to the study of superchargers and the cooling of The records of the committee show that there has engine cylinders, and special high-speed photo- been a continuous increase in the distribution of tech- .—-- graphic equipment for the study of fuel sprays. nical publications During the year 12,S17 written 8 REPORTNATIONALADVISORYCOMMITTEEFORAERONA~lOS

requests for reports were received in addition to a as the committee’s technical assistant in Europe since large number of telephone and personal requests and April, 1921. 72,090 reports were distributed upon request. FINANCIALREPORT The technical publications were distributed as fol- The appropriation for the National Advisory Com- lows : mittee for Aeronautics for the fical year 1931, as car- (.!ommitteeand subcommittee members______5, !229 ried in the independent offices appropriation act– Langley Memorial Aeronautical Laboratory- 2,719 approved April 19, 1930, was $1,306,000. Of this Paris office of- the committee------6,986 amount $7,000 was later transferred to the appropria- &my Air corps ------2,58’7 tion for printing and binding, fiscal year 1931, by the Naval Air Service, including Marine Corps- 3,797 second deficiency act, fiscal year 1931,approved bfarch hfanufacturers ------18,825 < 1931,-to provide funds for the increasingly large Ilducational institutions_l------17’,120 number of technical reports being issued by the com- Bureau of Standards------495 mittee. This left a balance of $1,299,000 in the gen- bIiscellaneous---______—______64,929 eral appropriation, under which the committee re- ports expenditures and obligations during the year Total distribution______ill!, 687 amounting to $1,173,014.74,itemized as folIows: The above figures include the distribution of 34#06 Personalservices______–.– $617,731.24 technical reports, 26,272 technical notes, 82,380 techni- Suppliesand materials______40,0s3.23 cal memorandums, and 10,762 aircraft circulars of the Communicationserv!&_--____—___ 1,904.42 ~ational Advisory Committee for Aeronautics. Part Travelexpenses______14,214.49 Transportationof tangs-_..___ --—-_ —__ IV of this report presents the titles of the publica- 1,604.90 Furnishingof ehxtricity__-_-__-— _____ la 1s3.Ml -. tions issued during the past year, the distribution of Rent of oftlce(Pmfs)______000.cm which is included in the foregoing figures. Repairsandalterations___ -_—____—___ 98,973.95 To handle efficiently the work of securing and ex- Speeialinvestigationsand reports______53,600.00 chq$ng reports in foreign countries, the committee Equipment______32%,873.Ii Structuresand parts_ -__. _____-__— Go,093.59 maintains a technical assistant in Europe, with head- quarters at the American Embassy in Paris. It is his ,Expenditure&______1,178,014.74 cluty to visit the Government-and private laboratories, Unobligatedbalance______l%, 98S.!?6 cente~%of aeronautical information, and private indi- vjduaIs in England, France, Italy, Germany, and Total,generalappropriation______1,229,000.00 other European countries and endeavor to secure for The appropriation for printing and binding for America not only printed matter which would in the 1931 was $15,000, which, with the $7,000 transferred ordinary course of events become available in this from the general appropriation, made available the country but more- especially advance information as amount of $22,000, out of which $21,982,67 was ex- tc work in progress and technical data not prepared pended. . in. printed form, which would otherwise not reach The appropri~tions for the fiscal year 1932 total this country. John Jay Ide, of New York, has served $-1,051,070. FIGURE 1.—FULL-SCALE WIND TUNNEL .FOR. . . INVESTIGATION.. .. -—. .—. . ..—. ..OF. . AERODYNAMIC CHARACTERISTICS OF MILITARY AND COMMERCIAL AIRPLANES. THE AIRPLANE IS SUPPORTED ON A 6-COM- PONENT BALANCE BY MEANS OF STRUTS IN THE CENTER OF AN AIR STREAM 60 FEET WIDE BY 90 FEET HIGH AND HAVING A VELOCITY OF 112 MILES PER HOUR. THE BOUNDARIES OF THE AIR STREAM ARE CONFINED BY THE ENTRANCE AND EXIT CONES SHOWN. FIGURE 2.—FULL-SCALE WIND TUNNEL SHOWING METHOD OF ATTACHMENT OF AIRPLANE TO BALANCE SlJPPOR13 AND ONE OF THE 4-BLADE 35)j-FOOT PROPELLERS. EACH PRO. PELLER IS OPERATED BY A 4,000-HORSEPOWER ELEffRIC MOTOR. FIGURE 3.—N. A. C. A. TANK

r.nn ,F.,\,rc-rteaTrnN.Ifir uvn Rnnvrd . . .Awlc...... - CI-IARACTERISTICS...... — ------OF MODEL SEAPLANE I=LOATS AND HIJLH. TOWING CARRIAGE WITI+ MODEL FLOAT rum ,, W” AGJ, ,-rl .,-!. -, ., . ------IN PLACE. CARRIAGE HAS A RUN OF 2,000 FEET AT SPEEDS VARYING FROM 4 TO 5a MILES PER HOUR. FIGURE 4.—PROPELLER RESEARCH TUNNEL

FOR INvESTIGATION OF FULL-SCALE PROPELLERS AND LARGE MODELS OF AIRPLANES AND AIRSHIPS. 20-FOOT MODEL OF U. S. S. “AKRON” UNDER INVESTIGATION TO DETERMINE LI17, DRAG. PITCHING MOMENTS, AND PRE.SURE DISTRIBUTION. THE TUNNEL HAS AN AIR STREAM 20 FEET IN DIAMETER WITH A VELOCITY OF 100 MILES PER HOUR. PART II GENERAL ACTMTIES

STUDY OF AIRCR.4Fl’ ACCIDENTS :he chart in these three departments has definitely demonstrated its practical value, and has made it In response to the need for a standard baais for the possible to obtain certain standard and definite in- classification and comparison of aircraft accidents, formation regarding each accident, to mSkS a com- both civil and military, the National Advisory Com- parative study of accidents from the information thus mittee for Aeronautics, in October, 1928?issued a ch~rt ~btained, and to compile statistical data of the highest for the analysis of aircraft accidents. This chart, importance. which, together with a detailed explanation of its use, By this method of analysis it has been possible to was published as Technical Repoti No. 808, protided determine with reasonable accuracy the percentage of — for the study of the immediate causes, the underlying accidents due to faulty piIoting and other errors of —— causes, and the results of accidmts. T~ chart had personnel, and the percentage due to mat6riel fail- been prepared after a thorough study of the problem ures; to separate the percentage of faulty piloting into by a special committee on the nomenclature, subdivi- various kinds of errors of pilots, such as errors of sion, and classification of aircraft acciden~ -whichhad judgment, poor technique, disobedience of orders, etc.; been organized by the National Advisory Cmnmittee and to separate the mat4riel failures into the failures for Aeronautics at the requess of the air coordination of various parts of the airplane. A sidar detailed committee, consisting of the Assistant Secretaries for study is made of the underlying causes, such as poor Aeronautics in the War, Navy, and Commerce reaction, inherent or temporary; lack of experience, Departments. special or general. ALI these causes are studied in This chart was oilicialIy adopted by the War, Navy, their relation to the total number of accidents and to ... and Commerce Departments for use in the study of the number of fatal accidents. lVith this information aircraft accidents. In order to assist in the coordi- at hand it is potible for the two miIitary services and nation of this work and to provide for the considera- aIso for the Department of (lommerce to talre immed- tion of such other problems relating to aircraft acci- iate action toward the elimination of those condi- dents as might be desirable, the National Advisory tions, either of personnel or of mattiel, which have — Committee for Aeronautics, on completion of the work been shown as productive of SSMOUSrmlts in aircraft of the epeciaI committee on the nomenckdure, subdi- operation. vision, and classification of aircraft accidents! or@n- The National Advisory Committee for Aeronautics ized a standing committee on aircraft accidents. This keeps in touch with this work and through the tom- ....—._ standing committee has since prepared a revision of mittee on aircraft accidents cooperates whenever the ,— Technical Report No. 809, in which a number of the need arises. .- definitions in the original report were clarified and During the past year, Dr. George K. Burgess, who statistical information -waspresented showing a com- had given most whole-hearted and effective service as .— parison of the types of accidents and causes of acci- chairman of the special subcommittee on the nomen- dents in the military sertices on the one hand and in clature, subdivision, and classification of aircraft acci- ‘“— civil aviation on the other? together with explana- dents and as chairman of the standing committee on tions of some of the important differences noted in &is aircraft accidents, was relieved from the chairmanship -. comparison. The revised report was issued by the at his own requestl and Hon. Edward P. Warner was committee in 1980 as Technical Report A’o. 357. appointed to succeed him. The actuaI study and analysis of the various indi- The present organization of the committee on air- vidual accidents and the preparation of statisticrd craft accidents is as follows: information on the problem are made by the Army Hon. Edward P. Warner, editor of “Aviation~ Air Corp~ the Bureau of Aeronautics of the Navy, chairman. and the aeronautics branch of the Department of Lieut. Harold Brand, United States Army, &r Commerce for their respective organizations. In this corps. study the chart issued by the National Advisory Com- George W. Lewis, National Advisory Committee mittee for Aeronautics forms the basis. The use of for Aeronautics. 13 14 REPORTXATIOXALADVISORYCOMMITTEE FOR AERONAUTICS

W. Fiske Marshall, aeronautics branch, Depart- to tie consideration of submissions which have re- ment of Commerce. ceived competent--preliminary examination and are Lieut. Commander Frank D. Waener, “United deenmd ~orthy of further consideration, States Navy, Bureau of Aeronautics. The aeronautical patents and desi=~ board has been Lieut, Frank Ward. United States Navy, Bureau in operation five years. During the past year the of Aeronautics. National Advisory Committee for Aeronautics re- Lieut, Lyman P. Whitten? United States “Army, ceived about 2,050 letters relating to inventions, Ap- .&r Corps. proximately 800 of these represented new submissions. The majority of these cass, being addressed to the CONSIDERATIONOF AERONAUTICALINVENTIONS committee, were acted on by direct correspondence By act of Congress approved July 2, 19?26,a patents with the submitters. Seventy-six cases were submit- and design board was creatqd, and it was provided that ted ttithe aeronautical patents and design board, and upon recommendation of the National Advisory Com- the committee prepared an individual report M to- mittee for Aeronautics the board should determine the merits of each particular invention or design for questions as to the use and value to the Government of the action of the board. aeronautical inventions submitted to the Government. REL.4TIONS WITH THE AIRCRAFT INDUSTRY By ~ct of Congress approved March 3, 1927,the act of July 2, 1926, was amended in such a manner as to The committee cooperates closely with representa- limit the board to the consideration of such cases as tives of the aircraft industry in planning research were favorably recommended to it by the National programs which are of particular interest.to commer- Advisory Committee for Aeronautics. This reIieved cial aeronautics. The general,program of research as the board of the burden of considering cases which formulated by the committee for the cowling and cool- were unfavorably recommended by the commitk, but ing of radial air-coded engines was circulated tvengi- at the same time it made the National Advisory Com- neers of the industry and their comments obtuined, mittee for Aeronautics responsible for the &al disap- and the result of this investigation was the develop- ‘lJrOVd of the large majority of the devices submitted ment of the N. A. C. A. cowling. During the past year as applications for awards. a prcigram for the study of the interference drag of In order to discharge the duties devolving upon the combinations of engine nacelle and wing has been conl- committee under this legislation, a committee on plete& and the preliminary results have been for- aeronautical inventions and designs was created, the warded to the airplane manufacturers and used by present membemhip of which is as follows: them in recent designs of various types of airplanes, Dr. D. W. Taylor, chairman. The committee has under way a study of the landing Dr. George K. Burg-, vice chairman. and take-off characteristics of airplanes, and prelimi- Prof. Clmrles F. Marvin. nary ‘resuRs have been forwarded to various n~anu- J. F. Victory, secretary. facturers for their comments and suggestions, The Inventions and designs submitted are considered by committee takes advantage of every opportunity to the director of aeronautical research. The committee obtain the comments and suggestions of the industry on aeronautical inventions and designs considers only in cirrying out research programs. such inventions or designs as are presented by the One problem in connection with which there has director of aeronautical research or are recommended been active cooperation with the industry is the study for committee consideration by a member of the Na- of load factors in flight due to atmospheric disturb- tional Advisory Committee. The director of aero- ances. A number of air transport companies have nautical research is authorized to submit his unfavor- cooperated with the committee in this investigation. able recommendations direct &r the aeronautical pat- A special type of accelerometer was developed by the ents and design board, but any favorable recommen- committee for this purpose, and instruments have been dation must be considered and made by the commit- or are being instalIed by the Boeing Air Transport, tm on aeronautical inventions and designs. American Airways, Ford Motor Co., Pan American Under the present procedure careful consideration Airways (between Brownsville, Tex., and Mexico is given to all inventions and desi=~s submitted.. The City), and Ludington Air Line, on airplanes in regu- aeronautical patents and design board and the Na- lar operation, Records of special interest were ob- tional Advisory Committee for Aeronautics are work- tsined by the Boeing Air Transport in operation ing in harmony, and the burden of considering large hetwegg Cheyenne, Wyo., and Oakland, Calif., and be- numbers of inventions is placed so as to limit the de- tween Oakland and Seattle. An improved instrument mands on the time of the members of the committee has recently been developed by the committee which on aeronautical inventions and designs and of the will register both applied load factors and correspond- members of the aeronautical patents and design board ing air speeds, and this will greatly facilitate the task REPORTNATIONALADVISORY COXMIT!CEE FOE AEEONAUTKM 15 of obtaining the information needed in the study of the tank, described in a general way the tank, the tow- this problem. ing carriage, and the electrical equipment. Doctor Annual research oonferenoe,+.n 1926 the National Taylor then pressed the button which gave the signal -— Advisory Committee for Aeronautics estabIiehed the for plac~u the tank in operation, and the towing .— policy of holding at its laboratory at Langley Field, carria=~ me-red through the -watercarrying an observer the Langley Memorial Aeronautical Laboratory, an- and tovring a modeI of an XPH-1 flying-boat hull. . nual conferences with representatives of the manu- The dedication of the tank was followed by the facturers and operators of aircraft. The purpose of dedication of the fuII-scale tunnel by Doctor Ames. these conferences is to give to the representatives of He referred briefly to some of the important develop- the industry an opportunity to become acquainted ments in the history of the science of aerodynamics, with the faciIitiee for aeronautical research at the and particularly in the history of wind tunnels, men- committee’s laboratory and also b afford them an tioning the early wind tunueh of Sir Hiram Maxim opportunity to make suggestions to the committee as and Orville and Wilbur Wright. He then told to aeronautical research problems of interest to the briefly the study of the development of the full-wale industry -ivbich in their opinion the committee is wind tunnel, stating that the committee submitted to especially equipped to solve. the Bureau of the Budget in 1928 a request for author- In accordance with this policy, the sixth annual air- ity to expend $5,000 for the desi=mof such a tunnel; craft engineering research conference was held at the that this authority was obtained in act of Congress .. committee’s laboratory on 31ay 27, 1931. The com- approved May 16, 1928; that an appropriation of not mittee vms represented by its ofieers, members of the to exceed $900,000 for the construction of the tunnel, main committee, and the members of its committee on to be available during a perio,d of two years, was aerodynamics, committee on materials for aircraft, provided in act appro~ed February 20, 1929; and tii and subcommittee on airships. The conference was the contract for its construction was awarded on Feb- presided over by Dr. Joseph S. Ames, chairman of Iuary ill, 1930. The more important details of the the h’ational Advisory Committee for Aeronautics. tunnel, inchding its balance and other equipment> This year the most important featurw of the con- were then described by the engineer in charge of its construction and operation, Mr. Smith J. DeFrance, ference -werethe dedication and placing in operation .- of the committee% two new pieces of research equip- after which Doctor &nes with the follow@ com- .— ment, the full-scale wind tunneI and the seaphme tow- ment, pressed the button by means of which the ing channel, now officially designated the N. A. C. A. propellers were rotated and the air stream of the Tank. These ceremonies were held immediately pre- tunnel was set in motion: ceding the opening of the afternoon -ion of the ‘ ‘This committee started its work in 1915. I re- conference. The fuI1-scaIewind tunnel was dedicated gard this moment as probably the most important -. and formally placed in operation by Dr. Joseph S. moment in the history of the committee, because it kes, chairman of the National Advisory Committee is to set in operation a piece of apparatus which .— for Aeronautics, and the N. A. C. A. Tank by Dr. promises to give in the shortest time the most im- -— David W. Taylor, vice chairman of the committee. portant information desired in the development of The dedication of the N. A. C. & Tank was held aerodynamics; an instrument which is unique in the immediately after lunch. In dedicating the tank, world, and which we owe to the ingenuity of our Doctor Taylor etated that the uee of towing tanks engineers and to a Congress and a budget committee for the study of the resistance of ships, initiated by who understood our problem and were willing to William Froude, had become general in connection cooperate with US.” with ship design, but that ship tanks were not suit- At the morning session of the conference, the prin- able for tests of seaplane floats and hulk on account cipal investigations under way at the laboratory, both of the low speeds to which they -were limited. He in aerodynamics and power plants, were exphiined referred to the need for a tank adapted to research by the engineem in charge of the work, and charts on seaplane design, and outied briefly the history were exhibited showing some of the results obtained. of the N. A. C. A. Tan% stating that it had been Among the more important aerodynamic inve&ig&- recommended to the executive committee on January tions outkmd were the comprehensive study in the 29, 1929, by the director of aeronautical research, Mr. variable-density wind tunnel of the effect of changes George W. Lewis; that estimates for its construction of shape of systematic series of airfoiIs; study had been submitted to the Bureau of the Budget of the effects of various locations of engine nacelle on February H, 1929; and that the appropriation had with reference to a wing; investigation in the 20-foot been provided by Congress in a deficiency act ap- wind tunnel of the lift, drag, and pitching moments proved March 4, 1929. Mr. Starr Truscott, the engi- on a model of the airship U. S. S. ~km; comparison neer in charge of the construction and operation of of the drq~ characteristics of various airships; study 16 REPORTNATIONALADVISORYUOMM~EE FORAERONAUTICS

of the factors affecting the behavior of an airplane AH the suggestions for investigation presented in in a spin; determination of the effect of wing-tip connection with the conference, totaling 43, includ- shape on the load distribution; study of the loads on ing both those presented in the discussion in the after- the leading edge of a w-ing; fundamental investiga- noon sesion and those submitted in correspondence, tion of stressed skin, or monocoque, construction; have been carefully studied and classified. Those determination of tail surface loads in high-speed relating to aerodynamics, aircraft power plants! and dives and sudden pull-ups; and investigation of lat- aircraft structures have been considered by the appro- eral control and stability at low speeds and high priate-subcommittee in each case. The suggestions angles of attack, including tests tith a special long- for investigations in the N. A. C, A. Tank have not travel shock-absorbing Ianding gear ancl the study of- as yet-been referred to a subcommittee for considera- slots ~nd flaps. tion, as the general program for the tank is still in The power-plant projects described were those re- formulation. Most of the aerodynamic, power plant, h-iting to: First, the study of superchargers for air- and materials problems were already rI part of the craft engines, which included a comparison of the committee’s research program, and in a number of performance of superchargers of the centrifugal, other crisesthe program for a certain investigation Roots, and vane types; second, the investigation of has been modified to include the particular phnse of methods of increasing the power of aircraft engines, the problem suggested. including a study of the effect on engine performance of increasing the carburetor pressure for various com- COOPERATION OF ARBIY AND NAVY pression ratios, and the development of a 2-stroke Through the personal contact of the heads of the cycIe single-cyIinder air-cooled engine for aircraft, Army Air Corps and of the Bureau of Aeronautics of using gasoline injection and spark ignition; third, the the Navy serving as members of the National Advis- study of methods of decreasing the fire hazard in air- ory Committee for Aeronautics and of their chief craft engines, in connection with which a method of subordinates acting as members of the subcommittees, reducing the temperature of long exhaust stacks had there is first-hand discussion of the technical prob- been developed, and a study had been made of fueIs lems of these organizations, and this has served to of higher ffash point than gasoline (hydrogenated promote the coordination of research and experi- fuels); and, fourth, the study of the compression-igni- mental work in both aerodynamics and power plants. tion engine, which included investigation of the inject- Through this contact also the problems of these or- ion characteristic and the combustion characteristics ganizations are brought b-the attention of the com- of fuel sprays. mittee, and much of the fundamental research of the At the close of the session; the representatives of committee has resulted from requests received from the industry were conducted on a tour of- inspection the Army and Navy for the study of particular prob- of the committee’s laboratories, and the research lems. The successattained in the study of these prob- equipment was shown in operation. lems is to a large extent+ependent upon the uxq)era- The afternoon session was devoted to the discus- tion of the Army and Navy in placing at the commit- sion of the problems of commercial aeronautics. Prior tee’s disposal airplanes and engines required for to the conference, the committee had requested the research purposes. The committee desires to give representatives of the industry to submit suggestions special reco=~ition to this splendid spirit of cwopera+ in writing, and a large number were received. In tion, without which many of the invcstigathms re- addition, several such suggestions were presented and quested could not have been conducted effectively. discussed at the conference. Among these were the The committee wishes in particular to acknowhle the study of the vibration characteristics of airplanes and many courtesies extended by the Army authorities at the development of a vibration indicator; the inves- Langley Field, where the committee’s laboratories are tigation of tandem engine arrangements with refer- located, and by the naval authorities at the Hampton ence to an airplane wing, and the study of the effi- Roads T7aval Air Station. ciency of propellers in tandem; the investigation of slipstream effect; the problem of the maneuverability INVESTIGATIONS UNDERTAKEN FOR THE ARMY AND THE NAVY nnd controllability of an airplane; the investigation of flying boats with sponsons; the study of the charac- As a rule research progrmns covering fundanmutal teristics of forms of hull bottoms for flying boats; problems demanding solution are prepared by the the coding of air-cooled cylinders, including the study technical subcommittees and recommended to the ex- of the air flow over the cylinder head; and the inves- ecutive committee for approval. These programs sup- tigation of the effect of propeller efficiency and pitch ply the problems for investigation by the Lm@ey setting on fuel consumption, Memorial Aeronautical Laboratory. l\7hen,however, REPORTNATIONALADVISORY00MMITTEEFOEAERONAUTICS 17 the Army Air Corps, the Bureau of AeroDautim of Investigation of methods of improving wing char- — .. the Navy, or the aeronautics branch of the Depart- :eristim by control of the “ boundary Iayer?’ — ment of Commerce desires speciaI investigations to be Ice formation on aircraft. undertaken by the committee, such investigations, upon Investigation of comparative aerodynamic re&t- upproval by the executive committee, are added to the mce of riveted and bolted construction. ..- current research programs. Investigation of effect of sags in wing surface. The investigations thus under conduct by the com- Investigation of -windshields and fairings for pro- mittee during the past year for the Army and the xction from air currents. Naq may be outlined as follows: Investigation of flight-path characteristics. Investigatio~ of autorotation. FOETHEAIRCORPSOFTEEAEMY Development of solid-injection type of aeronauti- Investigation of pressure distribution and accelera- cal engine. tions orI pursuit-type airplane. Study of effect of diflerent degrees of supercharge .- ~cceleration readings on the ~~-11 airplane. kg with several compression ratios. — Investigation of pressure distribution on obeerva- COOPERATIONWITH STATE D~A.RTMENT ABROAD tion-type airplane. Investigation of tail surface loads in maneuvers. The committee cooperates with the Department of Determination of coefficients of contraction for oleo State by making available, as the occasion arises, tie landing gear orifices. services of its technical assistant in Europe, Mr. John Investigation of slipstream velocitiw near airplane J. Ide, for attendance as an unofficial observer or tech- . tail surfaces. nical adviser on behalf of the United States at various Determination of standard design characteristic= international air conferences abroad. In response to — for certain airfoils. invitation from the League of Nations and at the re- Pressure distribution on ring cowling. quest of the State Department, Mr. Ide served as a Wind-tunnel investigation of biplane cellules. member of a special committee of experts which met study of ice formation. at Geneva April 20 to 24, 1931, for the purpose of

Investigation of velocity distribution in plane of establishing a standard of horsepower measurement 3 .-— propeller disk. for aircraft engines, for U& at the general disarma- Investigation of cowIi.ng for protection of gunners ment conference to be held by the Lergue of ~atione .— and pilots from air currents. in 1932. This committee of experts recommended a Determination of moment coefficients and hinge formula for horsepower measurement based on the .— moment coefficients for different tail surfaces volume of the engine cylinders and the -weight of the .— Determination of aileron hinge moments versus engine. roIIing moments for various types of ailerons and On designation of the Department of State, Mr. Ide wings. served as a delegate on the part of the United States Investigation of wing flutter. to the fit international congress on aerial safety held Investigation of the flat spin. at Paris in December, 1930. In response to inquiry from the State Department, FOR THE BURSAU OF AERONAUTICS OF TBE NAW DEP==NT the National Advisory Committee for Aeronautics, by resolution adopted at its semiannual meeting held on Investigation of design of floats for racing eea- April 23, 1931, expressed the opinion that the time planes. has arrived for the adoption of a definite policy with Study of loads on wings of miLitary-type airplanes. respect to the degree of participation by delegates Investigation of aerod~mnic loads on U. S. S. of the United States in future international air Ah-ron. congresses. Study of water-pmure distribution on seaplane floats and hulls. REVISION OF NOMENCLATUREFOR AERONAUTICS Development of cowling combining cooling, accessi- The h’ational Advisory Committee for Aeronautics ...— bility, and low drag, for rafi~ air+oo~ed eng~es has recently organized a speciaI conference on aero- .—- installed in nacelle. nautical nomenclature, for the revision of its stand- Investigation of lift, stabfity, and control cha~c- ard nomenclature for aeronaut=, whi~ was pub- .—— terietics of XSL4 airpkne. ushed in 1926 as Technical Report No. 240. The Comparative tests of rubber and oleo type h-ding nomenclature for aeronautics is adopted by the com- gears. mittee for the purpose of securing greater uniformity Study of design factors for metal propellers. tmd accuracy in the use of terms relating to aero- 18 REPORTNATIONALADVISORYCOMMITTEEFORAERONAUTICS nautics in official documents of the Government and, Representing the Army Air Corps- as far as possible, in technical and other commercial Capt. Karl S. Axtater, United Sttil,esArmy. publications. Revisions in the nomenclature are made Capt. Albert C. Foulk, United Stutes Army. from time to time as the occasion arises, to conform Lieut, A. F. Hegenberger, United Stat* with changes in the general use of aeronautical terms. Army. Before proceeding with the organization of the Maj. C. W. Howard, United States Army. special conference, the committee requested sugges- Capt. E, R. Page, United States Army. tions from a large number of organizations and indi- Representing the Bureau of Aeronautics of the viduals interested as to modifications in the present ISa-ry— authorized nomenclature. These suggestions now are Lleut. Commander W. S. Diehl (C. C.), being carefully considered by the spe&al conference. The nomenclature includes within its scope terms United States Navy. relating to types of aircraft, to lighter-than-air craft, Commander Garland Fulton (C. C.), United to airplanes, to aircraft materials and structures, to States Navy. airports and landing fiehis, to aerodynamics, to pro- Lieut.. Commmder R. D. MacCart (C, C.), pellers, to instruments and auxiliary apparatus, and United States Navy, tO en@es. Suggestions as to terms dealing with Commander C. A. Pownall, United Sttites these various subjects are being requested from indi- Navy. viduals particularly interested, and all the suggestions Commander R. D. Weyerbacher (C. C.), received will be given careful consideration by the United States Navy. conference. Representing the Bureau of Standards- The organization of the special conference on aero- Dr. L. J. Briggs. nautical nomenclature is as foI.Iows: Dr. TV. G. Brombacher. Dr. Joseph S. Ames, chairman. Dr. H. C. Dickinson. Representing the National Advisory Committee Dr. H. L Dryden. for Aeronauti- Representing the aeronautics brunch, Department Charles H. Helms. Carlton Kemper. of Commerce- George W. Lewis. Col. H. H. Blee. H. J. E. Reid. Richard C. Gazley. Hon. Edward P. Warner. Capt. F. C. Hingsburg. PART 111 REPORTS OF TECHNICAL COMMITTEES

REPORT OF COMMITTEE ON AERODYNAMICS in aeronautics, is in close contact with s.Uaerodynmn- -— ORGANIZATION ical -workbe~a carried out in the United States. The current -work of each organization is therefore made The committee on aerodynamics is at present com- known to aII, duplication of effort- being thus pre- posed of the foIlow&~ members: -rented. Also all research work is stimulated by the Dr. David W. Taylor, chairman. prompt distribution of new ideas and new resrdts, Dr. L. J. Briggs, Bureau of Standards. which add greatly to the efficient conduct of aero- Lieut. Commander W. S. DiehI (Construction —— dynamic research. The committee keeps the research Corps), United States Navy. workers in this county supplied with information of Dr. H. L. Dr-@en, Bureau of Standards. European progress in aerodynamics by means of a Capt. Albert C. ForJk, United States &my, ma- foreigg representative, who is in close touch with ttriel division, Air Corps, Wright Field. aeromuticaI activities in Europe. This direct infor- Richard C. GazIey, aeronautics branch, Depart- mation is supplemented by the translation and circula- ment of Commerce. tion of copies of the more important foreign reports Maj. C. W. Howard, United States Army, mat6- — and articks. riel division, Air Corps, W%oht Field. George W. Lewis, NationaI Advisary Committee The committee on aerodynamics has direct control for Aeronautics (ex officio member). of the aerodynamical research conducted at Langley Prof. Charles F. Mamin, weather Bureau. Field and of a number of special investigationa con- Hon. Edward P. Warner, editor of “Aviation.” ducted at the Bureau of Standards. The areod~am- ical investigations undertaken at the Washington Commander W. TV. Webster (C. C.], United Nrav-yYard, the mat&iel division of the Amy Air States ISavy. Dr. A. F. Zahm, division of aeronautics, Library Corps at Wright Field, and the Bureau of Standarda are reported to the committee on aerodynamics. of congress. .- During the past year the subcommittee on aero- — FUNCTIONS nautical research in universitiw, -which had been The functions of the committee on aerod~amics established in 1929 as a subcommittee of the commit- are as follows: tee on aerodynamics, -was d~sarged. This subcom- 1. To determine what problems in theoretical and mittee was originally organized to aid in the estab- .— experimental aerodynamics are the most important olishmentof contact and cooperation between repre- for investigation by governmental and private agen- sentatives of the various educational institutions cies. engaged in the teaching of aeronautical engineering, 2. To coordinate by counsel and suggestion the re- which had been initiated by the Daniel Guggenheim search work involved in the investigation of such Fund for the Promotion of Aeronautics. It was the .- -— problems. opinion of the committee that such contact and coop- 3. To act as a medium for the interchange of infor- eration had been dellnitely estab~=hed and was be~~ mation regard@ aerodynamic investigations and de- continued by a national conference on aeronautical velopments in progress or proposed. education held annually under the joint auspices of 4. To direct and conduct research in experimental the educational committee of the Aeronautical Cham- aerodynamics in such laboratory or laboratories as ber of Commerce and the Daniel Guggenheim Fund may be pIaced either in vrhole or in part under its committee on elementary and secondary aeronautical dire&ion. education. 5. To meet from time to time on call of the chair- SUBCO-TEE OX AIRSELPS man and report i~ actions and recommendations to the executive committee. In order that the committee on aerodynamics may The committee on aerody&unics, by reason of the be kept in close touch with the latest developments in representation of the various organizations interested the field of airship design and construction and that 19 20 REPORTNATIONALADVISORYOOMMI!PI?EEFOR-AERONAUTICS research on lighter-than-air craft may be fostered and safety and those affecting efficiency. & in previous encouraged, a subcommittee on airships has been or- years, the aerodynamic work of the laboratory has ganized under the committee on aerodynamics, the been devoted to the solution of-problems f ailing under membership of which is as follows: both these heads; investigations of stability and con- Hon. Edward P. Warner, editor of ‘Aviation? trol, landing, spinning, structural loading, and the chairman. prevention of ice formation are examples of those Starr Truscott, National Advisory Committee for affectirig safety, while investigations of aerodynamic Aeronautics, vice chairman. interference and drag, maneuverabiIity, propellers, Dr. Karl Arnstein, Goodyear-Zeppelin Corpora- and airfoils are examples of those made in the interest tion. of greater efficiency. &in previous years, there have Capt. Karl S, Axtater, united States Army, mat6- been additions to the testing equipment of the riel division, Air Corps, Wright Field. laboratory. Commander Garland Fulton (C. C.), United StaWity and control.—From the standpoint of the States Navy. aerodynamics of the airplane, it appears that the most George W. Lewis, National Advisory Committee promising immediate line of attack in the interest of for Aeronautics (ex officio member). safety is to find means of decreasing landing and Ralph H. Upson, Dearborn, Mich. take-off speeds and of providing adequate stability The subcommittee on airships has kept in close and control at the attitudes corresponding to-these touch during the pati year with the investigations speeds. Because of-their known ability to increase conducted at the Langley Memorial Aeronautical Lab- the lift coefficient, slots and flaps constitute one oratory on models of the U. S. S. A&m. At u meet- method of accomplish’ this object. ing of the subcommittee held on January 10, 1931, As a part of its general research on safety the com- preliminary remdts obtained in the variable-density mittee is therefore undertaking the investigation in tunnel on a l/200-scale model of the airship were flight. of aerodynamic performance and of the land- presented and discussed, and details of the program ing, take-off, stability, maneuverability, and control of further bats, both in this tunnel and on a larger characteristics of an airplane equipped with slots model in the propeller-research tunnel, were decided (extending over the entire span of the wings) and upon and action taken to expedite these &ts in view flaps (extending only to the ailerons), so that the of the importance of the results in connection with the influence uf these devices can be appraised not-only design of the full-size airship. At this meeting there with regard to safety but with regard to performance was also discussion of teds in the variable-density in general. One phase of the investigation, the effect tunnel on a model of a proposed large metal-clad ~f the slots and flaps on the lift and drag character- airship and of the problem of the ground handling of isticsof the airplane, has been completed and a report.- airships. &asbeen prepared for publication. The results shuw At a special meeting of the subcommittee on air- !hat with this particular airplane the slots used alone ships held on May 27 at the Langley Memorial Aero- increasethe maximum lift coefficient 54 per cent; the nautical Laboratory in connection with the sixth an- Raps alone increase it 38 per cent; and the slots and nual aircraft engineering research conference, results laps in combination give a total increase in lift coeffi- were presented from the tests in the propeller research :ientmf 94 per cent. The slots and flaps in combina- tunnel on a l/40-scale model of the Akron, including tion decreasethe landing speed from 60 to 43 miles pm- hinge moments and forces on the model {or various hour; increase the sped range of the airpltine 40 per angles of rudder setting and various angles of attack, :ent; and increase the glide angle at landing speed 4.2°. the rudder being equipped with balancing vanes. Ile- The rmtogiro offers another very promising method tails of further teats to obtain the information most ]f increasing the safety of flight,- The committee has needed in connection with the completion of the full- ?urchased an autogiro of the latest type and is just. size airship -werea=greedupon. fi.arting an extensive research, including both flight The subcommittee on airships has also cooperated E&Sand twits in the full-scale wind tunnel, to study with the subcommittee on meteorological problems of he aerodynamic characteristics of this type of the committee on problems of air navigation in con- ~ircraft. nection with the study of wind gustiness A joint It appears that the spinning problem, as it applies meeting of the two subcommittees for the discussion o commercial airplanes, could be best .scdvedhy prc- cf this problem was held on January 10, 1931. ~entingthe spin entirely. To this end a flight inves- tigation was continued i-n which the elevator control LM?GLEYMEMORIAL AERONAUTICAL. LABOEATOEY vas Iirnited to prevent-the stall and the effect on the The problems confronting aeronautics may be di- ~rformance determined. This Fas done Wit]l ~ven vided into two general categories-those affecting [ifferent designs of airplanes, and with the elevator REPORTNATIONALADVISORYUONtIKtTTEEFOEAERONAUTICS 21 travel limited to the point where the airplanea could Wind-tunnel pressure-distribution tests have been -- riot be made to spin without the aid of power. The made on a series of models to study the effect on sta- lateral control and aileron effectiveness were in e-wry bility in ro~ of the distribution of the lift along the -.— case satisfactory up to the highest angles of attack span. Three methods of changing the distribution which could be obtained in a glide, although this was were employed-twist or washout, sweepback, and -—__ riot true in any case without the limited control. All ~ariation in profile to a thin symmetrical section at ordinary flight maneuvers could be performed with the tip. The results, which have been published, the elevator clisplacement limited, but usually there showed that washout, whether obtaiged by merely was not sufficient control to get the tail down for a twisting the wing or by varying the airfoil section — normal three-point landing. On this account a dif- along the span, appreciably reduced the maximum in- — ferent form of landing called a a glide landing” was stability in rolling, but that smepback or sweepfor- investigated. This type was made by gliding straight vvardhad no clea.rly d&ned effect. to the ground -with the full but limited amount of Further pressure-distribution tests of the same na- .-. tail-displacing longitudird control in use. - Since the ture were made on biplanes havi~m various amounts -— vertical velocities in these gfides range from 12 to of gap, stagger, decalage, and overhang. These tests 24 feet per second with different airplanes, it was showed that unstable rolling moments due to a low evident that a landing gear having a long stroke and rate of roll are usually decreased by a gap-chord .-— excellent shock-absorbing qualities would be required. ratio of less than one, by pmitive stagger alone, or .— One of the airplanes, the Vertille AT, vvasfitted with by positive sta~~er and negative decalage. The com- .— long-travel shock-absorber struts and actual landing bination of positive stagger and negative decalage teats -weremade in which the accderations upon con- gives the best lateral and aIso the best Longitudinal -— tact with the ground were measured. The glide land- stabiIity of any wing arrangement investigated. A ...— ings with the control stick full back to, the limited technical report covering this work is in process of -— position were satisfactory, the land~~ runs, as weLl publication. as the air distances required to clear a 50-foot obstruc- Aerodynamic force tests on a slotted Clark Y wing .— tion and alight on the ground, being .wbstantially were conducted in the vertical wind tunnel to deter- shorter than with the shortest present-day conven- mine the best position for a given auxiliary airfoil tional landing. It was concluded that most conven- -with respect to the main wiqg. A systematic series tional airplsms, if their elevator control and landing of 100 changes in location of the auxiliary airfoil gear -were modified in this reamer, could be landed was made to cover all the probable useful ranges. –-— with less skill in a small space and with no possibility The ~~ts are being prepared for publication. ti of falling into a spin without the aid of power. One increase of 41.5 per cent in the maximum Iift coefE- - question that arises in connection with this type of cient above that of the plain wing was obtained with landing is the effect of rough air conditions on the the beat position. Following this investigation an- -— vertical =relocityat landing. It is possible that down other was undertaken to develop a Ioivdrag fied slot currents in the atmosphere near the ground will pro- for an airplane wing that would avoid the compli- duce greater -verticalvelocities than those experienced cations and maintenance difficulties of the present in the tests at higher altitudes. The investigation is movable-type Handley Page slots. The best combi- -— being continued by providing the airplane with a nation of w~m and fied slot that was developed had longer-travel landing gear and properly strengthened a mtimum lift coefficient which was 34.6 per cent primary structure in preparation for an extensive higher than that of the plain wing, and the ratio of. series of actual landings in air of various degrees of maximum lift to minimum drag was but slightly roughness to determine the effect of the air conditions lower than for the p~ain wing. It is estimated that near the ground on the vertical -velocities. if these fixed slots were used only at the tips of the bother flight investigation has been completed in win= for the purpose of ‘hproving the lateral sta- which the Longitudinal stability of a small high-wing bility at high angles of attack, the total drag of an — rnonoplane -was determined. It is expected to use airplane would be increased very slightly. A techni- this airplane to try out in tlight any control devices cal report on this work is in process of publication. that wind-tunnel testa now in progress indicate to A rather extended investigation has been started have possibilities of improving stability and control, in which it is intended to compare the rdative merits particulmly at low speeds. In the investigation con- of aII ordinary and some special forms of ailerons ducted, the important resistance and rotary deriva- tives and the damping co&cienta were measured in and other lateral-control devices in regard to their two conditions of flight, power on and power off. A effect on lateral controlIability and lateral stability . paper is beirg prepared giving these results compared at high angles of attack, and also their effect on air- ..- to values of the same quantities pr@cted by theory. plane performance. The comparisons are based on 22 BEPORTNATIONALADVISORYCOMM&T33FORAERONAUTICS

wind-tunnel test data, aI1 the control devices being During the year there became available the results fitted to model wings having the same span, area, of yind-tunnel tests at high angles of attack, of a and airfoil section and being subjected to the same model of an airplane -whichhad been previously flight- series of force and rotation tests. These tests, which tested in spin. A study is now in progress to deter- are being made in the 7 by 10 foot tunnel, have been mine, the practicability of computing the full-scale completed for ordinary ailerons of three different spin characteristics from the results of standard model sizes, all mounted in the usual position at the trail- tests at high angles of attack, and of possibly deter- ing edge of the wing, and with five different types of mining the correction factors necessary to make such movement, including two differential systems, an computed characteristics applicable to full scale. arrangement permitting upward movement only, and The momentsnmd ellipsoids of inertia of all air- one in which the ailerons -werearranged to float. The planes used in flight investigations htive )weu meas- results showed that, although the ailerons with the ured as in the past. Two reports have been published, commordy used motions gave very unsatisfactory con- one describing the method of making these measure- trol above the stall, satisfactory control -wasobtained ments, and another giving the moments of--inertia of by short, wide ailerons with upward deflection oily, 12 different airplanes. and satisfactory control was closely approached by the Structural hxzding,-Recent structural failures on same ailerons with an extreme differential motion. several milihmy and commercial airplanes, both in this The floating ailerons had the smallest yawing mo- country and abroad, have focused the attention of de- ments and gave a decided ,bprovement in lateral signers more than ever on questions of the external stability. Tests have also been completed on clotted loads acting on airplanes in flight. This subject has ailerons and Frise ailerons. None of these gave as been studied actively for several years by the flight good control above the staII as the plain ailerons, research section and still remains a major problcm. A although the Frise ailerons gave somewhat better report on the magnitude and distribution of the areo- yawing moments. Several technical reports covering dynamic and inertia loads on the wings and tail this work are in preparation. surfaces of a pursuit-type airplane in a wide variety ~p”nning.—~ith military airplanes the spin is con- of maneuvers has been published, A report on the sidered a necessary maneuver. Both flight and wind- mab~itude and distribution of aerodynamic loads tunnel work are being carried on by the committee to over the fuselage of the same airplane has also been add to the present kno-wledge in regard to the spin published. These reports have served principrdly tu and to make it possible to design airplanes that will call attention to important phenomena affecting struc- spin satisfactorily and recova quickly and surely. A tural loads, which have been given no attention in the report- has been published during the year describing past, and they have therefore contributed greatly to the methods used in fight for the determination of the our insight into the broad problem of structural load- flight path, the motion, the attitudes, the forces and ing. In two instances they have, in conjunction with coupks of a fuIly developed spin. The flight investi- other data previously and since obtained, enabled spe- gation of spinning has been in progress throughout cific design rules to he formulated. One of these, a this year on one airplane, and the phase which deals formula for the determination of design tail 10M1s,]Ms with the effect-af mass distribution on the spin char- beenincorporated in the latest Army design handbook. acteristics has been completed. In this work the ef- A report is now in process of publication which fect of changes of mass distribution along the three gives-a method of calculating the design load for the axes of the airplane has been determined. With this leading-edge portion of the wing. This method is airphme, as was the case with a previous one which based on theory and pressure data, all of which are was tested in flight, it was not possible to produce an products of the committee’s laboratory. uncontrollable spin with the ehangea possible either The investigation of the pressure distribution o;~er in mass distribution or balance. While the results m airplane wing fitted with a series of wing tips of have not been completely analyzed as yet, it appears ~iflerent shapes has been continued, and tests on seven that with the data now available the effect of the mass tips have been completed. The results for five of distribution on the character of the spin of any air- bhesetips have already been published, and a report plane can be calculated if a certain few of the aero- m the other two that have been tested is now in prepa- dynamic characteristics of ths spin are known, This ration. The objects of this investigation are to de- spin investigation is to be carried further on this same wlop a tip ofi such shape that the center-of-pressure tiirphme to fid the effect of changes in the control [ocue will be a straight line in the critical loading con- surfaces and wing section and the geometric propor- ditions and to formulate laws of load distribution over . tions of the airplane on the character of the spin and wing tips of any shape. Work on this investigation the entry and recovery from same. hs far has been centered mainly on the accumula. REPORTNA’IZONAIJADVISORY00~MI~E FOR~ONAUTICS 23 tion of data, but sutlicient study has been gi-ren the being taken from the exhaust gases. Flight teak results to indicate that the object will be attained. proved that this method offers a solution with practi- A number of flight investigations have been made, cal possibilities. and se~eral are now in progress, to determine the bother investigation was carried out in the refrig- proper load factors or total loads to use in design. erated wind tunnel in response to inquiries regarding — These investigations cover a wide field, inchiiing the construction of gasoline-tank vents that would not measurements of acceleration on transport airphmes freeze up during flight under ice-forming conditions. flying commercial routes, as vrell as measurements on Tests were made on a variety of vent forms arranged military and naval aircraft in special tactimd maneuv- in a number of different orientations relative to the ers. A report has been published gitig some of the air stream. Both the size of the tube and its orienta- results obtained on commercial airplanes in bumpy at.hg the need for more systematic tests, particularly air, and several cotidential reports on load factors arrangements were recommended as being immune to for mifitary and naval airplanes have been issued to blocking by ice. the services. It has been concluded that, -whiIe the Aeroclynanzic t%terferena and drag.—lt is believed load factor can be determined by rational means when that the greatest opportunity for increa&~ the speed the conditions to which the airplane is to be sub- and diciency of aircraft lies in reducing drag and jected are known, so Iittle is lmown about these con- unfavorable interference effects. In the past, the Na- ditions that extensive statistical information -will be tional Advisory Committee for Aeronautics has con- required before the load-factor problem can be satis- dhcted several interference investigations, which have — factorily solved. In this connection, data on the dealt with spedc practical problems with a tiew to accderations encountered by transport airplanes fly- arriving at solutions that could be made immediately ing in rough air have been accundated during the available. Such investigations have usually been year on several airplamelines throughout the country made in compliance with ~ecific requests from the by means of the special acce.Ierometersdeveloped for &my, the Ffavy, or the aircraft industry. Appreci- this work. The value of these records has been liru- ating the need for more systematic tests, particularly ited by the lack of fdl information on the conditions at ReyuoMs Numbers corresponding to full scale, the of the flight, particuldy the air speed when encoun- committee has begun several in~estigationa along this tering rough air, which is required to interpret the Iine, which have been in progress throughout the records properly, but there are indications that the year in the variabIe-density wind tunnel and the pro- importance of this work is being more appreciated pdler research tunnel. by operating companies and that more complete in- In the variabIe-density wind tunneI, the drag of -— formation may be expected in the future. ~arious simple combinations of basic forma is being TO facilitate obtaining the information required, a measured, two parts of the pro=mamhaving been com-

special instrument is now being developed that wiLI pIeted. !l%e first part dealt with effects of emalI pro- “- register the applied load factors and corresponding tuberances from the surface of a streamline body of air speeds over an extended period of operation for revolution. The interference for such a combination any airplane. By distributing such instruments judi- may be compared with the interference between air- ciously on both commercial and service airplanes, it ship hulls and protuberances, such as radiato~ or —- is expected that enough information dl be obtained cars. The additional drag due to a small rectangular to solve the load-factor problem in a satisfactory way. plate protrud@ normaIly from the surface to a dis- prevention of ice formation on m“?@ane8.—~nder tance of about one-thirtieth of the body diameter was certain weather conditions a heavy coating of ice may measured over a wide ra~oe of values of the Reynolds — form on the wings of airplanes, with the result that Number. The measurements were repeated with the the aerodynamic properties of the Iifting surfacw are protuberances placed successively at different posi- so altered that a forced landing becomes necessary. tions along the surface of the body. At the highest The committee has undertaken an investigation of the value of the Reynolds Number? the calculated drag practicability of employing heat as a means of pre- of the plate aIone was 10.5 per cent of the drag of venting such ice formation on wings. A study of the the body alone. The actual increased drag varied heat tranamision from an airfoil, supplemented by from 10.5 per cent when the protuberance was placed ice-prevention experiments both in the refrigerated near the bow to 5.7 per cent when the protuberance wind tunnel and in fight, demonstrated that it is was near the stern. Additional tests made with necessary to heat only the front portion of the wing streamline protuberances instead of the flat plate indi- surface to effect complete prevention, and that the cated that at the highest va.he of the Reynolds Num- quantity of heat needed is small. A vapor system was ber the interference effects from such a combination found to offer the most desirable solution, the heat are very small. 24 REPORTNATIONALADVISOBYCOMMITTEEFORAERONAUTICS

The second combination to be investigated -wasthat the propeller has practically no effect on the lift of an airfoil with a flat plate inserted at the midspan under the conditions named. It was noted, howeverj position parallel with the wind. This combination that when an uncowled radial engine was placed di- may be compared with a wing intersecting a flat-sided rectly in front of the wing a large loss of li~hresulted. – fuselage or with a strut intersecting a wing. The in- Airship~.—At the request of the Bureau of Aero- terference effects were deterr&ed from tests of the nautics of the Navy Departn-mat a one-fortieth-scale airfoil and plate separately and in combination. model of the new airship, the U. S, S. Aknm, has been Tests were also made with several sizes of fillets placed tested in the propeller research tunnel. In the tests ut the intersection between the plate and the airfoil the usual lift, drag, and pitching moments were de- surfaces. The results indicated that the fillets had a termined, and in addition a special balance was in- arnall favorable effect on the interference, but that stalled to measure the forces and moments on the ele the interference effects arising from such a combina- vator hinge. Also, pressures were measured at more tion of airfoil and plate are very small. than 400 points on the hull and at more than 800 The third investigation, which is now being under- points on the fins. Certain special tests were also taken, deals with the interference of small protuber- made +Wdetermine the effect of a new design of bal- ances from an airfoil surface. First, the interference ancing control surface which had been proposed for effects of small rectangular protuberances extending the airship. By means of a very small Pitot tube the across the entire span of the airfoil will be measured velocity close to the surface of the model was explored with the protuberance placed successively at different at nine stations along the axis of the ship. The im- positions along the surface. Later, the effects of pro- pact pressure ahead of the airship and in the rear of tuberances of the type that fair into the surface will the model was also measured. & a result of all these be measured, and, finally, protuberances which extend measurements the pressure drag and frictional drag only over a part of the span will be investigated, with Gf the model have been computed and checked with a view to studying the so-called induced-interference the measured values. A preliminary report covering eflects resuMng from a modification of the lift dis- the force tests has been submitted to the Navy Depart- tribution across the span. ment, and the report on the pressure-distribution tests ‘- The research on the relative merits of various wing- is now in preparation. and-nacelle combinations has been carried on practi- In conjunction with the Navy Department- and the cably continuously during the past year in the pro- Goodyear-Zeppelin Corporation, a series of flight tests peller research tunnel. As a result several parts of the has just been completed on the U. S. S. Akron. These investigation have been brought to a conclusion and tests consisted of speed and turning trials, decelera- reports have been completed, or are in preparation, tion txzsts,and pressure-distribution measurements on covering the work accomplished. Tests with two mon- part of the hull and one complete tail surface and por- oplane wings with a tractor propeller and naceIles tions ofi two others, in maneuvers and in rough air. with various cowlings have been completed. A report It may be mentioned that-the flight tests confirmed giving the results obtained with a thick monoplane the results of the wind-tunnel tests with reference to wing and a completely cowled nacdle has been com- the effectiveness of the controls. pleted; the results indicate that a nacelle located about Maneuverability. —The collection of quantitative 25 per cent of the chord of the wing directly ahead of data on the maneuverability of military airplanes, the leading edge gives the best over-all efficiency, A which is expected to result in definite criteria for report giving the results obtained with various cowl- maneuverability and the factors affecting it, has been ings on the nacelle in several positions with respect to continued. Two reportzrgiving the measurementsob- the same wing is now being prepared, as is also a re- tained in all types of maneuvers of two fighter air- port on the drags of nacelkx alone, which were meas- planw have been published. Another report has been ured during the progress of the tests.- made b the Navy Department on the results of an The question of the effect of locked or idling pro- investigation in which dives and pull-outs from dives pellers on the Iift of wings has been of some interest were performed on three different Navy fighter air- to airplane designers. The fast landings of several planes, each airplane being flown by three different airplanes when the engine was stopped has been at- Navy pilots in the normal manner employed in diving tributed to the effectiof the stopped propeller on the bombing maneuvers. Another flight investigation d lift of the wing. A large number of tests were made this same type on a Navy observation airplane has with the propeller locked and also with the propeller hen completed and reported to the Navy Department. idhg, -with various nacelle-wing combinations and In all the dive tests the flight path throughout the with various cowlings. The results of these tests have dive and recovery has been measured; the empirical been prepared in the form of a report and show that relation between altitude lost in recovering from a REPORTNATIONALADVISORYCOMMJ.13’EEFORAEEONAUTIOS 25

dive, the maximum acceleration encountered, and the ‘ mum lift, a small center-of-pressure movemen~ and air speed have been more accurately established and for structural rw=ons should be thick enough to pro- -— have been extended to include not, only -iertical dives tide room for an efficient structure inside. Before .- but dives at any angle. the requirements which are usually conflicting can be l%pelZers.-The propeller work of the laboratory baIanced, the relations between them must be known. —— during the past year has been incidental to the m@- For example, a designer wishing to investigate the ___ nacelIe tests in progress in the propeller research possibility of Lightening a wing structure could cal- tunnel and has consisted of numerous tests of the culate the weight-saving resrdting from the substitu- _. same propeller with ~arious nacelle locations. A num- tion of a thicker airfoil section, but unless he knew — ber of reports ha~e been prepared, howe~er, covering how the change w-ould affect the aerodynamic proper- - more detailed analyses o~ the re&dts of an investi-- 1 ties of the T&Z, he could not know whether or not gateion carried out during 1929, -which made possible the change vio~d be desirable. — an extensive study of propeller forms and character- The object of an investigation now being carried istics. Reports have been published giving the results out in the variable-density wind tunnel is to obtain of tests of prope~ers up to tip speeds of 1,350 feet the characteristics, at large values of the Reynolds per second, which show a large loss of efllciency begin- Fhunber, of a wide variety of related airfoils. Not ning at about 1,000 feet per second. Another report only do the results of such an investigation greatly gives a comparison of similar propellers with Clark facilitate the choice of the most satisfactory airfoil Y and R. A, F.-6 propeIler sections. The CIark Y for a given application but-,because the results maybe .— section is shown to be no better than the IL A. F.-6 correlated to indicate the trends of the aerodynamic section? except at very low pitches, and there onIy at characteristics with changes of shape, they ako may maximum eficiency. For the climb and take-off con- point the way toward the development of new shapes —. dition the R. A. F.-6 propeller section is decidedly having better characteristics. — -. superior. Another report has been prepared giving In the development of the airfoils for the investi- the resnl~sof tests on the effect of yaw and pitch on gation, the sections were considered as made up of ,- the propeller characteristics. An angle of pitch of certain profile thiclmess forms disposed about certain 10° had small effect on the propeIIer characteristics! mean camber lines. The major shape variables then the propeller being in the nose of a fuselage. A mere two, the thiclmess form and the mean camber- greater drop in eiliciency with increase in angle of the Iine form. The thiclmwssis of particular importance propeIIer axis to the air stream was found with a from a structural standpoint. on the other hand, combination of naceIIe and wing. the form of the mean camber line determines aImost During the tests of propellers at high tip speeds independently of thickness some of the most impor- above mentioned, the velocity and direction of the air tant aerodpunic properties of the airfoil; e. g., the — flow in the rear of the propellers were measured. pitching moment characteristics and the angle of zero From these data the thrust and torque distribution lift. A preliminary investigation showed that well- ahmg the bladea of the propellers has been computed known airfoiLs of a certain class, including the Got- and shows clearly what part of the blades is most t~uen 398 and the C1arli Y, which ha~e proved to be —— aifected by the increase of tip speed. It is also pro- efficient, are nearly alike when their mean camber is .- posed to compute from the data obtained a series of rernored and they are reduced to the same thicknem. airfoil characteristics that can be used in propeller A similar basic thickness variation was therefore —. design in cases where the chart system proposed be- chosen for the related airfoils, but related airfoiIs hav- fore can not be used. Reports giting the rwmlts of ing maximum thickness-to-chord ratios varying be- these computations are now in preparation. t-men 0.06 and 0.21 -were obtained by scaling, up or — Airfo38.—AIthough -ivind-tunnal test data are clown, all of the ordinat= of the basic thicdmeasform. already avaiIable co-rering a wide variety of airfoil The shapes of the mean lines about which the thick- shapes! the data are of little comparative value be- rlf?~ forma were disposed to produce the cambered cause the tests -weremade under different conditions airfoik -werevaried by chan=gingthe camber and the and at different dynamic scales at various labora- distance from the leding edge to the positions of .= tories, and, furthermore, the results can not be maximum camber. In this way a large variety of expected to apply to full-scale airplane vvings. The related airfoiki were obtained. design of an efficient airplane entails the careful bal- The tests of these airfoils are no-iv in progress in ancing of many conflicting requirements. This state- the variable-density wind tunnel, and the results are -. ment is particularly true of the choice of the wing. be@ made available in the form of tech.nical notes The airfoil section should have a very low drag over as the tests “are completed. Information as to the the operating range of lift coefficients, a high maxi- -~aracteristics of 40 of the related airfoiIs is now —— swoc+w+ 26 REPORTNATIONAJ.IADVISOBY00MMITTEE I?OR AERONAUTNX

available in published form. Some of these have shown to be due to the fact that the additional lift in characteristics superior to the beet commordy used potential flow becomes infinite at the leadlng edge. Sirfoils. The location and magnitude of the maximum lilt in- In addition to the main investigation, a secondary tensity were determined, Comparison with preasurc- investigation of the effect of the nose shape has been distribution measurements obtained in the variable- carried out. Three of the symmetrical family air- density wind tunnel gave a satisfacbmy confirmation foils, having maximum thickness-to-chord ratios of of the validity of the theory. 0.06, 0.12, and 0.18, were modiiied to produce sections A second investigation presents for the first time a of the same maximum thickness, but in each case sec- solution of the problem of the theoretical potential tions having a sharper and a bhmter leading edge. flow around bodies of arbitrary form, which gives the The results of this investigation have been published. exact velocity of the two-dimensional flow for any In addition to the investigation of the characteris- point of the surface and for any orientation, by an tics of related airfoils, many commonly used airfoils expression containing a number of parameters which have been tested in the variable-density wind tunnel. are functions of the form only, and which may be At the request of the Army and the Navy, the charac- evaluated with any de~red accuracy by convenient teristics of additional commonly used airfoils are being graphical met~ods. The method is particularly simple determined, and to provide data for the formulation and convenient for bodies of streamline form. This of rational loading rules for the dive and the inverted- theory of actual airfoils has been brought into a t%ght conditions several of these airfoils are being much simpler form than has “hitherto been the case “ investigated throughout the range of negative angle with the theory of thin airfoils, in which certain of attack tm beyond the negative maximum lift. A approximations have restricted its applications to preliminary report presenting a portion of these re- small cambers only. The results have been applied sults has been prepared. to typical airfoils and compared with experimental A short series of tests was made in the variable- data. density wind tunnel to investigate the possibility of A further theoretical study of the effect of the controlling the boundary layer on the upper surface boundaries of an air stream of finite extent on the of an airfoil, without employing supplementary equip- flow past an airfoil showed that it is possible to ment, by use of the low pressure existing near the devise three distinctly new types of wind tunnels lewiling edge. The low pr~ure was used to induce which are superior to the conventional types as re- flow through slots in the upper surface of the wing, gards tunnel-wall interference. I?ormulas were de- The tests showed that the angle of attack for maxi- duced for the interference in each case, and the cor- mum lift could be increased at the expense of a re- rection, applicable to small airfoils placed in the duced maximum lift coefficient and an increased drag center of the section, is given in terms of the width- coefficient. to-height ratio of the various tunnels. It is, in fact-,—- Tiieof-et~caZaerodynamioe.-The va.rnous types of possible to design these types of tunnels having zero airfoils in general use exhibit quite different proper- wal~ interference. The properties of these tunneLs ties. The determination of the characteristics of the have been investigated. Attention has aIso been several forms has been the object of a large number called to the fact that instability of the flow mny pre- of extensive tests by many institutions. Without an vent the predict ability of- the interference effect in understanding of the theory of air flow around air- certain types “of open-throat tunnek. foils, it is quite difficult to interpret the results of Changes in. eguipnwnt.-The spinning balance for experimental work intelligently or ta make other than the _5-foot vertical tunnel has been designed and the random improvements at the expense of much ‘useless construction is well advanced. Pending the comple- testing. The laboratory has, to meet this need, carried tion of this balance the tunnel is being operated with on a number of theoretical investigations. a temporary balance measuring lift: drag, and rolling– A simple and exact method of calculating the lift moment, distribution on thin wing sections has been developed. The 7 by 10 foot tunnel has been completed and The essentiaI feature of the new theory is the intro- has been in satisfactory operation for several months. duction of an “ ideal angle of attack”; i. e., that It is provided with a novel balance with which either ... angle for which the lift at the leading edge is zero. 6-component force tests or autorotation tests crm be It is shown that the lift of a wing section may be con- made, and the results read off dircctly in coefficient sidered to consist of a “ basic distribution;’ which is form This feature eliminates the necessity of com- the lift distribution at the ideal angle of attack and is puting the various coefficients and consequently saves characteristic of- the section, and of an additional dis- an appreciable amount of time. A technical rq)ort tribution that is identical for all thin sections. The describing the tunnel and the balance is in process 01 poor aerodynamic qualities of thin wing sections are publication. .— REPORTNATIONALADVISORY00MMITTEEFOBAEEONAUTICIS 27

DuMng the past few months the outer -wallsof the Irnprovenumt of apparatue for m.einuring turbu.- propeller research tunnel, which were of wood siding, lence.-Considerable effort has been expended to in- .-— have been replaced with corrugated arbestos siding, crease the range of frequencies which may be accu- -— and the inner waIIs of the coma and the test chamber rately reproduced by the hot-wire anemometer and have been partially lined with sheet metaL These its associated equipment. & a rmult of a study of --- changes in the tunnel, which make it nearly &proof, the several elements, investigations of the accuracy of and the addition of pifing underneath the propeller- the theory of the behavior of the hot wire, ete., it is .-— shwft supports have placed this equipment in a much now possible to secure a uniform response to fre- -—- more satisfactory operating condition. quencies from a few cyc.k up to 4,000 cycles per The full-scale wind tunnel has been completed and second. The incksion of the higher frequencies in is now in operation. ~elocity surveys are being made this new equipment has been found to have little effect and several preliminary tests have been conducted on on the measured mean energy of the turbulence. airplanes. During these tests it was found that the Inoream”ng the aerodynamic e@ienoy of jet8.— tunnel and balances worked very satisfactorily, and a Becaw of the interest in jet propulsion, a number of suitable operating procedure is being rapidly estab- experiments were made to determine whether the lished. A rather elaborate survey apparatus is being thrust react-ion of a jet could be increased by the uss built by which it wiH be possible to measure the air- of deflectors, guide vanes, or by suitable arrangement flow velocity and direction about all parts of an air- of the nozzle. The jets used were about 0.25 inch in plane mounted in the stream. diameter and preasures up to about 20 pounds per - square inch were applied. The nozzles were mounted BUBEAUOFSTANDAEDS on a wind-tunnel balance so that the eflect of for- — lThND-TUNNELI?rvxsmwrtoxs.-The aerodynamic ward motion could be reproduced. Combinations of activities of the Bureau of Standards have been con- the jet with airfoils, botl straight and riug+haped, ducted in cooperation with the &ronautics Branch of Venturi tubes, deflecting van=, and streamline bodies the Department of ~mmerce and the ~at.ional Ad- have been tried, but no promising resuks have been ..— visory Committee for Aeronautics. The work com- secured. pleted and in progr=s may be summarized under the Aerodymzm”c charmteristia of conven&naJ con- —— following heads: troz 8urfaces.-The results of measurements of hirqge Reduction of twbuleme in m“mi!.tunnds.-This in- moments of ailerons of various chords and spans on vestigation was completed and the resubk described in 10 by 60 inch models of Clark Y and U. S. A. 27 Technical Report No. 392. The report gives an out- wing sections at large angles of attack have been pub- line of modern views as to the effect of turbulence and IiShedas Technical Report No. 370. Further measure- their bearing on the design of wind tunneIs. Experi- ments have been made to clear up disputed points as ments are described which indicate the effect of certain b the interference between ailerons on opposite wing featuras of the design on the turbtience. tips. Tranim”tionfrom Zaminar to turbu.?d fZow.-Meas- Measurements of yawing moments due to rudders urements of the speed and turbulence in the flow past a of several spans and chords have been completed and thin flat plate placed paraIIel to the air stream were the results are being prepared for publication. brought to completion. The efiects of pressure gradi- Reduction of airplam notie.-b investigation is ent and of initial air-stream turbulence on the transi- in pro=gr= on the reduction of noise made possible tion from laminar to turbulent flow were investigated. by the mdling of aircraft erqggines.A test set-up has The magnitude of the pressure gradient was found to been provided in which the reduction of noise and the affect the distance from the front edge at which the reduction of engine horsepower can be measured. transition begins, but the thiclmess of the boundary AEBo~~uma- INSTRUWINT-LxiTsmcamoKs. — The layer at the transition was nearly independent of the work on aeronautic instruments was conducted in magnitude of the pressure gradient. cooperation with the National Advisory Committee .- — The exponent of the power law of variation of the for Aeronautics and the Bureau of Aeronautics of speed vvith distance from the vvall in the turbulent the h’avy Department and included the investiga- part of the layer was also found to vary with the tions and the development of particular instruments pressure gradient. The eilect of increasing the turb- outlined below: ulence was to cause the transition to occur much 17vue8tig7at2bnof damp”ng [email protected] program of .-— nearer the leading edge of the plate. experimental work has been completed and the resuhts An attempt has been made to account for some of are being publish~ as Technical Report No. 398. these results on the basis of a new theory of the tran- Data are g-hen in the report on the kinematic ticos- --- sition. The mathematical -work in connection with ity in the temperature range +30° to —50° C. of pure this theory is stiIl in progress. Iiquids and solutions apparently otherwise suitable for 28 REPORTNATIONALADVISORYCOMMII’TEEFOEAERONAUTICS

damping. It is shown that the temperature coefficient on one caused both to deflect, When each bellows of kinematic viscosity for the three classes of liquids was ‘connected to one of the two Venturi openings for which data were obtained is, within about 10 per their deflection was proportional to the differential. cent and for a more or less extended temperature pr~ure developed by the Venturi and when multi- range, a function only of the kinematic viscosity. plied indicated the rate of flow. ~emperaiure coejh%ientof elaatic modwZi.-Experi- Maainnm indicating accelerometer8.—Tvvo types of mental work has continued on the determination of instruments to measure acceleration along the Z-axis the temperature coefficient of the elastic moduli of were designed and constructed. Each iosh’ument con- elastic materials for aircraft instruments in the tem- tains an unbalanced weight supported by a heIical perature range –50° to + 50° C. Complete data have spring. The indication in one case is obtained by thus far been obtained on the temperature coefficient two pointers operating over a graduated dial, one of of the modulus of rigidity and the modulus of elas- which is so arranged that it imlicatw the maximum ticity of 32 ferrous and nonferrous samples, both reading until released. Inertia damping is used, ob- when annealed and when strain-hardened or heat- tained by adding a disk to the pointer shaft. The treated to the degree commonly given the material second instrument is of the cartridge type. l’he when used to make an elastic element.. The coefficient cmly indication is that of the maximum acceleration, varies greatly with heat treatment in some cases and which is obtained by measuring the deflection of a particularly with the amount of cold work or internal friction pin, the position of wh;ch is controlled by strew. OrJy second:order differences have thus far the lo-westposition of the uubalanced weight. been found between the temperature coefficients for WASHINGTON NAVYYARD the two moduli for a given material, At present the wind-tunnel equipment at the WrKh- Reports on aircraft in8tiW?iWfi.t8.-A repOrt on in- ington hTavyYard consists of an 8 by 8 fouk closwd- struments for the measurement of the speed of air- circuit closed-throat type which is continuously craft is practically completed, and a first draft of a employed on current design work for the Bureau of report on power-plant instruments has been prepared. Aeronautics. A new 6-foot closed-circuit opcn- Similar reports on altitude instruments and instru- throat type has been installed during the past year ments for determining the direction of travel and the and calibration tests are now under way. The new attitude of aircraft are in course of preparation. tunnel is intended to be used for airplane-model tests Each report wiII include the present methods of exclusively, although other tests may be made if measurement, the instruments available for use on found desirable. A balance of the Zahm type, similar aircraft, data on the performance of the instruments, to the one used in the 8-foot tunnel, is being con- and the methods of test in the laboratory. structed for the new tunnel. Calibration twts show pivot&-Additional data have been ob- Friction of that a speed of 1.20miles per hour is attained with tained on the dependence of the friction of steel step about 250 horsepower. There is considerable ques- and shoulder-bearing pivots in brass bearings upon tion as to the ability to use speeds above 80 miles the finish and the wear of the pivots. As in all inves- per hour, however, clueto excessive vibration frOIUt.hc tigations of friction, considerable difficulty is experi- motor-propeller unit. Some trouble has been en- enced in duplicating botl””test specimens and experi- countered with objectionable air currerits in the test mental results. section and certain modifications are l.ming tried to Pre8ent 8tatw of ahnaviga-twn in8tmnum$8.-The remedy this condition prior to completion of the report on this subject has been published as Techni- balance. cal Report No. 371. The work of the ‘ivashington Navy Yard is con- ~iaphr~m [email protected] further study of the cerned almost entirely with design problen~ssubmittwl subject indicated the necessity of obtaining additional by the Bureau of Aeronautics, although tests of a re- data on the relation of drift and time in order to com- search nature are made from time to time. Routine plete the report on The Evaluation of Elastic After- tests on airplane models constitute approximately 90 working for Instruments with Elastic Elements, An per cent of the work. Such tests are made on prac- attempt was made to obtain these data by experiments tically all designs submitted for naval use, ancl include on altimeters, but it appears necessary to supplement investigation of stability and controI. these with more precise measurements. M.AThUEL DIVISION,ARMY Am CORPS Fuel-flow meter.—An indicator for a fuel-flow meter of the Venturi type in which the fuel was kept Routk w&..d4umel model .te-8t8.-The usual lif~, confined to the pressure capsules instead of fiI1ing the drag, and moment tests were made on models of the instrument case, was developed and constructed. The B/J X%16, Boeing XB-901 (two models), Curtiss new indicator contained two sensitive metaI bellows XA-6, Martin XB-W7 (two models), nnd Douglas rigidly coupled so that a differential pressure acting XO-36 airplanes. REPORTNATIONALADVISORYCOMMITTEE FORAEROIYAUTKH 29

Performance data.—A record of the predicted and The vacancy in the chairmanship of the committee actual performance of Army airpIanes has been com- on power plants for aircraft has not yet been fllkxl, piled. This record includes as far as possible the and in the meantime the activiti= of the committee manufacturer’s estimate, the hfat6riel Division’s esti- me being continued under the leadership of the vice mate, and the flight-test results. chairman, Mr. George ~. Le-wis. performance 8.fudiei?.-semral studies have been The present membership of the committee on power made to determine the effects on the performance of plants for aircraft is as fo~ows: existing airplanes of ~arious changes in the power George ~. Lewis, ~atiomd ~dvisory Committee. plant, propeller, wing loading, etc. for Aeronautics, rice chairman. A study was also made to determine the effect of Henry Ml Crane, Society of Automotive Engi- changes of horsepower on the high speed of pursuit neers. airplanes with a view to predicting a practicaI limit Prof. Harvey N. Davis, Stevens Institute of Tech- for the increase of power. nology. Low-wing monoplane e~eots.-A wind-tunnel study Dr. H. C. Dickinson, Bureau of Standards. was made for the purpose of determining the best Carlton Kemper, National Advisory Committee practical means for minimizing the undesirable chm- for Aeronautics. acteristics of the low--wing monoplane. The portion Capt. E. R. Page, lhited States Army, Matfriel of the wing directly in front of the tail assembly was Division, Air Corps, Wright FieId. first modified by the addition of permanent slotE,then Commander C. A. PownaIl, United States Navy. by a reversal of the rear portion of the mean cambq Prof. C. Fayette Taylor, Mawachusetts Institute line. of Technolo~. 17ano%ook of in8tructiom for airplane de8ignera.— FONCI!IONS The handbook has been retised for the purpose of bringing the material up to date and of changing The functions of the committee on power pkmts for from engineering to absolute units. aircraft are as follows: Oflc.sm’ 8chooL-A ,ZLvieeks’course of instruction in 1. To determine which problems in the field of aero- wind-tunnel operation was given for the Air Corps nautic power-plant research are the most important Engineering School cIsss. for investigation by governmental and private agen- ~leo 8hock ab80rber8.-~outine tests were made on Cia severt-dexperimental and Servicdype oleo shock ab- 2. To coordinate by counsel and suggestion the re- ..— sorbers in the jig and in flight. This has led to the search work invoIved in the investigation of such redesign@ of the metering mechanisms in some caws. problems. 3. To act as a medium for the interchange of in- — REPORT OF C03LWTTEE ON POWER PLANTS FOR formation rsgarding aeronautic power-plant &ear& A3RCR4FJ! ti progress or proposed. 0BGAh=TI02J 4. To direct and conduct research on aeronautic The committee on power plants for aircraft has power-pIant problems in such laboratories as may be recently suffered the loss of its chairman, Dr. SamueI placed either in whole or in part under its-direction. W. Stratton, by his death in Boston on October 19, 5. To meet from time to time on caII of the chair- 1931. Doctor Stratton had seined continuously as man and report its actions and recommendations to .— chairman of the committee on power plants for air- the executive committee. craft since its organization under the name of the By reason of the representation of the Army, the .- motive power subcommittee in June, 1916. He ex- h’avy, the Bureau of Standards, and the industry upon erted a marked influence in the formulation of pro- this subcommittee, it is possible to maintain c.Iose grams of power-plant research, especially during the contact with the research work behg carried on in war period, and with his experience as an organizer this country and to exert an influence toward the es- he did much to promote cooperation between the pen&-ture of energy on those problems whose solution various gowmunental agencies concerned with the appears to be of the greatest importance, as well as .- probkms of aircraft-engine development. The Fia- to avoid waste of effort due to unnecessary duplication tional Advisory Committee for ~eronautics, at its of research. annual meeting held the day following Doctor strat- The committee on power plants for aircraft has ton’s funeral, recorded an expression of its sorrow at direct control of the power-plant rasearch conducted -. .- his death and its sincere appreciation of his long at LangIey l?ield and aIso of special investigations and faithfd sertice, including his leadership of &e authorized by the committee and conducted at the power plants committee, as -well as his other service Bureau of Standards. Other power-pknt investiga- .— to the committee. tions undertaken by the Army Air Ccmpsor the Bu- 30 REPORTNATIONALADVISORYCOMMITTEEFOBAERONAUTICS reau of Aeronautics are reported upon at the meet- mmcur, because of the increase in the maximum rate ings of the committee on power plants for aircraft. )fcombustion, The results show that by increasing he air temperature during injection the start of com- LANGLEYME~ORLALAERONAUTICALLABORATORY mstion can be forced to take place during injection COMPRESSION-IQNITION13rimNEs.-Recent tests made md so prevent detonation. The rate of fuel injection for the purpose of decreasing the ilre hazard in car- s slmwn to have little effect on the rate of combm~ion. buretor-type aircraft engines by cooling the exhaust rhe resndtsof this study are being published as Tech- manifolds and by preventing the ignition of gasoline ~icalReport No. 401. vapors by a back-fire from the engine have substan- Combustion ctimberinv~tig~+lntegrd type.— tiated the committee’s contention that the most prom- &spreviously reported, the principle of proportioning ising method of eliminating the fire hazard in air- :he area of the individual orifices of a multiorifice in- craft is to install engines which use low-volatile fuels ~ectionvalve to the volume of air served by the spray such as Diesel oil. Although there are available sev- las been adapted for combustion chamber shapes eral aircraft comprwsion-ia~ition engines, the power having little or no air flow. The effec~ of orifice size output per cubic inch of displacement of these en- md immber on the performance of a compression- gines does not compare favorably with carburetor- ignition engine has already been determined. A series type engines. The work of the committee on com- of tests was conducted in which the angle between the -_ pression-ignition engines is therefore directed toward xitices of a 6-orMce nozzle was varied frol~ 90°” to increasing the specific power output of this type of 29° by 3° increments. Although these tests showed engine, The investigation of the factors influencing that the angle between the fuel sprays w-asnot critical, the injection and combustion characteristics of fuel ~5° was chosen as the optimum angle. sprays in compression-ignition engines has been con- Since the full-load performance of a compression- tinued. The results indicate that sufficient informa- ignitjon engine is dependent upon the weight of air tion on the injection characteristics of fuel sprays has charge inducted, a method of increasing the power been obtained by the committee’s laboratory and other output is to supercharge the engine. A series of tests research laboratories to warrant the concentration of was made in which the inlet air pressure was varied further work upon tie determination of the combus- from atmospheric to 8.75 inches of mercury. The “– tion characteristics of fuel sprays. engine operation became very smooth during th- Analys& of indicator diagram&-The variations in tes@ and it was possible to advance the start uf fuel pressure within the cylinders of compression-ignition injection beyond the limit formerly set by allowable engines during combustion are being recorded with a knock conditions. With a supercharging pressure of modified T’arnboro indicator. These indicator dia- 8.75 inches of mercury the net brake mmn effective grams are of assistance in determining the effect on pressure developed by a single-cylinder test engine combustion of such factors tis fuel quantity, rate of at 1,500revolutions per minute was 26 per cent greater fuel injection, direction and rate of combustion, air than the full-load performance unsuperchargwl. movement, and injection advance angle. A method An analysis of the indicator diagrams taken dur- has been developed for analyzing these indicator dia- ing these tes~ showed the “desirability of initiating grams, which takes into consideration the variation in combustion as early as possible .in the injection cycle. weight and composition of-the mixture and the To increase the temperature of the combustion air at changes in specific heat, temperature, pressure, and the time of injection, the compression ratio of the volume during the engine cycle. This method has engine was increased from 12.6 to 15.6. & a result been applied to the analysis of a series of indicator of this increase in comparison ratio tho full-load diagrams taken for variable fuel quantities, but having brake mean effective pressure of the engine has been the start of injection maintained constant, Under increased 8.2 per cent. these conditions the results showed that the time lag Combum%on- chamher investigation — Audhy - of injection was practically constant, that the position chamber iype.—A new test engine has been installed of maximum rate of effective combustitmpreceded the for the work on the auxiliary-chamber type of com- position of maximum pressure, and that the combus- bustion chamber. The cylinder head for this test tion efficiency decreased with fuel quantity. A report engine is designed so that the spherical auxiliary of these tests is being prepared for publication. chamber is formed by a cap and a removable insert bother series of indicator cards was analyzed in the cylinder head proper. ticcording to the tangent method developed by The fimt tests with this cylinder head have been Schweitzer. The analysis shows that in a quiescent made to determine the effect of the size of the auxi~iary combustion chamber increasing the time lag of auto= chamber on engine performance. The range of aims ignition increases the combustion efficiency of the included spherical auxiliary chambers which con- engine, but also increases the tendency for detonation tained 20, 35, 50, and 70 per cent of the totul clear- BBPOETNATIONALADVISOBYCOM.MI- FOBAEROIYAUTIOS 31 -. ante volume at a constant compression ratio of 13.5. then measuring and counting the impressions made in The air flow -wasaxial in direction and was directed @e lampblack. The experiments were made in an at the fuel-injection-valve nozzle. The directing air-tight chamber in which the air density ma raised nozzle was so dimensioned in each case that the calcu- t.o values corresponding to engine conditions. It was .- lated air velocity was the same for each size of aux- found that each spray is composed of several million iliary chamber. The redts of the performance testa drops whose diameters range from k than 0.00025 -- indicate that the 50 per cent auxiliary chamber is inch to 0.0050inch and sometimes to 0.0100 inch. The best suited for further work on this type of combus- effects of injection pressure, chamber air density, ori- tion chamber. The performance obtained approached, fice diameter, and orifice length-diameter ratio on the .— but did not exceed, that of the auxiliary combustion fineness and uniformity of the atomization from pIain .. chamber with tangential air flow reported in Techni- round-hole oritiws were measured and the results com- — caI h70teh’o. 396. pared with those obtained by previous investigator. ~uel-spray characteridica.-l%e irrwstigation of The atomization of centrifugal sprays, of sprays pro- the effect of orifice length-diameter ratio on the duced by the impingement of two jets, and of a spray characteristics of fuel sprays has been comp~eted and strik@ a metal lip was t-h measured and compared a report prepared for publication. Orifice diameters with the atomization of sprays from plain nozzles. from 0.00S to 0.040 inch have been tested. Tl%en a The experiments indicate that with a given fuel the plain stem was used in the injection valve and the fineness and uniformity of the atomization increases — length-diameter ratio increased from 0.5 to 10.0, the with the injection velocity and -with a decrease in the spray penetration at first decreased reaching a mini- orfice size. Orifice length-diameter ratio and cham- .— .— mum between the ratios of 1.5 and 2.5; then in- ber air density were found to have no decided effect. creased, reaching a maximum between the ratios of Centrifugal and impin~~ sprays were found to have .— - 4.0 and 6.0; and decreased again as the ratio was no better atomization than”sprays from plain nozzks, increased to 10.0. The exact position of the maximum provided the injection whcity was the same; the and minimum points approached the ratio of zero as distribution was, however, much better. The results ..— the oritice diameter was increased. The spray cone of these experiments have been prepared for publi- -—-.-. angle varied inversely as the penetration. with a cation. helically-groowd stem in the injection valve a maxi- Because of the interest being shown m the substi- -- mum was reached at a ratio between 5.0 and &O. The tution of a fuel pump for the carburetor on the con- spray cone angle increased as the ratio of groore area ventional spark-ignition aircraft engine, a series of to orifice area was increased. tests was made to determine the characteristics of -. b instigation was conducted to determine the gasoline fueI sprays for injection pr-res from 100 effect of an open nozzle on the spray characteristics. to 500 pounds per square inch and for air densities The results showed that for injection systems in which of atmospheric and 0.325 pound per cubic foot. It the rate of pressure rise at the discharge orifice is was found that the penetration at these low injection high, open nozzles give spray tip velocities and pene- pressures and air densities compared favorably with trations which compare favorably with those , of the penetration at high injection pressures. The spray .— closed nozzles. It was found that in designing a sys- cone angles mere small, vary~~ from 2° to 15°, and tem to use open nozzles>particular care must be taken individual fuel drops were tisibIe in the sprays. The to avoid air pockets and that the check valve should gasoline and Diesel-fuel sprays had similar character- be placed close $0 the discharge nozzle. The results istics. of this -workha-rebeen pubLished as a TechnicaI Note. l%d-injection @enw.-The research started last By means of the N. & C. ~. spray photography year on the hydraulics of fuel pumps for compression- equipment, high-speed motion pictures were taken of ignition engines has been completed and the results the formation and development of fuel sprays when are being published as Technical Report No. 396. The directed counter to and normal to air mow@ at a effect of various injection valve-opening pressures on :— velocity of O to 600 feet per second. The results the spray tip penetration has been determined for sev- indicate that in a high-speed compression-ignition eral injection pressures. A common-rail fuel-injection engine it is nm=ary to have sir velocities of approx- system -wasused in these tests. For a given injection imately 300 to 400 feet per second to break up the pressure a maximum rate of penetration was obtained —._ center core of a fuel spray from a single round-hole with a valve-opening pressure equal to the injection -— orifwe. The results showed that high air velocities pressure. & the excess of the injection pressure over are an effective means of mixing the fuel and air. the injection valve-opening pressure was increased the The atomization and distribution of fuel sprays effect of the injection valve-opening presstire on the from automatic injection valves have been determined spray tip penetration was increased. These results by catching the fuel drops on smoked-ghws plates and have been prepared for publication. --—.- 32 REPORTNATIONALADVISORYCOMMITTEEFORAERONAUTICS

An investigation has been conducted on the forma- nomena demonstrated that tho length-diameter ratio tion and duration of fuel sprays from a pump injec- of the individual passages of the arrester was the tion systenl. The results show that the penetrationof factor of first importance in determining the effective- the spray tip, the time lag of injection, and the dura- ness of the device, and that the heat capacity and tion of injection can be controlled by the dimensions thermal conductivity of the material of which it was of the injection tube, the mea of the discharge otice, made were only of secondary influence. An arrester and the injection valve-opening and closing pressures. was constructed and was found in actual t~st trprE- Under ordinary conditions the spray characteristics vent an indefinite number of back fires from reaching were satisfactory. At low speeds, such as experienced the carburetor. Air-flow and power measurements in starting and in idling, the injection consisted of a showed that the increase in engine-pumping loss due series of sprays of short duration following each other to the presence of such an arrester was negligible, ml in rapid succession. These data have been prepared that the decrease in volumetric etliciency was of the for publication. order of a few per cent. An apparatus has been designed and constructed Air-inducting eakzuat m.unifoZd.-The danger of for determining the instantaneous rates of fuel dis- fuel or oil coming in contact with the heatccl exhaust --- charge from a pump injection system, A series of manifold of an aircraft engine, especially in a crash, tests has been started to determine the effect of injec- is a serious fire hazard. During the past year the tion-tube length, injection-tube diameter, discharge- probkcn of reducing the temperature of the manifold ._ orifice diameter, injection valve-opening pressure, below the ignition temperature of the fuel has been pump speed, and similar factors on the instantaneous investigated. An ‘

8 34 REPORTNATIONAL’ADVISORYCOM.MI’KKEEFORAERONAUTICS an impeller-shaft bearing under high-altitude condi. Iiminary measurements have been made of the total tions. Complete test data at the rated speecl of 2,300 infra-red radiation to a wave length of 10IJthrough a revolutions per minute Fere obtained for altitudes fluorite window placed in the cylinder head, using a from sea Ievel to 20,000 feet, the mixture ratio being stroboscope to follow the variations in radiation adjusted for maximum power in each case. through the cycle. Datm obtained were sufficiently Reexamination ofidata obtained -with a 150-horse- promising to warrant the construction of a sensitive power Hispano-Suiza engine (Fourth Annual Report galvanometers-whichwill be used for further radiation of the lYationaI Advisory Committee for Aeronautics, measurements, p. 508) showed, for this engine, as well as for the Pre8aure8 and ten~peratures in aircraft enp”ne8.- C!urtissD–IQ engine, linear variation of brake horse- A considerable amount of information regarding the power -with edaust pressure -when air is supplied to effects of fuel, operating condition, and combustion the carburetor under constant conditions of temper- chamber geometry on pressure de-relopment in the ature and pressure. The curves for the Curtiss engine cylinder is being accumulated in connection engine have been made available to tha National Ad- with the flame movement and radiation experiments, visory Committee as well as to the &my and tha partial indicator diagrams being macle with a bal- Navy, pending completion of a technical report on the anced diaphragm engine indicator during the com- performance of this engine under supercharged con- pression, combustion, and expansion periods for each ‘- ditions. The brake-horsepower correction for ex- run. As a preliminary to obtaining torque measure- haust back pressure determined for the Curtiss engine ments and complete indicator diagrams of impro~ed has recently been found to be directly applicable to precision for the purpose of comparing “ dynamom- the correction of approximate altitude tests of a Pratt eter” and “ indicator card” power, a technical note is & ‘Whitney Hornet engine Vhere ahitude conditions being prepared which describes various concepts of were maintained only at the carburetor entrance. indicated power and discusses their significance as “- Phenmnenu of com6u.8tion.-The latest thermody- applied to 4-stroke-cycle engines. namic studies by Wohl of the gaseous explosive reac- 17flect of- 8park character on ignition aWity,-In “ “‘ tion at constant volume have been applied to the order to defile spark discharges precisely in terms determination of the relation between the temperature of their voltage and current characteristics, a cathode- of the explosion and the rate of transformation in ray oscillograph wrLsobtained. Extended experimen- homogeneous mixtures of explosive gases at constant tation waa required to develop satisfactory methods pressure. As a preliminary, a higher precision was of measuring voltage and current without apprccia- sought in the determination of final volume than pre- My altering the character of the spark. A report on vious workers have been able to attain in their deter- the use of the cmthode-ray oscillograph in measuring mination of final pressure by manometric methods. spark dk.charges and a second report on the effective- . This involved simplification and improvement of the ness of ignition sparks, as measured by the amount of ‘-” experimental apparatus and special precautions to chemical reaction occurring when different sparks are insure homogeneity of each exphsive charge. Pho- passed through lean mixtures of oxygen and hydrogen tographic time-volume explosion records of increased at atmospheric pressure, are being written for pub- accuracy have been obtained over the entire range of lication by the National Advisory Committee for the explosive reaction of carbon monoxide and oxygen Aeronautics. Apparatus has been construct fur con- ‘ and approximate explosion temperatures at constant tinuing at higher pressures the work on the amount pressure have been computed, The experiments are of chemical reaction produced by diB.erentsparks. being continued -with mixtures of carbon monoxide Work undertaken by the ia~ition laboratory for the and oxygen in equivalent proportions, to which argon Navy Department has included (1) measurements 01 is added as an inert diluent. sparking potential and of the distribution of energy Combudion in an engine oylinder.-Resnlts of ob- in different spark gaps; (2) the use of absorption servations of flame travel and pressure development spectra i% study the effect of temperature on the during combustion of gaseous fuels in a eingle-cylin- oxidation ofhydrocarbon-air mixtures; and (3) tests der engine under various operating conditions. will of gasoline stability as influenced by exposure to ultra- soon be published as Technical Report No. 399. As violet light and passage through a hemtedmetal tube. aids to the interpretation of the engine experiments, lijfect of air humidity on engine perfvnnancc.— photographic records were made of flame travel across Aircraft engine tests with constant air temperature the center of a bomb similar in size and shape to the at altitudw from sea level to 25,000 feet showed n~axi- engine combustion chamber, and a mathematical anal- mum indicated power to be linearly proportional to ysis of the elfect of thermal expansion on the move- dry-air pressure, the average deviation being *0.16 ment of flame during gaseous combustion in symmet- per cent. On the basis of these test-sand extended rical closed conttrinershas d~o been ~dertaken. P~- twts on other engines, made at the request of the Navy . ● REPORTNATIONALADTILSOBYCOMMITTEEFOBAERONAUTICS 35

Department, it vvas remmmended that humidity be significant test methods for determining the gum con- .— recognized major factor in engine power varia- mt of gasoIinw and its tendency ta increase during as a ---- tion and it has been proposed (1) that sea-level en- storage. Gum-content data obtained on numerous ~gi.netests be corrected to a totaI pressure of tBOmilli- gasolines by several methods indicated that the meas- meters of mercury, but a dry-air pressure of ’750 med gum content depends very materially upon the ..—— millimeters of mercury; and (2) that standard hu- method employed in evaporating the gasoline. Since . ..— midities, decreasing from 10 millimeters of mercury at :he air-jet method showed the most promise, an ex- sea le~el to 0.18 millimeters of mercury at 25,000 feet, !ended study has been made of the variables affecting —. be added to the specifications of the standard atmos- evaporation by this method. In connection with the ...- phere for tests of aircraft engines. iendency of gasolines to form gum during storagel ~ study of the injection of water spray into the Lheresistance to oxidation of a number of gasolines combustion chamber of an e.rgge ahowed high anti- kasbeen measured at various temperatures and under .— knock action without loss of power -ivith optimum ~arious oxygen preesures. Since quantitative rela- timing of spark advance and of injection. tions mere found between resistance to oxidation and”- Tests at aItitudes up to 30,000 feet and over wide gum stability under a~ conditions of test, measure- .- ranges of temperature and relative humidity indicate mentsof resistance to osidation give prorniss of be&O -. an accuracy better than 0.25 per cent for the modided sitidcant as regards gum formation under normal ..— psychrometer developed during this rwiearch. storage conditions. Taper lock in airplane fuel systems.-To round out In the contemplated revision of Federal specifica- the laboratory work on airplane fuel-feed system de- tions for atiation gasolines, a specification for gum sign, the efficiency of all types of fuel primps in gen- has been proposed which would replace the present eral use is being compared under a chosen set of rep- copper-dish test. The g~oline is required to have resentative operating conditions. Temperature-flow kss than a specified amount of ~gpunafter being sub- curves have been obtained on the C-5, G3, and Romec jected to accderated oxidation. pumps with one kind of gasoline at each of three at- Type testing of commercial aircraft a@u?8.—The mospheric pressures. The ~avy seaplane pump and aircraft engines tested at the iwlington laboratory ——. _ the autopulse pump will also be tested. shomed somewhat greater variety both as to type and Analysis of flight-test data on airphme fuel-line size. There were l-l radial engties, including one .--— temperatures obtained during the past two years in Diesel; 8 inverted in-line engines; 4 horizontal- cooperation with the Army, the Navy, and the ~a- opposed engines; and 4 V-type engines, inchding a —— tional Advisory Committee for Aeronautics showed 12-cylinder inverted V. Five engines tested had less r-. — ‘ that in au cases the temperature of the fuel in the than 200 cubic inch displacement and three engines feed system tended to drop very slowly as the air- had more than 700 cubic inch displacement. of 27 plane climbed. To overcome this tendency, fuel engines received for test during the year, 14 passed, .— tanks should be so instalIed as to insure good heat 11 failed, and 2 -were withdrawn. Eight of the intemhunge with the atmospheric air or else small engines which failed were new types and three had fuel radiators placed in the air stream should be receiwd one previous test each. Crank-case break- employed. The temperature of the fuel in the tank age was the most common source of major failure, — as the airplane leaves the ground and the rate of heat At the end of June, 73 three cases being noted. .— interchange with the atmospheric air are factors engines had recei~ed approved-type certificates from which outweigh any minor differences in fuel-system the Department of Commerce. desia~, although much can be done to improve de- Each engine is approved only for use with fuels sign. equal or superior to that used during the official test Ee=&ed speci5cations for aviation gasolines, under and the important fuel characteristic is its detonation consideration by the Federal Specifications Board, rat~~ or octane number. Preliminary experiments permit the use of gasoline having a vapor pressure cm five atiation gasolines ranging from below 60 to of 10 pmmds per square inch in airplane-s equipped above 80 octane number were undertaken in coopera- with fuel systems -which are satisfactory as regards tion with the Army, the Navy, and four indmtrial vapor lock, while for airplanes -with unimproved fuel laboratories. The fueLa were rated by a variety of systems the vapor pressure is limited to 7 pounds per available methods and the results showed that the square inch. This emphasizes the desirability of re- detonation ratiqg assigned to an aviation gasoline de- quiring suitably designed fuel-f~ed systems in all new pends on the test method and equipment used. Fur- airplanes. ther -work must be done to determine the particular G%muning characteri%%c~of gasoZine8.-An investi- type of test which gives ratings most indicative of gation of the gumming characteristics of gasolines the reIative behavior of aviation fuels under actual was undertaken for the Army Air Corps to develop service conditions. 36 REPORT NATIONAL ADVISORY COMM17+EEFORAEROI?AUTIOS

REPORT OF COMMITTEE ON MATERIALS FOR information regarding investigations on matmids for AIRCRAF1’ amcraft, is enabled to keep in close touch with re- ORGANIZATION march in this field of aircraft development, Much of The present organization of the committee on ma- the research, especially in the development of light terials for aircraft is as follows: alloys; must necessarily be conducted by the manufac- Dr. George K. Burgess, Bureau of Standards, turers interested in the particular problems, and both chairman, the aluminum and steel industries are represented on Prof. H, L. Whittemore, Bureau of Standards, the committee, vice chairman and acting secretary. Much of the research in connection with the devel- opment of materiak for aircraft is financed directly Lieut. Commander R.. S. Barmby (C. C.), United by the Bureau of Aeronautics of the Navy Depart- States Navy. “--” ment, the mat4ricl division of the Army Air Corps, S. K. Colby, American Maamesium Corporation. and the National Advisory Committee for Aero- Warren E. Emley, Bureau of Standards, nautics, and many of the problems are apportioned to Commander Garland FuIton (C. C.), Uhited the Bureau of Standards for investigation. States Navy. Dr. H. W. Gillett, Battelle Memorial Institute. SUBCOMMITTEES C. H. Helms, National Advisory Committee for In order to cover effectively the large and varied Aeronautics. field of research on aircraft materials, subcommittees have been established from time to time under the Dr. Zny Jeffries, Aluminum Company of America. -- J. B. Johnson, matiriel division, Army Air Corps, committee on materials for aircraft. During the past Wright Field, year, in a general reorganization of subcommittees George W. Lewis, National Advisory Committee eflected by the executive committee, two of these sub- for Aeronautics (ex officio member). committees, the subcommittee on woods and glues and — Capt. Alfred J. Lyon, United States Army, the subcommittee on coverings, dopes, and protective matikiel division, Air Corps, Wright Field. coatings, were discontinued, and in their steud a. new H. S. Rawdon, Bureau of~tandards. subcommittee on miscellaneous materials was ap- E. C, Smith, Republic Steel Corporation. pointed. G. W. ‘Ihyer, Forest Products Laboratory, For- Another important change during the past year in est Service. the subcommittee organization under the committee Starr Truscott, National Advisory Committee for on materiak for aircraft was thO establishment in * Aeronautics.. April, 1931, of a temporary subcommittee on research Hon. Edward P. Warner, editor of “Aviation.” program on monocoque design as a subcommittee of the subcommittee on aircraft structures, The func- F~OTIO~S tions of this new subcommittee are to offer suggestions Following is a statement of the functions of the from time to time as to details of the program of the committee on materials for aircraft: investigation of stressed-&in construction for air- 1. To aid in determining the problems relating to craft, under way at the Langley Memorial Aeronauti- materials for aircraft to be solved experimentally by cal Laboratory, and to present recommendations as to governmental and private agencies. investigations in connection with the problcm of mon- 2. To endeavor to coordinate, by counsel and sug- ocoque design which can be undertaken by other gestion, the research and experimental work involved organizations. in the investigation of such problems. On rkxunmendation of the structures subcommittee & To act as a. medium for the interchange of in- and the materials committee, the executive committcw formation regarding investigations of materials for has recently provided for the appointment of a stand- aircraft in progress or proposed. ing su~committee on methods and devicw. for tcding QTo direct and conduct research and experiment aircraft materials and structures as an additional sub- on materials for aircraft in such laboratory or labora- committee of the committee on materials for aircraft, tories, either in whole or in part, as may be placed for the purpose of studying the present methods and >, under its direchion, devices-used in the testing of aircraft materials and 5, To meet from time to time on call of the chair- structureswith a view to standardization and improve- man and report its actions and recommendations to ment. This subcommittee has just been established the executive committee. sad has not yet begun its work. The committee on materials for aircraft, through its The present organization of the subcommit~ of personnel acting as a medium for the interchange of the committee on materiaIa for aircraft is as follows: REPORTNATIONALADVISOBYCOMMITTEE FOE AERONAUTICS 37

&uboom.mittee on metaL9: G. W. Trayer, Forest Products Laboratory. H. S. Rmrdon, Bureau of $ta.nilards, chairman. P. H. TValker, Bureau of Standards. Dr. H. IV. GilIett, Battelle 3iemoriaI Institute. G. P. Young, mat&ieI division, Army Air Corps, Dr. Zay Jedlries,Aluminum Company of America. Wright Field. J. B. Johnson, mat&ieI division, Army Air Corps, M&ornmit tee on method8 and de uioa for testing a&- TVright Field. craft m.aten”aZ8and 8h43We8: George TV. Lewis, NationaI Advisory Committee Henry J. E. Reid, Langley Memorial Aeronauti- for Aeronautics (ex officio member). cal Laboratory, chairman. — E. C. Smith, RepubIic SteeI Corporation. Lieut. Lloyd Harrison (C. C.), United States — Starr Truscott, National Advisory Committee for Navy. Aeronautics. Lieut. Paul H. Kemmer, United States Army, Prof. H. L. Whitkxnore, Bureau of Standards. mat&iel division, Air Corps, Wright Field. Subcommittee on aircraft 8tructure8: George W. Lewis (ex of6cio member). Starr Truscott, NationaI Advisory Committee for R. L. Templin, Aluminum Company of America. Aeronautics, chairman. Dr. L. B. Tuckerman, Bureau of Standards. Lieut. C. E. Archer, United States Army. SUECOM?rfrITEZON METALS C. P. Burge=, Bureau of Aeronautics, Navy Department. A number of investigations on metals and their Richard C. Gazley, aeronautics branch, Depart- applicability have been conducted at the Bureau of ment of Commerce. Standards in cooperation with the Bureau of Aero- Charles Ward Hall, HalI-Aluminum Aircraft nautics of the h’avy Department, the matfriel divi- Corporation. sion of the Army Air Corpst and the National Ad- Lieut. L1oyd Harrison (C. C.), lTnited States N’my. visory Committee for Aeronautics. The BatteW Lieut. Paul H. Kemmer, United States Army, 3iemoria1 Institute also volunteered to carry out an mab!riel division, Air Corps, Wright Field. investigation on the lo-w-temperature properties of — George W. Lewis (ex ot%ciomember). a number of metals which are of importance in air- Lieut. Commander R. D. 31acCart (C. C.), United craft construction. States Navy. 1%’opertie8 of metd8 at ~ow tempera#ure8,-A tech- Charles J. McCmthy, Chance Vought Corporation. nical note has been issued giving the redts of co- Prof. J. S. NewelI, Massachusetts Institute of operative tests carried out at the Battelle Memorial Technology. Institute on the properties of metals at low tempera- Dr. L. B. Tuckerman, Bureau of Standards. tures. In addition to steels already in use for air- Tanporq subcommittee on meearch program on craft construction, several other metals suggested for monocoque de~”gn: * corrosion-resistant streamline wire were studied. George W. Lewis, National Advisory Committee Monel metal, stainless iron (0.0’7per cent carbon, 13.8 -— for Aeronautics, chairman. per cent chromium), 18-8 stainless steel, 3.5 per cent Richard C. Gazley, aeronautics branch, Depart- nickel steel, and chromium-molybdenum steel vvere ment of C’ommerce. used. The endurance Iimit of the materials at —40° Lieut. Paul H. Kemmer, United States Army, F. was found to be raised in practically the same mat6riel division? Air Corps, Wright Field. ratio that the tensile properties and Brinell hardness Eugene E. Lunclquiat, National Advisory Com- were. There seems to be no reason to fear premature mittee for Aeronautics. faiIure from fatigue at low temperatures. The re- — Lieut. Commander It. D. MacCart (C. C.), United sistance of notched specimens to impact at the low Stales Navy. temperature was materially lowered, however, for Dr. L. B. Tuckerman, Bureau of Standards. some of the materials. &4bcommittee on miscdlaneous matetiaZ8: Identification of chromiu?n+ndybdenum 8tet?~.— Charles H. Helms, National Advisory Committee Work alo~~ chemical lines was continued during the for Aeronautics, chairman. year on a rapid method of distinguishing between Dr. W. Blum, Bureau of Standards. chromium-molybdenum and plain carbon steel, both C. J. Cleary, mat6rie1division, &my Air Corps, of which, in tubular form, are used in aircraft con- Wright Field. struction. The attempt to develop a satisfactory Warren E. Emley, Bureau of Standards. chemical “ spot” test for molybdenum has been un- George W. Lewis (ex ofEcio member). successful. However, a practical and rapid method to . J. E. Sullivan, Bureau of Aeronautics, Navy De- be used on driIlinga based on the stannous-c~oride .— partment. potasium-sdphocyanate reaction with molybdenum 38 REPORTNATIONALADVISORYCOMMIT?kEFORAERONAUTICS .“ has been developed. This method appears to be de the use of a saturated solution of mercuric chloride cidedly better than the one used hitherta. has been deveIoped. Films vvhich withstand a 15- I?u%rcryatdlint? t??nh%tk?nwnt of $heet d?wak- minute immersion will meet the requirement laid min.-This work has been continued; the series of down in the Navy specifications. The utility of solu- weather exposure tests in the three locations, Coco tions of chromic acid of various concentrations has Solo Na$a.1Air Station, Hampton Roads Naval Air been studied. Satisfactory coatings can be made wi~h Station, and Bureau of Standards, are now in the other concentrations besides the commonly used 3 per fifth year. The results of tension tests made on the cent solution. It has been shown that the corrosion corroded materials removed periodically from the teat resistance of the treated products is not impaired by racks continue to show the stability of the m@erials chromic-acid stains. Heat treatment of dumlumin if properly heat-treated. Sheet duralurhin which after the anodic flm has been formed does not impair has been given tlm fol~owing treatments has been the film. lVork is being continued on other aspects found to be susceptible to intercrystalline corrosion of the process, especially the useful “ life” of the when exposed to the weather: chromic solution in continuous use. l?xpowre te8t8 of magnesium and magnesium a.Z- Quench Joy~.—After 24 months’ continuous exposure to the weather on a roof at the Bureau of Standards no I TeInl#.r*Heating marked decrease was observed in the tensile strength tnreLC.) @od of the specimens of magnesium and magnesium alloys, — —— . — nor had the ductility, which was initially relatively Minuted 600---- 15. Water--- ;Ck Roomtemperature. low, decreased to any very marked extent; —AU of 5oo---- .--do--- 8 hours150°C. the coatings, however, regardless of the initial sur- 5oo---- ;: oil----- 2: Roo~oemperature. soo---- 15 .-Jio--- face treatment of the materials, showed evidence of tioo---- 60 .--do--- 2: Do: complete “ breakdown” by peeling and scaling. 426---- 60 Water-. 26 Do: : ---- ““ 560---- 60 .-do_- 100 96 hoursroom temperature High-frequency endurance te8t8 o~light id~oy 8hcct with10percentstretch. rnateriuZ8.—TVork has been continued on this project-- 600---- 60 .--do-- 0 ‘6a%%%5w%v’uF throughout the year, the seven units of air-driven 6001--- 20 .--do---- 25 8 to 16hours140°C. high-frequency endurance-testing machines at the Bu- reau of Standards bei~ utilized for the nurwsc. Of 12S6TtiOy. I the 14 materiak initifiy available for &u&, it has All of the numerous coatiw materials used, which proved possible to determine the enduranm- limit- of are applied by means of mbr&h, have been found to the nine materials which possess welI-defined elastic break clown within 86 months’ continuous exposure to properties. These results are summarized in the table. the weather, the test results secured at Hampton &mealed material could not be tested by this method. Roads being used as a basis for this statement. Alu- Attempts to determine the endurance limit for the minum-pigmented spar varnish was found superior following were unsucc~ful: 2S0 (annealed alumi- to all other brushed-on coatings used. b aluminum num), 8S0 (annealed aluminum-manganese alloy, coating which forms an integral part of the sheet as 1.25 per cent Mn), 310 (annealed magnesium), rmd in the A1clad materials has proved far superior to any 17S0 (annealed duralumin). Likewise it was in~- brushed-on coating in all of the exposure tests. possible to stress Alclad durahunin, which consists Of the various methods usecl for treating the sur- of a sheet of heat-treated alloy (17S) -with a layer face of duralumin so as to improve the adherence of of pure aluminum on each surftice integral with it, coatings to such sheets, the. anodic treatment has sufficiently in the machine to cmueefailure, -ivhercms proved by far the most satisfactory one. the plain heat-treated sheet without the surfncc layers A new series of exposure tests to supplement and of aluminum was readily tested. It has nut been found extend the present one has been planned, In this will possible to develop sufficientstress in steel-sheet speci- be included materials developed within the period mens so that the endurance limit could be determined since the first tests were started. by this means. Consequently the projected work cm Protection of dwwh.nnin, anodic omZatzk— vielded d.eel has been laid aside. I?rompted by the wide commercial use of the anodic The possible effect of the anodic oxidntion. treut- oxidation proc= as a means for increasing the cor- ment on the fatiguo properties of duralumin still re- rosion resistance of duralumin, a study has been car- mains to be determined. Preliminary tests indicated ried out during the year on the process. A method no marked change in the properties resulting from this for the rapid inspection of the oxide film consisting in treatment. REPORTNATIONALADVISOBYOOMMITTEEFOBM?zRONAUTKX3 39

Endurance limit of light aliog sheet rnati”ak ~ high- frequenq jkzre, lfi,00i1 ~cles per minute ..— Endr.uancalimit DesifgMtion Treatment NondnelcomDcsMon I I :- I I ! I 17ST.-----_--- Hea&treatedandaged------Cu4.0, Mn0.5, Mg 0.5,Al re@nder-----_ L and T------15,000 25ST------FuiIyheaWxeateci------Cu 4.5, Mn 0.8,Si0.S,Al remainder------L------1!$000 25ST------__--da ______---_d ______---- T____ 15,000 25SW------Quenched,not aged------do______L------11,000 -- 25SW------_da ------__do ______T------13,000 51ST------_- FuUyheabti~t&------_- Mg 0.6, Si 1.0,AI remhder------___ L andT------13,000 51sw----__--- Quench& not aged------____-do------L------10,500 51sw-_------_--_-do ______I-___-&------T------132000 2SH----.-.---- C~dmu4------__-_----- ,!J” Coolraerciallypure------_---- Land T------10,000 3SH-.-.------_do------JJtim remainder______-_-_-da ------~c&) MH--.------Hti-roH~------Magnesiu?n,commerciaUypure------_--_da ______MAH.-.------&roUed------AI&O,Mn0.4, Mg remainder------_do ------5,ooc-~ 000 .- I I t I .— lL+Ioagkdnal,paaIk4todkctIondmahg. T,tiansvei-sE+pwpendlcxdartodfrAoILdToI@.

Patigueof AZoZaddurahnin.-TVork oni%isproj- indicated by an accumulation of the powder clin=tig ectvvascontimed attheBureau of Standards during to the edges of the cracks. thepastyear. l%etest method used diflers fromthat AU the tubing was inspected by this method before referred to else-wherein this report in that a motor- welding and a number of indications of Iongitudimd driven endurance-testing machine for repeated flexure seams were found which were not detected on visual at a cycle frequency of 900 revolutions per minute inspection. It is beLieved that the majority of such was used. The results previoudyreported have been semns are not deep enough to Iovier materially the reviewed and checked and the following vaIues are strength of the tubing in tension or compression, but the approximate stresses for a life of 100,000,000 might lower the torsional etrength. Tests will be Cyclw : made to determine the @ect of such seams on the Ib9./in.1 strength of the tubing. After vrel~w, aII of the Regalar17ST (unmatedduralnmin)heat-treate~lon- gitudinal----— 16,000 joints wiU be inspected by the same method. Regular17S!J?(uncoateddnralnmin)heat-treata trsns- A series of joints is being made in tubing 1.5 inches Wrse—- 14.000 in diameter and 0.020 inch in viaII thicbwas. Tests Alclad17STheat-treate@longttndinsJ______10,500 will also be made on a group of joints to be heat- Alciad17S!Cheat-treated,transrerae—_-__—_——_ 10,600 SPeclal17ST (uncoateddmahunin)heat-treate@lon- treated after weMing. gttudhlsl-— 19,000 Form factors for twbing of dura,lumin and &eel Special17ST(unccmtedduralumin)heat-treated,trans- under cmiabined column and beam Zoade—The ex- wrs~ zl, 000 Iended series of tests corering tubes of duralumin AIcladspecialI?ST, heat-treat.@Longitudinal___—__ 13,0tM AlcIadepeclal17ST,heat-treat@ transverse_—____ ~200 and chromium-molybdenum steel having outside di- ameters of 1 inch, 1.5 inches, and 2 inches and having SUECOWTIEE OX AIRCRAFT STRUCTURES ratios of outside diameter to wall thickness rang@ Strength of welded jm”nts & tutndar mcmbem for from about 15 to 60 has been compIeted, and the aircraft.—The joints which will be tded in the sec- resuIts are being prepared for publication. ..— ond program of this investigation, sponsored by the The tests over this wider range have confirmed National Adtisory Committee for Aeronautic=, are at within experimental error the relations between -— the present time beirg vrelded. Special attention is moduIus of rupture, tensile yield point, and strength being paid to the cause and prevention of cracks in of the tubes found in the previous tests and pubLished welding this seMes of joints. It seems possible to in TecbnicaI Note h’.o. 307 of the h’ational Advisory eliminate all but a+ery few of such cracks by correct Committee for &ronautics. The results given in desiaw and technique. that publication are therefore vaIid within the limits The type of gusset reinforcement which ras found stated. to be strongest has beeII improved to eliminate high The extended series of tests, however, showed that residual stresses vvhich produce cracb Xo cracks o~er the wider range of diameter-t.hickneegratios the have been noted in the improved joint. For the de- ratio of the modulus of rupture to the tensile strength tection of cracks a maggetic flux is passsd through varied too wideIy to allow the choice of a reasonably the specimen and powdered iron dusted on it. The representative value for all diameter-thiclmess ratios, technique used is that deveIoped by A. V. DeForest. as was done in the design charts, Technical I!ToteNo. Any cracks, seams, or other discontinuities present are 307, covering a more limited range of d~t values. At ,. 40 REPORTNATIONALADVISORYCOMMITL’EEFORAERONAUTICS .- . l/r= ttOthe modulus of rupture, for duralumin tubes maximum shearing stress equal to l/~ timca the of 55,o0o pounds per %quare inch tanaile strength, tile yield point of the material, determined accord- ranged from 43,000 pounds per square inch at d/t= 60, ing to proposed revision of Navy Department Specifi- to 58,000 pounds per square inch at d/t= 15. For cation 44T18a, July 1, 1931. This does not take ad- chromium-molybdenum tubing the variation was even vantage of the full strength of one group of materhl greater, ranging for tubes of, 95,000 pounds per square at 10-wdiameter-thickness ratios, but without modifica- inch tensile strength f rorn 78,000 pounds per square tion of the specification it would be unsafe to design inch at d/t= 60, to 130,000 pounds per square inch at for material of that type. d/t== 15. A series of tests hm been started on duralumin . Although no theoretical basis for this variation has tubing having diameter-thickness ratios ranging from been worked out, the tests covered a sufficientrange to 8 to 90. It is expected that because of tl~euniformity give reliable empirical relationships between tensile of this material, as evidenced by past twits, more cer- strength, modulus of rupture, slenderness ratio, and tain progress can be made in the analysis and correla- diameter-thickness ratio for these two materials. At tion of the data. present a study is being made of the best method of &rahip girder8 and aklip structural m&nk?T8.- combining the results in conveniently usable design The study of the twisting type of failure found in charts. column tests of open sections used as chord members lVhen this work is completed further investigation of airship girders has been resumed. The twisting of the rel.ationship between the tensile properties and failure depends upon the torsional rigidity, and ako ,+ modulus of rupture of the tubes will be taken up in an upon the axis about which the section twists. endeavor to discover a theoretical basis for the resultzi Theoretical and experimental investigdions re- Tortinal 8trt?ngfh of-tuMng.—A series of. testi has ported in technical literature suggest that the axis — been completed on chromium-molybdenum tubing of of twist under column load may coincide with the diameter-thickness ratios ranging from 12.5 to 57. axis of shear determined in beam theory. In open The shortest specimens tested were 19 inches long; sections this axis does not, in general, coincide with — the longest specimens, 5 feet. All failures were buck- the axis of twist under uniform torque. ling failures in the plastic range. E@–eriments have been made on duralumin chan- The tubing supplied showed marked differences in nels (A.3 ) of the type used in the triangular girders physical properties, the tensile strengths ranging from of the A%enandoah, in which a specimen was twisted 88,000 to 133,000 pounds per square inch. Examina- at mid-length. The results indicated that the axis of tion of the stress-strain curves showed that the mate- twist was not constant in position, but lay outside tha rial could be grouped into two distinct classes, one section and closer to it than the computed. axis of with a rather sharp break in the stress-strain curve shear. — and the other with a gradual curve as the material The location of the axis for pure twist is not being passed from the range of elastic, into the range of determined experimentally, plastic deformation. An analytical study of the secondary longitudinal The results of the torsion tests coniirrnedthis group- stresses set up in the channel subjectcd to twist is ing. The ratios of the toraicmalstrength to the yield being made. These stressesbecome of special impor- point of the material, determined accordiig to pro- tance at large angles of twist, and their distribu- posed revision to Ilavy Department Specification tion is dependent upon the location of the axis of 44T18a, July 1, 1931, faII into two groups. For the twist. material with a sharp break in the stress-strain curve The tests on small preformed wire terminal loops the ratios decrease with increasi~~ diameter-thickness made by the Goodyear-Zeppelin Corporation by the ratio, the decrease being approximately 8 per cent same method as was employed in making the loops from d/t=20 to d/t=45. For the material with for the Zl?8-4 and ZZi!&-6 have been continued, As gradual curvature the ratios are greater at low the largest diameter of these loops is about 0,875 inch, diameter-thickness ratios, but decrease approximately measurements of- the change in curvature for various 40 per cd over the same range, re~ching about the loads are difficult; 3,415 individual measurements of same vaIue as the other group at d/t=45. curvature on four specimens have been made at va- Below d/t =45 there was, for the materials with a rious loads up to approximately 700 pounds, sharp break in the stress-strain curve, no noticeable hlaximmn stress differences, calculated according to effect of tube kngth, but above d/t =45 there was a the TVinkler cur-red-beam theory, of approximately smaII but noticeable decrease of strength with increas- 557,000 pounds per square inch, corresponding to a ing length of tube, load of 450 pounds, have been found in one of the within the limits of the sizes tested it seems safe lessperfect loops. For the more perfect loops the to design chromium-molybdenum torque tubes for a stresseswere only about 60 per cent as great. REPORTNATIONAIJADVZSORYOOMMITIXEFOBAERONAUTICS 41

These stress di.tlerences are surprisingly high and extended to the longer plates, i. e., 7.5 by 17.5 and 5 . emphasize the importance of careful design and work- by 30 inches. manship in terminal -wireloops. lnela#io behavior of durabnin and al~oy 8teeZ8in ~ number of pieces of duralumin channels and Iat- teneion and cornprem&m.-The tests to determine the tices ttiken from the U. S. S. LOS hge~es for the relative physical properties in tension and compres- annual inspection have been tested. The resdts con- sion of metals used in aircraft structures have been firm previous studi~ which indicated that, aIthough continued. These structures are often fabricated from there m-is a S1OWprogress in corrosion since the pre- thin-walled tubing or from thin sheet which has been vious sampling, no sampIe -was found in -which the cold worked after heat treatment. Many tensiIe tests corrosion had progresed eno~ah to reduce the strength have been made, some of -which show- significant dif- .— of the girders below the design values. ferences in the character of the stress-strain curws for :,— Tensile coupon specimens of thin sheet Alclad about specimens taken with and across the direction of 0.0095 inch thick, which had been cut from the metal- rolling. clad airship (Jf6’-g), have been tested. The metallo- It is diflicult, however, to obtain satisfactory results graphic examination showed s~cht traces of corrosion, for the physical properti~ of thin material in com- but the tensile tests shovied no measurable deteriora- pression because the specimens usually fail elastically tion. No specimen tested had less than 31,500 pounds by bending before the plastic range of the material is per square inch yield point, 54,600 pounds per square reaclwd. Satisfactory results may be obtained either inch tensile strength>or 16 per cent elongation. by preventing the bending by external forces or by End fixation of 8trui8.-The investigation has been testing a sufficiently short specimen. continued this year with the testing of three more Two 1-inch ‘Ihckerman optical strain gaug~ are complete series of chromium-molybdenum tubes L5 now available so that compression tests can be made inches in diameter and 0.058 inch thick. Restraints on specimens 1.5 inches long. A procedure has been of 250?000, 330@0, and 451,000 pouncl inches per developed for testing specimens of circular cross sec- radian of rotation of the fixture at each end were tion, wherein, by succ&ve adjustments, the strains used. The slenderness ratios varied from about 30 to as measured by the two gauges on opposite sides of .--— 150. Each specimen -wastested in duplicate. the specimen do not differ by more than 0.00001 inch. It was found as a result of these tests that by apply- TEMPORMZYSUBCOMMITTEEON RESEARCH PROGRA31 OX ing the Consid&e-E~uesser theory of column action ?dOXOCOQUE DESIGN the strength of a column with any given equal elastic &tre88ed-8hvk 8tncture8.—l?or some time it has restraint at.the two ends could be predicted from the been evident that designers and manufacturers -who strenatihof a freely supported column. This fact will desire to use the stressed-skin, or monoccque, type of result in the saving of an appreciable amount of -work construction for the fuselage or other pwts of air- .— in the laboratory and should hasten the completion of planes have difficulty in fiding sound theoretical the investigation. methods of analysis and reliable experimental data. I’echnique of te8ting flat p7ate8 under normal pr@- A survey was initiated for the purpose of learning xure.-C!ontours and deflections at the center, clue to -what methods and data were available and used in permanent set, were measured on a series of 17-ST design. This survey was conducted by Mr. Eugene cluralumin plates with clamped edges of sizes 5 by E. Lundquist, of the staff of the Langley Memorial 5 and 7.5 by 7.5 inches and of thicknesses ranging Aeronautical Laboratory, and showed that as a rule from 0.01 to 0.065 inch. A number of 5 by 5 inch the methods of design -wereempirical and depended plates with supported edges -were tested ih the same upon tests being made on full-scale examphss of the way. The results could not be brought into close structure under investigation. There w-as little agreement with existing theories, but it pro~ed pos- theory, and in general the information was scattered, sible to describe them by empirical formulas. uncorrelated, and often unavailable. A detailed a~alysis of the contou~ showed that the Under the direction of the temporary subcommittee square plates with clamped edges were most highly on research program on monocoque design, a sur~ey stressed in bending close to the e~ces near the center has been made of the available data on the compres- .— line, while those with supported edges were most se- sive strength of stiffeners of various forms as used verely bent along the diagonals cIo.% to the corners. in stressed-skin construction. 31uch of this data was Permanent deformation is thus produced near the of dubious value because of the neglect to include edges at loads which produce onIy very smaIl stresses information regarding the properties of the materials. ..- in the central portion of the plate. However, as a first result of this survey a technical -, A device has been constructed for observ@ deflec- note is beirg prepared on the column strength of - ‘ tion at points 0.05 inch apart in these highly stressed duralumin angles with equal legs. This vyill include portions of the plate. The tests are at present being a chart giving values for the more common sizes. S9SW2+ 42 REPORTNATIONALADVISOBYUOMMITTEEFORAERONAUTICS

A series of tests made at the Langley Nlemorial consisting of rubberized cloth on which are spread Aeronautical Laboratory on cylinders of paper and several htyers of a gelatin-latex mixture. This fabric celluloid indicated that valuable information could has proved very satisfactory from the standpoint of- – be obtained from tests of larger thin-walled cylinders performance, and it represents a marked reduction of duralumin. Accordingly, a program for these tats in the cost of production compared to the old gold- was prepared, and they are now under way at the beater’s-skin fabric. One-half of the gas cells of the _ laboratory. The conditions of loading will include U. S. S. Akron are constructed of this new fabric. compression, torsion, pure bending, combined &ear Since gas cells are subjected to tear due to handling - find bending, and additional combinations of Ioadings. and to the motions they undergo in their compart- Under these varied conditions of loading the effect ments in the airship, the problem of increasing the of systematic variation in the spacing of bulkheads, tear resistance of the cloth without change in its thickness of shell, or skin, and the diameter of the strength-weight ratio is being investigated. several cyIinders will be investigated. cloths have been woven using different constructions The results of the tests already made indicate that as to weave and yarn. The first samples have shown the distance between bulkheads. has a marked effect an increase in tear resistance of about five times that on the strength of thin-walled cylincIers, especially of the ordinary balloon cloth. on the strength in shear. ALso, it has been found study of m.ercerization of cotton for aeronuuticid that the bending strength of a cylinder in pure bend- uws.—The broad purpose of this investigation is the ing may be as much as 20 per cent less than the bend- improvement of domestic cotton textiles for aeronau- ing strength in combined shear and bending at. large tical uses. One of the principal requirements cd air- values of the moment shear ratio, even though the pIane wing-cover cloth, balloon cIoths, parachute type of failure may appear to be the same. cloth, webbings, etc., is maximum strength for a given These tests are expected to furnish a guide for the weight. The strength-weight ratio fop cothm yurns preparation of a program of further research on and cloths depends primarily upon the kind and sta- the strength of reinforced shells and also to supply ple Iength of the cotton, the size, twist, and ply of data by which to judge the e.fliciencyof various types the yarn, and the mercerization process. Of these, of reinforcement= A technicaI note now in prepara- mercerization especially requires invcstigation, be- tion wiIl present the results of the tests which have cause ordinary commercial mercerization is concerned been made and will inch.de a summary of similar -withluster and appearance rather than with increase tests made by manufacturers and others. in strength-weight ratio. The tests have emphasized the importance of full Apparatus for the mercerization of yarn under information as to the properties of the materials of strictly controlled conditions has been built and a which test specimens are made. It is particularly study of the factors in the mercerization process important in the thin materials and in the stressed- which affect the properties of yarn has been com- skin construction. The Bureau of Standards has pleted. The factors under consideration were tho made a study of the properties of the duralumin sheet tension on the yarn during mercerization, the strength used in the construction of the cylinders and cones of the alkali used, the temperature ma.intaincd during now being tested at the Langley Memorial Aero- the process, and the time of mercerization, ‘I’he op- nautical Laboratory. The tests thus far have been timum conditions resulted in an over-all increase in made on sheet durah~min 0.011 inch thick and indi- the strength-weight ratio of the yarn of 40 per cent cate that, for practical purposes, the modulus of based on the gray yarn. Twenty-five per cent of the elasticity is the same in all directions but that the increase r&sultedfrom the treatment of the yarn be- yield point and ultimate strength in the direction fore mercerization. The effect of-- the twist in the normal to the direction of rolling are approximately yarn on the strength-weight ratio after mercerization 88 and 95 per cent, respectively, of the corresponding is now being studied. Further coneid~ration is being values parallel to the direction of rolling. given to pretreatment. A report presenting the results of this investigation Substitute fw silk cloth fop parachute~.—A techni- will probably be prepared when more data are cal note entitled ‘{An Investigation of Cotton for Par- available. achute Cloth” has been published, In this note ap- pear the specifications for the material and construc- sm3commmE oN iirsf2ELuNE0usMATERIALS tion of a cotton cloth which will meet parachute re- (%-cell fah-ice.-The search for a durable and quirements as regards weight, strength, bulk, and flexible membrane of low permeability to hydrogen satisfactory operation. and helium, to supersede goldbeater’s skin in gas-cell This investigation is being continued. Two cotton construction, has led to the development of a fabric cloths of different construction are about ready to be “ REPORTNATIONALADVISOBYUOMMITllEEFORAERONAUTICS 43 fabricated into parachutes and will be given perform- L To determine the problems in the field of air ance tests in comparison -with the standard parachute navigation that are most important for investigation using silk. by governmental and private agencies. TVoodg and glues.—The final report of the series 2. To coordinate by counsel and suggestion the prepared by the Forest Products Laboratory covering research work involved in the investigation of ___ the investigations of wood in aircraft construction has approved problems. been pubh~hed. This report discusses two fundamen- 3. To act as a medium for the interchange of infor- tal probkms of elastic instabdity of members having mation regarding investigations and developments in .— :— sections common in aircra”ft. Formulas are given for air navigation, in proagressor proposed. calculating the critical stress at which a thin out- 4. To meet from time to time on call of the chair- standing flange of a compression member will either man and report its actions and recommendations to wrinkle into several waves or form into a single half the executive committee. wave and twist the member about its longitudinal In order to cover effectively the large and varied .- axis. These formulas -were mathematically derived field of research and development on problems of air and the experimental verification is given in the navigation, subcommittees on problems of communi- report. cation, on instruments, and on meteorological prob- lems -wereorganized under the committee on problems REPOR’I’OF C031311TTEEON PROBLEW3OF AIR NAVIGATION of air navigation. During the past year, however, in connection &th a general reorganization of its ORGANIZATION subcommittees by the executive committee, the sub- In response to the need for the coordination of scien- committee on problems of communication was dis- tific research being conducted by a number of differ- charged on account of the overlapping of its func- ---—— ent ageucies, both within and without the Govern- tions with the functions of the liaison committee on ment.,on the problems of air navigation, particularly aeronautic radio research which had recently been in the fields of navigation instruments, aerial com~ established by the aeronautics branch of the Depart- municatiom=: and meteorological problems, the Na- ment of Commerce. The final recommendation of tional Advisory Committee for Aeronautics in 1928 the subcommittee on problems of communication; for established a new standing committee on problems of the investigation of the trmmnission characteristics of .— uir navigation, with members representing the princi- the radio medium between aircraft and the ground . pal concerned -with the development of aids agencies and betvreen aircraft in flight., was referred to the ———. to air navigation. liaison committee on aeronautic radio research, and The committee on problems of air navigation is at this problem, as well as other problems in connection —— present composed of the follo-iviqg members: with aircraft communications, is being included in Hon. William P. McCracken, jr., chairman. the work of the liaison committee. Dr. L. J. Briggs, Bureau of Standards. SUBCOMMITTEE ON INSTBUXE’NTS Lloyd Espenschied, &nerican Telephone & Tele- graph Co. The subcommittee on instruments is at present or- Brig. Gen. B. D. Foulois, United States Army, ganized as follows: Air corps, 11’ar Department. Dr. L. J. Briggs, Bureau of Standards, chair- PauI IIenderson, Xational Air Transport (Inc]. man. Capt. S. C. Hooper, United States Nav-y, director Marshall S. Boggs, aeronautics branch, Depart- of naval communications} Navy Department. ment of Commerce. Dr. J. C. Hunsaker, Goodyear-Zeppelin Corpora- Dr. W. G. Brombacher, Bureau of fiitundards. tion. C. H. Colvin, Society of Automotive Engineers. George lV. Lewis, National Advisory Committee Lieut. A. F. Hegenberger, Ikited States &ny, for Aeronautics (ex officio member). mat&iel division, Air Corps, ~~oht FieId. Co]. Charles A. Lindbergh. Dr. A.. T. Hull, General Electric (!o. Prof. Charles F. Ntarvin, T’TeatherBureau. Carl TV. lIeuffel, IIeuffel & Esser. Lieut. J. P. TV. Vest, TJnited States Navy, Naval George TV. Lewis, National Advisory Committee IIydrographic Office. for Aeronautics (ex officio member) ~ C. 31. Young, Assistant Secretary of Commerce Lieut. C!. D. J1cALLister,United States Army, for Aeronautics. mati!riel division, &r C!orps,TVright Field. H. J. E. Reicl, National Advisory Committee for FUIWTIO?W Aeronautics. The functions of the committee on problems of air Lieut. L. D. TTebb, United States Navy, Bureau — navigation are as follows: of Aeronautics, Navy Department. 44 REPORTNATIONALADVISORYCOM~!tTEEFORAERONAUTICS

Investigations on the development of instruments is simple in design and comparatively light in weight, for air navigation conducted under the cognizance of has “been developed for the Bureau of Aeronautics of the committee on aerodynamics are outlined in the re- the Navy and is now commercially available. Im- port of that committee, In addition to these investi- provements in the watches and methods of deternlin- gations a great deal of progr~ has been made by ing time have been effected. . organizations, which are in the main represented on Radio aid8 to nazxigation.-An extensive program of the subcommittee on instruments, relating to a num- reswmchon radio aids to navigation is being conducted ber of problems listed in the subcommittee’s report on by the aeronautics branch of the Department of Cum- the Present Status of Aircraf t Instruments (Technical merce through its research division at the Bureau of Report No. %71), and certain other navigation prob- Standards. The development of a radio system as a lems. A number of these -which appear to be out- guide in making landings during fog has formed a standing will be briefly considered. large part of the program during the past year, nnd Vibration of instrument pane18.—An instrument efforts have centered on the simplification of the indi- -was developed by the Pioneer Instrument Co, for cators to be observed by the pilot. The perfcxd.ingof optically recording the frequency and amplitude of the visual indicator for the directive radio beacon vibration of aircraft instrument panels. It is of such has continued and has included the development of size and weight that it can be substituted for almost an indicator of the pointer type. any of the instruments with 2.75-inch dial. Results A%nplification oj%dicator&—The space on the in- of tests made on 10 airplanes indicate (1) that the & strument panel is limited. Instruments, many of quency of vibration of the instrument panel is the them essential, continue to multiply as the interest and same as the engine speed, (2) that the average ampli- .&iI1 in instrument flying increases. It is humanly tude (maximum displacement from equilibrium posi- impossible to observe and coordinate all of the large tion) is 0.006 inch, and (3) that the direction of r,umber of instruments which are now required for vibration is in general at right angles to the plane of instrument flying, instrument Ianding, and for specinl The panel. This confirms the assumptions made in purposes. This has Ied to continual and widespread selecting the frequency of the standard vibration used study of the best possible grouping of the instru- for testing instruments and also shows that the ampli- ments on the panel and of the possibility of elin~i- tude selected is suiliciently severe. With some addi- nating or combining instruments so M to reduce the tions, these data. will furnish a basis on which to set total number. Thus, during the past year, a com- limits to the amplitude of vibration which an instru- bined turn meter and inductor compass was developed ment should be expected to withstand in service. commercially, with which it is hoped to eliminate the ~?np?’overnent8in gyro-in8trunwnt8.-Airphme op. dial of the turn indicator from the jnstrumcnt board. erators and testing laboratories have had further ex- Progress is being made in substituting a sensitive al- perience with the Sper~y artiticial horizon and direc- timeter for the customary altimeter and rate-of-climb tional gyro. In order to obtain satisfactory service indicator, An instrument recently adopted as an from these instruments it appears that greater atten- Army-Navy standard, in -whichthe mechanism of tho tion must be given to the control of the operating suc- fuel and oil pressure gauge-s and the engine ther- tion. At present the instrument% me operated by mometer are installed in a singIe case with a 2.’75- Venturi tubes which develop a suction that is depend- inch dial and with separate scales and pointers, is ent both on air speed and altitude. Each gyro-instru- EOWbeing made on a commercial scale for the Army ment now has its own Ventiiii tube. It is rather gen- Air Corps. It has been the common practice on out- erally believed that the solution of the problem is a board motors to have the engine instruments mounted mechanically operated pump, which is under develop- on a strut adjscent to the engines, but suitable elec- ment by a number of organizations. trical pressure gauges, thermometers, and tachometers Detewnination of position.—The instruments and hsve recentIy become available so that the indicators methods for determining the position of aircraft by can now be conveniently installed on the instrument astronomical observations have heen further improved panel. with a view to reducing the time and effort now neces- SUBCOMMITTEEONMETEOROLOGICALPEOBLEMS sary to obtain a Iine of position. The Hydrographic Office of the ITavy has published a volume entitled The membership of the subcommittee on nleteoro- ‘t Position Tables for Aerial and Service Navigation” Iogical problems is as follows: (H. O. IJo. 209), which may be preferred to the now Prof. ~arks F. bfarvin, lVeather 13ureau, wideIy used Navigation TabIes for 31ariners and Ati- chairman. ators (H. O. No. 208). A new type of sextant, which ~. R. Gregg, TVeatherBureau. REPORTNATIONALADVISORYCOMMITTZEFORAERONAUTICS 45

Dr. TV.J. Hmuphreys, TVeather Bureau. doctig, and navigation is di&ult. The discussion Dr. J. C. Hunsaker, Goodyear-Zeppelin Corpora- at the joint meet~~ of the two subcommittees was tion. helpful in that each group was thus enabled to visual- George V?. Lewis, National Advisory Committee ize more cIearIy than before the problems of the for Aeronautics (ex offico member). other dnd, therefore, to approach them with a more Lieut. F. TV. Reichelderfer, United States Xavy, dednite line of attack. In this connection it -wasan- .— hlaval Air Stution, Lakehurst. nounced that the ‘Weather Bureau had established a Dr. C. G. Rossby, 31assachusetts Institute of station at A.lmon and that special investigations are Teckmology. being pIanned there. The location of this station is Eugene Sibley, aeronautics branch, Department excellent for the purpose, since it will be possible for of Commerce. studies to be made joiutIy by meteorologists and air- Capt. Bertram J. Sherry, United States Amy, ship designers. Si5gnalCorpsl war Department. Announcement was made aLw that investigation of --— The principal agency engaged in the study of the problem will be continued at Lakehurst. ,.= meteorological problems as related to air navigation Vertical & owrrents.-Brief reports were submit- is the weather Bureau. However, practically every ted regarding in~estigations of vertical air currents -— organization concerned with the operation of aircraft by the Bureau of Aeronautics in connection with is interested in probIems of this nature, and studies glider operation; and in Europe by means of a bal- along this line hare been conducted by the Signal loon and two theodolites. Corps and Air Corps of the Army and the Bureau Meteorological suruey8 related to tnmatlantic fZy- of Aeronautics of the Navy in connection with the ing.—Reports were made concerning two fairIy ex- operation of aircraft. haustive studies on this general subject that have The work of this subcommittee du~m the past year been made during the pass year by the Goodyear- -wasconcerned chiefly -ivith problems connected with Zeppelin Corporation, in cooperation with the the navi~-tion of lighter-than-air craft, although Weather Bureau. The purpose of one was to deter- some of them apply, in a measure, to heavier-than-air mine the probable average annual number of trips craft also. that couId be made on schedule each way across the Wind gusiiness.-The subject that recei-red most Atlantic by airship; the average time required; and attention vras that of wind gustiness. At a meeting the probable number of deIayed and canceIed trips. of the subcommittee held in lVashington on January This study was based on a 5-year series of ocean 10, 1931, reports were submitted giving the results of weather maps. investigrttions of this problem that had been carried The purpose of the other stud-y was to determine on for more than a year at the weather Bureau in the best site, meteorologicdlyt for a commercial air- ‘Washington and at the Lakehurst Naval Air Station. ship base on the North. to Middle AtIantic seaboard. This meeting -washeld jointiy with the subcommittee This study is being continued. It is based in part cm airships of the committee on aerodynamics. The on severfl years? data, already available, and in part reports showed that considerable data hare been ac- on special local data now being secured at the precise cumulated and in part analyzed. but that the applica- locations under consideration. It is expected that this - tion of the results to the problems of airship mooring, survey will be completed within the next year. PART IV TECHNICAL PUBLICATIONS OF THE COMMITTEE

The Ifationrd Advisory Committee for Aeronautics 282; the fourteenth annual report, Nos. 283 to 308; – has issued technical publications during the past year the fifteenth rmnual report., Nos. 309 to 336; the six- covering R wide range of subjects. There are four teenth annual report, Nos. 337 to 361; and since the series of publications, namely, technical reports, tech- preparation of the sixteenth annual report fur the year nical notes, technical memorandums, and aircraft cir- 1930.fie committee has authorized the publicdion of cuIars. the following technical reports, Nos. 365 to 400: The technical reports present the rasults of funda- mental research in aeronautics carried on in different Report iVo. 366, entitled “ Aerodynamic Characteris- Laboratories in this country, irduding the Langley tics of Circular-Arc Airfoils at High Speeds,” by L. J. Briggs and H. L. Dryden, Bureau of Shmd- Memorial Aeronautical Laboratory, the aerodynamical laboratory at the Vlashington Navy Yard, the Bureau ards. of Standmds, the YTeather Bureau, Stanford Uni- The aerodynamic characteristics of eight circular- versity, and the MassachusettsInstitute of Technology. arc airfoils at speeds of 0.5, 0.65, 0.8, 0.95, and 1.08 In all casw the reports were recommended for publi- times the speed of sound liave been determined in an cation by the technical subcommittees having cogni- cpen-jetmir stream 2 inches in diameter, using models zance of the investigations. During the past year 39 of l-inch chord. The lower surface of each oirfoil technical reports were submitted for publication. was plane; the upper surface was cylindrical. As - Technical notes present the results of short research compared with the measurements described in N. A. investigations and the results of studies of specific C. A. Technical Report No. 319 (reference 1), the detail probIems which form parts of long investiga- circular-arc airfoils at speeds of 0.95 and 1.08 times tions. The committee has issued during the past the speed of sound are more efficient thun nirfoils 01 year, in mimeographed form, 44 technical notes. the R. A. l?. or Clark Y fwuilics. At a speed of 0.5 Technical memorandums contain translations and times the speed of sound, the thick circuhm-arc sec- reproductions of important foreign aeronautical arti- tions are extrwneIy inefficient, but thin sections corn- _ cles of a miscellaneous character. A total of 55 tech- pare favorably with those of the ~. A. l?. fwnily. A nical memorandums w-asissued during the past year. moderate rounding of the sharp edges changes k Aircraft circulars contain translations or reproduc- characteristics very little and is in n-my instances tions of articIes descriptive of new types of foreign benedcial. The results indicate that the section of the aircraft. During the past year 2.5 aircraft circuIars blades of propellers intended for use ahhigh tip speeds were issued. should be of the circular-arc form for the outer part Summaries of the 39 technical reports and lists of of the blade and should be changed gradually to the the technical notes, technical memorandums, and air- R. A, F, or Clark Y form as the hub .is approached. craft circulars follow.: Report ZVo.866, entitled “ Dyminic and Fligh~ Tests SUMMARIESOF TECENICALREPORTS on Rubber-Cord and OIeo-Rubber-Disk I.anding Gears for an IWY7-j AirpIane/’ by TVilliam C. peck, The First Annual Report of the National Ad~isory National Adtisory Committee for Aeronautics. Committee for Aeronautics for the fiscal year 1915 -. contained Technical Reports Nos. 1 to T; the second The investigation described in this report \Ynscon- annuaI report, ?!Tos.8 to 12; the third annual report, ducted for the purpose of comparing an oleo-rubber- Nos. 18 to 23; the fourth annual report, Nos. 24 to 50; disk and a rubber-cord landing gear, built for use on the fifth annual report, Nos. 51 to 82; the sixth annual an PBO–-# airplane. The investigation consisted of - report, Nos. 83 to 110; the seventh annual report, Nos. drop tests under various 16ading conditions and flight _ 111 to 132; the eighth annual report, Nos. 133 to 158; tests on an 176U-4 airplane. Ik the drop teks the the ninth annual report, Nos: 159 to 185; the tenth an- total work done on each gear and the work done on nual report, Nos. 186 to 209; the eleventh annual re- each of the shock-absorbing units were determined. port, Nos. 210 to 232; the twelfth annual report, Nos. For both drop tests and flight tests the maximum 233 to 256; the thirteenth annual report, ~os. 25?’ to loads and accelerations were determined. 40 REPORTNATIONALADVISOBY00~ FORAERONAUTICS 47

The comparative results showed that the oleo gear This investigation was made for the purpose of was slightly superior in reducing the ordinary land- obtainirg information on the maneuverability of the ing shocks, that it had a ~greatercapacity for work, F6C% fighter airplane. It is the first in a series of and that it was very superior in the reduction of the similar inwsstigations under way on a number of mil- — rebound. The results further showed that for drops itary airpIanee for the purpose of comparing the abil- “” comparable to very severe landin~, the rubber-corcl ities of these airplanes to maneu~er, and also to estab- gem was potentially more effective as a shock-reducing lish a fund of quantitative data which may be used in forrnrdat~u standards of comparison for rating mechanism. However, due to the construction of this — chsssis~which limited the maximum elongation of the the maneuverability of any airplane. A Iarge part corik, this gear -was incapable of -withstanding as of this initial in-re.stigation was necessarily devoted severe tests M the oleo gear. The action of the ohm to the de-relopment and trial of methods suitabIe for gear during the tests tvasgreatly inferior to the action use in subsequent investigations of this nature. of an ideal gear. The maximum accelerations en- h speed, anatiar velocity, linear acceleration, and .— countered during the fight tests for severe landings position of the control surfaces were measured by were 3.64g for the rubber-cord gear and 2.27g for the instruments in the airpIane during loops, push-downs, 01s0 gear. These mere less than those experienced in pull-outs from dives, puI1-ups from level flight, barrel —— free drops of’7 inches on either gear. rolls, and spins. The coordinates of the flight paths were deduced from the data whenever possible, and 12eportLYO.W’, entitled “ Pressure Distribution Over were checked in some cases by the uss of a camera a Thick, Tapered and Twisted JIonopIane TTi~~ obscura. The results are given in curves showing the 310cleI-N. A. C!. A. 81-J: by Carl J. Ti’enzingerj variation of the measured quantities vvith respect to AVational Advisory Committee for Aeronautics. time, and maximum values are tal.ndated. This report presents the results of pressure distri- bution tests on a thick, tapered and twisted mono- Report lVo. 370, entitled, u Effect of Variation of plane wing model. The investigation was conducted Chord and Span of Ailerons on Hinge Moments at --- ..— for the purpose of obtaining data on the aerodynamic Sewmd Angles of Pit~’ by B. H. Moniah, Bureau characteristics of the new wing and to pro~ide addi- of Standarik. tional information suitable for use in the design of This report pr=ente the results of an investigation tapered cantilever wings. The tests included angles of the hinge moments of ailerons of various chords of attack up to 90° and mere made in the committee’s and spans of two airfoils havi~u the Clark 1“ and ..— 5-foot atmospheric wind tunnel. U. S. A. 27 wing sectio~c, supplementing the investi- The span loading o-rer the wing was approximat.dy gations described in references 1 and 2, of the rolling of elliptical shape, which gave rise to relatively small and yawing moments due to similar ailerons on these ,. bending moments about the root. The angle of zero two airfoil sections. — Iift for aIong the span varied only within aLlsections The measurements -weremade at various angles of .— &0.4! of the angle of zero lift for the -whole wing, pitch, but at zero an@e of roll and yaw, the wing rewdting in small leading e~~e loads for the high- chord being set at an angIe of + 4“ to the fuseIage ..- speed condifion of fhght. The results aIss &dd to the axis. In the case of the Clark Y airfoil the measure- available information for the study of stability at. ments have been extended to a pitch angle of 40°, -— large angks of attack. using ailerons of span equal to i?7per cent of the -wing Report No. S68, erititled “A New Chart for Eeti- semispan and chord equal to 20 and 30 per cent of rnating the Absolute Ceiling of an Airplane,” by the wing chord. IValter S. Diehl, Bureau of Aeronautics, Kav-y The work was done in the 10-foot tunnel of the Department. Bureau of Standards on models of 60-inch span and 10-inch chord, having square tips, no taper in pIan This report is concerned with the derivation of a form or thickmw, zero dihedral, and zero sweepback chart for estimating the absolute ceiling of an air- plane. This chart may be used in conjunction with Report No. 971, entitled “ Present i%atus of Air- the usual cur-m of power required and power avail- craft hstruments,” prepared by subcommittee on abIe as an accurate substitute for extended. calcula- instruments, National Advisory Committee for tion, or it may be used in the estimation of absolute Aeronautics. ceiling when power curves are not available. This report gives a brief description of the present Report No. $69, entitled “ Maneuverability Investiga- state of development and of the performance charm- .— tion of the F6G-3 Airplane with Special Flight teristics of the instruments included in the following Instruments by C. H. Dearborn and H. ~. group : IIirschbaum, National Advisory (!ommittee for 1. Speed instruments. Aeronautics. 2. Altitude instruments. 48 FWPORTNATIONALADVISORYCO~EE FORAERONAWIW2S

8. I?avigation instruments. at which it propagates itself within the gases, thus 4. Power-plant instruments. e.ilecting their transformation. This is because wing tip. The shock-reducing qualities, under severe tests, Report No. 380, entitled “ Pressure Distribution over and the ~ergy-iiissipating characteristics of the tires, the l?useIage of a PIV# Pursuit AirpIana in under all tests, were poor. The latter was evidenced Flight”, by Richard V. Rhode and Eugene E. Lund- by the rebound present in all landings made.. In th~ quist, Natiomd Advisory Committee for Aeronautics. severe drop tests the free rebound reached as much as 60 per cent of the free drop. This report presents the results obtained from pres- The results indicate that a shock-reducing and cn- sure distribution tests on the fuselage of a HP-4 pur- er=~-dissipating mechanism should be used in con- suit airpIane in a number of conditions of flight. The junction with airwheels. investigation was made to determine the contribution of the fuselage to the total lift in conditions con- li!epop~iVo. 38f?,entitIecl“ Elastic Instability of illem- sidered critical for the wing structure, and also to bers Having Sectious Common in Aircraft Con- determine whether the fuselage loads acting simul- struction~’ by George IV, Trayer rind H. TV.March, hmeously with the maximum tail Iods were of such Forest Products Laboratory. u character as to be of concern with respect to the Two fundamental problems of elastic sttibility are structural design of other parts of the airplane. disc~ed in this report. In Part I formu]ns am The results she-wthat the contribution of the fuse- givegf or calculating the critical stress at which a — lage toward the total lift is small on this airplane, thin, outstanding fIange of a compression member ranging from slightly less than 8 per cent at the lower will either wrinkle into several wavas or form into angles of attack to about 4 per cent at the higher a singIe haIf wave and twist the member about its angks, which approximately compensates for the por- longitudinal axis. A mathematical study of the prob- tion of the wing area replaced by the f udage. Aero- lem, which together with experimental work has led to dynamic Iods on the fuselage are, in general, unim- thesa formulas, is given in an appendix. Rcsulh. of portant from the structural viewpoint, and in most tests substantiating the recommended formulas aro cases they are of such character that, if neglected, a also presented. In Part II the Iateral buclding of conservative desiem results. In spins, aerodynamic beams is discussed., The results of a number of forces on the fuselage produce diving moments of mathematical studies of this phenomenon havo been appreciable magnitude and yawing moments of small published prior to this writing, but very little experi- ma~mitude,but opposing the rotation of the airplane. mentally determined information relating to the prob- A table of cowling pressures for various maneuvers lem has been avaiIable heretofore. Experimental is included in the report, verification of tl]e mathematical deductions is sup- plied in this report. Report ~o, 381, entitled “ Static, Drop, and I?light Tests on Mussehnan Type Airvvheels/’ by ~illiam Report 11’o. $.W, entitled ‘{On the Theory of lVing C. Peck and Albert P. Beard, National Advisory Sections with Particular ReferencO to the Lift Dis- Committee for Aeronautics. tribution:’ by Theodore Theodorsen, National Ad- The investigation described in this report was con- visory Committee for Aeronautics. ducted for the purpose of obtaining quantitative in- This report describes a simple and exact method formation on the shock-reducing and energy-dissipat- of calculating the lift distribution on thin wing sec- ing quaIities of a set of 30 by l&6 Musselman type tions. The most essential feature of the new theory nirwheels. The investigation consisted of static, drop, is the introduction of an “ ideal angle of attack;’ and flight tests. The static tests were made with in- this angle being defined as that at which the flow flation pressures of approximately O,5,10, 15,20, and enters the leading edge smoothly or, more precisely, 26 pounds per square inch and loadings up to 9,600 as the angIe of attack at which the lift at the leading pounds. The drop tests were made with inflation edge equals zero. The lift &stribution at this par- pressures of approximately 5, 10, 15, 20, and 25 ticular angle is shown to be a characteristic proporky REPORTNATIONALADVLSOBY00MMITTEEFOBAERONAUTICS 51 of the section and has been termed the Ubasic distri- oint -when compared with the method used on the bution.” It is shown that the lift of a wing section Roots or turbocentrifugal type. may al-ivaysbe considered to consist of (a) the basic Report No. 385, entitled “ wind Tunnel Tests on Air- , distribution and (5) the a&litional distribution, foil Boundary Layer Control using a Backward- where the latter is independent of the mean camber Opening Slot,” by lfiHard ~. Bamber, h’atiomd line and thus identicaI for dl thin sections. The ~dvisory Committee for Aeronautics. specific reason for the poor aemd~amic qualities of =.- thin wing sections is pointed out as being due to the This report presents the results of an investigation fact that the additional lift in potential flow becomes to determine the &ect of boundary layer control on infinite at the leading edge. the lift and drag of an airfoil. Boundary layer con- The theory is in consequence adapted to describe trol was accomplished by means of a back-ward- some of the properties of actual wi~u sections. It opening slot in the upper surface of the hollow airfoil. is established that the essential parameter occurring in Air was caused to flow through this slot by a pressure this analysis is the radius of curvature at the leading which was maintained inside the airfoil by a blower. edge The location and ma=~itude of tie mafim~ Various slot locations, slot openings, and -@g pres- lift intensity is detemnined. lt is further pointed out sums were used. The tests -were cbnducted in the that the actual slope of the lift curve is dependent committee’s 5-f oot atmospheric wind tunnel. on this parameter. The quantity of air flowing through the slot per — The theoretical lift distribution is compared with unit time -wasmeasured and is presented in coefficient the distribution obtained by direct measurement on form. A coeilicient is deri~ed from -which the power a number of the more conventional wing Sectiom required to maintain the air flow through the slot may The results check satisfactorily and may be consid- be computed. ered as a confmmation of the validity of the theory. The effect of each variable is illustrated by charac- The new theory will be of value in the further im- tmistic curms. A discussion indicating the advan- provements of airphme wings. It is pointed out that tages -which might be possible by the application of . . ‘- airplanea should be operated near the ided angle of boundary layer control to an airplane is included. — attack. The theory will also be of use in calcuIat&U A discussion of the various forces produced on the the structural strength of wing sections. airfoil by this type of boundary layer control and their resultants is given in Appendix I. Report No. 384, entitled “ The Comparative Perform- Under the test conditions, the maximuin lift coelli- ance of Superchargers,” by Oscar W. Schey, Na- .—— cient was increaeed about 96 per cent for one slot ..— tional Advisory Committee for Aeronautics. .. arrangement and the minimum drag coefficient was This report presents a comparison of superchargers decreased about 27 per cent fur another, both being “-- on the basis of the porer required to compress the compared -withthe results obtained with the undotted air at a detiIte rate, and on the basis of the net en- airfoil. It is belie~ed from the results of this investi- gine power developed at altitudes from 0 to 40,000 gation that the above effects may be increased by the feet. The instigation included geared centrifugal, use of larger .slotopenings, better slot locations, multi- tnrbine-dri-isn centrifugal, Rootsl and vane-type su- ple slots, improved airfoil profl~ and trailing edge perchargers. It also includes a brief discusson of flaps. the mechanical limitations of each supercharger and tixplains how the method of control affects the povver Report No. 386, entitled “ 31aneuverability Investiga- requirements. tion of an F6C–-$ Fighting Airplane/’ by C. H The results of this investigation show that for crit- Dearborn and E. W. Kirschbaum, National Ad- ical altitudes below 20,000 feet there is a maximum visory Committee for Aeronautics. difference of about 6 per cent between the amounts of In order to compare the relative maneuverability of net engine power developed by the various types of two fighting airplanes and to accumulate additional superchargers -ivhenideal methods of control are em- data to assist in establishing a satisfactory criterion .— ployed, but for critical altitudes above 20,000 feet an for the maneuverability of any airplane, the National engine de~elops considerably more povier vihen Advisory Committee for Aeronautics, at the requeit . equipped with a turbocentrifugal supercharger than of the Bureau of Aeronauticsj Navy Department, has with any other type. The Roots type gives the loviest conducted maneuverability instigations on the net engine power of all at high critical altitudes, be- F6C=3 (water-cooled engtie) and the F6C–4 (air- cause it has the lewt efllcient type of compression. cooled en=gine) airplanes. The investigation made on The throttling method of control ussd on the gearecl- the F’6C-9 airplane has been previously reported. — centrif~~al type of supercharger is very unsatisfac- This report contains the results of the investigation tory at low altitudes from a net engine-power standp- made on the F6C–4 airplane. 52 REPORTNATIONALADVISORYCOMMITTTMFOBAERONAUTICS

Measurements of air speed, angular velocity, linear It was established that the temperature dependency acceleration, temperature, pressure, and the position of the stiffness was due to difference in the Lhermal of the controls were made for practically all the kinds expansj_vity between the diaphragm proper and the of military maneuvers required of this type of air- supporting body of the cell, and convenient methods. phme. Flight path coordinates were secured for most for its compensation have been developecl. The dia- of the maeuvers by means of a special camera obscura phragm is furnished with a small centrnl hushing developed for this investigation, The results are of a differentmnetal, and it is possible to determine n given in the form of curves, some showing the varia- size of this bushing which gives the diaphragm exactly tion of the measured quantities with respect to time; the same thermal expansivity as the cell body. others, the variation of some maximum quantities It was further established that the intwmd hyster- with respect to air speed. In addition, all maximum esis in the diaphrabg-nwas of a negligible magniludc quantities are tabulated. and that the observed Iag was due, primmily, to the A comparison of the resuks with those obtained in force of the hairspring on the stylus point. The re- the investigation conducted on the F6C-S airplane sultant acloption of weaker hairsprings rnadc it pos- shows that: With practically the same speed and con- sible to extend the useful range of the instrument trol movement, the F6C-4 completed a loop in 10 per considerably downward. Satisfactory instruments cent less time than did the F6C’-3; in dives the F6C-3 having n range of less than 3 inches of wutcr were increased its speed more rapidly than did the F6C–4; made possible. and the minimum radius of turn was found to be 135 It was found that the tendency to change calibra- feet at 61.5 miles per hour for the F60–.4, and 155 feet tion with time was caused, to a great extintj by in- at 70 miles per hour for the F6C-3. sufficient clamping of the diaphragm. The adoption of double copper gaskets improvecl this condition. Report No. 387, entitled “ The Vertical Wind Tunnel The required diaphragm thickness and the desirable of the National Advisory Committee for Aeronau- rate of mechanical maamification have been deter- tics’ by Carl J. Wenzinger and Thomas A. Harris. mined on the basis of several hundred tests. National Advisory Committee for Aeronautics. The vertical open-throat wind tunnel of the com- Report iVo. 389, entitled “ The Effec&of Srndl Angles mittee is described in this report. The tunnel was of Yaw and Pitch on the Characteristics of Air- built mainly for studying the spinning characteristics plane Propellers,” by Hugh B. Freeman, National of airphme modek, but may be used as well for the Advisory Committee fur Aeronautics. usual types of wind-tunnel tests. A special spinning The tests desclibed in this report were carried out balance is being developed to measure the desired in the committcc’s 20-foot propeller research tunnel forces and moments with the model simulating the to deteimine the effect on the characteristics of a actual spin of an airplane. propeller of inclining the propeller ffxis nt small Satisftictory air flow has been attained with a veloc- angles to the relative -wind. Tests were mm.lc of u ity that is uniform over the jet to within Y 0.5 per full-scale propeller and fuselage combimition rtt four cent. The turbulence present in the tunnel has been angles of yaw (0°, + 5°, + 10°, and + 15°), and of n compared with that of severaI other tunnels by means moclel propeller, nacelle, and wing combination at five of the results of sphere drag tests and was found to tinglesof pitch (–5°, 0°, +5°, +10°, and +150). average well with the values of those tunnels. In- The reeuks of the full-scale tests of a propeller ml cluded also in the report are comparisons of results of fuselage, without a wing, show that the effect on the ‘– stable autorotation and of rd.ing-moment tests ob- propeller performance is small, Similar results arc tained both in the vertical tunnel and in the old shown by the model test data except that where the horizontal 5-foot atmospheric tunnel. propeller is directly in front of the wing there is an l?epo~t No. 388, entitled “ Investigation of the Dia- appreciable decrease in effective thrust and propulsive phragm-gpe Pressure Cdl,” by Theodore Theo- efficiency with increase of angle of pitch. c?orsen, h7ational Advisory Committee for Aero- Report No. WO, entitled “ The Effect of Val-re Timi ng nautics. upon the Performance of a Supercharged Engine This report relates to various improvements in the at Altitude and an Unsuperchargecl Engine at rJrOCW of manufacture of the N. A. C. A. standard Sea Level,” by Oscar W. Schey and Arnold pressure cell. Like most pressure-recording devicw E. 13iermann, National Advisory Commitleo for employing thin diaphragms, they would in general Aeronautics. show considerable change in calibration with tempera- The investigation described in this report was con- I ture and also some change of calibrmtion with time or clucted to determine the comparative effects of valvc aging eilect. Some instruments exhibited considerable timing on the performance of an unsuperchtwged en- internal friction. gine at sea level and a supercharged engine at alti- REPORTNATIONti ADVISORYCOMMITTEEFOEAEEONAWI!K?S 53 tude. The tests mere conducted on the N. A. C. A. tion in the entrance cone, with the honeycomb at the .- Universal test engine. The timing of the four ~alve extreme entrance end. events was varied over a wide range; the engine speeds The mcmsurementsof turbulence were made by the were varied between 1,050 and 1,60Urevolutions per uss of spheres and also by the use of the hot wire minute; the comprtion ratios were varied between anemometer as described in reference 5. .4.35:1 and 7.35:1. The conditions of exhaust pressure and carburetor pressure of a supercharged engine were Report No. S93, entitled “ Span-Load Distribution as simulated for altitude between Oand 18,000 feet. The a Factor in StabiIity in Roil,’Y by Montgomery ~ght and Richard W. Noyes, National Advisory results she-ivthat optimum valve timing for a super- charged engine at an altitude of 18,000 feet differs Committee for Aeronautics. slightly from that for an unsupercharged enagineat This report gives the results of pressure-distribution sea level. A small increase in power is obtained by te~~ made to study & efi~b on lateral stability of using the optimum timing for 18,000 feet for altitudes chang~o the span-load distribution on a rectangular — above 5,000 feet. The t&ing of the intake opening monoplane w~m model of fairly thick section. Three find exhaust closing becomes more critical as the com methods of changgng the distribution were employed: pression ratio is increased. Variation in profile along the span to a thin symmetri- cal section at the tip, twist from + 5° to —lfi” at the Report LYo.S91, entitled “The Aerodynamic Charac- tip, and smepback from +20° to –20°. The tests teristics of Eight Very Thick Airfoils from Tests -wereconducted in the committee’s 5-foot closed-thoat in the Variable Density lTGnd ‘llmnel~) by East- atmospheric wind tunneL man hl. Jacobs, h’ational Advisory Committee for ‘ The rolling moment due to roll at a rate of rotation Aeronautics. equivalent to that resulting from the maximum rolling This report describes tests made in the committee’s dissurbanceg encountered in normal flight is USedss variabledensity wind tunnel on a group of e&ht very the principal basis of comparison. Normal force thick airfoils having sections of the same thickness curves are given for the purpose of cxstimatiqg the as those used near the roots of tapered airfoils. The general tiectiveness of each V@ arrangement. tests were made to study certain &continuities in the The irmestigation shows the following outstanding .__.— characteristic curves that ha~e been obtained from results: prerious tests of these airfoils, and to compare the L C~~e in pro~e along the span from the N. A. .— characteristics of the different sections at Yalues of C. A. 84 at the root to the N. A. C. A.-M2 at the the Reynolds Number comparable with those attained tip considerably reduces lateral instability, but also in flight. The discontinuities vvere found to dkap- reduces the general effectiveness of the wing. .— pear as the Reynolds Number was i.ncreass The re- 2. Washout up to 11° progressively reduces Iuasi- dts obtained from the large-sale tests in this .wries mum lateral instability. indicate that the N. A. C. A. 0021airfoil! a.symmetrical 3. Transition from sweepforward to sweepback --— airfoil having a thicknem ratio of 21 per cent, has the gradually reduces the USsful angle-of-attack range, best general characteristics. but has no clearly defined effect on maximum IateraI instability. Report A’o. 3921,entitled “ Reduction of Turbulence in ‘Wind Tunnels< by H~~h L. Dryden, Bureau of Report No. 394, entitled “Airship 310del Tests in the Standarda. Variable Density Wind Tunnel:’ by Ira H. Abbott, A brief nonmathematical outline is ghen in this LTationalAdvisory Committee for Aeronautics. report of modern views as to the nature of the effect This repmt describes an investigation of the aero- of turbrdence?and their bearing on the desirnbility of dynamic characteristics of airship models made in designing wind tunneIs for small or large turbulence. the committee’s variable-density wind tunnel. Eight Experiments made on a particular wind tunnel for Goodyear-Zeppelin airship models, supplied by the the purpose of reducing the turbulence are described, Bureau of Aeronautics of the Navy Department, were “ to illustrate the influence of certain factors on the tested in the original closed-throat tunnel. After the magnitude of the turbulence. Moderate changes in tunnel was rebuilt -with an open throat a new model .— the size, shape, and vvdl thickm%sof * of the w-astested, and one of the Goodyear-Zeppeh models honeycomb were found to ha~e little effect. The ad- was retested. These tests were made at tank pres- ..— dition of a room honeycomb at the entrance waa also sures varying from 1 to 20 atmospheres, and the ex- .— of little value in reducing the turbulence. The tur- treme range of Reynolds Number was about 1,000,000 bulence decreased with increasing distance between to 40,000,000. The Iift, drag, and moment coefi~ents the honeycomb and the measur~~ station. A further of the models were determined, and the effects upon decrease -was obtained by using a large area reduc- them coefficients of pitch, fineness ratio, scale, surface 54 REPORT NATIONAL ADVISORY C10MM17XCEE FOR AERONAUTI(YS texture, initial degree of air-stream turbulence, and li?epo~tNo. 396, entitled “ Hydraulics of Fuel Injec- the effects of the addition of fins and cars were in- tion Pumps for Compression-Ignition Engines;’ by vestigated. The resulting curves are included. A. M. Rothrock, National Advisory Committee for The reedts show that the addition of fins and car Aeronautics. to the bare hull of a model causes an increase in lift In this report formukis are derived for computing at positive augles of pitch and causes an additional the instantaneous pressures delivered by a fuel pump. drag which increa&s with the pitch. Little change The first-derivation considers the compressibility of in drag coefficient was found between a fineness ratio the fuel and the second the compressibility, elasticity, of about five and seven. The effect of surface rough- and inertia of the fuel. The second derivation fol- ness on drag was found to be very large. The drag lows that given by Sass; it is shown to be the more coeilicient and the apparent effect of scale depend accurate of the two. Additional formulas me given upon the initial degree of air-stream turbulence. The for determining the resistance losses in the injection results indicate that much may be done to determine tube. Experimental data are presented in support of the drag of airships from evaluations of the pressure the analyses, The report is concluded with an appli- and skin-frictional drags on- models tested at large cation of the theory to the design of fuel-putnp injec- Reynolds Numbers. tion systems for -which sample calculations are li?eportNo. 396, entitled “A New Principle of Sound- included. Frequency Analysis/’ by Theodore Theodorsen, Na- Report No. 337, entitled “ The Drag Characteristics of tional Advisory Committee for Aeronautics. Several Airships Determined by Deceleration In connection with a study of aircraft and propeller Tests?’ by F. L. Thompson and H. W. lIirschbaum, noises, the committee has developed an instrument for National Advisory Commit&e for Aeronautics. sound-frequency analysis which differs fidamentally The results of decelcrntion tasts conducted for tho from previous types, and which, owing to its simplic- purpose of determining the drag characteristics of ity of principle, construction, and operation, has six airships are given in this report. Tie t&~ -ivero proved to be of value in the investigation described made during the past few years with airships of va- in this report. The method is based on the -well- rious shapes and sizes belonging to the Army, tho knovrn fact that the ohmic 10ss in an electrical Navy, ”and the Goodyear-Zeppelin Corporation. In resistance is equal to the sum of the hsses of the each instance the agency owning the airship coop- harmonic components of a complex wave, except for erated with the hTational Advisory Committee for the case in which any two componenkrapproach or Aeronautics in conducting the tests. Although the attain vectorial identity, in which case the ohmic loss deceleration tests with the U. S. S. Loa Angeles have M increased by a definite amount. This fact has been been previously reported, the final results obtuincd utilized for the purpose of frequency analysis by with that airship are included in this report for applying the unknown complex voltage and a known comparison. voltage of pure sine form to a common” resistance. Drag coefficients for the fallowing airships arc By varying the frequency of the latter throughout ehown: Army TO-O, TG1O, and TE+?; Navy L08 the range in question, the individual components of Angeles and ZilfC-g; Goodyear Puritan. The coelE- the former will manifest themselves,both with respect cients vary from about 0,045 for the small blunt air- to intensity as -weI1as frequency, by changes in the ships to 0,023 for the relatively large slender Los temperature of the resistance. This principle of fre- AngeZe8. This variation may be due to a comMnation quency analysis has been presented mathematically of effects, but the most important of t.hwe is probably and a number of distinct advantages relative to pre- the effect of length-diameter ratio. vious methods have been pointed out. Among these is the fact that the frequency discrimination or Report No. $98, entitled “ investigation of Damping resolving power is inherently large and remains con- Liquids for Aircraft Instrumen&II,’} by 11, R. stant for the entire working range. No diiliculties “Houswnan and G. H, Keulegrm, Bureau of exist as to distortions of any kind. The fidelity of Standards. operation depends solely on the quality of the associ- This report presents data on the kinematic viscosity ated vacuum-tube equipment. in the temperature range –50° to +30° C., of pure An automatic recording instrument embodying thk liquids and of solutions of animal oik, vegetable oils, priniiple is deserted in detail. It employs a beat- mineral oils, glycerine, and ethylene glycol in various frequency oscillator as a source of variable frequency. low freezing point solvents. It is shown that the A large number of experiments have verified the pre- thermal coefficient of kimematicviscosity as I function dicted superiority of the method. A number of of the kinematic viscosity of the solutions of glycerine representative records are presented. and ethylene glycol in alcohols is practically inde- RRPORT NATIONALADVISOEY00MIUITTREFOBAERONAUTICS 55 pendent of the temperature and the chemical compo- w~~. Hovrever, with one slot position, an increase of sMon of the individual liquids. This is Similarly true 25°, together with an increasa in the maximum lift -- for the mineral-oil group ‘=md,for a limited tempera- coet%cient of 23.3 per cent, was obtained. The best ture interval, for the pure animal and vegetable oils. positions of the auxiliary airfoil -werecovered by the The ticiency of ~-naphthol, hydroquinone, and di- range of the tests, and the position for desired aero- .— . phenylamine to inhibit the change of viscosity of dynamic characteristics may easily be obtained from .- poppyaeed and linseed oils was aIso investigated. charts prepared especially for the purpose. Report iVo. 399, entitled “ Flame lfovement and Pres- LIST OF TECHNICAL NOTES ISSUED DURING THE .—== sure Development in an Engine C1-ylinder/’ by PAST YEAR .— Charles F. 31arvin, jr., and Robert D. Best, Bureau 3%0. 31ethods for the Identi6cation of Aircraft Tub- of Standards. —. ing of P1ain (2arbon Steel and Chromium- The investigation described in this report, which JIolybdenum Steel. By ~. K ~utchler and was carried out at. the Bureau of Standards at the R. TV.Buzzard. request of the h’ational Advisory Committee for ~ero- 351. An Accurate 31ethod of ~easuring the lioments .. .— nautics, presents a visual method for makirg strobo- of tiertia of Airplanes. By 31. P. 31iller. scopic observations, through a large number of small 152. Effect of Oriiice Length-Diameter lhtio on Spray . windows, of the spread of flame throughout the com- Characteristics. By A. G. Gelalks. bustion chamber of a gasoline engine. Datal secured 353. Analytical Determination of the Load on a TraiL by this method on a small engine burning gaseous ing Edge Flap. By Robert X Pinkerton. fuels, are given to show the effects of mixture ratio, 354. .ti Investigation of the Phenomenon of Separa- — spark advance, engine speed, charge density, degree tion in the Air Flow hound Simple Quadric of dilution, compression ratio, and fuel composition Cylinders. By John F. Parsons and Jru-visA. on flame mo-iement in the cylinder. Partial indicator lYaLlen. diagrams showing pressure development during the 355. Effect of the kgular Position of the Section of combustion period me included. Although present a Ring Cowling on the High Speed of an knowledge is not .d3icient t.opermit qualitative evacu- ..— X~lG–1 Airplane. By 31elti F1.Gough. _ ation of the separate effects on flame movement of 356. Some Characteristics of Fuel Sprays frcim Open chemical reaction velocity, thermal expansion of h’ozzles. By A. 3L Rothrock and D. ‘W. Lee. burned @ws, resonance, turbulence, and piston move- 357. Bending Tests of hletal 310nocoque Fuselage .- ment, the qualitative infhence of certain of these fac- Construction. By Ralph ~. 3fossman and tors on some of the diagrams is indicated. Russell G. Robinson. Report No. 400,entitled UThe Aerodynamic Charac- 358. Experiments with a Ilodel water Tunnel. By terstices of a slotted Clark Y Wing as Affected by Eastman 2J.Jacobs and Ira K Abbott. the Auxiliary Airfoil Position/J by Carl J. Wen- 359. A Balanced Diaphragm Type of Jkcimum Cyl- zinger and Joseph A. Shortal, National Advisory inder Pressure Indicator. By J. ~. Spanogle Committee for Aeronautics. and John K Cobs. Aerodynamic force teets on a slotted Clark Y wing 360. The Pressure Distribution Over a Square ‘iViig Tip on a Biplane in Flight. By Richard V. described in this report, -were conducted in the com- Rhode and Eugene E. Lundquist. mittee’s vertical wind tunnel to determine the best position for a given auxiliary airfoil with respect to 361. The Effect of Small Vm.iations in Profile of Air- the main fig. A systematic series of 100 changck in foils. By Kemeth E. ward. location of the auxiliary airfoil were made to cover 362. IXft and Drag Characteristics of a Cabin Lf.ono- .- all the probable useful ranges of slot gap, slot width, plane Determined in Flight. By F. L. Thomp- and slot depth. The results of the investigation may son and P. H. Keister. be applied to the design of automatic or controlled 863. The Behavior of Conventional &rplanes in Sib .- slots on wings with geometric characteristics similar uations Thought to Lead to ktost Crashes. By to the w~~ tested. Fred E. ~tiCk. An increase of 4L5 per cent in the maximum lift 364. ”Tests in the Variable Density wind Tunnel to above that of the plain wing was obtained for the Investigate the Effects of Scale and Turbu- slotted Clark Y wing. At the same time, the angle lence on Airfoil Characteristics. By John of attack for maximum lift was increased lfl”. It Stack. was found that a maximum increase of about 30° was 365. Interference Effects and Drag of Struts on a possible in the highest sta.Iling angle, but at a maxi- hionoplane ‘iV&u. By Kenneth E. ‘Ward. mum lift coefEcientslightly less than that of the plain 366. Torsion in Box ~ings. By John B. ~heatley. 56 EEPOILT NATIONAL ADVISORY COMMJ.TTEE FOR AERONAUTICS . &. The Aerodynamic characteristics of Three Ta- 3&, Effect of Nose Shape on the Characteristics of pered Airfoils Tested in the Variable Density Symmetrical Airfoils. By Robert M. Pinker- Wired Tumel. By”Raymond F. Anderson. ton. 368. The Variation in Pressure in the Cabin of an 387. The Pressure Distribution Over a Modified El- Airplane in Flight.. By Melvin N. Gough. liptical Wing Tip on a Biplane in F1ight. By 369. Effect of Orifice I&@h-Diameter Ratio on the Richard V. Rhode and Eugene E. Lundquist. Coefficient of Discharge of Fuel-Injection No;- 388. A Comparison of the Aerodynamic Character- zles, By A. G. Gelalles and E. T. Ma~h, istics ~f Three h70rmal and Three Reffexcd 370. Strength Tests on Paper CyLinders in Compres- Airfoils in the Variable Density Wind Tun- sion, Bending, and Shear. By Richard V. nel, By George L. DeFoe. Rhode and Eugene E. Lundquist. 3891The N. A, C, A. Apparatus for Studying the l?or- 371. Experiments with an Airfoil Mode] on Which the mation and Combustion of Fuel Sprays and Boundary Layer is Controlled without the Use the Results from Preliminary Tests. By A. of Supplementary Equipment. By “I. H. Ab- M, Rothrock. bott4 390, A Method for Reducing the Temperature of Ex- 372. Development of an Impinging-Jet l?uel-lnjec- haust Manifolds. By Oscar W. Schey and tion Valve Nozz.Ie. By J. A. Spanogle and Alfred W. Young. G. T. Hemrneter. 391.-Tests of N. A. C. A. Airfoils in the variable Den- 378. Investigation of the Discharge Rate of a Fuil- sity Wind Tunnel, Series 43. and 63. By Injection System. By Harold C. Gerrish and Eastman N. Jacobs and Robert M. Pinkerton. Fred Voss. 392, Tests of N. A. C. A. Airfoils in the Variable Den- 374. Preliminary Study of AppIied Load Factors in sity Wind Tunnel. Series 45 and 65. By Bumpy Air. By Richard V, Rhode and Eu- Eastman N. Jacobs and Robert 31. Pinkerkm. gene E. Lundquist. 393. An Investigation of Cotton for Parachute Cloth. 375. Moments of Inertia of Several Airplanes. By By Wm. D. Appel and R. K. Werner. Marvel P. Miller and Hartley A. Souhi 376. Effect of High Air Velocities on the Distribu- LIST OF TECHNICAL MEMORANDUMS ISSUED DURING THE PAST YEAR tion and Penetration of a Fuel Spray. By A. hf. Rothrock, 585. Velocity Distribution in the Boundary Luycr of 377. An Integrating Manometer for Use in Wind Tun- a Submerged Plate. By hf. Hmsen. l?rom nel Pressure Distribution Measurements. By Abhandlungen aus dem Aerodynnmischen In- Richard W. Noyes. - stitut an der Technischen Hochschule Aachcn, 378. Comparison of Weights of 17ST and Steel Tubu- No. 8, 1928. lar Structural Members Used in Aircraft Con- 586. G&Mngen Six-Component Scale Mewurenwnts struction. By E. C. Hartmann. on a Junkers A 35 Airplane Model. By IIer- 379. The Pressure Distribution Over a Semicircular mann Blenk. From Jahrbuch 1930 der Dcut - Wing Tip on a Biplane in FIight. By Rich- schen Versuchsanstalt fiir Luft fahrt. - ard V. Rhode and E~oene E. Lundquist, 587. Counter-Propellers. By Ugo de Caria. l?rom -. 380. A Suggested Method f~r .Meas@ng Turbulence. Aeronautic, June, 1930. By C, Fayette Taylor. 588. The Behm Acoustic sounder for ~irplancs with 381. Endurance and Other Properties at Low Tem- Reference tc-Its Accuracy. B~ lhmcst Schrci- peratures of Some Alloys for Aircraft Use. ber. From Jahrbuch 1930 der Deut.schenVer-” By H. W. Russell and W. A. Welcker, jr, suchsanstalt fur Luftfahrt, 882. Basic Requirements of Fuel-Injection Nozzles 589. Diesel-Engine Investigations, Ignition-Chamber for @iescent Combustion Chambers. By J. Engines. By Kurt l!feumann. I?rom Diesel- A. Spanogle and H. H. Foster. ” maschinen IV, published by the V. D. 1. l?ub- 383. Metal-Truss Wing Spars. By hdrew E. ]~hing C!O.,Berlin, 1929. Swiclmrd. 590. “Riveted Joints in Thin Plates. By W. Hilbcs. 884. The Effect of Injection-Valve Opening Pressure From JahTbuch 1929 der yVi~enschaf t.lichen on Spray-Tip Penetration. By A. M. Roth- Gesekchaft fiir Luftfahrt. rock and E. T. Marsh. 691. Ifathematical Treatise on the Recovery from a -- 385. Tests of Six Symmetrical Airfoils imthe Varia- Flat Spin. By R. Fuchs. From Jahrlmch ble Density Wind Tunnel. By Eastman N. 1929 der Wissenchaftlichen Gcsellschaf t f iir Jacobs. Luftfahrt. REPORT NATIONAL ADTZSOEY COMMITTEE FOR AERONAUTICS 57

No. 5=. Metal Covering of Airplanes By J. Mather. ing-The Stress in Uprights-Diagonal From Jahrbuch 1929 der ‘iViasenschaftlichen Tension FieIds. From Zeitschrift fiir Fhg- . GeseIIschaft fiir Luftfahrt. technik und Motarluftsahitklmt, June 14, and 593. Practical Tests with the ‘Auto Control Slot?’ June %3, 1929. By G. Lachmann. Part I: Lecture. (Paper 607. The Aerodynamic ‘iVind Vane and the Inherent read before the W. G. L., March 17, 1930.) Stability of Airplanes. By A. Lapresle. From Zeitschrift fir Flugtechnik uud Motor- From BuIletin Teehnique of the Sertices Tech- Mt.sohiffahrt, August 28, 1980. niques de L’Atronautique, Feb., 1930, No. 66. 594. Practical Tests with the “Auto Control Slot.” 608. The Use of Elektron Metal in Airphme Construc- -— By G. Lachmann. Part II: Discussion. tion. By E. L de Ridder. From Jahrbuch (Paper read before the IV. G. L., March 17, 1929 der ‘il%wnschafthhen Gesellscha.ft fiir 1930.) From Zeitsehrift & Flugtechnik tmd Luftfahrt. Motorluftachiffahrt, September 15, 1930. 609. The Production of Turbulence. By W. Tollmien. 595. English Airplane Construction. By D. Schwenc. ‘From Nachrichten der Gesellschaft der Wissen- From Zeitschrift des Vereines duetscher In- schaften zu Gottingen, Mathematisch-Physi- genieure, Aug. 2, 1930. kalische Klasse, 1929. 596. Riveting in Metal Airplane Construction. By 610. Optico-Photographic 31easurement.sof Airplane ‘WilheIm Pleines. Part I. From Luftfahrt- Deformations. By Hans Georg K&ner. forschung, Apr. 30, 1930. From Zeitschrift fiir F1ugtechnik und Motor- 597. Riveting in Metal Airplane Construction. By luftschiffahrt, Sept. 15, 1930. Wilhelm P1eines. Part II. From Luftfahrt- 611. Mechanical Similitude and Turbulence. By ‘1%. forschung, Apr. 30, 1930. v. Karman. From Nachrichten von der Gesell- 598. Riveting in Metal Airplane Construction. By whaft der Wiasenschaften zu G?ittingen, 1930. — 612. Static Longitudinal Stability of UEnte” Air- Wilhehn Pleines. Part III. From Luftahrt- . forschung, Apr. 30, 1930. planes. By Heinrich Georg KieL From Zeitschrift fur Flugte&uik und MotorMt- 599. Riveting in Metal Airplane Construction. By &ahrt, Dec. 15, 1930. Wilhelm Pleines. Part IV. From Luftfahrt- (313.Ehnira Soaring Contest, 1930. By Wolfram K. forschung, April 30, 1930. E. Hirth, Martin H. Schempp and Jack Her- 600. Resistance of Plates and Pipes at High Reynolds rick. Paper originally prepared for and at Numbers. By L. Schiller and R. Hermann. the request of the N’ational Glider ksocintion. From Ingenieur-Archiv, Sept., 1930. 614. The Transference of Heat from a Hot Plate to an 601. ‘iVrinkling Phenomena of Thin Flat Plates Sub- Air Stream. By Franz EJ.i6s. From Ab- jected to Shear Stresses. By F. Bollenrath. handlungen ma dem Aerod~amischen Insti- From Luftfahrtfor.dmng, Dec. lfi!,1929. tut an der Technischen Hochschule Aachen, 602. wrinkling of Reinforced Plates Subjected to Nov. 9, 1930. t Shear Strcxses. By Edgar Seydel. From 615. A Study of Curvilinear Flight. By Helmuth Jahrbuch 1930 der Deutschen Versuchsanstalt Kruse. From Zeits&rift fiir Flugtechnik und fiir Lufthart. Motorluftachiffahrt, Jan. 28,1931. 608. Clerget 100 h. p. Heavy-Oil Engine. By Pierre 616. Aeronautical Education and Research at the —.— IAglise. From L’A6ronautique, Nov., 1930. Swh Iistitute of Technology in Zurich. By 604. Flat Sheet Metal Ghder with Very Thin Metal L. Karner and J. Ackeret. From Aero-Reme, Web. By Herbert Wagner. Part I: General Xov. 15, 1930. — Theories and bumpt.ions. From Zeitschrift 617. Investigation of Certain Wing Shapes with Sec- f iir Flugtechnik und Motorluftachiffahrt, tions Varying Progressively Along the Span. — Apr. 29, nnd May 14, 1929. By L. Arsandaux. From L’A4ronautique, 605. Fiat Sheet Metal Girder -with Very Thin MetaI Mar., Apr., and May, 1928. Web. By Herbert lVagner. Part II: Sheet 618. Relative Economy of Different Methods of Air- Metal Girders with Spars Resistant to plane Construction. By H. Herrmann. From Bending-Oblique UprightAtiffness. From Zeitschrift fiir F1ugtechnik und bfotorluft- Zeitschrift f iir Flugtechnik und 310torMt- schiffahrt, h’ov. 14, and Nov. 28, 1930. schiffahrt, May 14, May 28, and June 14, 1929. 619. Determination of Resistance and Trimming Mo- ..— 606. Flat Sheet Metal Glrdem with Very Thin Metal ment of Planing Water Craft. By P. Schroe- Web. By Herbert Wagner. Part III: Sheet der. From Zeitschrift fiir Flugtechnik und Metal Girders with Spars Resistant to Bertd- Motorluftschiffahrt, Nov. 28, 1930. s!33m-s24 58 REPORT NATIONAL ADVISORY dOMMITTEE FOE””@OFfAUT~CS

No. 6~0. Combined Pitching and Yawing Motion of Air- 636. Experiments with Airplane Brakes. By Franz planes. By A. v. Baranoff and L. Hopf. From Michael. From Zeitschrift fiir Flugtechnik Luftfahrtforschung, Mar. 20,1929. und MotorluftschMahrt, May 28, and June 15, 621. The Take-Off of Seaplanes, Based on the New 1931. Hydrodynamic Reduction Theory. By Paul 637. The Dewlopment, Design, and Construction of Schroeder. From Zeitschrift fiir Flugtechnik Gliders and Sailplanw. By A. Lippisch. und Motorluftschiffahrt, Jan, 14, 1931. From the Journal of the Royal Aeronautical 022. Landing of Seaplanes. By Herbert Waagner. Society, July, 1931. From Zeiikchrift fiir F1ugtechnik und Motor- 638. The Dangerous Sideslip of a Stalled Airplane luftchiffahrt, Jan. 14, 1931. and Its Prevention. By Richard Fuchs and 623. Eleventh Rh?m Soaring-Flight Contest, 1930. By Wilhelm Schmidt. From Zeitwhrift ftir Walter Georgii. From Zeitschift fiir Flug- F1ugtechnik und Motorluftschiffahrt, July 14, technik und Motorluftschiffahrt, Mar. 14, 1981. 1931. 624. Landing Impact of Seaplanes. By Wilhelm 639. On Floats and Float Tests. By Friedrich See- Pabst. From Zeitschrift fiir Flugtechnik und wald, From Zeitschrift fiir Flugtechnik uncl Motorluftschiflahrt, Jan. 14,1931. Motorluftschiffahrt, May 15,1931. 625. Effect of Stabilizing Forces on Turbulence. By LIS’l?OF AIRCRAF”I’CIRCULARS ISSUED DURING L. Prandtl. From a reprint of Vortrage aus THE PAST YEAR dem Gebiete der Aerodynamic und verwandter Gebiete, Aachen, 1929. l% Wwhhmd “ Wewea” Commercial Airplane 626. The Frictionless Flow in the Region Around TWO (British). A High-Wing %.micantilever Men- __ oplane. From Flight, Oct. 3,1930. Circles. By M. Lagally. From Zeitschrift fiir “ Vimtra I” Commercial Airplane angewandte Mathematik und Mechanik, Aug., 129. Vickers 1929. (British). A High-Wing All-Metal Semican- tilever Monoplane. From Flight, Sept. 26, 627. Airplane Landing Gear. By Salvatore Maiorca. .- 1930. From L’Aerotecnica, Sept.-Ott,, 1930. 130. The Fiat “T, R. 1” Training and Touring Air- 628. Fire Prevention”“on Aircraft. By Fritz Kiihn. pla.ne (Itplian). A Two-Place High-Wing From Zeitschrift fiir Fh@echnik und Motor- Monoplane. From a pamphlet issued by the luftschiffahrt, Apr. 14, and Apr. 28,1931. Fiat Co., Turin, Italy, 629. The Dangerous Flat Spin and the Factors Af- 13L The Handley Page Type ~ Commercial Air- fecting It. By Richard Fuchs and WilheIm plane (British). A Metal Sesquiplane. From Schmidt. From Zeitschrift fiir Flugtechnik Flight, Nov. !28,1930. und Motorkfts.chiffahrt, July 14, and July 28, 132. Focke-Wulfe F M% “ Ente” Commercial Air- 1930. plane (German). A Tail-First High-Wing 630. The Steady Spin. By Richard Fuchs and Wil- Monoplane. From a pamphlet issued by the helm Schmidt. From Luftfahrtforsclmng, manufacturers, and from Flight, Jan, 2, 1?31. Feb. 27, 1929. 133. The Hanriot H .&UMilitary Airplane (French). 63L Superchargers. By Pierre L6gliee. From L’A6- A General Purpose Biplane. From a pam- ronautique, Mar., ‘and Apr., 1931. phlet issued by the manufacturers. 632. Downwash Measurements behind Wings with 184. The Amiot -L@ M Military Airplane (French), — Detached Flow. By E. Petersohn. From An .411-Metal 3fultiplace High-Wing Mono- Zeitschrift f iir Flugtecbnik nnd Motorluft- plane, From L’A&onautique, Dec., 1930. schiffahrt, May 2$, 1931. 135, The Dewoitine D, M Commercial Airplane 633. Effect of Viscosity in Speed Measurements with (French). A FGgh-Wing Cantilever Mono- Double-Throat Venturi Tubes. By H. Peters. plane. From data supplied by makers and From Zeitschrift fiir Flugtechnik und Motor- from L’A&onautique, Dec., 1980. lnftscbillahrt, June 15, 1931, 136. Lat4co&e $84? Flying Boat (French). A Long- 634. Experiments with a Wing from Which the Range Sesquiplane for Carrying Mail. From Boundary Layer is Kemoved by Suction. By Les Ailes, Jan. 1, 1931; L’A&onautique, Dec., Oskar Schran.k. From Zeitschrift fiir F1ug- 1930; and data furnished by the makers. technik und MotorluftschMahrt, May 15, 1931. 13’7. Polish P Type Single-Seat Fightem. Ail-Metal 635. The Use of Slots for Increasing the Lift of Air- ‘Gull-Type Wmg Monoplanesi From a plane Wings. By Fr. Hans. From L’A6ro- pamphlet published by the P. Z. L. (Polish nautique, June, 1931. National Aircraft Factory). REPORT NATIONAL ADVISOBY00MMITIXEFOB~ONAUTICIS 59

No. m 188. The Bleriot 11(1 Airplane (I?rench). A Long- 148. The Jlcmo-i3pa~ Light Airplane (British). A __ Distmce High-fiing ‘310nop1ane. Fro~ Twin-Engined Low-Wing Cabin Monopbne...... L’A&onautique, Dec., 1930. From The Aeroplane, July 8,1931, and Flight, 139. The Bernard L2U Seaplane (French). A 1,400 July 10,1931. h. p. Single-Seat Monoplane Racer. By Pierre 149. Breguet $90 T. Commercial Airplane (French). L4glise. From L’A6ronautique, Dec., 1930. A Ten-Seat AU-Steel Sesquiplane. From 140. The WibauIt 280 T. 10 Commercial Airplane L’A&onautique, Dec., 1930, and Lea Ailes, (French). & All-Metal Cantilever Lo-w- Apr. 28, 1931. Wing Monoplane. From Les AiIes, Nov. 27, 150. The Avro 6g7 c’Xailplane” (English). ~ Single- -—— 1930; L’A6ronautique, Dec., 1930; and data Seat Biplane. From FIight, ~ug. 14, 1931, furnished by the manufacturers. and The &ropIane, Aug. U?,1931. 141. The (7.A.M. S. 60 Seaplane (French). A T-win- 151. Breguet hliIitary Airplane, Type 39. ~ Two- Engine Bombing and Torpedo Monoplane. P1ace Long-Distance Sesqm”planefor Observa- From L’ik%cmautique, Mar., 1931, and Les tion and Bombing. From Repertoire des - Ailes, Oct. 18, 1930. Avions Louis Breguet June, 1931. 142. The Mureaux 111 l?. g Military Airplane 152. Potez iWl?2 31ilitary Airplane. A Two-Place -- (French). A Long-Distance All-Metal Ob- Long-Distance Observation Monoplane. From ..< servation Monoplane. From L’A6ronautique, Bulletin Technique des Avions H. Potez, Jan., Dec., 1930, and a pamphIet issued by the man- 1931. ufacturers. BIBLIOGRAPHYOF AEBONAllTICS 143. The S. P. 0. A. .@ T. Commercial Airplane (French). An A.U-31etaI Cantilever 310no- During the past year the committee issued a bib- plane. From L’A6ronautique, Dec., 19.30,and liography of aeronautics for the year 1929. It had data furnished by the manufacturer. previously issued bibliographies for the years 1909 to 144. The 1. A. R. Pursuit Airplane (Roumanian). A 1916, 1917 to 1919, 1920 to 1921, 1922, 1923, 1924, One-P1ace Cantilever Low-Wing 310noplane. 1925, 1926, 1927, and 1!%28. A bibliography for the By bdr6 Frachet. From Les AiIes, March 5, year 1930 is now in the hands of the printer and 1981. shouId be ready for distribution during the coming 145. The Mauboussin M 11 Touring Airplane year. A bibliography is now being published an- (French). A Two-Place High-Wing 310no- nually by the committee. All issues of the Bibliog- plane. By hdr4 Frachet. From Les Ales, raphy of Aeronautics to date were prepared by Paul Feb. 5, 1931, and data furnished by the manu- Brockett. facturers. Citations of the publications of aI1 nations are in- 146. The Dewoitine D SS Commercial Airplane cluded in the language in which the publications orig- —— (French). A Ikw-’il%g Cantilever Mono- inally appeared. The arrangement is in dictionary plane. By Pierre L4glise. From L’A6ronau- form, with author and subject entry, and one alpha- tique, May, 1931. betical arrangement. Detail in the matter of subject 147. The Bernard W G. l?. Long-Distance Airplane reference has been omitted on account of cost of pres- (French). A Two-P1ace Cantilever 3iono- entation, but an attempt has been made to give suffi- plane. By Pierre L6glise. From L’A6ronau- cient cross reference to make possible the finding of tique, June, 1931. items in special lines of research. PART v SUMMARY OF PROGRESS IN AERONAUTICAL RESEARCH

AERODYNAMICS wind tunnel which was completed last year is being equipped with a 6-component spinning bahwc for From all points of view the progress i-n aerody- fundamental investigations of spinning. A new 7 by namic development has bwm gratify ing., Work has 10 foot wind tunnel completed during the past year been done and valuable results obtained on all major Lasbeen employed on the general investigation of low- lines of research. A better and more general under- speed control. The new 30-by-60-foot full-scale wind standing of the fundamental problems of aeronautics tunnel, which was completed in May, 1931, opens an and their relative importance has led to a more de.6- entirely new field in the study of detail design, since nite program for study and testing. New equipment full-scale airplanes may be quickly tested for the ef- is now available for investigation along lines formerly fects of small structural changes affecting drag or inaccessible. The pregress during the past year has control that are not subject to accurate investigation been particularly satisfactory. by other means. It is too soon to appraise the appli- In any survey of the contributions made by the cation of this wind tunnel to steady-flight probierns, National Advisory Committee for Aeronautics tc- but preliminary tests indicate that it will be of even aerodynamic development; three general lines of greater value than originally anticipated. investigation are outstanding in importance. These The N. A. C. A. Tank, which was also complcted in are the complete justi.tication of the variable-density May, 1931, has been in operation on the calibration wind tunnel and ita valuable contributions to the of equipment and on general investigations. The tank knowledge of full-scale air forces; the contributions of has a channel length of 2,020 feet and a carriage speed the propeller research tunnel to the knowledge of- in excess of 55 miles miles per hour. With this tank propuleive efficiencies and drag components; and the it will be possible to make accurate tests on large- contributions of the flight-testing program to the size models of seaphme floats, flying-boat hulls, and knowledge of loads and load distribution in flight. other important hydrodynamic problems. Wmda- Further extension of existing information and greater mental information of this character is essentitil to refinement of existing theories are demanded for con- the development of commercial and military seaplanes tinued progress. s and of large flying boats. It is the policy of the committee to cooperate closely There follows a brief summary of the work done with the War, hTavy,and Commerce Departments and during the past year and an indication of the most conduct investigations which they request. Most of promising lines of investigation to be undertaken in the problems submitted by these departments are con- the future, cerned with the immediate needs of air commerce or Spinning,-The airplane spin is still the most im- of the military services These problems are usually portant general problem under investigation. Dur- of an urgent nature, and it ~ the committee’s policy ing the past year considerable work has been done to make these studies as parts of general investiga- on various phasea of this problem, with definite prog- tions whenever possible, and to extend the work in ress in the matter of preventing involuntary spins all cases to cover as much fundamental information near the ground. Repeated &ts have shown that m pfacticable within the limitations of time, person- an involuntary spin is practically impossible with nel, and equipment. airplanes which have the elevator control limited to The major problems with which the committee has prevent a stall. This work is being continued with been concerned may be ckwsified under the general a study of landing-gear design made necessary by groups of safety in flight, improvements in aerotiy- the limited elevator control, namic eiliciency, and improvements in design and oper- AIl phases of the steady spin have been studied in ation; Many of the problems are studied simultm~e- some form either in the wind tunncd or in flight tests. ously in the wind tunnels and in free fight. The wind-tunnel work for the greater part has con- The addition of several items of new equipment has sisted in the measurements of forces and moments on greatly extended the facilities of the committee for various wing arrangements for a systematic series of conducting certain investigations. The 5-foot vertical angles in pitch and yaw. The flight tests have been 60 — REPORT NATIONAL ADVISOBY 00 MMITTZE FOB AEBONAUTIOS 61 concerned chiefly with the eflects of mam distribu- very satisfactory results. A form of wing tip having tion. This part of the investigation has been recently a straight-line center-of-pressure locus has been clevel- completwl, with rather surprising results. In neither oped and sutlicientdata are now available to formulate of two airplanes tested was it poesible to produce an lavrs of load distribution over wing tips of any con- uncontrdhible spin by any practicable change in ma= rentional shape. distribution or balance. This leads to a presumption Reduction of drag.—The greatest source of real im- that most uncontrollable spins are probably due ta provement in airplane diciency lies in the reduction aerodynamic causes rather than to the inertia effects. of all drag components to their minimum v-dues. The The effects of varying the mass distribution and bal- possibilities appear very promising along this line. ance ha~e been thoroughly cover@ and the next step The published work of the National Advisory Com- is to apply these data to the calculation of spins from mittee for Aeronautics on air-cooled-engine cowlings static wind-tunnel tests. The spinui~~ balance in the has resulted in an improvement in commercial and new 5-foot vertical wind tunnel is expected to prove military airplane performance, and work now under of great value k the study of the for&s under spin- way on interference drag between nacelles and wings ning conditions. gives promise of additional improvements for multi- }Vhile the testing so far completed has indicated engine airplanes. The subject of interference dr~o — that mass distribution is of less importance than was is being given special attention in the variable-density expected, the routine measurement of moments and and propeller research tunnels. As the data accumu- ellipsoids of inertia has been continued. A report late the importance of this field becomes more evident. giving these data for 12 types of airplanes has been The new fuI1-scale wind tunnel will be of valuable published. assistance in the 6na1 stages of this research. Various methods of preventing spins or of assisting Upon completion of the nacelle-propeller investiga- .— in the recovery are being considered. Tests being tion in the propeller research trmnel an extended .--— conducted, chiefly in the new 5-foot and the new study of landing-gear resistance is to be made. — ? by 10 foot wind tunne~ cover ths effects of various Stability and controL-The program of longitudi- types of slots, pIan form of wings, twist of wings, —- nal-stability tests on a light. commercial airplane has f!oating ailerons, and differential ailerons. Full-scaIe been completed and a report covering this -workis now tests on promising schemes are to be made from time being prepared. The next step in %is investigation to time. —. IWucturat Zoading.-Improvement in structural is to study the lateral stability on the same airplane. safety and design efficiency is dependent to a great The purpose of this work is to find some satisfactory extent on the knowledge of uir loads and load distri- method for predictkg stabiIity characteristics. bution. Lacking esact and complete information the Control at lo-iv speeds has received considerable attention as a part of the spinning investigation. airplane designer must efkt some compromise be- .- tween safety and excess structural weight. One of Teds have been made in the 7 by 10 foot wind tun- the most important services rendered by the committee nel on a seriw of ailerons including the d&rential has been the investigation of ioads and load distri- and floating types. The important findings of this butions for various service conditions, thus supplying study are being covered by technical reports no-w in information leading to more exact desiagprules. Dur- preparation. A continuation of the research is to ing the past year the continuation of work on pulI- cover more completely the wing-tip floating-type ups from dives has led to the adoption of new design aileron and the ‘t spoiler” flap. requirements for various types of military airplanes. A number of flight tess have been made with This step appears to be of the greatest importance in Ii@ted elevator control as a part of the spinning that for the fist time the load factors are being invdgation. This line of work is being continued — based on rational factors depending on the chmac- with special landing geam, and -withan airplane fitted teristics of each individual type of airplane. -withslots and flaps. This investigation is being extended to cover aIl Wind-tunnel pressure-distribution tests on the ef- types of airplanes, including commercial air trans- fects of changing the lift distribution along the span ports. A special continuously recording combined have been completed. A definite reduction of maxi- air-speed indicator and accelerometer has been de- mum instability in rolling was obtained with either sibged for installation in typical airplanes. This in- geometric or aerodynamic washout, but sweepback strument is espected to gi~e definite information on or sweepfomvard appeared to have no appreciable the loads encountered under various conditions of effect. A technical report is now being prepared to service. cover the pressure-distribution tests on biplanes show- The study of pressure distribution on wing tips of ing the arrangements giving the best lateral and longi- various shapes has been practically completed, with tudinal stability. --— 62 REPORT NATIONAL ADVISORY COMM13ZYHI FOR AEBONAUTICS

The National Advisory Committee for Aeronautics viously mentioned. These changes required data from has recently obtained an autogiro and an airplane fit- maximum negative to maximum positive lift, so that ted with slots and flaps, both to be used in extensive it has been necessary to extend the original program to researches involving tests in the new full-scale wind cover the required negative-lift range. The extended tunnel as well as in flight. tests have now been completed for practically all Maneuverability-The investigation of maneuver- wicIely used sections and the data are being released ability has been combined for the greater part with for publication, the study of loads in various maneuvers; the angular In view of the desirable stability characteristics of acceleration, angular velocity, and flight path being the M-6 and CYH sections, the Navy Department sug- obtained whenever possible. ~ special program of gested thatmertain well-known sections be tested with testing on the Corsair observation-type airplane has their trailing edges reflexed to give stabIe moments, been completed for single control movements, and the It was found that all of the sections guve practically eflects of simultaneous control movements are to be identical characteristics when reflexed comparable investigated in the second part of the program. amotints. Theoretical aerodynmnice.-The laboratory staff at Several other airfoil investigations of 1* general Langley I?ield has completed several important theo- interest and importance have been completed during retical investigations during the past year. The most the past year. important of these is a simple and exact method of %ope&?’8.-During the past year the investigation calculatimg the lift or pressure distribution on tiin of propellers has been incidental to the wing-nacelle wing sections. It was demonstrated by theory and investigation. Most of the tests completed to date verified by wind-tunnel tests, that the total pressure have been for tractor arrangements, but pusher and distribution consisted of two parts, one a basic &s- tandem arrangements are to be tested during the next tribution for each section and the other the same for year. While these tests are not concerned primarily all sections. The practical applications of these data with the propellers it is believed that the propulsive enable accurate estimation of pressure-distribution efEciency and similar data being obtained are oi? the curves. greatest practical value to the airplane designer. A solution has aIso been obtained for the theoretical Tests have been made with a number of locked pro- potential flow around bodies of- airfoil form for any pellers and idling propoIIers during the wing-nacelle attitude, by an expression conttiining parameters that investigation. It has been dellnitely shown that the tire functions of the form ordy. The graphical solu- propeller has practically no effect on lift in either tions by this method are particularly simple and con- condition, but that an uncowled radial air-cooled venient for streamline forms. engine located directly in front of the leading edge A study of the effect of boundaries of a finite stream causes a large 10ssin lift. on the flow past an airfoiI in the stream has shown In investigating propeller characteristics at high that it is possible to devise three new types of wind tip speeds, the velocity and direction of the air flow tunnels having superior characteristics in regard to in the rear of the propellers were measured. From minimum or zero vaIue of the wall-interference cor- the data obtained the thrust and torque along the rection. blades of the propellers been computed and the Air~oiZ&—A series of 96 airfoils with systematic have variation in thickness, mean camber, and position of redts show clearly the part of the blade most maximum thickness is now being tested in the vari- affected by high tip speeds. able-density wind tunnel. Tests have been completed Zca @mation.-The research on the prevention of and data released for publication an about half of.the ice formation has been continued with studies of series. It -is of interest to note that some of these heat transmission from airfoil surfaces in the refrig- are distinctly superior to the best commonly ussed erated wind tunnel and in flight. It was found neces- sections. The information supplied by this investi- sary to heat mdy the front portion of the wing and gation when completed will enable accurate prediction the quantity of heat needed for complete prevention of the full-scale characteristics of new airfoils. is small. A vapor heating system utilizing the heat The complete verification of the data from the from the exhaust gases has been tried in flight and variable-density wind tunnel has led to an insistent found to offer considerable promise. demand from the industry and the nir services f cm A study has been made of gas-tank Tents to find full-scale data on all standard sections. Before the a form that would be immune to closure from ice tests being made for this purpose were completed, formation, Both the size cif the tube and its orien- changes in strew-analysis methods were found to be tation were found important, certain combinations necessary from the analyses of the flight tests of the being free from blocking by ice. These results have National Advisory Committee for Aeronautics pre- been published. . REPORT NATIONAL ADTTSOFtY00MMITTEE FOE AERONAUTICS 63

AIRCRAFTENGINES injection pressures of 100 to 500 pounds per square inch. -— The need still exists for the de~elopment of an air- The use of the ~. A. C. & and the Townend ring crafi power plant delivering approximately 1,000 types of cowIing for radial air-cooled engines has brake horsepower. The miIitary services are cog- increased to such an extent that almost every radial nizant of this need and lm~e undertaken the neces- air-coded engine installation above 300 horsepower sary development work to produce a 1,000-horsepower is equipped with some form of one of these covvlings- liquid-cooled aircraft e~cine. Ckmsideration has been given to possible methods of The power output of present aircraft engines is cowIing radial en=tiw more completely and admit- . .. continually being increased as better fuels are devel- ting only enough air through an opening in the oped, which permit operation without detonation at cowIin.g for efficient cooling. The remarkable endur- higher compression ratios. The ehination by im- ance and speed records made by commercial airplanes proved design of hot spots in the engine cylinder indicate that en=tie re~ability is not being sacriilced heads, and the use of exhaust valves having the head for increased power. ‘l?& radial air-cooled engine and stem 6.1.ledwith sodium, ha~e sIso contributed to still continues to be the most popular type of airoraft the permissible increase in compression ratio. Sev- power plant for power outputs below 600 horsepower. eral commercial air-cooled engines have been designed The use of ethylene glyccd as a cooling agent for to operate at.a compression ratio of 6. TVith a V-type aircraft engines continues to be sponsored mainly by engine designed to use ethylene-glycol cooling, satis- the &my &r Corps. There has been, hoviever, one .- factory teats have been made by the Army Air Corps commercial 6-cylinder in-hne inverted engine con- at a compression ratio of ~.8. This type of power structed to use ethylene glycd in a sealed cooling sys- plant appears to be capable of developing large power tem. Although steam cooling is used extensively in outputs -without coohg difficulties. England, Iittle interest is shown by our engine man- Increasing the engine rotative speed and increasing ufacturers in this method of cooIing. the weight of charge taken into the engine cyIinder The problem of reducing the noise from aircraft is have also been used to increase the engine power. being given considerable study both by the committee Boosting tests conducted by the committee show that and by commercial aircraft manufacturers. The com- —- a net gain in brake mean effective pressure of approx- mittee has devised a fundamentally new method of imately 5 pounds per square inch can be obtained for sound-frequency analysis which has led to the devel- each inch of mercury increase in carburetor pressure opment of a sound analyzer for use in this work. A above atmospheric pressure. To obtain greater pres- number of testa have ver-iiied the value of this new sure in the inlet manifold on radial air-cooled en- instrument. The aircraft manufacturers have di- gines, the impeller gear ratio has been increased from rected their efforts to muilling the engine exhaust, to ---- 6 h 12. The higher engine speed has necessitated the decreasing engine vibrations, and to imndating the use of propeller reduction gearing in order to obtain &i of commercial airplanes so as to improve the good propeller efficiencies. comfort of the paawngers. The construction of double-row radial air-cooled By breaking the world’s nonrefueling endurance engines is another solution of the problem of greater record for airplanes, the Packard aircraft Diesel en- ... -—— engine power. The greater number of engine cylin- gine has demonstrated that the decrmsed specific fuel .— ders gives smoother operation and leas engine tibra- consumption obtained with this type engine is an im- tion. This type of en=gineis being developed by two portant factor in making long-distance flights. The -— aircraft~ngine manufacturers. company is already e~oaged in developing a more To obtain better fuel distribution, which results in powerfuI engine of this type. increased pwer, decreased fueI consumption, and Considerable interest is being shown by some engine . ..— more rapid acceleratio~ attention is being given to manufacturers in the radial air-cooled 2-stroke-e@e . the development of fuel-injection systems to replace compression-ignition engine. An investigation of the --- ~ the carburetors on present aircraft engines. The fuel factors influencing the performance of this type of .. systems are designed for the injection of gasoline, aircraft engine is being cmducted at the committee’s either into the irdet manifold or directiy into the laboratory. cmgine cylinder. Since the air densities into which The development of hydrogenated “ safety fuels” ...— these gasoline sprays are injected are approximately having high flash points for use in prwnt carburetor ---- — atmospheric and the time available for injection com- aircraft engines would seem to hold considerable paratively long, low fuel-injection pressures may be promise as a possible means of reducing the fire haz- used. The committee’s investigation of fuel-spray ard in aircraft. The present safety fueIs tested by characteristics has been extended to include the deter- the committee can not be successfully carburetted. To mination of the spray characteristics of gasoline for overcome this difficulty the committee is inveatigatirg # 64 REPORT NATIONAL ADVISORY OOMMITTEE FOB AERONAUTICS the performance obtained from these fuels when and look about the same as they did before the test. sprayed directly into the engine cylinder. The re- Since it has been definitely shown that corrosion sults obtained on a single-cylinder carburetor-type reduces the fatigue limit of metals, anything which engine show that with the optimum injection rate used can be gained in resistance to corrosion is a gain in in the tests the power output with the safety fuel hav- the structure itself. This has been satisfactorily ing a flash point of 120° F. was equal to that obtained demonstrated in connection with Alclad. Alclad may using a carburetor and gas@ne, although the fuel not have quite as high tensile properties as plain consumption was from 6 to 8 per cent greater with duralumin, but if given a year or two in service the the safety fuel. retention of its original physical properties shows it to be ultimately superior. STRU~URAL MATERIALS Aluminum alloys having high strength at high The outlook for aluminum alloys appears more temperatures for use in engine parts such as cylinder promising from the standpoint of their utilization in heads are being developed. One of-these alloys which aircraft than it has been at any time in their history, will be available for tests in the near future has a especially with reference to making their use more tensile strength at 600° F., 25 per cent greater than dependable and certain. the alloys now in use. Progre~ in the forging art The development of the high-frequency fatigue- has been very rapid in the last year or so and the teating machine for the determination of the endur- number of engine parts fabricated by dies and forg- ance limit of metals was a pioneering effort and has ing has gradually increased. The quality of forged greatly reduced the time required for such an investi- propeller blades has shown marked improvement. gation. Heretofore it required nearly 300 days to ln the rduminum-casting field four or five different make m-ievaluation of the fatigue limit of nonferrous alloys are under development that appear from pre- alloys, while with the present equipment an evaluation liminary tests to be resistant to salt-water corrosion can be made in approximately 30 days. The tests and at the same time lend themselves to both foundry “ so far conducted with this machine have demonstrated and plant manufacture to a satisfactory dcamee. that frequencies of reversal up to 12,000 per minute, Stainless steel in aircraft construction is still being which is very high as far as testing is concerned but investigated both in the laboratory and under actual -withinthe possible range encountered in practice, give service conditions. Its use in engine exhaust mani- approximately the same results as frequencies of 1,200 folds, wing ribs, seaplane floats, control cables, struts, per minute previously used. and streamline wire has proved satisfactory and has A new situation has arisen in connection with the met expectations with reference to its corrosion-resist- endurance properties of aluminum alloys. The heat- ance properties. In the case of streamline wire the treatable and heat-treated alloys now in use have en- progress has been such as to warrant the placing of durrmce limits of approximately 25 per cent of their fairly large production orders with the manufuctur- tensile strength. This is relatively small, and work ersj with the rwdt that the manufacturers have been in the direction of increasing the tensile strength to uble to improve their methods of fabrication and in- increase the endurance limit seems to meet with only crease the quality of the product at least 50 per cent. moderate success. For instance, raising the tensile Beiyllium and its aIloys still hold considerable in- strength 10,000 pounds per square inch increases the terest on account of their higher strength-weight endurance only 2,000 pounds per square inch. ratio in comparison with aluminum alloys. However, With the other aluminum alloys, the endurance limit is approximately 50 per cent of the tensile stren=@h, the art of producing this material has not sufficiently but the tensile strengths are only 50 to 75 per cent of developed to bring its cost of production within a that for durrdumin. This situation suggests a divi- range to attract attention as a structural material for sion of materials with reference to their uses. Where aircraft, high yield point is especially demanded, stronger rna- Although wood and textiles are used to a consider- teriaLswill naturally be ctdled for, but where endur- able extent in both nditary and commercial aircraft, ance limit is a critical factor it is very probable that they do not present the diversity of problems which m alloy of lower tende strength will be used. metals do, nor do they lend themselves to improve- Regarding the question of coatings for corrosion ment in their mechanical properties to any apprecia- resistance, it may be said that marked progress has te degree. However, close attention to the fabrica- been made both in the anodic processes and in the tion of mechanical cloths for use as wing coverings, protective films themselves, Some samples, after a gas-cell and tiirship cloths, and parachute cloths, has year’s exposure to salt sprays, show practically no resulted in improvement in such properties as deterioration of the physical properties of the metal, strength-weight ratio and resistance to tear. REPORT NATIONALADVISOEY00MMITTEEFOBAEBONAUTIOS ti5

AIRSHIPS The use of special materials in the construction Airship progress during the past year has been of the airship, notably an aluminum alloy marked by one outstanding event, namely, the comple- which has been subjected to a slight degree of tion and satisfactory trials of the TJ. S. S. Aihm. cold rolling after heat treatment, thereby rais- This airship of 6,500,000 cubic feet volume (helium) ing the yieId point of the material at the ex- was contracted for by the Navy Department in Octo- pense of a slight reduction in elongation; and ber, 1928; erection of frames was started in Novem- special high-strength hard-steel wire galvanized ber, 1929; and the airship was completed and ready before the last drawing operation. ..— for trials in September, 1931. Trial flights amount- Special attention to protection of all metal parts against corrosion ing to approximately 100 hours were successfully car- ried out within a period of four weeks and the airship Increased strength factors. was thereupon accepted by the &’av-yDepartment and The fhal results from the trial flights of the U.S. S. commissioned as a United States naval airship. Akron have not been completely evaluated, but enough -- The lJ. S. S. Akron represents a complete new de- has been learned to warrant the belief that the air- sign of airship conceived and built entirely within ship design is fundamentally sound. A new set of .-. the United States. This fact is significant because it propellers will be required before the maximum pos- means the establishment -within the borders of the sible speed of the airship can be attained. United States of an industry capable of meeting prob- The second airship included in the airship pro- able demands, military or commercial, as to construc- gram of the ~a~ Department, for -which contract tion of airships. was made at the same time as that for the U. S. S. The design of the U. S. S. Akron embodies a num- Akron, is scheduled for completion about January, ber of features which either are entirely new, or are 1933. new in their present form, to airship construction, The material condition of the U. S. S. Los Ange?esj Some of the more important of these features are: as revealed by periodic inspection and check tests — A somewhat lomr finene5s ratio than used in of representative samples, continues to be satisfactory. .—.— former practice. Operations of small airships of the nonrigid type Inherently stiff main frames as compared with ha-re been continued by the Army, the ~avy, and by the wire type of main frames heretofore used. private intereats. The performance of these airships Easier and better access to all parts of the inte- in sweral instances has been noteworthy. rior of the airship for inspection purposes and The small experimental metal