AIAA JOURNAL Vol.41,No.6, June 2003 TheWright Brothers: First Aeronautical Engineers andT est Pilots F.E.C.Culick CaliforniaInstitute of Technology,P asadena,California 91125 Nomenclature v =translationalvelocity W C D =dragcoef cient = weight W S CL =liftcoef cient w =wingloading, = x CLt =liftcoef cient (tail) =coordinatepositive from center of gravity y CLw =liftcoef cient (wing) =coordinatepositive along starboard wing Cm =pitchingmoment coef cient ® =angleof attack ¯ =sideslipangle Cm ac =pitchingmoment coef cient (aircraft) ° = path angle Cm cg =pitchingmoment coef cient about the center of gravity c = wing chord ±c =canardde ection D = drag force ±w =warpde ection Fx = x componentof force ±’ =incrementof theproperty ’ Fy = y componentof force " =downwashangle120 g ´t =tailef ciency, qt =q [Eq. (5)] =accelerationdue to gravity 1 H V C C µ =pitchattitude angle = Nt d Lt =d L h =fractionof chord ½ =gasdensity K =gainin controllaw, proportional control Á = bank angle L = lift force `np =separationof center of gravity and neutral point Subscriptsand Superscripts `t0 =distancebetween aerodynamic centers ofcanard and wing ac= aerodynamiccenter M = mass cg= centerof gravity m =pitchingmoment cp= centerof pressure np= neutralpoint mnp =pitchingmoment about neutral point p =rateof rotation t = tail = wing qt =dynamicpressure at a horizontallifting surface w 1 2 0=zerolift condition q =dynamicpressure, 2 ½V r 1 = yaw rate 1 —=steadyvalue S = wing area T =thrustforce IRGeorgeCayley invented the conventional con guration of T theairplane at theturn of the19th century. Otto Lilienthal re- µ1 =low-frequencyfactor S Tµ2 =high-frequencyfactor alizedthat building a successfulaircraft meant learning how to y; u =averageforward translational velocity hebecamethe rsthang glider pilot and also the rst ightfatality VN S cS in1896.Beginning in thelate 1890s, the Wright Brothers absorbed Nt =dimensionlesstail volume, ´t `t0 t = V =ightspeed allthat was known in aeronauticsbefore them, then added their own 1 Fred E.C.Culick joined the facultyof the CaliforniaInstitute of Technologyafter receivinghis Ph.D in Aero- nauticsand Astronautics from the MassachusettsInstitute of Technologyin 1961. He is currently RichardL. and DorothyM. HaymanProfessor ofMechanicalEngineering and Professor ofJetPropulsion. Dr .Culick’s Ph.D. dissertationtreated combustioninstabilities in liquid rockets. Muchof his research since hasbeen concerned with problemsof unsteady motions in combustion chambers generally. He beganworking on solid rocket combustion instabilitiesin 1965; since 1979he hasbeen addressingthe problemin airbreathingsystems, with recent emphasis onfeedbackcontrol applied to combustion systems, and measurements of combustion dynamics. Dr .Culickis a Fellowof the AIAA andof the InternationalAcademy of Astronautics. In 1981, he received the AIAA Pendray Aerospace Literature Awardand in 1988 the JANNAF CombustionSubcommittee Recognition A ward.From 1977 to1986, Dr .Culickwas a memberof the AGARD Propulsionand Energetics Panel,resuming that position in 1994, untilthe destructionof AGARD. He hasbeen aconsultantto all of the majorU.S. rocket companiesas well asto variousgovernment organizations. As partof his interest inaeronauticalhistory and early aviation, since 1978 Dr.Culickhas been Project Engineerand designated First Pilotin a project sponsoredby the LosAngeles Section ofthe AIAA. The project exists tobuild a full-scalewind tunnel model of the Wright1903 Flyer (tests completed ) anda yingversion to be ownin 2003. Dr .Culickhas publishednumerous papers on aviationhistory, the work ofthe WrightBrothers, andthe AIAA project.He coauthoredthe recent book OnGreat WhiteWings— The Wright Brothersand the Race forFlight ,anillustratedhistory of the race toinvent the rst powered aircraft.Currently, he is alsocollaborating with the Chairof Aerodynamics at the MoscowA viationInstitute and the Director of TsAGI, the RussianCenter forAerodynamics and Hydrodynamics, on reviews ofRussian aerodynamics in the 20thcentury. Presentedas Paper2001-3385 at theAIAA/ ASME/SAE/ASEE37th Joint Propulsion Conference, Salt Lake City,UT, 8– 11 July 2001; received 3August 2002;revision received 5December 2002;accepted forpublication 9 December 2002.Copyright c 2002by F. E. C.Culick.Published by the American Instituteof Aeronautics and Astronautics, Inc., with permission. Copies of this paper may bemade° forpersonal or internaluse, on condition that the copier paythe $10.00 per-copy fee totheCopyright Clearance Center,Inc., 222 Rosewood Drive, Danvers, MA 01923;include the code 0001-1452/ 03$10.00in correspondencewith the CCC. 985 986 CULICK discoveriesand developed the rstsuccessful airplane. Technically, inventedby Benjamin Robins in 1742. Cayley himself invented theirgreatest fundamental achievement was their invention of three- dihedralas ameansfor maintaining equilibrium in roll.The vertical axisaerodynamic control. Less obviously, their success was a con- tailprovided directional stability, like the feathers on an arrow,and sequenceof style,their manner of workingout theirideas and of pro- inCayley’s viewwould also be usedfor steering, as aboat’s rudder gressingsystematically to their stunning achievements. They were serves.By analogy, the horizontal tail gave stability in pitch. It turned indeedthe rstaeronautical engineers, understanding as best they outlaterthat Cayley was half right on bothcounts. couldall aspects of their aircraft and ying.They were thinkers, de- Cayleydid not formally apply Newton’ s lawsfor translational and signers,constructors, analysts, and especially ight-testpilots. Their rotationalmotions to the airplane. He produced no mathematical powersof observationand interpretationof thebehavior of theirair- descriptionsfor the motions of an aircraft and, therefore, had no craftin ightwere remarkable and essential to their development quantitativebasis for designing his yingmachines. However, he oftheairplane. Their work in theperiod 1899– 1905 constitutes the hadthings right at the level he worked. With his rstefforts he rsttrue research and development program carried out inthe style establishedthe principle that he later explained thoroughly in a ofthe20th century. As the centenary of their rstpowered ights seriesof papers: The means of producinglift to compensateweight 2 4 approaches,the Wright Brothers’ magni cent achievements excite mustbe distinct from the means of generating thrust. ¡ It was growingadmiration and respect for their achievements. The broad arevolutionaryidea at the time. He properly shifted attention to featuresof their accomplishments have long been well known. Only articial ightfrom simple imitation of birds to development of inthe past two decades has serious attention been directed to the xed-wingaircraft. scientic andtechnicalcontent of theirwork, to explain the nature of Thoseideas dominated all attempts to inventaircraft in the19th theproblems they faced and how they solved them. After a century’s century.Three immediate predecessors of the Wrights were par- progressin aeronautics, the principles, understanding, and methods ticularlyimportant to their work. Alphonse P´ enaud(1850– 1880) notavailableto theWrights provide the basis for interpreting in mod- inFranceadopted Cayley’ s designand ewthe rstpowered me- ernterms the experiencesthat the Wrights themselves documented chanical yingmachine, a smallrubber-powered model. He had the someticulouslyin theirdiaries, papers, and correspondence. It isa cleveridea to usetwisted rubber strips as the source of powerfor uniqueopportunity in the history of technology. apropeller.In ashortpaper describing his model, P´ enaudgave the rstexplanation for the action of anaft horizontal tail to providesta- I.Historical Background bilityin pitch. 5 InFrance, the surface became known as the P´ enaud Aconsiderablebody of aeronautical knowledge existed at the tail. endof the 19th century. The basic aerodynamics required to invent Themost important immediate predecessor of theWrights was asuccessfulaircraft had long been known: the lift and drag on a OttoLilienthal (1848– 1896). Educated and professionally success- surfaceplaced in a steadystream. Construction methods familiar fulas a mechanicalengineer, Lilienthal made his mark following frombridges, boats, and kites could be and were adapted for y- hisboyhood ambition to build a successful yingmachine. His two ingmachines. Finally, recent progress in the development of inter- mostin uential contributions were his realization and demonstra- nalcombustion engines and lightweight steam engines practically tionthat, to build a successfulairplane, it was necessary to learnhow solvedthe problem of havingsuf cient power. toyandhis extensive tests of airfoils,producing the rstsystem- Thusthe problem of mechanical ightcame down to oneof ge- aticdata for lift and drag of avarietyof airfoils. Less well known is ometry:Find an arrayof surfaces large enough to generate the lift thatone ofLilienthal’s resultsalso contributed to Kutta’ s rstpaper requiredand so arranged that the pilot can control stable and ma- onairfoil theory 6:Heemphasized the property of a goodairfoil neuverable ight.That was essentially the problem that the Wrights thatthe owshould be smoothat thetrailing edge. Carrying out his solvedto make possible their rstpowered ight(Fig. 1) and for owninstruction to y,Lilienthal built a seriesof successful gliders whichthey received their 1906 patent, never broken. The Wrights havingessentially Cayley’ s conguration. Lilienthal’