NASACONTRACTOR REPORT N COPY: RETURN YO AFWL (DOUL) KBWTEAND AFB, N. MI. RIDINGAND HANDLING QUALITIESOF LIGHT AIRCRAFT - A REVIEW AND ANALYSIS by Frederick 0. Smetum, Delbert C. Summey, und W. Dondld Johnson Prepared by C AR O LINA STATE UNIVERSITYNORTH STATE CAROLINA ,, Raleigh, N. C. 27607 for LalzgleyResearch Center NATIONALAERONAUTICS AND SPACE ADMINISTRATION WASHINGTON,D. C. MARCH 1972 TECH LIBRARY KAFB, NM 1. Report No. AccessionGovernment 2. No. 3. Recipient's Catalog No. - NASA CR - 1975 4. Title and7 5. Report Date RIDING AND HANDLING QUALIII?ES OF LIGHT AIRCRAFT - A REVIEW March 1972 AND ANALYSIS "- 7. Author(s1 Organization 0. Performing Report No. Frederick 0. Eknetana, Delbert C. flunmey, andW. Donald Johnson None 10.Work Unit No. 9. MamingOrganization Name and Address 736-05-10-01-00 North Carolina State University at Raleigh Department of Mechanical and Aerospace Engineering 11.Contract or Grant No. Raleigh, North, Carolina 27607 NASL-9603 13. Type of Report andPeriod Covered 12. SponsoringAgency Name and Address Contractor Report National Aeronautics and Space Administration Washington, DC 20546 14. SponsoringAgency Code I 15. SupplementaryNotes 16. Abstract Design procedures and supporting data necessary for configuring light aircraft to obtain desired responsesto pilot commands and gusts are presented. The procedures employ specializations of modern military and jet .transport practice where these provide an improvement over earlier practice. General criteria for riding and handling qualities are discussed in terms of the airframe dynamics. Methods available in the literature for calculating the coefficients required for a linearized analysis of the airframe dynamics are reviewed in detail. The review also treats the relation of spin and stallto airframe geometry. Root locus analysis is usedto indicate the sensitivity of airframe dynamics to variations in individual stability derivatives and to variations in geometric parameters. Computer programs are given for finding the frequencies, damping ratios, and time constants of all rigid body modes and for generating time histories of aircraft motions in responseto control inputs. To the end that the work serveas a self-contained riding and handling characteristics design handbook, appendices are included presenting the derivation of the linearized equations of motion; the stability derivatives; the transfer functions; approximate solutions for the frequency, damping ratio, and time constants; an indication of methods to be used when linear analysis is inadequate; sample calculations; andan explanation of the use of root locus diagrams and Bode plots . 117. Key'(Suggested Words by Authoris) 1 10. Distribution Statement Stability derivatives Bode plots Unclassified - Unlimited Sample calculations Computer programs I 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21.No. of Pages 22. Rice* Unclassified . Unclassified 409 $6 .oo For sale by the National Technical InformationService, Springfield, Virginia 22151 " " TABLE OF CONTENTS Page GENERAL I NTRODUCT I ON 1 Background 2 Objectives and Organization 4 Factors Contributing to the Pilot's Opinion of Aircraft Handling Qualities 6 Flight Motions of Light Aircraft-General Considerations 11 Control Forces and Deflect ions-General Considerations 14 I: I TERATURE REV I EW 15 Scope 16 Syrnbo I s 18 Stability Derivatives 27 Power Effects 110 Contro I Forces and Def I ect i ons 122 Inertial Characteristics 152 Stal I 156 \ 'i Spin Entry 165 Human Factors 179 Design for DesirableRiding Qualities 187 THE EFFECT OF VARIATIONSIN STABILITY DERIVATIVES ON THE MOTIONS OF A TYPICAL LIGHT AIRCRAFT 193 194 iii TABLE OF CONTENTS (continued) Page LongitudinalVariations 198 LateralVariations 203 REFERENCES 30 1 APPENDICES 31 1 A - Derivationof Equations of Mot ion 31 1 B - Definition of Stability Deriva ti ves 333 C - TransferFunctions 337 D - Simplified Response Characteristics 347 E - Use of theNon-Linear Forms of the Equations of Motion 353 F - Some Noteson the Construction and Interpretation of Bode Plots andRoot Locus Diagrams 355 G - Sample Calculations 363 Longitudinal Sample Calculations Latera I Samp le Calculations H - Computer Programs 379 Longitudinal Program Latera I Program Longitudinal and Lateral Sample Output T ime Response Program I - Bib1iography 393 iv GENERAL INTRODUCTION BACKGROUND Recentengine advances, the upsurge Inbusiness flying, and generalaffluence have greatlyaccelerated the development of new and alteredmodels of generalavia- tionaircraft. Thesedevelopments follow thetraditional industry pattern of ev- olutionary change ratherthan revolutionary change.For example, a particular model may notbe.selling as well as expected, so it is determinedthat offering theaircraft with additional powerwould increase itssales appeal. It isthen up to the company'sengineering department to accomplish this refitting with a minimum of. expense.There are the obvious structural modifications to make, the weight and. balance to check,and then a check flight to determinewhether the ride and handlingcharacteristics remain, according to thesubjective opinion of the company pilot,satisfactory. It is, of course,not possible to explore,in this type of flight test program, all possible flight modes and conditions so that one may omit tests at a conditionwhich formerly was notuncomfortable or unsafebut has, because of thechanges become so. Thisseldom happens of course, butplace an aircraft with a largerengine in the hands of aninexperienced pilot, andhe will probably be surprisedthat the periods of thelongitudinal short pe- riod and dutch rol I modes increaseand their dampingdecreases; similarly, it is seldomexpected by the novice that moving the engine to thewing and adding a secondengine may, because ofthe nacelle design, give a seriouspitch-up condi- tion at high ang!es of attack or thatproviding adequate static longitudinal stability or weathercock stability at some particular flight condition does not guaranteeacceptable dynamic characteristics. Yet these things can, givensuf- ficient and reliableanalytical andexperimental data, be forecast quite accu- rately andcan be included in the pilot's handbook. To expectthe manufacturer of light aircraft to carryout the comprehensive preliminarydesign analyses, the extensive wind tunnel tests, and theexhaustive flight tests that wereperformed for the C-5A, for example, for each of his new aircraftis not being economically realistic. If onecould, however, supply the designer of lightaircraft with simple-to-use, accurate means of predicting all aspects of theflight performance of his airplane, this would go a long way to- wardenabling these manufacturers to providesafer, more enjoyable aircraft more economically. Despitemore than 50 years of scientific study, much of the preliminary designis still an art. Desirable handling qualities, for example, arestill largelyunquantified. Theusual procedure is to have anexperienced pilotdecide whetheran airplane handles "satisfactorily." Little effort hasbeen made until recentlyto determine--by a series of the best available quantitative tests-- thosecontrol forces andresponse rates with which a human isconfortable and thelimiting aircraft accelerations, oscillatory amplitudes, and frequencies for acceptableriding qualities andthen incorporating this information into a de- terminationof the geometric, inertial, andpower characteristicsnecessary to achieve them. Anothermajor problem in light aircraft design is the diversity and frag- mentation of reliableexperimental and analytica,l information. In an attempt to contribute to a solution of this problem,the National Aeronautics and Space 2 Administrationsupported a reviewof its published research since 1940 (Refs. I, 2, 3) with a viewtoward identifying those items of pertinence to light aircraft design. The presentstudy is anin-depth review, selection, and extensionof that portion of thisinformation and certainother information specifically related tothe handling and ridingqualities of lightaircraft. It isintended to serve as a compilation of applicable,available experimental data as well asmodern analysisprocedures for those interested in these aspects of light aircraft design 3 OBJECTIVESAND ORGANIZATION Thiswork was undertakenwith the intention of providing a recentengineer- inggraduate with sufficient understanding, information, and procedures to permit him to predict,with reasonable accuracy, certain riding and handlingcharacter- isticsof projected light aircraft. To facilitatethe presentation, the discus- sionis limited, for the most part, tothose facets of the riding andhandling qualities which have a common basis:they trace their origin to the general dynamicalbehavior of the airframe and its components.This approach takes ad- vantageof the fact that few recentstudents have not at some time during their collegiatecareers seen derivedthe equations of motion of a rigid body in space and thesolution of a systemof linear differential equations by the method of LaplaceTransforms. Recent graduates are also generally familiar with some of thevocabulary of feedback control systems analysis. The presentwork, therefore, seeks to build upon thisfoundation in elaborating modern techniques for predict- ingessential features of the riding andhandling qualities of light aircraft. As a consequence of this choice, however, many perfectlyrespectable problem areasand effective analysis techniques are not discussed. For these omissions theauthors request the reader's forebearance. Thework