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showsthattheX-CGtrimmedaircraftusesslightlylesspowerinthesesegments.Intheclimbanddescentsegments,Segs1,3,and5,wherethepowersettingisprogrammedtoa xedsetting,theX-CGtrimmedaircraftexperiencesslightlymoreacceleration(Fig.11).Bothofthesephenomenaareattributabletothereductionindragcoef cient,,whichistheresultoftrimmingbyvaryingtheX-CGpositionasopposedtousingthestabilator.ThisisshowninFig.12.

StabilityResults

StabilitymarginsforeachtrimmedconditionareshowninFig.13.Althoughtheresults

betweenthetwotrimparadigmsaremixedoverthereferencemissionpro le,theX-CGtrimmedcaseseemstohavemoretendencytogotoanegativestabilitymarginthanthestabilatortrimmedcase.

Thelateraleigenvaluesarewellbehaved,consideratelyseparatingintotheconventional

spiralmode,rollmode,andDutchrollpair.Thespiralmoderemainsstable(Fig.14),asdoestherollmodewhichisshowninFig.15andtheDutchrollpairwhoserealandimaginarypartsareplottedasafunctionof ightconditionnumberinFig.16.Dutchrolldampingalsoseemsadequate.

Thelongitudinaleigenvalueswerenotsoreadilyidenti able.Fig.17showstherealpart

ofthemostunstablelongitudinaleigenvalue.Fig.18givesascatterplotofallthelongitudinaleigenvalueswiththetwotrimparadigmsplottedseparately.Theraweigenvaluedataaretabulatedattheendofthisreport.

Acknowledgement

TheauthorsaregratefultoDr.ChristopherGraceyofNASALangleyResearchCenterfor

hishelpinlocatingdataforthisstudyandinformulatingtheapproach.

References

[1]RajivSinghChowdhryandCareyButtrill,“Reference-HAssessment:BareAirframeStability

andTrimDragReduction,”MemotoGFCITD,September13,1995.[2]“HighSpeedCivilTransportReferenceH–Cycle3SimulationDataBase.”ABoeingreport

forNASAContractNAS1-20220,TaskAssignmentNo.36,WBS4.3.5.1.2.1.[3]“HighSpeedResearchProgramHSRII–Airframetask20;Task2.1–TechnologyIntegration;

Sub-task2.1.1.1Re neTechnologyConceptAirplane:Con gurationDescriptionDocument;DeliverableReport.”ApprovedbyJ.B.Coffey,BCAG;J.K.Wechsler,MDC;P.F.Sweetland,BCAG;H.R.Welge,MDC.PreparedforNASALangleyResearchCenter,NASAContractNAS1-20220.April1,1996.[4]RajivS.Chowdhry,“User’sManualforMATLABReference

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