Elodie Roux. Septembre 2003
Appendix C : Basic Landing Conditions
Chapitre 38
AppendixD :[WheelSpin-Up and Spring-Back Loads]
Sommaire
FAR23.D1:Wheel spin-up loads. . . . . . . . . . . . . . . . 464
463
AppendixD:[WheelSpin-Up andSpring-BackLoads]
FAR 23.D1 : Wheel spin-up loads.
(a) The following method for determining wheel spin-up loads for landing conditions is based on NACA T.N. 863. However, the drag component used for design may not be less than the drag load prescribed in Sec. 23.479(b).
12Iw (VH .VC)nFV max
=
FHmax
retz
where–
FHmax :maximumrearwardhorizontalforceactingonthe (inpounds); wheel
re :e.ectiverolling radiusof wheel underimpactbased infeet; on recommended operating tirepressure(which may be assumed to be equal to the rolling radius under a static load of nj We)
Iw :rotational massmoment ofinertiaof rolling assembly (inslugfeet); VH :linearvelocity ofairplaneparalleltoground atins-infeetpersecond); tant of contact(assumedtobe1.2VS0,
VC :peripheral speed of tire,ifpre-rotationisused(there (infeetpersecond); mustbe apositive means ofpre-rotationbeforepre-rotation may be considered)
n :e.ective coe.cient offriction(0.80 may be used); FV max :maximumverticalforceonwheel = njWe, where We (pounds); and nj are de.ned in Sec. 23.725
tz :timeintervalbetweengroundcontact and attainment (seconds) of maximum verticalforce on wheel.(However,if the value of FV , from the above equation exceeds
max0.8FV max, thelatter value mustbe usedfor FHmax.)
(b)
This equation assumes a linear variation ofloadfactor with time until thepeakload is reached and under this assumption, the equation determines the drag force at the time that the wheelperipheral velocity at radius re equals the airplane velocity. Most shock absorbers do not exactly follow a linear variation of load factor with time. Therefore, rational or conservative allowances must be made to compensate forthese variations.On mostlandinggears,thetimefor wheel spin-up willbeless thanthetime requiredtodevelop maximum verticalloadfactorforthe speci.ed rate of descent and forward velocity. For exceptionally large wheels, a wheel peripheral velocity equal to the ground speed may not have been attained at the time of maximum verticalgearload.However,asstated above,thedrag spin-up load need not exceed 0.8 of the maximum vertical loads.
(c)
[Dynamic spring-backof thelandinggear and adjacent structure attheinstantjust after the wheels come up to speed may result in dynamic forward acting loads of considerable magnitude. This e.ect must be determined, in the level landing condition, by assuming that the wheel spin-up loads calculated by the methods of this appendix are reversed. Dynamic spring-back is likely to become critical for landing gear units having wheels of large mass or high landing speeds.]
Amdt. 23-45, E.. 09/07/93
Chapitre 39
Appendix E : Limited Weight Credit For Airplanes Equipped with Standby Power
Sommaire
FAR23.E:[Removed andReserved.] . . . . . . . . . . . . . . 466
465
FAR23.E :[Removed andReserved.]
[Removedand Reserved.] Amdt. 23-50, E.. 03/11/96
Chapitre 40
AppendixF :[TestProcedure]
Sommaire
FAR 23.F : [Acceptable test procedure for self-extinguishing materials for showing compliance with Secs. 23.853,
23.855 and23.1359.] .................. 468
467
AppendixF :[TestProcedure]
FAR 23.F : [Acceptable test procedure for self-extinguishing materials for showing compliance with Secs. 23.853, 23.855 and 23.1359.]
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