(i)
The VD/MD envelope determined by Sec. 25.335(b); or
(ii)
An altitude-airspeed envelopede.nedby a15percentincreasein equiva-lent airspeed above VC at constant altitude, from sea level to the altitude of the intersection of 1.15 VC with the extension of the constant cruise Mach number line, MC, then a linear variation in equivalent airspeed to MC +0.05 at the altitude of the lowest VC/MC intersection; then, at hi-gher altitudes, up to the maximum .ight altitude, the boundary de.ned by a .05 Mach increase in MC at constant altitude.
(c)
Balance weights. If concentrated balance weights are used, their e.ectiveness and strength, including supporting structure, must be substantiated.
(d)
Failures, malfunctions, and adverse conditions.Thefailures, malfunctions, and adverse conditions which must be considered in showing compliance with this section are :
(1) Any critical fuel loading conditions, not shown to be extremely impro-bable, which may result from mismanagement of fuel.
(2)
Any single failure in any .utter damper system.
(3)
For airplanes notapprovedfor operationinicing conditions,the maximum likely ice accumulation expected as a result of an inadvertent encounter.
(4)
Failure of any single element of the structure supporting any engine, in-dependently mountedpropeller shaft,large auxiliarypower unit, orlarge externally mounted aerodynamicbody(such as an externalfueltank).
(5)
For airplanes with engines that have propellers or large rotating devices capable of signi.cantdynamicforces, any singlefailure ofthe engine struc-ture that would reduce the rigidity of the rotational axis.
(6)
The absenceof aerodynamicorgyroscopicforcesresulting fromthe most adverse combination of feathered propellers or other rotating devices ca-pable of signi.cant dynamic forces. In addition, the e.ect of a single fea-thered propeller or rotating device must be coupled with the failures of paragraphs(d)(4) and(d)(5) of this section.
(7)
Any single propeller or rotating device capable of signi.cant dynamic forces rotating at the highest likely overspeed.
(8)
Anydamageorfailure condition,required orselectedforinvestigationby Sec.25.571.The single structuralfailuresdescribedinparagraphs(d)(4) and(d)(5) ofthis section need notbe consideredin showing compliance with this section if :
(i)
The structural element could not fail due to discrete source damage resulting from the conditions described in Sec. 25.571(e), and :
(ii)
A damage tolerance investigation in accordance with Sec. 25.571(b) shows that the maximum extent of damage assumed for the purpose of residual strength evaluationdoes notinvolve completefailure of the structural element.
(9)
Anydamage,failure,or malfunction considered underSecs.25.631,25.671, 25.672, and 25.1309.
(10)
Any other combination of failures, malfunctions, or adverse conditions not shown to be extremely improbable.
(e) Flight .utter testing. Full scale .ight .utter tests at speeds up to VDF/MDF mustbe conductedfor new typedesigns andfor modi.cations to a typedesign unless the modi.cations have been shown to have an insigni.cant e.ect on the aeroelastic stability. These tests must demonstrate that the airplane has a proper margin of damping at all speeds up to VDF/MDF, and that there is no large and rapid reduction in damping as VDF/MDF is approached. If a failure, malfunction, or adverse condition is simulated during .ight test in showing compliance withparagraph(d) of this section, the maximum speed investigated need not exceed VFC/MFC if it is shown, by correlation of the .ight test data with other test data or analyses, that the airplane is free from any aeroelastic instability at all speeds within the altitude-airspeed envelope describedinparagraph(b)(2) of this section.]
Amdt. 25-77, E.. 7/29/92
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本文鏈接地址：FAA規(guī)章 美國聯(lián)邦航空規(guī)章 Federal Aviation Regulations 3(74)
