(2)
[The minimum speedmargin mustbe enough toprovidefor atmospheric varia-tions(such ashorizontalgusts, andpenetration ofjet streams and coldfronts) and for instrument errors and airframe production variations. These factors maybe considered on aprobabilitybasis.The margin at altitude where MC is limited by compressibility e.ects must not be less than 0.07M unless a lower margin is determined using a rational analysis that includes the e.ects of any automatic systems. In any case, the margin may not be reduced to less than 0.05M.]
(c)
Design maneuvering speed, VA . For VA , the following apply :
√
(1)
VA may not be less than VS1 nz where–
(i)
nz is the limit positive maneuvering load factor at VC ; and
(ii)
VS1 is the stalling speed with .aps retracted.
(2)
VA and VS must be evaluated at the design weight and altitude under consi-deration.
(3)
VA need not be more than VC or the speed at which the positive CNAmax curve intersects the positive maneuver load factor line, whichever is less.
(d) Design speed for maximum gust intensity, VB .
(1) VB may not be less than
Kg UREF VC a
VS1 1+ 498w
′
Elodie Roux. Septembre 2003
Subpart C : Structure
where-
Kg = 0.88μ 5.3+μ
2w
μ = ρc a g
VS1 : the 1-g stalling speed based on CNAmax with the .aps retracted at the particular weight under consideration; VC :design cruise speed(knots equivalent airspeed); UREF :the referencegust velocity(feetper second equivalent airspeed) from Sec. 25.341(a)(5)(i);
w :averagewingloading(poundsper squarefoot) attheparticular
weight under consideration. ρ :density of air(slugs/ft3);
c : meangeometric chord ofthe wing(feet);
g : accelerationduetogravity(ft/sec2);
a : slope of the airplane normal force coe.cient curve, CNA per ra-dian;
(2) At altitudes where VC is limited by Mach number–
(i)
VB may be chosen to provide an optimum margin between low and high speed bu.et boundaries; and
(ii)
VB need not be greater than VC.
(e)
Design .ap speeds, VF.. For VF, the following apply :
(1)
Thedesign .apspeedforeach.apposition(establishedinaccordancewithSec. 25.697(a))mustbe su.cientlygreater than the operating speed recommended forthecorresponding stageof .ight(includingbalkedlandings) toallowfor probable variations in control of airspeed and for transition from one .ap position to another.
(2)
If anautomatic .appositioning orloadlimiting deviceisused,thespeedsand corresponding .ap positions programmed or allowed by the device may be used.
(3)
VF may not be less than–
(i)
1.6 VS1, with the .aps in takeo. position at maximum takeo. weight;
(ii)
1.8 VS1,with the .apsinapproachpositionat maximumlanding weight; and
(iii) 1.8 VS0with the .aps in landing position at maximum landing weight.
(f)
Design drag device speeds, VDD .The selecteddesign speedfor eachdragdevice must be su.cientlygreaterthanthe speed recommendedforthe operation of thedevice to allowforprobable variationsin speed control.Fordrag devicesintendedfor use in high speed descents, VDD may not be less than VD. When an automatic drag device positioning or load limiting means is used, the speeds and corresponding drag device positions programmed or allowed by the automatic means must be used for design.
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本文链接地址：FAA规章 美国联邦航空规章 Federal Aviation Regulations 3(47)
