(1)
13 inches from the lowest point of the landing gear to the ground; or
(2)
Anylesserheight, notless than eightinches, resultingin adropcontact velocity equal tothegreatestprobable sinking speedlikely to occur atground contact in normal power-o. landings.
(b)
If considered, the rotor lift speci.ed in Sec. 27.473(a) must be introduced into the drop test by appropriate energy absorbing devices or by the use of an e.ective mass.
(c)
Eachlandinggear unit mustbetestedinthe attitude simulating thelanding condi-tion that is most critical from the standpoint of the energy to be absorbed by it.
(d)
When an e.ective massis usedin showing compliancewithparagraph(b) ofthis section,thefollowingformulamaybe usedinstead of morerational computations:
h+(1 .L)d
We = W
h+ d W
n = nj + L We
where :
We : the e.ective weight to be used in the drop test (lbs.);
W = WM : for main gear units, equal to the static reaction on the par- (lbs.)
ticular unit with the rotorcraft in the most critical attitude.
A rational method may be used in computing a main gear
static reaction, taking into consideration the moment arm
between the main wheel reaction and the rotorcraft center
of gravity.
W = WN : for nose gear units, equal to the vertical component of the (lbs.)
static reaction that would exist at the nose wheel, assuming
that the mass of the rotorcraft acts at the center of gravity
and exerts a force of 1.0g downward and 0.25g forward.
W = WT : for tailwheel units, equal to whichever of the following is (lbs.)
critical :
(1)
The static weight on the tailwheel with the rotorcraft resting on all wheels; or
(2)
The vertical component of the ground reaction that would occur at the tailw-heel, assuming that the mass of the rotorcraft acts at the center ofgravity and exerts a force of 1g downward with the rotorcraft in the maximum nose-up attitude considered in the nose-up landing conditions.
h : speci.ed free drop height (inches).
L : ratio of assumed rotor lift to the rotorcraft weight.
d :de.ection underimpact ofthetire(attheproperin.ation pressure) plus the vertical component of the axle travels (inches)relative to the drop mass.
n : limit inertia load factor.
nj :theloadfactordeveloped,duringimpact, onthemassused inthedrop test(i.e.,the accelerationdv/dting’srecorded in the drop test plus 1.0).
FAR 27.727 : Reserve energy absorption drop test
The reserve energy absorption drop test must be conducted as follows :
(a)
The drop height must be 1.5 times that speci.ed in Sec. 27.725(a).
(b)
Rotorlift, where consideredin a manner similar to thatprescribedinSec.27.725(b), may not exceed 1.5 times the lift allowed under that paragraph.
(c)
[Thelandinggear mustwithstandthistest without collapsing.Collapse ofthelanding gear occurs when a member of the nose, tail, or main gear will not support the rotorcraft in the proper attitude or allows the rotorcraft structure, other than the landing gear and external accessories, to impact the landing surface.]
Amdt. 27-26, E.. 4/5/90
FAR27.729 :[Retracting mechanism.]
[For rotorcraft withretractable landing gear, the following apply :
(a) Loads. The landing gear, retracting mechanism, wheel-well doors, and supporting structure must be designed for–
(1) The loads occurring in any maneuvering condition with the gear retracted;
′
Elodie Roux. Septembre 2003
Subpart D : Design and Construction
(2)
The combined friction, inertia, and air loads occurring during retraction and extension at any airspeed up to the design maximum landing gear operating speed; and
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本文链接地址：FAA规章 美国联邦航空规章 Federal Aviation Regulations 4(92)
