(1)
The landing gear and directly a.ected attaching structure must be designed for the maximum vertical ground reaction combined with an aft acting drag component of not less than 25% of this maximum vertical ground reaction.
(2)
The most severe combination of loads that are likely to arise during a lateral driftlandingmustbe takeninto account.In absence of a more rational analysis of this condition, the following must be investigated :
(i)
A vertical load equal to 75% of the maximum ground reaction of Sec.
25.473 must be considered in combination with a drag and side load of 40% and 25% respectively of that vertical load.
(ii)
The shock absorber and tire de.ections must be assumed to be 75% of the de.ection corresponding to the maximum ground reaction of Sec. 25.473(a)(2). This load case need not be considered in combination with .at tires.
(3)
The combination of vertical and drag components is considered to be acting at the wheel axle centerline.]
Amdt. 25-91, E.. 7/29/97
FAR 25.481 : Tail down landing conditions.
(a) In the tail-down attitude, the airplane is assumed to contact the ground at forward velocity components, ranging from VL1 to VL2 parallel to the ground under the conditions prescribed in Sec. 25.473 with–
(1)
VL1 equal to VS0 (TAS)attheappropriatelanding weight andinstandard sea level conditions; and
(2)
VL2 equal to VS0 (TAS)at the appropriate landing weight and altitudes in a hot day temperature of 41 degrees F. above standard.
(3)
[The combination ofvertical and drag components considered to be acting at the main wheel axle centerline.]
(b)
For the tail-down landing condition for airplanes with tail wheels, the main and tail wheelsareassumed tocontacttheground simultaneously,inaccordancewith .gure 3 ofAppendix A. Ground reaction conditions on the tail wheel are assumed to act–
(1)
Vertically; and
(2)
Up and aft through the axle at 45 degrees to the ground line.
(c)
For the tail-down landing condition for airplanes with nose wheels, the airplane is assumed to be at an attitude corresponding to either the stalling angle or the maximum angle allowing clearance with the ground by each part of the airplane other than the main wheels, in accordance with .gure 3 of Appendix A, whichever is less.
Amdt. 25-94, E.. 3/25/98
FAR25.483 :[One-gearlanding conditions.]
[Forthe one-gearlandingconditions,the airplaneis assumedtobein thelevel attitude and to contact the ground on one main landing gear, in accordance with Figure 4 of Appendix A of this part. In this attitude–
(a)
The ground reactions must be the same as those obtained on that side under Sec. 25.479(d)(1), and]
(b)
Each unbalanced external load must be reacted by airplane inertia in a rational or conservative manner.
Amdt. 25-91, E.. 7/29/97
FAR 25.485 : Side load conditions.
[In addition to Sec. 25.479(d)(2)the following conditions must be considered :]
(a)
For the side load condition, the airplane is assumed to be in the level attitude with only the main wheels contacting the ground, in accordance with .gure 5 of Appendix A.
(b)
Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with one-half of the maximum vertical ground reactions obtained in the level landing conditions.Theseloadsareassumed tobe applied attheground contactpointand to be resisted by the inertia of the airplane. The drag loads may be assumed to be zero.
Amdt. 25-91, E.. 7/29/97
FAR 25.487 : Rebound landing condition.
(a)
The landing gear and its supporting structure must be investigated for the loads occurring during rebound of the airplane from the landing surface.
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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(57)
