503 

Federal Aviation Administration, DOT 

§ 27.501 

(i) For the forward wheels, 0.8 times 

the vertical reaction (on one side) act-
ing inward, and 0.6 times the vertical 
reaction (on the other side) acting out-
ward; and 

(ii) For the rear wheel, 0.8 times the 

vertical reaction. 

(2) The loads specified in paragraph 

(f)(1) of this section must be applied— 

(i) At the ground contact point with 

the wheel in the trailing position (for 
non-full swiveling landing gear or for 
full swiveling landing gear with a lock, 
steering device, or shimmy damper to 
keep the wheel in the trailing posi-
tion); or 

(ii) At the center of the axle (for full 

swiveling landing gear without a lock, 
steering device, or shimmy damper). 

(g) 

Braked roll conditions in the level 

landing attitude. 

In the attitudes speci-

fied in paragraphs (b) and (c) of this 
section, and with the shock absorbers 
in their static positions, the rotorcraft 
must be designed for braked roll loads 
as follows: 

(1) The limit vertical load must be 

based on a limit vertical load factor of 
not less than— 

(i) 1.0, for the attitude specified in 

paragraph (b) of this section; and 

(ii) 1.33, for the attitude specified in 

paragraph (c) of this section. 

(2) For each wheel with brakes, a 

drag load must be applied, at the 
ground contact point, of not less than 
the lesser of— 

(i) 0.8 times the vertical load; and 
(ii) The maximum based on limiting 

brake torque. 

(h) 

Rear wheel turning loads in the 

static ground attitude. 

In the static 

ground attitude, and with the shock 
absorbers and tires in their static posi-
tions, the rotorcraft must be designed 
for rear wheel turning loads as follows: 

(1) A vertical ground reaction equal 

to the static load on the rear wheel 
must be combined with an equal 
sideload. 

(2) The load specified in paragraph 

(h)(1) of this section must be applied to 
the rear landing gear— 

(i) Through the axle, if there is a 

swivel (the rear wheel being assumed 
to be swiveled 90 degrees to the longi-
tudinal axis of the rotorcraft); or 

(ii) At the ground contact point, if 

there is a lock, steering device or shim-

my damper (the rear wheel being as-
sumed to be in the trailing position). 

(i) 

Taxiing condition. 

The rotorcraft 

and its landing gear must be designed 
for loads that would occur when the 
rotorcraft is taxied over the roughest 
ground that may reasonably be ex-
pected in normal operation. 

§ 27.501

Ground loading conditions: 

landing gear with skids. 

(a) 

General. 

Rotorcraft with landing 

gear with skids must be designed for 
the loading conditions specified in this 
section. In showing compliance with 
this section, the following apply: 

(1) The design maximum weight, cen-

ter of gravity, and load factor must be 
determined under §§ 27.471 through 
27.475. 

(2) Structural yielding of elastic 

spring members under limit loads is ac-
ceptable. 

(3) Design ultimate loads for elastic 

spring members need not exceed those 
obtained in a drop test of the gear 
with— 

(i) A drop height of 1.5 times that 

specified in § 27.725; and 

(ii) An assumed rotor lift of not more 

than 1.5 times that used in the limit 
drop tests prescribed in § 27.725. 

(4) Compliance with paragraphs (b) 

through (e) of this section must be 
shown with— 

(i) The gear in its most critically de-

flected position for the landing condi-
tion being considered; and 

(ii) The ground reactions rationally 

distributed along the bottom of the 
skid tube. 

(b) 

Vertical reactions in the level land-

ing attitude. 

In the level attitude, and 

with the rotorcraft contacting the 
ground along the bottom of both skids, 
the vertical reactions must be applied 
as prescribed in paragraph (a) of this 
section. 

(c) 

Drag reactions in the level landing 

attitude. 

In the level attitude, and with 

the rotorcraft contacting the ground 
along the bottom of both skids, the fol-
lowing apply: 

(1) The vertical reactions must be 

combined with horizontal drag reac-
tions of 50 percent of the vertical reac-
tion applied at the ground. 

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