593 

Federal Aviation Administration, DOT 

§ 29.505 

(ii) An assumed rotor lift of not more 

than 1.5 times that used in the limit 
drop tests prescribed in § 29.725. 

(4) Compliance with paragraph (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. 

(2) The resultant ground loads must 

equal the vertical load specified in 
paragraph (b) of this section. 

(d) 

Sideloads in the level landing atti-

tude. 

In the level attitude, and with the 

rotorcraft contacting the ground along 
the bottom of both skids, the following 
apply: 

(1) The vertical ground reaction must 

be— 

(i) Equal to the vertical loads ob-

tained in the condition specified in 
paragraph (b) of this section; and 

(ii) Divided equally among the skids. 
(2) The vertical ground reactions 

must be combined with a horizontal 
sideload of 25 percent of their value. 

(3) The total sideload must be applied 

equally between skids and along the 
length of the skids. 

(4) The unbalanced moments are as-

sumed to be resisted by angular iner-
tia. 

(5) The skid gear must be inves-

tigated for— 

(i) Inward acting sideloads; and 
(ii) Outward acting sideloads. 
(e) 

One-skid landing loads in the level 

attitude. 

In the level attitude, and with 

the rotorcraft contacting the ground 

along the bottom of one skid only, the 
following apply: 

(1) The vertical load on the ground 

contact side must be the same as that 
obtained on that side in the condition 
specified in paragraph (b) of this sec-
tion. 

(2) The unbalanced moments are as-

sumed to be resisted by angular iner-
tia. 

(f) 

Special conditions. 

In addition to 

the conditions specified in paragraphs 
(b) and (c) of this section, the rotor-
craft must be designed for the fol-
lowing ground reactions: 

(1) A ground reaction load acting up 

and aft at an angle of 45 degrees to the 
longitudinal axis of the rotorcraft. 
This load must be— 

(i) Equal to 1.33 times the maximum 

weight; 

(ii) Distributed symmetrically among 

the skids; 

(iii) Concentrated at the forward end 

of the straight part of the skid tube; 
and 

(iv) Applied only to the forward end 

of the skid tube and its attachment to 
the rotorcraft. 

(2) With the rotorcraft in the level 

landing attitude, a vertical ground re-
action load equal to one-half of the 
vertical load determined under para-
graph (b) of this section. This load 
must be— 

(i) Applied only to the skid tube and 

its attachment to the rotorcraft; and 

(ii) Distributed equally over 33.3 per-

cent of the length between the skid 
tube attachments and centrally located 
midway between the skid tube attach-
ments. 

[Amdt. 29–3, 33 FR 966, Jan. 26, 1968, as 
amended by Amdt. 27–26, 55 FR 8002, Mar. 6, 
1990] 

§ 29.505

Ski landing conditions. 

If certification for ski operation is 

requested, the rotorcraft, with skis, 
must be designed to withstand the fol-
lowing loading conditions (where 

P 

is 

the maximum static weight on each ski 
with the rotorcraft at design maximum 
weight, and 

n 

is the limit load factor 

determined under § 29.473(b)): 

(a) Up-load conditions in which— 
(1) A vertical load of 

Pn 

and a hori-

zontal load of 

Pn/4 

are simultaneously 

applied at the pedestal bearings; and 

VerDate Sep<11>2014 

12:50 Apr 30, 2019

Jkt 247046

PO 00000

Frm 00603

Fmt 8010

Sfmt 8010

Y:\SGML\247046.XXX

247046

spaschal on DSK3GDR082PROD with CFR