255 

Federal Aviation Administration, DOT 

§ 25.523 

each of the prescribed landing condi-
tions. However, for the drift landing 
condition of § 25.485, 100 percent of the 
vertical load must be applied. 

(e) 

Taxiing and ground handling condi-

tions. 

For one and for two deflated 

tires— 

(1) The applied side or drag load fac-

tor, or both factors, at the center of 
gravity must be the most critical value 
up to 50 percent and 40 percent, respec-
tively, of the limit side or drag load 
factors, or both factors, corresponding 
to the most severe condition resulting 
from consideration of the prescribed 
taxiing and ground handling condi-
tions; 

(2) For the braked roll conditions of 

§ 25.493 (a) and (b)(2), the drag loads on 
each inflated tire may not be less than 
those at each tire for the symmetrical 
load distribution with no deflated tires; 

(3) The vertical load factor at the 

center of gravity must be 60 percent 
and 50 percent, respectively, of the fac-
tor with no deflated tires, except that 
it may not be less than 1g; and 

(4) Pivoting need not be considered. 
(f) 

Towing conditions. 

For one and for 

two deflated tires, the towing load, 

F

TOW,

must be 60 percent and 50 percent, 

respectively, of the load prescribed. 

§ 25.519

Jacking and tie-down provi-

sions. 

(a) General. The airplane must be de-

signed to withstand the limit load con-
ditions resulting from the static 
ground load conditions of paragraph (b) 
of this section and, if applicable, para-
graph (c) of this section at the most 
critical combinations of airplane 
weight and center of gravity. The max-
imum allowable load at each jack pad 
must be specified. 

(b) Jacking. The airplane must have 

provisions for jacking and must with-
stand the following limit loads when 
the airplane is supported on jacks— 

(1) For jacking by the landing gear at 

the maximum ramp weight of the air-
plane, the airplane structure must be 
designed for a vertical load of 1.33 
times the vertical static reaction at 
each jacking point acting singly and in 
combination with a horizontal load of 
0.33 times the vertical static reaction 
applied in any direction. 

(2) For jacking by other airplane 

structure at maximum approved jack-
ing weight: 

(i) The airplane structure must be de-

signed for a vertical load of 1.33 times 
the vertical reaction at each jacking 
point acting singly and in combination 
with a horizontal load of 0.33 times the 
vertical static reaction applied in any 
direction. 

(ii) The jacking pads and local struc-

ture must be designed for a vertical 
load of 2.0 times the vertical static re-
action at each jacking point, acting 
singly and in combination with a hori-
zontal load of 0.33 times the vertical 
static reaction applied in any direc-
tion. 

(c) Tie-down. If tie-down points are 

provided, the main tie-down points and 
local structure must withstand the 
limit loads resulting from a 65-knot 
horizontal wind from any direction. 

[Doc. No. 26129, 59 FR 22102, Apr. 28, 1994] 

W

ATER

L

OADS

 

§ 25.521

General. 

(a) Seaplanes must be designed for 

the water loads developed during take-
off and landing, with the seaplane in 
any attitude likely to occur in normal 
operation, and at the appropriate for-
ward and sinking velocities under the 
most severe sea conditions likely to be 
encountered. 

(b) Unless a more rational analysis of 

the water loads is made, or the stand-
ards in ANC–3 are used, §§ 25.523 
through 25.537 apply. 

(c) The requirements of this section 

and §§ 25.523 through 25.537 apply also to 
amphibians. 

§ 25.523

Design weights and center of 

gravity positions. 

(a) 

Design weights. 

The water load re-

quirements must be met at each oper-
ating weight up to the design landing 
weight except that, for the takeoff con-
dition prescribed in § 25.531, the design 
water takeoff weight (the maximum 
weight for water taxi and takeoff run) 
must be used. 

(b) 

Center of gravity positions. 

The 

critical centers of gravity within the 
limits for which certification is re-
quested must be considered to reach 

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