255 

Federal Aviation Administration, DOT 

§ 25.527 

(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 
maximum design loads for each part of 
the seaplane structure. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5673, Apr. 8, 
1970] 

§ 25.525

Application of loads. 

(a) Unless otherwise prescribed, the 

seaplane as a whole is assumed to be 
subjected to the loads corresponding to 
the load factors specified in § 25.527. 

(b) In applying the loads resulting 

from the load factors prescribed in 
§ 25.527, the loads may be distributed 
over the hull or main float bottom (in 
order to avoid excessive local shear 
loads and bending moments at the lo-
cation of water load application) using 
pressures not less than those pre-
scribed in § 25.533(c). 

(c) For twin float seaplanes, each 

float must be treated as an equivalent 
hull on a fictitious seaplane with a 
weight equal to one-half the weight of 
the twin float seaplane. 

(d) Except in the takeoff condition of 

§ 25.531, the aerodynamic lift on the 
seaplane during the impact is assumed 
to be 

2

⁄

3

of the weight of the seaplane. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Doc. No. FAA–2022–1355, Amdt. 
25–148, 87 FR 75710, Dec. 9, 2022; 88 FR 2813, 
Jan. 18, 2023] 

§ 25.527

Hull and main float load fac-

tors. 

(a) Water reaction load factors 

n

W

 

must be computed in the following 
manner: 

(1) For the step landing case 

n

C V

W

w

S

=

⎛

⎝

⎞

⎠

1

0

2

2
3

1
3

Tan

β

(2) For the bow and stern landing 

cases 

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