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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