Code of Federal Regulations - Title 14

231

Federal Aviation Administration, DOT

§ 23.561

K=0.8, except that lower values may be used

if it is shown that the floats are incapa-
ble of submerging at a speed of 0.8 V

normal operations;

=seaplane stalling speed (knots) with

landing flaps extended in the appropriate
position and with no slipstream effect;
and

g=acceleration due to gravity (ft/sec

(g)

Float bottom pressures. The float

bottom pressures must be established
under § 23.533, except that the value of
K

in the formulae may be taken as 1.0.

The angle of dead rise to be used in de-
termining the float bottom pressures is
set forth in paragraph (b) of this sec-
tion.

[Doc. No. 26269, 58 FR 42162, Aug. 6, 1993; 58
FR 51970, Oct. 5, 1993]

§ 23.537

Seawing loads.

Seawing design loads must be based

on applicable test data.

[Doc. No. 26269, 58 FR 42163, Aug. 6, 1993]

MERGENCY

ANDING

ONDITIONS

§ 23.561

General.

(a) The airplane, although it may be

damaged in emergency landing condi-
tions, must be designed as prescribed in
this section to protect each occupant
under those conditions.

(b) The structure must be designed to

give each occupant every reasonable
chance of escaping serious injury
when—

(1) Proper use is made of the seats,

safety belts, and shoulder harnesses
provided for in the design;

(2) The occupant experiences the

static inertia loads corresponding to
the following ultimate load factors—

(i) Upward, 3.0g for normal, utility,

and commuter category airplanes, or
4.5g for acrobatic category airplanes;

(ii) Forward, 9.0g;
(iii) Sideward, 1.5g; and
(iv) Downward, 6.0g when certifi-

cation to the emergency exit provi-
sions of § 23.807(d)(4) is requested; and

(3) The items of mass within the

cabin, that could injure an occupant,
experience the static inertia loads cor-
responding to the following ultimate
load factors—

(i) Upward, 3.0g;
(ii) Forward, 18.0g; and
(iii) Sideward, 4.5g.

landing gear must be designed to pro-
tect each occupant in a landing—

(1) With the wheels retracted;
(2) With moderate descent velocity;

and

(3) Assuming, in the absence of a

more rational analysis—

(i) A downward ultimate inertia force

of 3

g; and

(ii) A coefficient of friction of 0.5 at

the ground.

(d) If it is not established that a

turnover is unlikely during an emer-
gency landing, the structure must be
designed to protect the occupants in a
complete turnover as follows:

(1) The likelihood of a turnover may

be shown by an analysis assuming the
following conditions—

(i) The most adverse combination of

weight and center of gravity position;

(ii) Longitudinal load factor of 9.0g;
(iii) Vertical load factor of 1.0g; and
(iv) For airplanes with tricycle land-

ing gear, the nose wheel strut failed
with the nose contacting the ground.

(2) For determining the loads to be

applied to the inverted airplane after a
turnover, an upward ultimate inertia
load factor of 3.0g and a coefficient of
friction with the ground of 0.5 must be
used.

(e) Except as provided in § 23.787(c),

the supporting structure must be de-
signed to restrain, under loads up to
those specified in paragraph (b)(3) of
this section, each item of mass that
could injure an occupant if it came
loose in a minor crash landing.

(1) For engines mounted inside the

fuselage, aft of the cabin, it must be
shown by test or analysis that the en-
gine and attached accessories, and the
engine mounting structure—

(i) Can withstand a forward acting

static ultimate inertia load factor of
18.0 g plus the maximum takeoff engine
thrust; or

(ii) The airplane structure is designed

to preclude the engine and its attached
accessories from entering or protruding
into the cabin should the engine
mounts fail.

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