title-14-part-25-sec25-562

259

Federal Aviation Administration, DOT

§ 25.562

set forth in paragraph (b) of this sec-
tion.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5673, Apr. 8,
1970; Amdt. 25–148, 87 FR 75710, Dec. 9, 2022; 88
FR 2813, Jan. 18, 2023]

§ 25.537

Seawing loads.

Seawing design loads must be based

on applicable test data.

MERGENCY

ANDING

ONDITIONS

§ 25.561

General.

(a) The airplane, although it may be

damaged in emergency landing condi-
tions on land or water, must be de-
signed as prescribed in this section to
protect each occupant under those con-
ditions.

(b) The structure must be designed to

give each occupant every reasonable
chance of escaping serious injury in a
minor crash landing when—

(1) Proper use is made of seats, belts,

and all other safety design provisions;

(2) The wheels are retracted (where

applicable); and

(3) The occupant experiences the fol-

lowing ultimate inertia forces acting
separately relative to the surrounding
structure:

(i) Upward, 3.0g
(ii) Forward, 9.0g
(iii) Sideward, 3.0g on the airframe;

and 4.0g on the seats and their attach-
ments.

(iv) Downward, 6.0g
(v) Rearward, 1.5g
(c) For equipment, cargo in the pas-

senger compartments and any other
large masses, the following apply:

(1) Except as provided in paragraph

(c)(2) of this section, these items must
be positioned so that if they break
loose they will be unlikely to:

(i) Cause direct injury to occupants;
(ii) Penetrate fuel tanks or lines or

cause fire or explosion hazard by dam-
age to adjacent systems; or

(iii) Nullify any of the escape facili-

ties provided for use after an emer-
gency landing.

(2) When such positioning is not prac-

tical (e.g. fuselage mounted engines or
auxiliary power units) each such item
of mass shall be restrained under all
loads up to those specified in paragraph
(b)(3) of this section. The local attach-

ments for these items should be de-
signed to withstand 1.33 times the spec-
ified loads if these items are subject to
severe wear and tear through frequent
removal (e.g. quick change interior
items).

(d) Seats and items of mass (and

their supporting structure) must not
deform under any loads up to those
specified in paragraph (b)(3) of this sec-
tion in any manner that would impede
subsequent rapid evacuation of occu-
pants.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5673, Apr. 8,
1970; Amdt. 25–64, 53 FR 17646, May 17, 1988;
Amdt. 25–91, 62 FR 40706, July 29, 1997]

§ 25.562

Emergency landing dynamic

conditions.

(a) The seat and restraint system in

the airplane must be designed as pre-
scribed in this section to protect each
occupant during an emergency landing
condition when—

(1) Proper use is made of seats, safety

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

(2) The occupant is exposed to loads

resulting from the conditions pre-
scribed in this section.

(b) Each seat type design approved

for crew or passenger occupancy during
takeoff and landing must successfully
complete dynamic tests or be dem-
onstrated by rational analysis based on
dynamic tests of a similar type seat, in
accordance with each of the following
emergency landing conditions. The
tests must be conducted with an occu-
pant simulated by a 170-pound
anthropomorphic test dummy, as de-
fined by 49 CFR Part 572, Subpart B, or
its equivalent, sitting in the normal
upright position.

(1) A change in downward vertical ve-

locity (

v) of not less than 35 feet per

second, with the airplane’s longitu-
dinal axis canted downward 30 degrees
with respect to the horizontal plane
and with the wings level. Peak floor de-
celeration must occur in not more than
0.08 seconds after impact and must
reach a minimum of 14g.

(2) A change in forward longitudinal

velocity (

v) of not less than 44 feet

per second, with the airplane’s longitu-
dinal axis horizontal and yawed 10 de-
grees either right or left, whichever

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260

14 CFR Ch. I (1–1–24 Edition)

§ 25.563

would cause the greatest likelihood of
the upper torso restraint system
(where installed) moving off the occu-
pant’s shoulder, and with the wings
level. Peak floor deceleration must
occur in not more than 0.09 seconds
after impact and must reach a min-
imum of 16g. Where floor rails or floor
fittings are used to attach the seating
devices to the test fixture, the rails or
fittings must be misaligned with re-
spect to the adjacent set of rails or fit-
tings by at least 10 degrees vertically
(

i.e., out of Parallel) with one rolled 10

degrees.

ures must not be exceeded during the
dynamic tests conducted in accordance
with paragraph (b) of this section:

(1) Where upper torso straps are used

for crewmembers, tension loads in indi-
vidual straps must not exceed 1,750
pounds. If dual straps are used for re-

straining the upper torso, the total
strap tension loads must not exceed
2,000 pounds.

(2) The maximum compressive load

measured between the pelvis and the
lumbar column of the anthropomorphic
dummy must not exceed 1,500 pounds.

(3) The upper torso restraint straps

(where installed) must remain on the
occupant’s shoulder during the impact.

(4) The lap safety belt must remain

on the occupant’s pelvis during the im-
pact.

(5) Each occupant must be protected

from serious head injury under the con-
ditions prescribed in paragraph (b) of
this section. Where head contact with
seats or other structure can occur, pro-
tection must be provided so that the
head impact does not exceed a Head In-
jury Criterion (HIC) of 1,000 units. The
level of HIC is defined by the equation:

HIC

a t dt

−

(

)

−

(

)

⎡

⎣

⎢

⎤

⎦

⎥

⎧

⎨

⎪

⎩⎪

⎫

⎬

⎪

⎭⎪

∫

2 5

( )

max

Where:

is the initial integration time,

is the final integration time, and

a(t) is the total acceleration vs. time curve

for the head strike, and where

(t) is in seconds, and (a) is in units of gravity

(g).

(6) Where leg injuries may result

from contact with seats or other struc-
ture, protection must be provided to
prevent axially compressive loads ex-
ceeding 2,250 pounds in each femur.

(7) The seat must remain attached at

all points of attachment, although the
structure may have yielded.

(8) Seats must not yield under the

tests specified in paragraphs (b)(1) and
(b)(2) of this section to the extent they
would impede rapid evacuation of the
airplane occupants.

[Amdt. 25–64, 53 FR 17646, May 17, 1988]

§ 25.563

Structural ditching provi-

sions.

Structural strength considerations of

ditching provisions must be in accord-
ance with § 25.801(e).

ATIGUE

VALUATION

§ 25.571

Damage-tolerance and fatigue

evaluation of structure.

(a)

General. An evaluation of the

strength, detail design, and fabrication
must show that catastrophic failure
due to fatigue, corrosion, manufac-
turing defects, or accidental damage,
will be avoided throughout the oper-
ational life of the airplane. This eval-
uation must be conducted in accord-
ance with the provisions of paragraphs
(b) and (e) of this section, except as
specified in paragraph (c) of this sec-
tion, for each part of the structure that
could contribute to a catastrophic fail-
ure (such as wing, empennage, control
surfaces and their systems, the fuse-
lage, engine mounting, landing gear,
and their related primary attach-
ments). For turbojet powered air-
planes, those parts that could con-
tribute to a catastrophic failure must
also be evaluated under paragraph (d)
of this section. In addition, the fol-
lowing apply: