422
14 CFR Ch. I (1–1–14 Edition)
§ 25.563
0.08 seconds after impact and must
reach a minimum of 14g.
(2) A change in forward longitudinal
velocity (
D 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
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.
(c) The following performance meas-
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
t
t
t
t
a t dt
t
t
=
−
(
)
−
(
)
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
⎧
⎨
⎪
⎩⎪
⎫
⎬
⎪
⎭⎪
∫
2
1
2
1
2 5
1
1
2
( )
.
max
Where:
t
1
is the initial integration time,
t
2
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).
F
ATIGUE
E
VALUATION
§ 25.571
Damage—tolerance and fa-
tigue 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
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