656
14 CFR Ch. I (1–1–14 Edition)
§ 27.563
(2) The occupant is exposed to the
loads resulting from the conditions
prescribed in this section.
(b) Each seat type design or other
seating device approved for crew or
passenger occupancy during takeoff
and landing must successfully com-
plete dynamic tests or be demonstrated
by rational analysis based on dynamic
tests of a similar type seat in accord-
ance with the following criteria. The
tests must be conducted with an occu-
pant, simulated by a 170-pound
anthropomorphic test dummy (ATD),
as defined by 49 CFR 572, subpart B, or
its equivalent, sitting in the normal
upright position.
(1) A change in downward velocity of
not less than 30 feet per second when
the seat or other seating device is ori-
ented in its nominal position with re-
spect to the rotorcraft’s reference sys-
tem, the rotorcraft’s longitudinal axis
is canted upward 60
°
with respect to
the impact velocity vector, and the
rotorcraft’s lateral axis is perpen-
dicular to a vertical plane containing
the impact velocity vector and the
rotorcraft’s longitudinal axis. Peak
floor deceleration must occur in not
more than 0.031 seconds after impact
and must reach a minimum of 30g’s.
(2) A change in forward velocity of
not less than 42 feet per second when
the seat or other seating device is ori-
ented in its nominal position with re-
spect to the rotorcraft’s reference sys-
tem, the rotorcraft’s longitudinal axis
is yawed 10
°
either right or left of the
impact velocity vector (whichever
would cause the greatest load on the
shoulder harness), the rotorcraft’s lat-
eral axis is contained in a horizontal
plane containing the impact velocity
vector, and the rotorcraft’s vertical
axis is perpendicular to a horizontal
plane containing the impact velocity
vector. Peak floor deceleration must
occur in not more than 0.071 seconds
after impact and must reach a min-
imum of 18.4g’s.
(3) Where floor rails or floor or side-
wall attachment devices are used to at-
tach the seating devices to the air-
frame structure for the conditions of
this section, the rails or devices must
be misaligned with respect to each
other by at least 10
°
vertically (i.e.,
pitch out of parallel) and by at least a
10
°
lateral roll, with the directions op-
tional, to account for possible floor
warp.
(c) Compliance with the following
must be shown:
(1) The seating device system must
remain intact although it may experi-
ence separation intended as part of its
design.
(2) The attachment between the seat-
ing device and the airframe structure
must remain intact, although the
structure may have exceeded its limit
load.
(3) The ATD’s shoulder harness strap
or straps must remain on or in the im-
mediate vicinity of the ATD’s shoulder
during the impact.
(4) The safety belt must remain on
the ATD’s pelvis during the impact.
(5) The ATD’s head either does not
contact any portion of the crew or pas-
senger compartment, or if contact is
made, the head impact does not exceed
a head injury criteria (HIC) of 1,000 as
determined by this equation.
HIC
t
t
1
t
t
a(t)dt
2
1
2
1
t
t
2.5
1
2
=
−
(
)
−
(
)
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
∫
Where: a(t) is the resultant acceleration at
the center of gravity of the head form ex-
pressed as a multiple of g (the accelera-
tion of gravity) and t
2
¥ t
1
is the time
duration, in seconds, of major head im-
pact, not to exceed 0.05 seconds.
(6) Loads in individual upper torso
harness straps must not exceed 1,750
pounds. If dual straps are used for re-
taining the upper torso, the total har-
ness strap loads must not exceed 2,000
pounds.
(7) The maximum compressive load
measured between the pelvis and the
lumbar column of the ATD must not
exceed 1,500 pounds.
(d) An alternate approach that
achieves an equivalent or greater level
of occupant protection, as required by
this section, must be substantiated on
a rational basis.
[Amdt. 27–25, 54 FR 47318, Nov. 13, 1989]
§ 27.563
Structural ditching provi-
sions.
If certification with ditching provi-
sions is requested, structural strength
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