Sec. 25.562 - Emergency landing dynamic conditions.
(a) The seat and restraint system in the
airplane must be designed as prescribed 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 prescribed 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 demonstrated 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 occupant simulated by a 170-pound anthropomorphic test dummy, as
defined by 49 CFR Part 572, Subpart B, or its equivalent, sitting in the
normal upright position.
(1) A change in downward vertical
velocity (Δ v) of not less than 35 feet per second, with the airplane's
longitudinal axis canted downward 30 degrees with respect to the
horizontal plane and with the wings level. Peak floor deceleration must
occur in not more than 0.08 seconds after impact and must reach a minimum
(2) A change in forward longitudinal
velocity (Δ v) of not less than 44 feet per second, with the airplane's
longitudinal axis horizontal and yawed 10 degrees either right or left,
whichever would cause the greatest likelihood of the upper torso restraint
system (where installed) moving off the occupant'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 minimum 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 respect to the adjacent set
of rails or fittings by at least 10 degrees vertically (i.e., out of
Parallel) with one rolled 10 degrees.
(c) The following performance measures
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 individual straps must not exceed 1,750
pounds. If dual straps are used for restraining 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
(4) The lap safety belt must remain on
the occupant's pelvis during the impact.
(5) Each occupant must be protected from
serious head injury under the conditions prescribed in paragraph (b) of
this section. Where head contact with seats or other structure can occur,
protection must be provided so that the head impact does not exceed a Head
Injury Criterion (HIC) of 1,000 units. The level of HIC is defined by the
(6) Where leg injuries may result from
contact with seats or other structure, protection must be provided to
prevent axially compressive loads exceeding 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]