CS 25.562 Emergency landing dynamic conditions

ED Decision 2018/005/R

(See AMC 25.562)

(a)     The seat and restraint system in the aeroplane must be designed as prescribed in this paragraph 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 paragraph.

(b)     Each seat type design approved for occupancy must successfully complete dynamic tests or be demonstrated by rational analysis based on dynamic tests of a similar seat type, in accordance with each of the following emergency landing conditions. The tests must be conducted with an occupant simulated by a 77kg (170 lb) anthropomorphic, test dummy sitting in the normal upright position:

(1)     A change in downward vertical velocity, (∆v) of not less than 10·7 m/s, (35 ft/s) with the aeroplane’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 of 14 g.

(2)     A change in forward longitudinal velocity (∆v) of not less than 13·4 m/s, (44 ft/s) with the aeroplane’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 16 g. With the exception of flight deck crew seats that are mounted in the forward conical area of the fuselage, 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 sub-paragraph (b) of this paragraph:

(1)     Where upper torso straps are used tension loads in individual straps must not exceed 794 kg. (1750lb) If dual straps are used for restraining the upper torso, the total strap tension loads must not exceed 907kg (2000 lb)).

(2)     The maximum compressive load measured between the pelvis and the lumbar column of the anthropomorphic dummy must not exceed 680 kg. (1500lb)

(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 impact.

(5)     Each occupant must be protected from serious head injury under the conditions prescribed in sub-paragraph (b) of this paragraph. 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 1000 units. The level of HIC is defined by the equation –

Where –

t₁ is the initial integration time,

t₂ 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 structure, protection must be provided to prevent axially compressive loads exceeding 1021 kg (2250 lb) 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 sub-paragraphs (b)(1) and (b)(2) of this paragraph to the extent they would impede rapid evacuation of the aeroplane occupants.

[Amdt 25/15]

[Amdt 25/17]

[Amdt 25/21]