CS 25.345 High lift devices

• ED Decision 2016/010/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

CS 25.345 High lift devices ED Decision 2016/010/R (See AMC 25.345) (a) If wing-flaps are to be used during take-off, approach, or landing, at the design flap speeds established for these stages of flight under [CS 25.335(e)](#_DxCrossRefBm1709820916) and with the wing-flaps in the corresponding positions, the aeroplane is assumed to be subjected to symmetrical manoeuvres and gusts. The resulting limit loads must correspond to the conditions determined as follows: (1) Manoeuvring to a positive limit load factor of 2·0; and (2) Positive and negative gusts of 7.62 m/sec (25 ft/sec) EAS acting normal to the flight path in level flight. Gust loads resulting on each part of the structure must be determined by rational analysis. The analysis must take into account the unsteady aerodynamic characteristics and rigid body motions of the aircraft. (See [AMC 25.345(a)](#_DxCrossRefBm1709820955).) The shape of the gust must be as described in [CS 25.341(a)(2)](#_DxCrossRefBm1709820927) except that – Uds = 7.62 m/sec (25 ft/sec) EAS; H = 12.5 c; and c = mean geometric chord of the wing (metres (feet)). (b) The aeroplane must be designed for the conditions prescribed in sub-paragraph (a) of this paragraph except that the aeroplane load factor need not exceed 1·0, taking into account, as separate conditions, the effects of – (1) Propeller slipstream corresponding to maximum continuous power at the design flap speeds VF, and with take-off power at not less than 1·4 times the stalling speed for the particular flap position and associated maximum weight; and (2) A head-on gust of 7.62m/sec (25 fps) velocity (EAS). (c) If flaps or other high lift devices are to be used in en-route conditions, and with flaps in the appropriate position at speeds up to the flap design speed chosen for these conditions, the aeroplane is assumed to be subjected to symmetrical manoeuvres and gusts within the range determined by – (1) Manoeuvring to a positive limit load factor as prescribed in [CS 25.337(b)](#_DxCrossRefBm1709820886) ; and (2) The vertical gust and turbulence conditions prescribed in [CS 25.341](#_DxCrossRefBm1709820927). (See [AMC 25.345(c)](#_DxCrossRefBm1709820954).) (d) The aeroplane must be designed for a manoeuvring load factor of 1.5 g at the maximum take-off weight with the wing-flaps and similar high lift devices in the landing configurations. [Amdt 25/1] [Amdt 25/18]