CS 25.345 High lift devices

Large Aeroplanes (CS-25) · CS-25 · EAR revision 26 Jan 2023

IRImplementing rule

CS 25.345High lift devices

(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) 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).) The shape of the gust must be as described in CS 25.341(a)(2) 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) ; and

(2)The vertical gust and turbulence conditions prescribed in CS 25.341. (See AMC 25.345(c).)

(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]

IR · CS 25.345 — CS-25 · ED Decision 2016/010/R · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMCAcceptable means of compliance

AMC 25.345(a)High lift devices (Gust conditions)

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Compliance with CS 25.345(a) may be demonstrated by an analysis in which the solution of the vertical response equations is made by assuming the aircraft to be rigid. If desired, the analysis may take account of the effects of structural flexibility on a quasi-flexible basis (i.e. using aerodynamic derivatives and load distributions corresponding to the distorted structure under maximum gust load).

AMC · AMC 25.345(a) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMCAcceptable means of compliance

AMC 25.345(c)High lift devices (Procedure flight condition)

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1 En-route conditions are flight segments other than take-off, approach and landing. As applied to the use of high lift devices the following flight phases are to be included in en-route conditions: holding in designated areas outside the terminal area of the airport, and flight with flaps extended from top of descent. The following flight phases are not to be included in en-route conditions: portion of the flight corresponding to standard arrival routes preceding the interception of the final approach path, and holding at relatively low altitude close to the airport. 2 To apply CS 25.341(a) gust conditions to CS 25.345(c), the speeds VFC and VFD should be determined for the flap positions selected in en-route conditions. These procedures should ensure proper speed margins for flap retraction in the case of severe turbulence when the aeroplane is in a low speed en-route holding configuration. 3 The manoeuvre of CS 25.345(c)(1) is to be considered as a balanced condition. (See CS 25.331(b) for definition.)

AMC · AMC 25.345(c) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

All rules in SUBPART C – STRUCTURE

Consolidated from the EASA Easy Access Rules (revision 26 Jan 2023, extracted 17 Aug 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.

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