CS 25.201 Stall demonstration

The power for all power-on stall demonstrations is that power necessary to maintain level flight at a speed of 1·5 VSR1 at maximum landing weight, with flaps in the approach position and landing gear retracted, where VSR1 is the reference stall speed in the same conditions (except power). The flap position to be used to determine this power setting is that position in which the reference stall speed does not exceed 110% of the reference stall speed with the flaps in the most extended landing position.

Stall demonstrations for compliance with CS 25.201 should include demonstrations with deceleration devices deployed for all flap positions unless limitations against use of the devices with particular flap positions are imposed. ‘Deceleration devices’ include spoilers when used as air brakes, and thrust reversers when use in flight is permitted. Stall demonstrations with deceleration devices deployed should normally be carried out with power off, except where deployment of the deceleration devices while power is applied is likely to occur in normal operations (e.g. use of extended air brakes during landing approach).

The intent of evaluating higher deceleration rates is to demonstrate safe characteristics at higher rates of increase of angle of attack than are obtained from the 0.5 m/s2 (1 knot per second) stalls. The specified airspeed deceleration rate, and associated angle of attack rate, should be maintained up to the point at which the aeroplane stalls.

1 The behaviour of the aeroplane includes the behaviour as affected by the normal functioning of any systems with which the aeroplane is equipped, including devices intended to alter the stalling characteristics of the aeroplane. 2 Unless the design of the automatic flight control system of the aeroplane protects against such an event, the stalling characteristics and adequacy of stall warning, when the aeroplane is stalled under the control of the automatic flight control system, should be investigated. (See also CS 25.1329(h).)

[Amdt 25/19]

[Amdt 25/21]

An acceptable interpretation of holding the pitch control on the aft stop for a short time is: a. The pitch control reaches the aft stop and is held full aft for 2 seconds or until the pitch attitude stops increasing, whichever occurs later. b. In the case of turning flight stalls, recovery may be initiated once the pitch control reaches the aft stop when accompanied by a rolling motion that is not immediately controllable (provided the rolling motion complies with CS 25.203(c)). c. For those aeroplanes where stall is defined by full nose up longitudinal control for both forward and aft C.G., the time at full aft stick should be not less than was used for stall speed determination, except as permitted by paragraph (b) above.