(a) V_S0 and V_S1 are the stalling speeds or the minimum steady flight speed (CAS) at which the aeroplane is controllable with –

(1) For reciprocating engine-powered aeroplanes, engine(s) idling, the throttle(s) closed or at not more than the power necessary for zero thrust at a speed not more than 110% of the stalling speed; and

(2) For turbine engine-powered aeroplanes, the propulsive thrust may not be greater than zero at the stalling speed, or, if the resultant thrust has no appreciable effect on the stalling speed, with engine(s) idling and throttle(s) closed;

(3) Propeller(s) in the take-off position;

(4) The aeroplane in the condition existing in the test in which V_S0 and V_S1 are being used;

(5) Centre of gravity in the position which results in the highest value of V_S0 and V_S1; and

(6) Weight used when V_SO and V_S1 are being used as a factor to determine compliance with a required performance standard.

(b) V_S0 and V_S1 must be determined by flight tests using the procedure and meeting the flight characteristics specified in CS 23.201.

(c) V_S0 at maximum weight must not exceed 113 km/h (61 knots) for –

(1) Single-engined aeroplanes; and

(2) Twin-engined aeroplanes of 2 722 kg (6 000 lb) or less maximum weight that cannot meet the minimum rate of climb specified in CS 23.67 (a) (1) with the critical engine inoperative.

Each aeroplane with a V_S0 of more than 113 km/h (61 knots) must be able to maintain a steady climb gradient of at least 1·5% at a pressure altitude of 1524 m (5 000 ft) with –

(i) The critical engine -inoperative and its propeller in the minimum drag position;

(ii) The remaining engine at not more than maximum continuous power;

(iii) The landing gear retracted;

(iv) The wing flaps retracted; and

(v) A climb speed not less than 1·2 V_S1.

‘V_S’ means the stall speed or the minimum steady flight speed at which the aeroplane is controllable.

‘V_S0’ means the stall speed or the minimum steady flight speed in the landing configuration.

‘V_S1’ means the stall speed or the minimum steady flight speed obtained in a specified configuration.

(a) It must be possible to produce and to correct roll by unreversed use of the rolling control and to produce and to correct yaw by unreversed use of the directional control, up to the time the aeroplane stalls.

(b) The wings level stall characteristics must be demonstrated in flight as follows. Starting from a speed at least 18.5 km/h (10 knots) above the stall speed, the elevator control must be pulled back so that the rate of speed reduction will not exceed 1.9 km/h (one knot) per second until a stall is produced, as shown by either –

(1) An uncontrollable downward pitching motion of the aeroplane; or

(2) A downward pitching motion of the aeroplane which results from the activation of a device (e.g. stick pusher); or

(3) The control reaching the stop.

(c) Normal use of elevator control for recovery is allowed after the downward pitching motion of (b) (1) or (b) (2) has unmistakably been produced, or after the control has been held against the stop for not less than the longer of 2 seconds or the time employed in the minimum steady flight speed determination of CS 23.49.

(d) During the entry into and the recovery from the manoeuvre, it must be possible to prevent more than 15° of roll or yaw by the normal use of controls.

(e) Compliance with the requirements must be shown under the following conditions:

(1) Wing flaps. Retracted, fully extended and each intermediate normal operating position;

(2) Landing gear. Retracted and extended;

(3) Cowl flaps. Appropriate to configuration;

(4) Power

(i) Power off; and

(ii) 75% maximum continuous power. If the power-to-weight ratio at 75% of maximum continuous power results in extreme nose-up attitudes, the test may be carried out with the power required for level flight in the landing configuration at maximum landing weight and a speed of 1·4 V_S0, but the power may not be less than 50% maximum continuous power.

(5) Trim. The aeroplane trimmed at a speed as near 1·5 V_S1 as practicable.

(6) Propeller. Full increase rpm position for the power off condition.

For normal utility and aerobatic category aeroplanes, the rotation speed V_R, is the speed at which the pilot makes a control input with the intention of lifting the aeroplane out of contact with the runway or water surface.

(1) For twin-engined landplanes, V_R must not be less than the greater of 1·05 V_MC or 1·10 V_S1;

(2) For single engined landplanes, V_R, must not be less than V_S1.

‘V_MC’ means minimum control speed with the critical engine inoperative.

‘V_R’ means rotation speed.