CS 25.103 Stall speed

(See AMC 25.103)

(a)The reference stall speed VSR is a calibrated airspeed defined by the applicant. VSR may not be less than a 1-g stall speed. VSR is expressed as:

where – VCLMAX = Calibrated airspeed obtained when the loadfactor-corrected lift coefficient is first a maximum during the manoeuvre prescribed in sub-paragraph (c) of this paragraph. In addition, when the manoeuvre is limited by a device that abruptly pushes the nose down at a selected angle of attack (e.g. a stick pusher), VCLMAX may not be less than the speed existing at the instant the device operates; nzw = Load factor normal to the flight path at VCLMAX; W = Aeroplane gross weight; S = Aerodynamic reference wing area; and q = Dynamic pressure.

(b)VCLMAX is determined with:

(1)Engines idling, or, if that resultant thrust causes an appreciable decrease in stall speed, not more than zero thrust at the stall speed;

(2)Propeller pitch controls (if applicable) in the take-off position;

(3)The aeroplane in other respects (such as flaps, landing gear, and ice accretions) in the condition existing in the test or performance standard in which VSR is being used;

(4)The weight used when VSR is being used as a factor to determine compliance with a required performance standard;

(5)The centre of gravity position that results in the highest value of reference stall speed; and

(6)The aeroplane trimmed for straight flight at a speed selected by the applicant, but not less than 1.13 VSR and not greater than 1.3 VSR. (See AMC 25.103(b))

(c)Starting from the stabilised trim condition, apply the longitudinal control to decelerate the aeroplane so that the speed reduction does not exceed 0.5 m/s2 (one knot per second). (See AMC 25.103(b) and (c)).

(d)In addition to the requirements of sub-paragraph (a) of this paragraph, when a device that abruptly pushes the nose down at a selected angle of attack (e.g. a stick pusher) is installed, the reference stall speed, VSR, may not be less than 3,7 km/h (2 kt) or 2%, whichever is greater, above the speed at which the device operates. (See AMC 25.103(d))

[Amdt 25/3]

[Amdt 25/18]