Sec. 25.103 - Stall speed.
(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:
VCLMAX = Calibrated airspeed
obtained when the load factor-corrected lift coefficient
is first a maximum during the maneuver prescribed in
paragraph (c) of this section. In addition, when the maneuver 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
W = Airplane gross weight;
S = Aerodynamic reference wing area; and
q = Dynamic pressure.
(b) VCLMAX is
(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 takeoff position;
(3) The airplane in other respects (such
as flaps and landing gear) 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
(5) The center of gravity position that
results in the highest value of reference stall speed; and
(6) The airplane trimmed for straight
flight at a speed selected by the applicant, but not less than 1.13VSR
and not greater than 1.3VSR.
(c) Starting from the stabilized trim
condition, apply the longitudinal control to decelerate the airplane so
that the speed reduction does not exceed one knot per second.
(d) In addition to the requirements of
paragraph (a) of this section, 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 2 knots or 2 percent, whichever is greater, above the speed at which
the device operates.
[Doc. No. 28404, 67 FR 70825, Nov. 26, 2002]