226
14 CFR Ch. I (1–1–24 Edition)
§ 25.181
(2) From V
MO
/M
MO
to V
FC
/M
FC
, unless
the divergence is—
(i) Gradual;
(ii) Easily recognizable by the pilot;
and
(iii) Easily controllable by the pilot.
(c) The following requirement must
be met for the configurations and speed
specified in paragraph (a) of this sec-
tion. In straight, steady sideslips over
the range of sideslip angles appropriate
to the operation of the airplane, the ai-
leron and rudder control movements
and forces must be substantially pro-
portional to the angle of sideslip in a
stable sense. This factor of proportion-
ality must lie between limits found
necessary for safe operation. The range
of sideslip angles evaluated must in-
clude those sideslip angles resulting
from the lesser of:
(1) One-half of the available rudder
control input; and
(2) A rudder control force of 180
pounds.
(d) For sideslip angles greater than
those prescribed by paragraph (c) of
this section, up to the angle at which
full rudder control is used or a rudder
control force of 180 pounds is obtained,
the rudder control forces may not re-
verse, and increased rudder deflection
must be needed for increased angles of
sideslip. Compliance with this require-
ment must be shown using straight,
steady sideslips, unless full lateral con-
trol input is achieved before reaching
either full rudder control input or a
rudder control force of 180 pounds; a
straight, steady sideslip need not be
maintained after achieving full lateral
control input. This requirement must
be met at all approved landing gear and
flap positions for the range of oper-
ating speeds and power conditions ap-
propriate to each landing gear and flap
position with all engines operating.
[Amdt. 25–135, 76 FR 74654, Dec. 1, 2011]
§ 25.181
Dynamic stability.
(a) Any short period oscillation, not
including combined lateral-directional
oscillations, occurring between 1.13 V
SR
and maximum allowable speed appro-
priate to the configuration of the air-
plane must be heavily damped with the
primary controls—
(1) Free; and
(2) In a fixed position.
(b) Any combined lateral-directional
oscillations (‘‘Dutch roll’’) occurring
between 1.13 V
SR
and maximum allow-
able speed appropriate to the configu-
ration of the airplane must be posi-
tively damped with controls free, and
must be controllable with normal use
of the primary controls without requir-
ing exceptional pilot skill.
[Amdt. 25–42, 43 FR 2322, Jan. 16, 1978, as
amended by Amdt. 25–72, 55 FR 29775, July 20,
1990; 55 FR 37607, Sept. 12, 1990; Amdt. 25–108,
67 FR 70827, Nov. 26, 2002]
S
TALLS
§ 25.201
Stall demonstration.
(a) Stalls must be shown in straight
flight and in 30 degree banked turns
with—
(1) Power off; and
(2) The power necessary to maintain
level flight at 1.5 V
SR1
(where V
SR1
cor-
responds to the reference stall speed at
maximum landing weight with flaps in
the approach position and the landing
gear retracted).
(b) In each condition required by
paragraph (a) of this section, it must
be possible to meet the applicable re-
quirements of § 25.203 with—
(1) Flaps, landing gear, and decelera-
tion devices in any likely combination
of positions approved for operation;
(2) Representative weights within the
range for which certification is re-
quested;
(3) The most adverse center of grav-
ity for recovery; and
(4) The airplane trimmed for straight
flight at the speed prescribed in
§ 25.103(b)(6).
(c) The following procedures must be
used to show compliance with § 25.203;
(1) Starting at a speed sufficiently
above the stalling speed to ensure that
a steady rate of speed reduction can be
established, apply the longitudinal
control so that the speed reduction
does not exceed one knot per second
until the airplane is stalled.
(2) In addition, for turning flight
stalls, apply the longitudinal control
to achieve airspeed deceleration rates
up to 3 knots per second.
(3) As soon as the airplane is stalled,
recover by normal recovery techniques.
(d) The airplane is considered stalled
when the behavior of the airplane gives
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Federal Aviation Administration, DOT
§ 25.207
the pilot a clear and distinctive indica-
tion of an acceptable nature that the
airplane is stalled. Acceptable indica-
tions of a stall, occurring either indi-
vidually or in combination, are—
(1) A nose-down pitch that cannot be
readily arrested;
(2) Buffeting, of a magnitude and se-
verity that is a strong and effective de-
terrent to further speed reduction; or
(3) The pitch control reaches the aft
stop and no further increase in pitch
attitude occurs when the control is
held full aft for a short time before re-
covery is initiated.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–84, 60 FR 30750, June 9,
1995; Amdt. 25–108, 67 FR 70827, Nov. 26, 2002]
§ 25.203
Stall characteristics.
(a) It must be possible to produce and
to correct roll and yaw by unreversed
use of the aileron and rudder controls,
up to the time the airplane is stalled.
No abnormal nose-up pitching may
occur. The longitudinal control force
must be positive up to and throughout
the stall. In addition, it must be pos-
sible to promptly prevent stalling and
to recover from a stall by normal use
of the controls.
(b) For level wing stalls, the roll oc-
curring between the stall and the com-
pletion of the recovery may not exceed
approximately 20 degrees.
(c) For turning flight stalls, the ac-
tion of the airplane after the stall may
not be so violent or extreme as to
make it difficult, with normal piloting
skill, to effect a prompt recovery and
to regain control of the airplane. The
maximum bank angle that occurs dur-
ing the recovery may not exceed—
(1) Approximately 60 degrees in the
original direction of the turn, or 30 de-
grees in the opposite direction, for de-
celeration rates up to 1 knot per sec-
ond; and
(2) Approximately 90 degrees in the
original direction of the turn, or 60 de-
grees in the opposite direction, for de-
celeration rates in excess of 1 knot per
second.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–84, 60 FR 30750, June 9,
1995]
§ 25.207
Stall warning.
(a) Stall warning with sufficient mar-
gin to prevent inadvertent stalling
with the flaps and landing gear in any
normal position must be clear and dis-
tinctive to the pilot in straight and
turning flight.
(b) The warning must be furnished ei-
ther through the inherent aerodynamic
qualities of the airplane or by a device
that will give clearly distinguishable
indications under expected conditions
of flight. However, a visual stall warn-
ing device that requires the attention
of the crew within the cockpit is not
acceptable by itself. If a warning de-
vice is used, it must provide a warning
in each of the airplane configurations
prescribed in paragraph (a) of this sec-
tion at the speed prescribed in para-
graphs (c) and (d) of this section. Ex-
cept for the stall warning prescribed in
paragraph (h)(3)(ii) of this section, the
stall warning for flight in icing condi-
tions must be provided by the same
means as the stall warning for flight in
non-icing conditions.
(c) When the speed is reduced at rates
not exceeding one knot per second,
stall warning must begin, in each nor-
mal configuration, at a speed, V
SW
, ex-
ceeding the speed at which the stall is
identified in accordance with § 25.201(d)
by not less than five knots or five per-
cent CAS, whichever is greater. Once
initiated, stall warning must continue
until the angle of attack is reduced to
approximately that at which stall
warning began.
(d) In addition to the requirement of
paragraph (c) of this section, when the
speed is reduced at rates not exceeding
one knot per second, in straight flight
with engines idling and at the center-
of-gravity position specified in
§ 25.103(b)(5), V
SW
, in each normal con-
figuration, must exceed V
SR
by not less
than three knots or three percent CAS,
whichever is greater.
(e) In icing conditions, the stall
warning margin in straight and turn-
ing flight must be sufficient to allow
the pilot to prevent stalling (as defined
in § 25.201(d)) when the pilot starts a re-
covery maneuver not less than three
seconds after the onset of stall warn-
ing. When demonstrating compliance
with this paragraph, the pilot must
perform the recovery maneuver in the
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