background image

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 

VerDate Sep<11>2014 

09:06 Jun 28, 2024

Jkt 262046

PO 00000

Frm 00236

Fmt 8010

Sfmt 8010

Y:\SGML\262046.XXX

262046

jspears on DSK121TN23PROD with CFR

background image

227 

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 

VerDate Sep<11>2014 

09:06 Jun 28, 2024

Jkt 262046

PO 00000

Frm 00237

Fmt 8010

Sfmt 8010

Y:\SGML\262046.XXX

262046

jspears on DSK121TN23PROD with CFR