228 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.231 

same way as for the airplane in non- 
icing conditions. Compliance with this 
requirement must be demonstrated in 
flight with the speed reduced at rates 
not exceeding one knot per second, 
with— 

(1) The most critical of the takeoff 

ice and final takeoff ice accretions de-
fined in Appendices C and O of this 
part, as applicable, in accordance with 
§ 25.21(g), for each configuration used in 
the takeoff phase of flight; 

(2) The most critical of the en route 

ice accretion(s) defined in Appendices C 
and O of this part, as applicable, in ac-
cordance with § 25.21(g), for the en 
route configuration; 

(3) The most critical of the holding 

ice accretion(s) defined in Appendices C 
and O of this part, as applicable, in ac-
cordance with § 25.21(g), for the holding 
configuration(s); 

(4) The most critical of the approach 

ice accretion(s) defined in Appendices C 
and O of this part, as applicable, in ac-
cordance with § 25.21(g), for the ap-
proach configuration(s); and 

(5) The most critical of the landing 

ice accretion(s) defined in Appendices C 
and O of this part, as applicable, in ac-
cordance with § 25.21(g), for the landing 
and go-around configuration(s). 

(f) The stall warning margin must be 

sufficient in both non-icing and icing 
conditions to allow the pilot to prevent 
stalling when the pilot starts a recov-
ery maneuver not less than one second 
after the onset of stall warning in slow- 
down turns with at least 1.5 g load fac-
tor normal to the flight path and air-
speed deceleration rates of at least 2 
knots per second. When demonstrating 
compliance with this paragraph for 
icing conditions, the pilot must per-
form the recovery maneuver in the 
same way as for the airplane in non- 
icing conditions. Compliance with this 
requirement must be demonstrated in 
flight with— 

(1) The flaps and landing gear in any 

normal position; 

(2) The airplane trimmed for straight 

flight at a speed of 1.3 V

SR

; and 

(3) The power or thrust necessary to 

maintain level flight at 1.3 V

SR

. 

(g) Stall warning must also be pro-

vided in each abnormal configuration 
of the high lift devices that is likely to 
be used in flight following system fail-

ures (including all configurations cov-
ered by Airplane Flight Manual proce-
dures). 

(h) The following stall warning mar-

gin is required for flight in icing condi-
tions before the ice protection system 
has been activated and is performing 
its intended function. Compliance must 
be shown using the most critical of the 
ice accretion(s) defined in Appendix C, 
part II, paragraph (e) of this part and 
Appendix O, part II, paragraph (d) of 
this part, as applicable, in accordance 
with § 25.21(g). The stall warning mar-
gin in straight and turning flight must 
be sufficient to allow the pilot to pre-
vent stalling without encountering any 
adverse flight characteristics when: 

(1) The speed is reduced at rates not 

exceeding one knot per second; 

(2) The pilot performs the recovery 

maneuver in the same way as for flight 
in non-icing conditions; and 

(3) The recovery maneuver is started 

no earlier than: 

(i) One second after the onset of stall 

warning if stall warning is provided by 
the same means as for flight in non- 
icing conditions; or 

(ii) Three seconds after the onset of 

stall warning if stall warning is pro-
vided by a different means than for 
flight in non-icing conditions. 

(i) In showing compliance with para-

graph (h) of this section, if stall warn-
ing is provided by a different means in 
icing conditions than for non-icing con-
ditions, compliance with § 25.203 must 
be shown using the accretion defined in 
appendix C, part II(e) of this part. Com-
pliance with this requirement must be 
shown using the demonstration pre-
scribed by § 25.201, except that the de-
celeration rates of § 25.201(c)(2) need not 
be demonstrated. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–7, 30 FR 13118, Oct. 15, 
1965; Amdt. 25–42, 43 FR 2322, Jan. 16, 1978; 
Amdt. 25–108, 67 FR 70827, Nov. 26, 2002; 
Amdt. 25–121, 72 FR 44668, Aug. 8, 2007; Amdt. 
25–129, 74 FR 38339, Aug. 3, 2009; Amdt. 25–140, 
79 FR 65526, Nov. 4, 2014] 

G

ROUND AND

W

ATER

H

ANDLING

 

C

HARACTERISTICS

 

§ 25.231

Longitudinal stability and 

control. 

(a) Landplanes may have no uncon-

trollable tendency to nose over in any 

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Federal Aviation Administration, DOT 

§ 25.239 

reasonably expected operating condi-
tion or when rebound occurs during 
landing or takeoff. In addition— 

(1) Wheel brakes must operate 

smoothly and may not cause any undue 
tendency to nose over; and 

(2) If a tail-wheel landing gear is 

used, it must be possible, during the 
takeoff ground run on concrete, to 
maintain any attitude up to thrust line 
level, at 75 percent of 

V

SR1

. 

(b) For seaplanes and amphibians, 

the most adverse water conditions safe 
for takeoff, taxiing, and landing, must 
be established. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–108, 67 FR 70828, Nov. 
26, 2002] 

§ 25.233

Directional stability and con-

trol. 

(a) There may be no uncontrollable 

ground-looping tendency in 90

° 

cross 

winds, up to a wind velocity of 20 knots 
or 0.2 

V

SR0

, whichever is greater, except 

that the wind velocity need not exceed 
25 knots at any speed at which the air-
plane may be expected to be operated 
on the ground. This may be shown 
while establishing the 90

° 

cross compo-

nent of wind velocity required by 
§ 25.237. 

(b) Landplanes must be satisfactorily 

controllable, without exceptional pilot-
ing skill or alertness, in power-off land-
ings at normal landing speed, without 
using brakes or engine power to main-
tain a straight path. This may be 
shown during power-off landings made 
in conjunction with other tests. 

(c) The airplane must have adequate 

directional control during taxiing. This 
may be shown during taxiing prior to 
takeoffs made in conjunction with 
other tests. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5671, Apr. 8, 
1970; Amdt. 25–42, 43 FR 2322, Jan. 16, 1978; 
Amdt. 25–94, 63 FR 8848, Feb. 23, 1998; Amdt. 
25–108, 67 FR 70828, Nov. 26, 2002] 

§ 25.235

Taxiing condition. 

The shock absorbing mechanism may 

not damage the structure of the air-
plane when the airplane is taxied on 
the roughest ground that may reason-
ably be expected in normal operation. 

§ 25.237

Wind velocities. 

(a) For land planes and amphibians, 

the following applies: 

(1) A 90-degree cross component of 

wind velocity, demonstrated to be safe 
for takeoff and landing, must be estab-
lished for dry runways and must be at 
least 20 knots or 0.2 V

SR0

, whichever is 

greater, except that it need not exceed 
25 knots. 

(2) The crosswind component for 

takeoff established without ice accre-
tions is valid in icing conditions. 

(3) The landing crosswind component 

must be established for: 

(i) Non-icing conditions, and 
(ii) Icing conditions with the most 

critical of the landing ice accretion(s) 
defined in Appendices C and O of this 
part, as applicable, in accordance with 
§ 25.21(g). 

(b) For seaplanes and amphibians, 

the following applies: 

(1) A 90-degree cross component of 

wind velocity, up to which takeoff and 
landing is safe under all water condi-
tions that may reasonably be expected 
in normal operation, must be estab-
lished and must be at least 20 knots or 
0.2 V

SR0

, whichever is greater, except 

that it need not exceed 25 knots. 

(2) A wind velocity, for which taxiing 

is safe in any direction under all water 
conditions that may reasonably be ex-
pected in normal operation, must be es-
tablished and must be at least 20 knots 
or 0.2 V

SR0

, whichever is greater, except 

that it need not exceed 25 knots. 

[Amdt. 25–42, 43 FR 2322, Jan. 16, 1978, as 
amended by Amdt. 25–108, 67 FR 70827, Nov. 
26, 2002; Amdt. 25–121, 72 FR 44668, Aug. 8, 
2007; Amdt. 25–140, 79 FR 65525, Nov. 4, 2014] 

§ 25.239

Spray characteristics, control, 

and stability on water. 

(a) For seaplanes and amphibians, 

during takeoff, taxiing, and landing, 
and in the conditions set forth in para-
graph (b) of this section, there may be 
no— 

(1) Spray characteristics that would 

impair the pilot’s view, cause damage, 
or result in the taking in of an undue 
quantity of water; 

(2) Dangerously uncontrollable 

porpoising, bounding, or swinging tend-
ency; or 

(3) Immersion of auxiliary floats or 

sponsons, wing tips, propeller blades, 

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