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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§ 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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