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229

Federal Aviation Administration, DOT

§ 25.231

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

; and

(3) The power or thrust necessary to

maintain level flight at 1.3 V

(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]

ROUND AND

ATER

ANDLING

HARACTERISTICS

§ 25.231

Longitudinal stability and

control.

(a) Landplanes may have no uncon-

trollable tendency to nose over in any
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

(b) For seaplanes and amphibians,

the most adverse water conditions safe

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