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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 

(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-

(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] 











§ 25.231

Longitudinal stability and 


(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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