209
Federal Aviation Administration, DOT
§ 25.105
associated with the conditions pre-
scribed in §§ 25.119 and 25.121(d) must be
established.
(h) The procedures established under
paragraphs (f) and (g) of this section
must—
(1) Be able to be consistently exe-
cuted in service by crews of average
skill;
(2) Use methods or devices that are
safe and reliable; and
(3) Include allowance for any time
delays, in the execution of the proce-
dures, that may reasonably be expected
in service.
(i) The accelerate-stop and landing
distances prescribed in §§ 25.109 and
25.125, respectively, must be deter-
mined with all the airplane wheel
brake assemblies at the fully worn
limit of their allowable wear range.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–38, 41 FR 55466, Dec. 20,
1976; Amdt. 25–92, 63 FR 8318, Feb. 18, 1998]
§ 25.103
Stall speed.
(a) The reference stall speed, V
SR
, is a
calibrated airspeed defined by the ap-
plicant. V
SR
may not be less than a 1-g
stall speed. V
SR
is expressed as:
V
V
SR
CL
≥
MAX
n
ZW
where:
V
CL
MAX
= Calibrated airspeed obtained when
the load factor-corrected lift coefficient
n
W
qS
ZW
⎛
⎝⎜
⎞
⎠⎟
is first a maximum during the maneuver
prescribed in paragraph (c) of this section. In
addition, when the maneuver is limited by a
device that abruptly pushes the nose down at
a selected angle of attack (e.g., a stick push-
er), V
CL
MAX
may not be less than the speed ex-
isting at the instant the device operates;
n
ZW
= Load factor normal to the flight path
at V
CL
MAX
W = Airplane gross weight;
S = Aerodynamic reference wing area; and
q = Dynamic pressure.
(b) V
CLMAX
is determined with:
(1) Engines idling, or, if that result-
ant thrust causes an appreciable de-
crease in stall speed, not more than
zero thrust at the stall speed;
(2) Propeller pitch controls (if appli-
cable) in the takeoff position;
(3) The airplane in other respects
(such as flaps, landing gear, and ice ac-
cretions) in the condition existing in
the test or performance standard in
which V
SR
is being used;
(4) The weight used when V
SR
is being
used as a factor to determine compli-
ance with a required performance
standard;
(5) The center of gravity position
that results in the highest value of ref-
erence stall speed; and
(6) The airplane trimmed for straight
flight at a speed selected by the appli-
cant, but not less than 1.13V
SR
and not
greater than 1.3V
SR
.
(c) Starting from the stabilized trim
condition, apply the longitudinal con-
trol to decelerate the airplane so that
the speed reduction does not exceed
one knot per second.
(d) In addition to the requirements of
paragraph (a) of this section, when a
device that abruptly pushes the nose
down at a selected angle of attack (e.g.,
a stick pusher) is installed, the ref-
erence stall speed, V
SR
, may not be less
than 2 knots or 2 percent, whichever is
greater, above the speed at which the
device operates.
[Doc. No. 28404, 67 FR 70825, Nov. 26, 2002, as
amended by Amdt. 25–121, 72 FR 44665, Aug. 8,
2007]
§ 25.105
Takeoff.
(a) The takeoff speeds prescribed by
§ 25.107, the accelerate-stop distance
prescribed by § 25.109, the takeoff path
prescribed by § 25.111, the takeoff dis-
tance and takeoff run prescribed by
§ 25.113, and the net takeoff flight path
prescribed by § 25.115, must be deter-
mined in the selected configuration for
takeoff at each weight, altitude, and
ambient temperature within the oper-
ational limits selected by the appli-
cant—
(1) In non-icing conditions; and
(2) In icing conditions, if in the con-
figuration used to show compliance
with § 25.121(b), and with the most crit-
ical of the takeoff ice accretion(s) de-
fined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g):
(i) The stall speed at maximum take-
off weight exceeds that in non-icing
conditions by more than the greater of
3 knots CAS or 3 percent of V
SR
; or
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14 CFR Ch. I (1–1–24 Edition)
§ 25.107
(ii) The degradation of the gradient
of climb determined in accordance with
§ 25.121(b) is greater than one-half of
the applicable actual-to-net takeoff
flight path gradient reduction defined
in § 25.115(b).
(b) No takeoff made to determine the
data required by this section may re-
quire exceptional piloting skill or
alertness.
(c) The takeoff data must be based
on—
(1) In the case of land planes and am-
phibians:
(i) Smooth, dry and wet, hard-sur-
faced runways; and
(ii) At the option of the applicant,
grooved or porous friction course wet,
hard-surfaced runways.
(2) Smooth water, in the case of sea-
planes and amphibians; and
(3) Smooth, dry snow, in the case of
skiplanes.
(d) The takeoff data must include,
within the established operational lim-
its of the airplane, the following oper-
ational correction factors:
(1) Not more than 50 percent of nomi-
nal wind components along the takeoff
path opposite to the direction of take-
off, and not less than 150 percent of
nominal wind components along the
takeoff path in the direction of takeoff.
(2) Effective runway gradients.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–92, 63 FR 8318, Feb. 18,
1998; Amdt. 25–121, 72 FR 44665, Aug. 8, 2007;
Amdt. 25–140, 79 FR 65525, Nov. 4, 2014]
§ 25.107
Takeoff speeds.
(a) V
1
must be established in relation
to V
EF
as follows:
(1) V
EF
is the calibrated airspeed at
which the critical engine is assumed to
fail. V
EF
must be selected by the appli-
cant, but may not be less than V
MCG
de-
termined under § 25.149(e).
(2) V
1
, in terms of calibrated air-
speed, is selected by the applicant;
however, V
1
may not be less than V
EF
plus the speed gained with critical en-
gine inoperative during the time inter-
val between the instant at which the
critical engine is failed, and the in-
stant at which the pilot recognizes and
reacts to the engine failure, as indi-
cated by the pilot’s initiation of the
first action (e.g., applying brakes, re-
ducing thrust, deploying speed brakes)
to stop the airplane during accelerate-
stop tests.
(b)
V
2MIN,
in terms of calibrated air-
speed, may not be less than—
(1) 1.13
V
SR
for—
(i) Two-engine and three-engine tur-
bopropeller and reciprocating engine
powered airplanes; and
(ii) Turbojet powered airplanes with-
out provisions for obtaining a signifi-
cant reduction in the one-engine-inop-
erative power-on stall speed;
(2) 1.08
V
SR
for—
(i) Turbopropeller and reciprocating
engine powered airplanes with more
than three engines; and
(ii) Turbojet powered airplanes with
provisions for obtaining a significant
reduction in the one-engine-inoper-
ative power-on stall speed; and
(3) 1.10 times
V
MC
established under
§ 25.149.
(c)
V
2
, in terms of calibrated air-
speed, must be selected by the appli-
cant to provide at least the gradient of
climb required by § 25.121(b) but may
not be less than—
(1) V
2MIN
;
(2)
V
R
plus the speed increment at-
tained (in accordance with § 25.111(c)(2))
before reaching a height of 35 feet
above the takeoff surface; and
(3) A speed that provides the maneu-
vering capability specified in § 25.143(h).
(d) V
MU
is the calibrated airspeed at
and above which the airplane can safe-
ly lift off the ground, and con- tinue
the takeoff. V
MU
speeds must be se-
lected by the applicant throughout the
range of thrust-to-weight ratios to be
certificated. These speeds may be es-
tablished from free air data if these
data are verified by ground takeoff
tests.
(e)
V
R,
in terms of calibrated air-
speed, must be selected in accordance
with the conditions of paragraphs (e)(1)
through (4) of this section:
(1)
V
R
may not be less than—
(i)
V
1
;
(ii) 105 percent of
V
MC
;
(iii) The speed (determined in accord-
ance with § 25.111(c)(2)) that allows
reaching
V
2
before reaching a height of
35 feet above the takeoff surface; or
(iv) A speed that, if the airplane is
rotated at its maximum practicable
rate, will result in a V
LOF
of not less
than —
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