372
14 CFR Ch. I (1–1–14 Edition)
§ 25.21
Subpart B—Flight
G
ENERAL
§ 25.21
Proof of compliance.
(a) Each requirement of this subpart
must be met at each appropriate com-
bination of weight and center of grav-
ity within the range of loading condi-
tions for which certification is re-
quested. This must be shown—
(1) By tests upon an airplane of the
type for which certification is re-
quested, or by calculations based on,
and equal in accuracy to, the results of
testing; and
(2) By systematic investigation of
each probable combination of weight
and center of gravity, if compliance
cannot be reasonably inferred from
combinations investigated.
(b) [Reserved]
(c) The controllability, stability,
trim, and stalling characteristics of
the airplane must be shown for each al-
titude up to the maximum expected in
operation.
(d) Parameters critical for the test
being conducted, such as weight, load-
ing (center of gravity and inertia), air-
speed, power, and wind, must be main-
tained within acceptable tolerances of
the critical values during flight test-
ing.
(e) If compliance with the flight
characteristics requirements is depend-
ent upon a stability augmentation sys-
tem or upon any other automatic or
power-operated system, compliance
must be shown with §§ 25.671 and 25.672.
(f) In meeting the requirements of
§§ 25.105(d), 25.125, 25.233, and 25.237, the
wind velocity must be measured at a
height of 10 meters above the surface,
or corrected for the difference between
the height at which the wind velocity
is measured and the 10-meter height.
(g) The requirements of this subpart
associated with icing conditions apply
only if the applicant is seeking certifi-
cation for flight in icing conditions.
(1) Each requirement of this subpart,
except §§ 25.121(a), 25.123(c), 25.143(b)(1)
and (2), 25.149, 25.201(c)(2), 25.239, and
25.251(b) through (e), must be met in
icing conditions. Section 25.207(c) and
(d) must be met in the landing configu-
ration in icing conditions, but need not
be met for other configurations. Com-
pliance must be shown using the ice ac-
cretions defined in appendix C, assum-
ing normal operation of the airplane
and its ice protection system in accord-
ance with the operating limitations
and operating procedures established
by the applicant and provided in the
Airplane Flight Manual.
(2) No changes in the load distribu-
tion limits of § 25.23, the weight limits
of § 25.25 (except where limited by per-
formance requirements of this sub-
part), and the center of gravity limits
of § 25.27, from those for non-icing con-
ditions, are allowed for flight in icing
conditions or with ice accretion.
[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 2320, Jan. 16, 1978;
Amdt. 25–72, 55 FR 29774, July 20, 1990; Amdt.
25–121, 72 FR 44665, Aug. 8, 2007 Amdt. 25–135,
76 FR 74654, Dec. 1, 2011]
§ 25.23
Load distribution limits.
(a) Ranges of weights and centers of
gravity within which the airplane may
be safely operated must be established.
If a weight and center of gravity com-
bination is allowable only within cer-
tain load distribution limits (such as
spanwise) that could be inadvertently
exceeded, these limits and the cor-
responding weight and center of grav-
ity combinations must be established.
(b) The load distribution limits may
not exceed—
(1) The selected limits;
(2) The limits at which the structure
is proven; or
(3) The limits at which compliance
with each applicable flight require-
ment of this subpart is shown.
§ 25.25
Weight limits.
(a)
Maximum weights. Maximum
weights corresponding to the airplane
operating conditions (such as ramp,
ground or water taxi, takeoff, en route,
and landing), environmental conditions
(such as altitude and temperature), and
loading conditions (such as zero fuel
weight, center of gravity position and
weight distribution) must be estab-
lished so that they are not more than—
(1) The highest weight selected by
the applicant for the particular condi-
tions; or
(2) The highest weight at which com-
pliance with each applicable structural
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