Federal Aviation Administration, DOT § 25.25
(2) By systematic investigation of ditions, are allowed for flight in icing
each probable combination of weight conditions or with ice accretion.
and center of gravity, if compliance [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
cannot be reasonably inferred from amended by Amdt. 25–23, 35 FR 5671, Apr. 8,
combinations investigated. 1970; Amdt. 25–42, 43 FR 2320, Jan. 16, 1978;
(b) [Reserved] Amdt. 25–72, 55 FR 29774, July 20, 1990; Amdt.
(c) The controllability, stability, 25–121, 72 FR 44665, Aug. 8, 2007]
trim, and stalling characteristics of
§ 25.23 Load distribution limits.
the airplane must be shown for each al-
titude up to the maximum expected in (a) Ranges of weights and centers of
operation. gravity within which the airplane may
(d) Parameters critical for the test be safely operated must be established.
being conducted, such as weight, load- If a weight and center of gravity com-
ing (center of gravity and inertia), air- bination is allowable only within cer-
speed, power, and wind, must be main- tain load distribution limits (such as
spanwise) that could be inadvertently
tained within acceptable tolerances of
exceeded, these limits and the cor-
the critical values during flight test-
responding weight and center of grav-
ing. ity combinations must be established.
(e) If compliance with the flight (b) The load distribution limits may
characteristics requirements is depend- not exceed—
ent upon a stability augmentation sys- (1) The selected limits;
tem or upon any other automatic or (2) The limits at which the structure
power-operated system, compliance is proven; or
must be shown with §§ 25.671 and 25.672. (3) The limits at which compliance
(f) In meeting the requirements of with each applicable flight require-
§§ 25.105(d), 25.125, 25.233, and 25.237, the ment of this subpart is shown.
wind velocity must be measured at a
height of 10 meters above the surface, § 25.25 Weight limits.
or corrected for the difference between (a) Maximum weights. Maximum
the height at which the wind velocity weights corresponding to the airplane
is measured and the 10-meter height. operating conditions (such as ramp,
(g) The requirements of this subpart ground or water taxi, takeoff, en route,
associated with icing conditions apply and landing), environmental conditions
only if the applicant is seeking certifi- (such as altitude and temperature), and
cation for flight in icing conditions. loading conditions (such as zero fuel
(1) Each requirement of this subpart, weight, center of gravity position and
except §§ 25.121(a), 25.123(c), 25.143(b)(1) weight distribution) must be estab-
and (b)(2), 25.149, 25.201(c)(2), 25.207(c) lished so that they are not more than—
and (d), 25.239, and 25.251(b) through (e), (1) The highest weight selected by
must be met in icing conditions. Com- the applicant for the particular condi-
pliance must be shown using the ice ac- tions; or
cretions defined in appendix C, assum- (2) The highest weight at which com-
ing normal operation of the airplane pliance with each applicable structural
and its ice protection system in accord- loading and flight requirement is
ance with the operating limitations shown, except that for airplanes
and operating procedures established equipped with standby power rocket
engines the maximum weight must not
by the applicant and provided in the
be more than the highest weight estab-
Airplane Flight Manual.
lished in accordance with appendix E of
(2) No changes in the load distribu- this part; or
tion limits of § 25.23, the weight limits (3) The highest weight at which com-
of § 25.25 (except where limited by per- pliance is shown with the certification
formance requirements of this sub- requirements of Part 36 of this chapter.
part), and the center of gravity limits (b) Minimum weight. The minimum
of § 25.27, from those for non-icing con- weight (the lowest weight at which
compliance with each applicable re-
quirement of this part is shown) must
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§ 25.27 14 CFR Ch. I (1–1–09 Edition)
be established so that it is not less § 25.33 Propeller speed and pitch lim-
(1) The lowest weight selected by the (a) The propeller speed and pitch
applicant; must be limited to values that will en-
(2) The design minimum weight (the sure–
lowest weight at which compliance (1) Safe operation under normal oper-
with each structural loading condition ating conditions; and
of this part is shown); or (2) Compliance with the performance
(3) The lowest weight at which com- requirements of §§ 25.101 through 25.125.
pliance with each applicable flight re- (b) There must be a propeller speed
quirement is shown. limiting means at the governor. It
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as must limit the maximum possible gov-
amended by Amdt. 25–23, 35 FR 5671, Apr. 8, erned engine speed to a value not ex-
1970; Amdt. 25–63, 53 FR 16365, May 6, 1988] ceeding the maximum allowable r.p.m.
(c) The means used to limit the low
§ 25.27 Center of gravity limits. pitch position of the propeller blades
The extreme forward and the extreme must be set so that the engine does not
aft center of gravity limitations must exceed 103 percent of the maximum al-
be established for each practicably sep- lowable engine rpm or 99 percent of an
arable operating condition. No such approved maximum overspeed, which-
limit may lie beyond— ever is greater, with—
(a) The extremes selected by the ap- (1) The propeller blades at the low
plicant; pitch limit and governor inoperative;
(b) The extremes within which the (2) The airplane stationary under
structure is proven; or standard atmospheric conditions with
(c) The extremes within which com- no wind; and
pliance with each applicable flight re- (3) The engines operating at the take-
quirement is shown. off manifold pressure limit for recipro-
cating engine powered airplanes or the
§ 25.29 Empty weight and cor- maximum takeoff torque limit for tur-
responding center of gravity. bopropeller engine-powered airplanes.
(a) The empty weight and cor- [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
responding center of gravity must be amended by Amdt. 25–57, 49 FR 6848, Feb. 23,
determined by weighing the airplane 1984; Amdt. 25–72, 55 FR 29774, July 20, 1990]
(1) Fixed ballast; PERFORMANCE
(2) Unusable fuel determined under
§ 25.959; and § 25.101 General.
(3) Full operating fluids, including— (a) Unless otherwise prescribed, air-
(i) Oil; planes must meet the applicable per-
(ii) Hydraulic fluid; and formance requirements of this subpart
(iii) Other fluids required for normal for ambient atmospheric conditions
operation of airplane systems, except and still air.
potable water, lavatory precharge (b) The performance, as affected by
water, and fluids intended for injection engine power or thrust, must be based
in the engine. on the following relative humidities;
(b) The condition of the airplane at (1) For turbine engine powered air-
the time of determining empty weight planes, a relative humidity of—
must be one that is well defined and (i) 80 percent, at and below standard
can be easily repeated. temperatures; and
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as (ii) 34 percent, at and above standard
amended by Amdt. 25–42, 43 FR 2320, Jan. 16, temperatures plus 50 °F.
1978; Amdt. 25–72, 55 FR 29774, July 20, 1990] Between these two temperatures, the
relative humidity must vary linearly.
§ 25.31 Removable ballast. (2) For reciprocating engine powered
Removable ballast may be used on airplanes, a relative humidity of 80 per-
showing compliance with the flight re- cent in a standard atmosphere. Engine
quirements of this subpart. power corrections for vapor pressure
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