Code of Federal Regulations - Title 14

404

14 CFR Ch. I (1–1–14 Edition)

§ 25.343

establish the dynamic response unless
more rational criteria are shown.

[Doc. No. 27902, 61 FR 5221, Feb. 9, 1996; 61 FR
9533, Mar. 8, 1996]

§ 25.343

Design fuel and oil loads.

(a) The disposable load combinations

must include each fuel and oil load in
the range from zero fuel and oil to the
selected maximum fuel and oil load. A
structural reserve fuel condition, not
exceeding 45 minutes of fuel under the
operating conditions in § 25.1001(e) and
(f), as applicable, may be selected.

(b) If a structural reserve fuel condi-

tion is selected, it must be used as the
minimum fuel weight condition for
showing compliance with the flight
load requirements as prescribed in this
subpart. In addition—

(1) The structure must be designed

for a condition of zero fuel and oil in
the wing at limit loads corresponding
to—

(i) A maneuvering load factor of

+2.25; and

(ii) The gust conditions of § 25.341(a)

but assuming 85% of the design veloci-
ties prescribed in § 25.341(a)(4).

(2) Fatigue evaluation of the struc-

ture must account for any increase in
operating stresses resulting from the
design condition of paragraph (b)(1) of
this section; and

(3) The flutter, deformation, and vi-

bration requirements must also be met
with zero fuel.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–18, 33 FR 12226, Aug. 30,
1968; Amdt. 25–72, 55 FR 37607, Sept. 12, 1990;
Amdt. 25–86, 61 FR 5221, Feb. 9, 1996]

§ 25.345

High lift devices.

(a) If wing flaps are to be used during

takeoff, approach, or landing, at the
design flap speeds established for these
stages of flight under § 25.335(e) and
with the wing flaps in the cor-
responding positions, the airplane is
assumed to be subjected to symmet-
rical maneuvers and gusts. The result-
ing limit loads must correspond to the
conditions determined as follows:

(1) Maneuvering to a positive limit

load factor of 2.0; and

(2) Positive and negative gusts of 25

ft/sec EAS acting normal to the flight
path in level flight. Gust loads result-
ing on each part of the structure must

be determined by rational analysis.
The analysis must take into account
the unsteady aerodynamic characteris-
tics and rigid body motions of the air-
craft. The shape of the gust must be as
described in § 25.341(a)(2) except that—

=25 ft/sec EAS;

H=12.5 c; and
c=mean geometric chord of the wing (feet).

(b) The airplane must be designed for

the conditions prescribed in paragraph
(a) of this section, except that the air-
plane load factor need not exceed 1.0,
taking into account, as separate condi-
tions, the effects of—

(1) Propeller slipstream cor-

responding to maximum continuous
power at the design flap speeds

and

with takeoff power at not less than 1.4
times the stalling speed for the par-
ticular flap position and associated
maximum weight; and

(2) A head-on gust of 25 feet per sec-

ond velocity (EAS).

are to be used in en route conditions,
and with flaps in the appropriate posi-
tion at speeds up to the flap design
speed chosen for these conditions, the
airplane is assumed to be subjected to
symmetrical maneuvers and gusts
within the range determined by—

(1) Maneuvering to a positive limit

load factor as prescribed in § 25.337(b);
and

(2) The discrete vertical gust criteria

in § 25.341(a).

(d) The airplane must be designed for

a maneuvering load factor of 1.5 g at
the maximum take-off weight with the
wing-flaps and similar high lift devices
in the landing configurations.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–46, 43 FR 50595, Oct. 30,
1978; Amdt. 25–72, 55 FR 37607, Sept. 17, 1990;
Amdt. 25–86, 61 FR 5221, Feb. 9, 1996; Amdt.
25–91, 62 FR 40704, July 29, 1997]

§ 25.349

Rolling conditions.

The airplane must be designed for

loads resulting from the rolling condi-
tions specified in paragraphs (a) and (b)
of this section. Unbalanced aero-
dynamic moments about the center of
gravity must be reacted in a rational
or conservative manner, considering
the principal masses furnishing the re-
acting inertia forces.

VerDate Mar<15>2010

10:12 Mar 18, 2014

Jkt 232046

PO 00000

Frm 00414

Fmt 8010

Sfmt 8010

Y:\SGML\232046.XXX

232046

pmangrum on DSK3VPTVN1PROD with CFR