240
14 CFR Ch. I (1–1–24 Edition)
§ 25.343
for the maximum response at the na-
celle center of gravity derived from the
following dynamic gust conditions ap-
plied to the airplane:
(1) A discrete gust determined in ac-
cordance with § 25.341(a) at each angle
normal to the flight path, and sepa-
rately,
(2) A pair of discrete gusts, one
vertical and one lateral. The length of
each of these gusts must be independ-
ently tuned to the maximum response
in accordance with § 25.341(a). The pene-
tration of the airplane in the combined
gust field and the phasing of the
vertical and lateral component gusts
must be established to develop the
maximum response to the gust pair. In
the absence of a more rational anal-
ysis, the following formula must be
used for each of the maximum engine
loads in all six degrees of freedom:
Where—
P
L
= limit load;
P
L-1g
= steady 1g load for the condition;
L
V
= peak incremental response load due to
a vertical gust according to § 25.341(a);
and
L
L
= peak incremental response load due to
a lateral gust according to § 25.341(a).
[Doc. No. 27902, 61 FR 5221, Feb. 9, 1996; 61 FR
9533, Mar. 8, 1996; Doc. No. FAA–2013–0142; 79
FR 73467, Dec. 11, 2014; Amdt. 25–141, 80 FR
4762, Jan. 29, 2015; 80 FR 6435, Feb. 5, 2015]
§ 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 and turbulence condi-
tions of § 25.341(a) and (b), but assuming
85% of the gust velocities prescribed in
§ 25.341(a)(4) and 85% of the turbulence
intensities prescribed in § 25.341(b)(3).
(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; Amdt.
25–141, 79 FR 73468, Dec. 11, 2014]
§ 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—
U
ds
= 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,
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