406
14 CFR Ch. I (1–1–14 Edition)
§ 25.363
in paragraphs (a)(1) and (2) of this sec-
tion, a limit engine torque cor-
responding to takeoff power and pro-
peller speed, multiplied by a factor ac-
counting for propeller control system
malfunction, including quick feath-
ering, acting simultaneously with 1
g
level flight loads. In the absence of a
rational analysis, a factor of 1.6 must
be used.
(b) For turbine engine installations,
the engine mounts and supporting
structure must be designed to with-
stand each of the following:
(1) A limit engine torque load im-
posed by sudden engine stoppage due to
malfunction or structural failure (such
as compressor jamming).
(2) A limit engine torque load im-
posed by the maximum acceleration of
the engine.
(c) The limit engine torque to be con-
sidered under paragraph (a) of this sec-
tion must be obtained by multiplying
mean torque for the specified power
and speed by a factor of—
(1) 1.25 for turbopropeller installa-
tions;
(2) 1.33 for reciprocating engines with
five or more cylinders; or
(3) Two, three, or four, for engines
with four, three, or two cylinders, re-
spectively.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5672, Apr. 8,
1970; Amdt. 25–46, 43 FR 50595, Oct. 30, 1978;
Amdt. 25–72, 55 FR 29776, July 20, 1990]
§ 25.363
Side load on engine and auxil-
iary power unit mounts.
(a) Each engine and auxiliary power
unit mount and its supporting struc-
ture must be designed for a limit load
factor in lateral direction, for the side
load on the engine and auxiliary power
unit mount, at least equal to the max-
imum load factor obtained in the yaw-
ing conditions but not less than—
(1) 1.33; or
(2) One-third of the limit load factor
for flight condition A as prescribed in
§ 25.333(b).
(b) The side load prescribed in para-
graph (a) of this section may be as-
sumed to be independent of other flight
conditions.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5672, Apr. 8,
1970; Amdt. 25–91, 62 FR 40704, July 29, 1997]
§ 25.365
Pressurized compartment
loads.
For airplanes with one or more pres-
surized compartments the following
apply:
(a) The airplane structure must be
strong enough to withstand the flight
loads combined with pressure differen-
tial loads from zero up to the max-
imum relief valve setting.
(b) The external pressure distribution
in flight, and stress concentrations and
fatigue effects must be accounted for.
(c) If landings may be made with the
compartment pressurized, landing
loads must be combined with pressure
differential loads from zero up to the
maximum allowed during landing.
(d) The airplane structure must be
designed to be able to withstand the
pressure differential loads cor-
responding to the maximum relief
valve setting multiplied by a factor of
1.33 for airplanes to be approved for op-
eration to 45,000 feet or by a factor of
1.67 for airplanes to be approved for op-
eration above 45,000 feet, omitting
other loads.
(e) Any structure, component or part,
inside or outside a pressurized com-
partment, the failure of which could
interfere with continued safe flight and
landing, must be designed to withstand
the effects of a sudden release of pres-
sure through an opening in any com-
partment at any operating altitude re-
sulting from each of the following con-
ditions:
(1) The penetration of the compart-
ment by a portion of an engine fol-
lowing an engine disintegration;
(2) Any opening in any pressurized
compartment up to the size H
o
in
square feet; however, small compart-
ments may be combined with an adja-
cent pressurized compartment and both
considered as a single compartment for
openings that cannot reasonably be ex-
pected to be confined to the small com-
partment. The size H
o
must be com-
puted by the following formula:
H
o
=PA
s
where,
H
o
=Maximum opening in square feet, need
not exceed 20 square feet.
P=(A
s
/6240)+.024
A
s
=Maximum cross-sectional area of the
pressurized shell normal to the longitu-
dinal axis, in square feet; and
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