316 

14 CFR Ch. I (1–1–19 Edition) 

§ 25.963 

the position that provides adequate 
cooling in the hot-day condition. 

(D) Engine operating within the max-

imum continuous power limitations. 

(E) Maximum takeoff weight; and 
(ii) For turbine engine powered air-

planes, the maximum airspeed estab-
lished for climbing from takeoff to the 
maximum operating altitude. 

(5) The fuel temperature must be at 

least 110 

°

F. 

(b) The test prescribed in paragraph 

(a) of this section may be performed in 
flight or on the ground under closely 
simulated flight conditions. If a flight 
test is performed in weather cold 
enough to interfere with the proper 
conduct of the test, the fuel tank sur-
faces, fuel lines, and other fuel system 
parts subject to cold air must be insu-
lated to simulate, insofar as prac-
ticable, flight in hot weather. 

[Amdt. 25–11, 32 FR 6912, May 5, 1967, as 
amended by Amdt. 25–57, 49 FR 6848, Feb. 23, 
1984] 

§ 25.963

Fuel tanks: general. 

(a) Each fuel tank must be able to 

withstand, without failure, the vibra-
tion, inertia, fluid, and structural loads 
that it may be subjected to in oper-
ation. 

(b) Flexible fuel tank liners must be 

approved or must be shown to be suit-
able for the particular application. 

(c) Integral fuel tanks must have fa-

cilities for interior inspection and re-
pair. 

(d) Fuel tanks must, so far as it is 

practicable, be designed, located, and 
installed so that no fuel is released in 
or near the fuselage, or near the en-
gines, in quantities that would con-
stitute a fire hazard in otherwise sur-
vivable emergency landing conditions, 
and— 

(1) Fuel tanks must be able to resist 

rupture and retain fuel under ultimate 
hydrostatic design conditions in which 
the pressure P within the tank varies 
in accordance with the formula: 

P = K

r

gL 

Where— 

P = fuel pressure at each point within the 

tank 

r 

= typical fuel density 

g = acceleration due to gravity 

L = a reference distance between the point of 

pressure and the tank farthest boundary 
in the direction of loading 

K = 4.5 for the forward loading condition for 

those parts of fuel tanks outside the fu-
selage pressure boundary 

K = 9 for the forward loading condition for 

those parts of fuel tanks within the fuse-
lage pressure boundary, or that form part 
of the fuselage pressure boundary 

K = 1.5 for the aft loading condition 
K = 3.0 for the inboard and outboard loading 

conditions for those parts of fuel tanks 
within the fuselage pressure boundary, or 
that form part of the fuselage pressure 
boundary 

K = 1.5 for the inboard and outboard loading 

conditions for those parts of fuel tanks 
outside the fuselage pressure boundary 

K = 6 for the downward loading condition 
K = 3 for the upward loading condition 

(2) For those parts of wing fuel tanks 

near the fuselage or near the engines, 
the greater of the fuel pressures result-
ing from paragraphs (d)(2)(i) or (d)(2)(ii) 
of this section must be used: 

(i) The fuel pressures resulting from 

paragraph (d)(1) of this section, and 

(ii) The lesser of the two following 

conditions: 

(A) Fuel pressures resulting from the 

accelerations specified in § 25.561(b)(3) 
considering the fuel tank full of fuel at 
maximum fuel density. Fuel pressures 
based on the 9.0g forward acceleration 
may be calculated using the fuel static 
head equal to the streamwise local 
chord of the tank. For inboard and out-
board conditions, an acceleration of 
1.5g may be used in lieu of 3.0g as speci-
fied in § 25.561(b)(3). 

(B) Fuel pressures resulting from the 

accelerations as specified in 
§ 25.561(b)(3) considering a fuel volume 
beyond 85 percent of the maximum per-
missible volume in each tank using the 
static head associated with the 85 per-
cent fuel level. A typical density of the 
appropriate fuel may be used. For in-
board and outboard conditions, an ac-
celeration of 1.5g may be used in lieu of 
3.0g as specified in § 25.561(b)(3). 

(3) Fuel tank internal barriers and 

baffles may be considered as solid 
boundaries if shown to be effective in 
limiting fuel flow. 

(4) For each fuel tank and sur-

rounding airframe structure, the ef-
fects of crushing and scraping actions 
with the ground must not cause the 
spillage of enough fuel, or generate 

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