475 

Federal Aviation Administration, DOT 

§ 25.965 

(C) Cowl flaps (or other means of con-

trolling the engine cooling supply) in 
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 within the fuselage 

contour must be able to resist rupture 
and to retain fuel, under the inertia 
forces prescribed for the emergency 
landing conditions in § 25.561. In addi-
tion, these tanks must be in a pro-
tected position so that exposure of the 
tanks to scraping action with the 
ground is unlikely. 

(e) Fuel tank access covers must 

comply with the following criteria in 
order to avoid loss of hazardous quan-
tities of fuel: 

(1) All covers located in an area 

where experience or analysis indicates 
a strike is likely must be shown by 
analysis or tests to minimize penetra-
tion and deformation by tire frag-

ments, low energy engine debris, or 
other likely debris. 

(2) All covers must be fire resistant 

as defined in part 1 of this chapter. 

(f) For pressurized fuel tanks, a 

means with fail-safe features must be 
provided to prevent the buildup of an 
excessive pressure difference between 
the inside and the outside of the tank. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–40, 42 FR 15043, Mar. 17, 
1977; Amdt. 25–69, 54 FR 40354, Sept. 29, 1989] 

§ 25.965

Fuel tank tests. 

(a) It must be shown by tests that the 

fuel tanks, as mounted in the airplane, 
can withstand, without failure or leak-
age, the more critical of the pressures 
resulting from the conditions specified 
in paragraphs (a)(1) and (2) of this sec-
tion. In addition, it must be shown by 
either analysis or tests, that tank sur-
faces subjected to more critical pres-
sures resulting from the condition of 
paragraphs (a)(3) and (4) of this section, 
are able to withstand the following 
pressures: 

(1) An internal pressure of 3.5 psi. 
(2) 125 percent of the maximum air 

pressure developed in the tank from 
ram effect. 

(3) Fluid pressures developed during 

maximum limit accelerations, and de-
flections, of the airplane with a full 
tank. 

(4) Fluid pressures developed during 

the most adverse combination of air-
plane roll and fuel load. 

(b) Each metallic tank with large un-

supported or unstiffened flat surfaces, 
whose failure or deformation could 
cause fuel leakage, must be able to 
withstand the following test, or its 
equivalent, without leakage or exces-
sive deformation of the tank walls: 

(1) Each complete tank assembly and 

its supports must be vibration tested 
while mounted to simulate the actual 
installation. 

(2) Except as specified in paragraph 

(b)(4) of this section, the tank assembly 
must be vibrated for 25 hours at an am-
plitude of not less than 

1

⁄

32

of an inch 

(unless another amplitude is substan-
tiated) while 

2

⁄

3

filled with water or 

other suitable test fluid. 

(3) The test frequency of vibration 

must be as follows: 

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