Section 29.957

14 CFR Ch. I (1-1-19 Edition)

Section 29.957 Flow between interconnected
tanks.
(a) Where tank outlets are interconnected and allow fuel to flow between them due to gravity or flight accelerations, it must be impossible for
fuel to flow between tanks in quantities great enough to cause overflow
from the tank vent in any sustained
flight condition.
(b) If fuel can be pumped from one
tank to another in flight - 
(1) The design of the vents and the
fuel transfer system must prevent
structural damage to tanks from overfilling; and
(2) There must be means to warn the
crew before overflow through the vents
occurs.
Section 29.959 Unusable fuel supply.
The unusable fuel supply for each
tank must be established as not less
than the quantity at which the first
evidence of malfunction occurs under
the most adverse fuel feed condition
occurring under any intended operations and flight maneuvers involving
that tank.

(c) Each integral fuel tank must have
facilities for inspection and repair of
its interior.
(d) The maximum exposed surface
temperature of all components in the
fuel tank must be less by a safe margin
than the lowest expected autoignition
temperature of the fuel or fuel vapor in
the tank. Compliance with this requirement must be shown under all operating conditions and under all normal or malfunction conditions of all
components inside the tank.
(e) Each fuel tank installed in personnel compartments must be isolated
by fume-proof and fuel-proof enclosures
that are drained and vented to the exterior of the rotorcraft. The design and
construction of the enclosures must
provide necessary protection for the
tank, must be crash resistant during a
survivable impact in accordance with
Section 29.952, and must be adequate to withstand loads and abrasions to be expected in personnel compartments.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29-26, 53 FR 34217, Sept. 2,
1988; Amdt. 29-35, 59 FR 50388, Oct. 3, 1994]

Section 29.965
Section 29.961 Fuel system hot weather operation.
Each suction lift fuel system and
other fuel systems conducive to vapor
formation must be shown to operate
satisfactorily (within certification limits) when using fuel at the most critical temperature for vapor formation
under critical operating conditions including, if applicable, the engine operating conditions defined by Section 29.927(b)(1)
and (b)(2).

spaschal on DSK3GDR082PROD with CFR

[Amdt. 29-26, 53 FR 34217, Sept. 2, 1988]

Section 29.963 Fuel tanks: general.
(a) Each fuel tank must be able to
withstand, without failure, the vibration, inertia, fluid, and structural loads
to which it may be subjected in operation.
(b) Each flexible fuel tank bladder or
liner must be approved or shown to be
suitable for the particular application
and must be puncture resistant. Puncture resistance must be shown by
meeting the TSO-C80, paragraph 16.0,
requirements using a minimum puncture force of 370 pounds.

Fuel tank tests.

(a) Each fuel tank must be able to
withstand the applicable pressure tests
in this section without failure or leakage. If practicable, test pressures may
be applied in a manner simulating the
pressure distribution in service.
(b) Each conventional metal tank,
each nonmetallic tank with walls that
are not supported by the rotorcraft
structure, and each integral tank must
be subjected to a pressure of 3.5 p.s.i.
unless the pressure developed during
maximum limit acceleration or emergency deceleration with a full tank exceeds this value, in which case a hydrostatic head, or equivalent test, must be
applied to duplicate the acceleration
loads as far as possible. However, the
pressure need not exceed 3.5 p.s.i. on
surfaces not exposed to the acceleration loading.
(c) Each nonmetallic tank with walls
supported by the rotorcraft structure
must be subjected to the following
tests:
(1) A pressure test of at least 2.0 p.s.i.
This test may be conducted on the
tank alone in conjunction with the test

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