title-14-part-29-sec29-965

635

Federal Aviation Administration, DOT

§ 29.965

§ 29.957

Flow between interconnected

tanks.

(a) Where tank outlets are inter-

connected and allow fuel to flow be-
tween them due to gravity or flight ac-
celerations, it must be impossible for
fuel to flow between tanks in quan-
tities 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 over-
filling; and

(2) There must be means to warn the

crew before overflow through the vents
occurs.

§ 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 oper-
ations and flight maneuvers involving
that tank.

§ 29.961

Fuel system hot weather oper-

ation.

Each suction lift fuel system and

other fuel systems conducive to vapor
formation must be shown to operate
satisfactorily (within certification lim-
its) when using fuel at the most crit-
ical temperature for vapor formation
under critical operating conditions in-
cluding, if applicable, the engine oper-
ating conditions defined by § 29.927(b)(1)
and (b)(2).

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

§ 29.963

Fuel tanks: general.

(a) Each fuel tank must be able to

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

(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. Punc-
ture resistance must be shown by
meeting the TSO-C80, paragraph 16.0,
requirements using a minimum punc-
ture force of 370 pounds.

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 re-
quirement must be shown under all op-
erating conditions and under all nor-
mal or malfunction conditions of all
components inside the tank.

(e) Each fuel tank installed in per-

sonnel compartments must be isolated
by fume-proof and fuel-proof enclosures
that are drained and vented to the ex-
terior 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
§ 29.952, and must be adequate to with-
stand loads and abrasions to be ex-
pected 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]

§ 29.965

Fuel tank tests.

(a) Each fuel tank must be able to

withstand the applicable pressure tests
in this section without failure or leak-
age. 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 emer-
gency deceleration with a full tank ex-
ceeds this value, in which case a hydro-
static 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 accelera-
tion loading.

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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636

14 CFR Ch. I (1–1–24 Edition)

§ 29.967

specified in paragraph (c)(2) of this sec-
tion.

(2) A pressure test, with the tank

mounted in the rotorcraft structure,
equal to the load developed by the re-
action of the contents, with the tank
full, during maximum limit accelera-
tion or emergency deceleration. How-
ever, the pressure need not exceed 2.0
p.s.i. on surfaces faces not exposed to
the acceleration loading.

(d) Each tank with large unsupported

or unstiffened flat areas, or with other
features whose failure or deformation
could cause leakage, must be subjected
to the following test or its equivalent:

(1) Each complete tank assembly and

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

(2) The tank assembly must be vi-

brated for 25 hours while two-thirds
full of any suitable fluid. The ampli-
tude of vibration may not be less than
one thirty-second of an inch, unless
otherwise substantiated.

(3) The test frequency of vibration

must be as follows:

(i) If no frequency of vibration result-

ing from any r.p.m. within the normal
operating range of engine or rotor sys-
tem speeds is critical, the test fre-
quency of vibration, in number of cy-
cles per minute, must, unless a fre-
quency based on a more rational anal-
ysis is used, be the number obtained by
averaging the maximum and minimum
power-on engine speeds (r.p.m.) for re-
ciprocating engine powered rotorcraft
or 2,000 c.p.m. for turbine engine pow-
ered rotorcraft.

(ii) If only one frequency of vibration

resulting from any r.p.m. within the
normal operating range of engine or
rotor system speeds is critical, that
frequency of vibration must be the test
frequency.

(iii) If more than one frequency of vi-

bration resulting from any r.p.m. with-
in the normal operating range of en-
gine or rotor system speeds is critical,
the most critical of these frequencies
must be the test frequency.

(4) Under paragraph (d)(3)(ii) and (iii),

the time of test must be adjusted to ac-
complish the same number of vibration
cycles as would be accomplished in 25
hours at the frequency specified in
paragraph (d)(3)(i) of this section.

(5) During the test, the tank assem-

bly must be rocked at the rate of 16 to
20 complete cycles per minute through
an angle of 15 degrees on both sides of
the horizontal (30 degrees total), about
the most critical axis, for 25 hours. If
motion about more than one axis is
likely to be critical, the tank must be
rocked about each critical axis for 12

⁄

hours.

(Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49
U.S.C. 1354(a), 1421, and 1423; sec. 6(c), 49
U.S.C. 1655 (c))

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29–13, 42 FR 15046, Mar. 17,
1977]

§ 29.967

Fuel tank installation.

(a) Each fuel tank must be supported

so that tank loads are not con-
centrated on unsupported tank sur-
faces. In addition—

(1) There must be pads, if necessary,

to prevent chafing between each tank
and its supports;

(2) The padding must be non-

absorbent or treated to prevent the ab-
sorption of fuel;

(3) If flexible tank liners are used,

they must be supported so that they
are not required to withstand fluid
loads; and

(4) Each interior surface of tank com-

partments must be smooth and free of
projections that could cause wear of
the liner, unless—

(i) There are means for protection of

the liner at those points; or

(ii) The construction of the liner

itself provides such protection.

(b) Any spaces adjacent to tank sur-

faces must be adequately ventilated to
avoid accumulation of fuel or fumes in
those spaces due to minor leakage. If
the tank is in a sealed compartment,
ventilation may be limited to drain
holes that prevent clogging and that
prevent excessive pressure resulting
from altitude changes. If flexible tank
liners are installed, the venting ar-
rangement for the spaces between the
liner and its container must maintain
the proper relationship to tank vent
pressures for any expected flight condi-
tion.

meet the requirements of § 29.1185(b)
and (c).