title-14-part-29-sec29-967

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).

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637

Federal Aviation Administration, DOT

§ 29.975

(d) No rotorcraft skin immediately

adjacent to a major air outlet from the
engine compartment may act as the
wall of an integral tank.

[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]

§ 29.969

Fuel tank expansion space.

Each fuel tank or each group of fuel

tanks with interconnected vent sys-
tems must have an expansion space of
not less than 2 percent of the combined
tank capacity. It must be impossible to
fill the fuel tank expansion space inad-
vertently with the rotorcraft in the
normal ground attitude.

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

§ 29.971

Fuel tank sump.

(a) Each fuel tank must have a sump

with a capacity of not less than the
greater of—

(1) 0.10 per cent of the tank capacity;

(2)

⁄

gallon.

(b) The capacity prescribed in para-

graph (a) of this section must be effec-
tive with the rotorcraft in any normal
attitude, and must be located so that
the sump contents cannot escape
through the tank outlet opening.

age of hazardous quantities of water
from each part of the tank to the sump
with the rotorcraft in any ground atti-
tude to be expected in service.

(d) Each fuel tank sump must have a

drain that allows complete drainage of
the sump on the ground.

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29–12, 41 FR 55473, Dec. 20,
1976; Amdt. 29–26, 53 FR 34217, Sept. 2, 1988]

§ 29.973

Fuel tank filler connection.

(a) Each fuel tank filler connection

must prevent the entrance of fuel into
any part of the rotorcraft other than
the tank itself during normal oper-
ations and must be crash resistant dur-
ing a survivable impact in accordance
with § 29.952(c). In addition—

(1) Each filler must be marked as pre-

scribed in § 29.1557(c)(1);

(2) Each recessed filler connection

that can retain any appreciable quan-
tity of fuel must have a drain that dis-

charges clear of the entire rotorcraft;
and

(3) Each filler cap must provide a

fuel-tight seal under the fluid pressure
expected in normal operation and in a
survivable impact.

(b) Each filler cap or filler cap cover

must warn when the cap is not fully
locked or seated on the filler connec-
tion.

[Doc. No. 26352, 59 FR 50388, Oct. 3, 1994]

§ 29.975

Fuel tank vents and carbu-

retor vapor vents.

(a)

Fuel tank vents. Each fuel tank

must be vented from the top part of the
expansion space so that venting is ef-
fective under normal flight conditions.
In addition—

(1) The vents must be arranged to

avoid stoppage by dirt or ice forma-
tion;

(2) The vent arrangement must pre-

vent siphoning of fuel during normal
operation;

(3) The venting capacity and vent

pressure levels must maintain accept-
able differences of pressure between
the interior and exterior of the tank,
during—

(i) Normal flight operation;
(ii) Maximum rate of ascent and de-

scent; and

(iii) Refueling and defueling (where

applicable);

(4) Airspaces of tanks with inter-

connected outlets must be inter-
connected;

(5) There may be no point in any vent

line where moisture can accumulate
with the rotorcraft in the ground atti-
tude or the level flight attitude, unless
drainage is provided;

(6) No vent or drainage provision may

end at any point—

(i) Where the discharge of fuel from

the vent outlet would constitute a fire
hazard; or

(ii) From which fumes could enter

personnel compartments; and

(7) The venting system must be de-

signed to minimize spillage of fuel
through the vents to an ignition source
in the event of a rollover during land-
ing, ground operations, or a survivable
impact.