spaschal on DSK3GDR082PROD with CFR

Federal Aviation Administration, DOT

Section 29.967

specified in paragraph (c)(2) of this section.
(2) A pressure test, with the tank
mounted in the rotorcraft structure,
equal to the load developed by the reaction of the contents, with the tank
full, during maximum limit acceleration or emergency deceleration. However, 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 vibrated for 25 hours while two-thirds
full of any suitable fluid. The amplitude 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 resulting from any r.p.m. within the normal
operating range of engine or rotor system speeds is critical, the test frequency of vibration, in number of cycles per minute, must, unless a frequency based on a more rational analysis is used, be the number obtained by
averaging the maximum and minimum
power-on engine speeds (r.p.m.) for reciprocating engine powered rotorcraft
or 2,000 c.p.m. for turbine engine powered 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 vibration resulting from any r.p.m. within the normal operating range of engine 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 accomplish 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 assembly 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 121-2
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]

Section 29.967

Fuel tank installation.

(a) Each fuel tank must be supported
so that tank loads are not concentrated on unsupported tank surfaces. In addition - 
(1) There must be pads, if necessary,
to prevent chafing between each tank
and its supports;
(2) The padding must be nonabsorbent or treated to prevent the absorption 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 compartments 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 surfaces 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 arrangement for the spaces between the
liner and its container must maintain
the proper relationship to tank vent
pressures for any expected flight condition.
(c) The location of each tank must
meet the requirements of Section 29.1185(b)
and (c).

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