Sec. 23.967 - Fuel tank installation.
(a) Each fuel tank must be supported
so that tank loads are not concentrated. In addition --
(1) There must be pads, if
necessary, to prevent chafing between each tank and its supports;
(2) Padding must be nonabsorbent or
treated to prevent the absorption of fuel;
(3) If a flexible tank liner is
used, it must be supported so that it is not required to withstand
(4) Interior surfaces adjacent to
the liner must be smooth and free from projections that could cause
wear, unless --
(i) Provisions are made for
protection of the liner at those points; or
(ii) The construction of the liner
itself provides such protection; and
(5) A positive pressure must be
maintained within the vapor space of each bladder cell under any
condition of operation, except for a particular condition for which it
is shown that a zero or negative pressure will not cause the bladder
cell to collapse; and
(6) Syphoning of fuel (other than
minor spillage) or collapse of bladder fuel cells may not result from
improper securing or loss of the fuel filler cap.
(b) Each tank compartment must be
ventilated and drained to prevent the accumulation of flammable fluids
or vapors. Each compartment adjacent to a tank that is an integral
part of the airplane structure must also be ventilated and drained.
(c) No fuel tank may be on the
engine side of the firewall. There must be at least one-half inch of
clearance between the fuel tank and the firewall. No part of the
engine nacelle skin that lies immediately behind a major air opening
from the engine compartment may act as the wall of an integral tank.
(d) Each fuel tank must be isolated
from personnel compartments by a fume-proof and fuel-proof enclosure
that is vented and drained to the exterior of the airplane. The
required enclosure must sustain any personnel compartment
pressurization loads without permanent deformation or failure under
the conditions of §§23.365 and 23.843 of this part. A bladder-type
fuel cell, if used, must have a retaining shell at least equivalent to
a metal fuel tank in structural integrity.
(e) Fuel tanks must be designed,
located, and installed so as to retain fuel:
(1) When subjected to the inertia
loads resulting from the ultimate static load factors prescribed in
§23.561(b)(2) of this part; and
(2) Under conditions likely to occur
when the airplane lands on a paved runway at a normal landing speed
under each of the following conditions:
(i) The airplane in a normal landing
attitude and its landing gear retracted.
(ii) The most critical landing gear
leg collapsed and the other landing gear legs extended.
In showing compliance with paragraph
(e)(2) of this section, the tearing away of an engine mount must be
considered unless all the engines are installed above the wing or on
the tail or fuselage of the airplane.
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964,
as amended by Amdt. 23-7, 34 FR 13903, Aug. 13, 1969; Amdt. 23-14, 38
FR 31823, Nov. 19, 1973; Amdt. 23-18, 42 FR 15041, Mar. 17, 1977; Amdt.
23-26, 45 FR 60171, Sept. 11, 1980; Amdt. 23-36, 53 FR 30815, Aug. 15,
1988; Amdt. 23-43, 58 FR 18972, Apr. 9, 1993]