278 

14 CFR Ch. I (1–1–14 Edition) 

§ 23.969 

that is vented and drained to the exte-
rior of the airplane. The required en-
closure must sustain any personnel 
compartment pressurization loads 
without permanent deformation or fail-
ure 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, lo-

cated, and installed so as to retain fuel: 

(1) When subjected to the inertia 

loads resulting from the ultimate stat-
ic 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 fuse-
lage 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] 

§ 23.969

Fuel tank expansion space. 

Each fuel tank must have an expan-

sion space of not less than two percent 
of the tank capacity, unless the tank 
vent discharges clear of the airplane 
(in which case no expansion space is re-
quired). It must be impossible to fill 
the expansion space inadvertently with 
the airplane in the normal ground atti-
tude. 

§ 23.971

Fuel tank sump. 

(a) Each fuel tank must have a drain-

able sump with an effective capacity, 
in the normal ground and flight atti-
tudes, of 0.25 percent of the tank capac-
ity, or 

1

⁄

16

gallon, whichever is greater. 

(b) Each fuel tank must allow drain-

age of any hazardous quantity of water 
from any part of the tank to its sump 

with the airplane in the normal ground 
attitude. 

(c) Each reciprocating engine fuel 

system must have a sediment bowl or 
chamber that is accessible for drain-
age; has a capacity of 1 ounce for every 
20 gallons of fuel tank capacity; and 
each fuel tank outlet is located so that, 
in the normal flight attitude, water 
will drain from all parts of the tank ex-
cept the sump to the sediment bowl or 
chamber. 

(d) Each sump, sediment bowl, and 

sediment chamber drain required by 
paragraphs (a), (b), and (c) of this sec-
tion must comply with the drain provi-
sions of § 23.999(b)(1) and (b)(2). 

[Doc. No. 26344, 58 FR 18972, Apr. 9, 1993; 58 
FR 27060, May 6, 1993] 

§ 23.973

Fuel tank filler connection. 

(a) Each fuel tank filler connection 

must be marked as prescribed in 
§ 23.1557(c). 

(b) Spilled fuel must be prevented 

from entering the fuel tank compart-
ment or any part of the airplane other 
than the tank itself. 

(c) Each filler cap must provide a 

fuel-tight seal for the main filler open-
ing. However, there may be small open-
ings in the fuel tank cap for venting 
purposes or for the purpose of allowing 
passage of a fuel gauge through the cap 
provided such openings comply with 
the requirements of § 23.975(a). 

(d) Each fuel filling point, except 

pressure fueling connection points, 
must have a provision for electrically 
bonding the airplane to ground fueling 
equipment. 

(e) For airplanes with engines requir-

ing gasoline as the only permissible 
fuel, the inside diameter of the fuel 
filler opening must be no larger than 
2.36 inches. 

(f) For airplanes with turbine en-

gines, the inside diameter of the fuel 
filler opening must be no smaller than 
2.95 inches. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964; 30 
FR 258, Jan. 9, 1965, as amended by Amdt. 23– 
18, 42 FR 15041, Mar. 17, 1977; Amdt. 23–43, 58 
FR 18972, Apr. 9, 1993; Amdt. 23–51, 61 FR 5136, 
Feb. 9, 1996] 

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