281 

Federal Aviation Administration, DOT 

§ 23.1001 

(c) Each valve and fuel system con-

trol must be supported so that loads re-
sulting from its operation or from ac-
celerated flight conditions are not 
transmitted to the lines connected to 
the valve. 

(d) Each valve and fuel system con-

trol must be installed so that gravity 
and vibration will not affect the se-
lected position. 

(e) Each fuel valve handle and its 

connections to the valve mechanism 
must have design features that mini-
mize the possibility of incorrect instal-
lation. 

(f) Each check valve must be con-

structed, or otherwise incorporate pro-
visions, to preclude incorrect assembly 
or connection of the valve. 

(g) Fuel tank selector valves must— 
(1) Require a separate and distinct 

action to place the selector in the 
‘‘OFF’’ position; and 

(2) Have the tank selector positions 

located in such a manner that it is im-
possible for the selector to pass 
through the ‘‘OFF’’ position when 
changing from one tank to another. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as 
amended by Amdt. 23–14, 38 FR 31823, Nov. 19, 
1973; Amdt. 23–17, 41 FR 55465, Dec. 20, 1976; 
Amdt. 23–18, 42 FR 15041, Mar. 17, 1977; Amdt. 
23–29, 49 FR 6847, Feb. 23, 1984] 

§ 23.997

Fuel strainer or filter. 

There must be a fuel strainer or filter 

between the fuel tank outlet and the 
inlet of either the fuel metering device 
or an engine driven positive displace-
ment pump, whichever is nearer the 
fuel tank outlet. This fuel strainer or 
filter must— 

(a) Be accessible for draining and 

cleaning and must incorporate a screen 
or element which is easily removable; 

(b) Have a sediment trap and drain 

except that it need not have a drain if 
the strainer or filter is easily remov-
able for drain purposes; 

(c) Be mounted so that its weight is 

not supported by the connecting lines 
or by the inlet or outlet connections of 
the strainer or filter itself, unless ade-
quate strength margins under all load-
ing conditions are provided in the lines 
and connections; and 

(d) Have the capacity (with respect to 

operating limitations established for 
the engine) to ensure that engine fuel 

system functioning is not impaired, 
with the fuel contaminated to a degree 
(with respect to particle size and den-
sity) that is greater than that estab-
lished for the engine during its type 
certification. 

(e) In addition, for commuter cat-

egory airplanes, unless means are pro-
vided in the fuel system to prevent the 
accumulation of ice on the filter, a 
means must be provided to automati-
cally maintain the fuel flow if ice clog-
ging of the filter occurs. 

[Amdt. 23–15, 39 FR 35459, Oct. 1, 1974, as 
amended by Amdt. 23–29, 49 FR 6847, Feb. 23, 
1984; Amdt. 23–34, 52 FR 1832, Jan. 15, 1987; 
Amdt. 23–43, 58 FR 18973, Apr. 9, 1993] 

§ 23.999

Fuel system drains. 

(a) There must be at least one drain 

to allow safe drainage of the entire fuel 
system with the airplane in its normal 
ground attitude. 

(b) Each drain required by paragraph 

(a) of this section and § 23.971 must— 

(1) Discharge clear of all parts of the 

airplane; 

(2) Have a drain valve— 
(i) That has manual or automatic 

means for positive locking in the 
closed position; 

(ii) That is readily accessible; 
(iii) That can be easily opened and 

closed; 

(iv) That allows the fuel to be caught 

for examination; 

(v) That can be observed for proper 

closing; and 

(vi) That is either located or pro-

tected to prevent fuel spillage in the 
event of a landing with landing gear re-
tracted. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as 
amended by Amdt. 23–17, 41 FR 55465, Dec. 20, 
1976; Amdt. 23–43, 58 FR 18973, Apr. 9, 1993] 

§ 23.1001

Fuel jettisoning system. 

(a) If the design landing weight is 

less than that permitted under the re-
quirements of § 23.473(b), the airplane 
must have a fuel jettisoning system in-
stalled that is able to jettison enough 
fuel to bring the maximum weight 
down to the design landing weight. The 
average rate of fuel jettisoning must be 
at least 1 percent of the maximum 
weight per minute, except that the 
time required to jettison the fuel need 
not be less than 10 minutes. 

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