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537 

Federal Aviation Administration, DOT 

§ 27.993 

not less than 2 percent of the tank ca-
pacity. It must be impossible to fill the 
fuel tank expansion space inadvert-
ently with the rotorcraft in the normal 
ground attitude. 

[Amdt. 27–23, 53 FR 34213, Sept. 2, 1988] 

§ 27.971

Fuel tank sump. 

(a) Each fuel tank must have a drain-

able sump with an effective capacity in 
any ground attitude to be expected in 
service of 0.25 percent of the tank ca-
pacity or 

1

16

gallon, whichever is great-

er, unless— 

(1) The fuel system has a sediment 

bowl or chamber that is accessible for 
preflight drainage and has a minimum 
capacity of 1 ounce for every 20 gallons 
of fuel tank capacity; and 

(2) Each fuel tank drain is located so 

that in any ground attitude to be ex-
pected in service, water will drain from 
all parts of the tank to the sediment 
bowl or chamber. 

(b) Each sump, sediment bowl, and 

sediment chamber drain required by 
this section must comply with the 
drain provisions of § 27.999(b). 

[Amdt. 27–23, 53 FR 34213, Sept. 2, 1988] 

§ 27.973

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 § 27.952(c). In addition— 

(1) Each filler must be marked as pre-

scribed in § 27.1557(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 50387, Oct. 3, 1994] 

§ 27.975

Fuel tank vents. 

(a) Each fuel tank must be vented 

from the top part of the expansion 

space so that venting is effective under 
all normal flight conditions. Each vent 
must minimize the probability of stop-
page by dirt or ice. 

(b) 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 operation, or a survivable 
impact. 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–23, 53 FR 34213, Sept. 2, 
1988; Amdt. 27–30, 59 FR 50387, Oct. 3, 1994; 
Amdt. 27–35, 63 FR 43285, Aug. 12, 1998] 

§ 27.977

Fuel tank outlet. 

(a) There must be a fuel stainer for 

the fuel tank outlet or for the booster 
pump. This strainer must— 

(1) For reciprocating engine powered 

rotorcraft, have 8 to 16 meshes per 
inch; and 

(2) For turbine engine powered rotor-

craft, prevent the passage of any object 
that could restrict fuel flow or damage 
any fuel system component. 

(b) The clear area of each fuel tank 

outlet strainer must be at least five 
times the area of the outlet line. 

(c) The diameter of each strainer 

must be at least that of the fuel tank 
outlet. 

(d) Each finger strainer must be ac-

cessible for inspection and cleaning. 

[Amdt. 27–11, 41 FR 55470, Dec. 20, 1976] 

F

UEL

S

YSTEM

C

OMPONENTS

 

§ 27.991

Fuel pumps. 

Compliance with § 27.955 may not be 

jeopardized by failure of— 

(a) Any one pump except pumps that 

are approved and installed as parts of a 
type certificated engine; or 

(b) Any component required for pump 

operation except, for engine driven 
pumps, the engine served by that 
pump. 

[Amdt. 27–23, 53 FR 34213, Sept. 2, 1988] 

§ 27.993

Fuel system lines and fittings. 

(a) Each fuel line must be installed 

and supported to prevent excessive vi-
bration and to withstand loads due to 
fuel pressure and accelerated flight 
conditions. 

(b) Each fuel line connected to com-

ponents of the rotorcraft between 

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