637 

Federal Aviation Administration, DOT 

§ 29.975 

(d) No rotorcraft skin immediately 

adjacent to a major air outlet from the 
engine compartment may act as the 
wall of an integral tank. 

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as 
amended by Amdt. 29–26, 53 FR 34217, Sept. 2, 
1988; Amdt. 29–35, 59 FR 50388, Oct. 3, 1994] 

§ 29.969

Fuel tank expansion space. 

Each fuel tank or each group of fuel 

tanks with interconnected vent sys-
tems must have an expansion space of 
not less than 2 percent of the combined 
tank capacity. It must be impossible to 
fill the fuel tank expansion space inad-
vertently with the rotorcraft in the 
normal ground attitude. 

[Amdt. 29–26, 53 FR 34217, Sept. 2, 1988] 

§ 29.971

Fuel tank sump. 

(a) Each fuel tank must have a sump 

with a capacity of not less than the 
greater of— 

(1) 0.10 per cent of the tank capacity; 

or 

(2) 

1

⁄

16

gallon. 

(b) The capacity prescribed in para-

graph (a) of this section must be effec-
tive with the rotorcraft in any normal 
attitude, and must be located so that 
the sump contents cannot escape 
through the tank outlet opening. 

(c) Each fuel tank must allow drain-

age of hazardous quantities of water 
from each part of the tank to the sump 
with the rotorcraft in any ground atti-
tude to be expected in service. 

(d) Each fuel tank sump must have a 

drain that allows complete drainage of 
the sump on the ground. 

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as 
amended by Amdt. 29–12, 41 FR 55473, Dec. 20, 
1976; Amdt. 29–26, 53 FR 34217, Sept. 2, 1988] 

§ 29.973

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 § 29.952(c). In addition— 

(1) Each filler must be marked as pre-

scribed in § 29.1557(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 50388, Oct. 3, 1994] 

§ 29.975

Fuel tank vents and carbu-

retor vapor vents. 

(a) 

Fuel tank vents. Each fuel tank 

must be vented from the top part of the 
expansion space so that venting is ef-
fective under normal flight conditions. 
In addition— 

(1) The vents must be arranged to 

avoid stoppage by dirt or ice forma-
tion; 

(2) The vent arrangement must pre-

vent siphoning of fuel during normal 
operation; 

(3) The venting capacity and vent 

pressure levels must maintain accept-
able differences of pressure between 
the interior and exterior of the tank, 
during— 

(i) Normal flight operation; 
(ii) Maximum rate of ascent and de-

scent; and 

(iii) Refueling and defueling (where 

applicable); 

(4) Airspaces of tanks with inter-

connected outlets must be inter-
connected; 

(5) There may be no point in any vent 

line where moisture can accumulate 
with the rotorcraft in the ground atti-
tude or the level flight attitude, unless 
drainage is provided; 

(6) No vent or drainage provision may 

end at any point— 

(i) Where the discharge of fuel from 

the vent outlet would constitute a fire 
hazard; or 

(ii) From which fumes could enter 

personnel compartments; and 

(7) 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 operations, or a survivable 
impact. 

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