320
14 CFR Ch. I (1–1–24 Edition)
§ 25.977
(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 airplane 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) Each fuel tank vent system must
prevent explosions, for a minimum of 2
minutes and 30 seconds, caused by
propagation of flames from outside the
tank through the fuel tank vents into
fuel tank vapor spaces when any fuel
tank vent is continuously exposed to
flame.
(b)
Carburetor vapor vents. Each car-
buretor with vapor elimination connec-
tions must have a vent line to lead va-
pors back to one of the fuel tanks. In
addition—
(1) Each vent system must have
means to avoid stoppage by ice; and
(2) If there is more than one fuel
tank, and it is necessary to use the
tanks in a definite sequence, each
vapor vent return line must lead back
to the fuel tank used for takeoff and
landing.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Docket No. FAA–2014–0500,
Amdt. No. 25–143, 81 FR 41207, June 24, 2016]
§ 25.977
Fuel tank outlet.
(a) There must be a fuel strainer for
the fuel tank outlet or for the booster
pump. This strainer must—
(1) For reciprocating engine powered
airplanes, have 8 to 16 meshes per inch;
and
(2) For turbine engine powered air-
planes, prevent the passage of any ob-
ject that could restrict fuel flow or
damage any fuel system component.
(b) [Reserved]
(c) The clear area of each fuel tank
outlet strainer must be at least five
times the area of the outlet line.
(d) The diameter of each strainer
must be at least that of the fuel tank
outlet.
(e) Each finger strainer must be ac-
cessible for inspection and cleaning.
[Amdt. 25–11, 32 FR 6913, May 5, 1967, as
amended by Amdt. 25–36, 39 FR 35460, Oct. 1,
1974]
§ 25.979
Pressure fueling system.
For pressure fueling systems, the fol-
lowing apply:
(a) Each pressure fueling system fuel
manifold connection must have means
to prevent the escape of hazardous
quantities of fuel from the system if
the fuel entry valve fails.
(b) An automatic shutoff means must
be provided to prevent the quantity of
fuel in each tank from exceeding the
maximum quantity approved for that
tank. This means must—
(1) Allow checking for proper shutoff
operation before each fueling of the
tank; and
(2) Provide indication at each fueling
station of failure of the shutoff means
to stop the fuel flow at the maximum
quantity approved for that tank.
(c) A means must be provided to pre-
vent damage to the fuel system in the
event of failure of the automatic shut-
off means prescribed in paragraph (b)
of this section.
(d) The airplane pressure fueling sys-
tem (not including fuel tanks and fuel
tank vents) must withstand an ulti-
mate load that is 2.0 times the load
arising from the maximum pressures,
including surge, that is likely to occur
during fueling. The maximum surge
pressure must be established with any
combination of tank valves being ei-
ther intentionally or inadvertently
closed.
(e) The airplane defueling system
(not including fuel tanks and fuel tank
vents) must withstand an ultimate
load that is 2.0 times the load arising
from the maximum permissible
defueling pressure (positive or nega-
tive) at the airplane fueling connec-
tion.
[Amdt. 25–11, 32 FR 6913, May 5, 1967, as
amended by Amdt. 25–38, 41 FR 55467, Dec. 20,
1976; Amdt. 25–72, 55 FR 29785, July 20, 1990]
§ 25.981
Fuel tank explosion preven-
tion.
(a) No ignition source may be present
at each point in the fuel tank or fuel
tank system where catastrophic failure
VerDate Sep<11>2014
09:06 Jun 28, 2024
Jkt 262046
PO 00000
Frm 00330
Fmt 8010
Sfmt 8010
Y:\SGML\262046.XXX
262046
jspears on DSK121TN23PROD with CFR