Federal Aviation Administration, DOT

Section 25.979

spaschal on DSK3GDR082PROD with CFR

(1) Each vent must be arranged to
avoid stoppage by dirt or ice formation;
(2) The vent arrangement must prevent siphoning of fuel during normal
operation;
(3) The venting capacity and vent
pressure levels must maintain acceptable differences of pressure between
the interior and exterior of the tank,
during - 
(i) Normal flight operation;
(ii) Maximum rate of ascent and descent; and
(iii) Refueling and defueling (where
applicable);
(4) Airspaces of tanks with interconnected outlets must be interconnected;
(5) There may be no point in any vent
line where moisture can accumulate
with the airplane in the ground attitude 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 carburetor with vapor elimination connections must have a vent line to lead vapors 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]

Section 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 airplanes, prevent the passage of any object 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 accessible 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]

Section 25.979

Pressure fueling system.

For pressure fueling systems, the following 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 prevent damage to the fuel system in the
event of failure of the automatic shutoff means prescribed in paragraph (b)
of this section.
(d) The airplane pressure fueling 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 pressures,
including surge, that is likely to occur
during fueling. The maximum surge
pressure must be established with any

319

VerDate Sep<11>2014

12:50 Apr 30, 2019

Jkt 247046

PO 00000

Frm 00329

Fmt 8010

Sfmt 8010

Y:\SGML\247046.XXX

247046