TM 55-1510-215-10
Section IV. FUEL SYSTEM
2-35. Fuel Supply System.
electrically-operated auxiliary fuel pump, located within
each nacelle tank, serves as a backup unit for the
The engine fuel supply system (fig. 2-11) consists of
engine-driven boost pump. The auxiliary pumps are
two identical systems sharing a common fuel
switched off during normal system operations, except for
management panel and fuel crossfeed manifold. Each
takeoff, landing or crossfeed. An auxiliary fuel pump
fuel system consists of four interconnected wing tanks, a
must be operated during crossfeed to pump fuel from
nacelle tank, an engine driven boost pump mounted on
one system to the other. The auxiliary fuel pumps are
each engine, an auxiliary fuel pump located within the
protected by two 10-ampere circuit breakers placarded
nacelle tank, a fuel transfer pump located within the
AUX PUMP, located on the fuel system circuit breaker
inboard wing tank, a fuel heater (engine oil-to-fuel heat
panel (fig. 2-12).
exchanger unit), a tank vent system, a tank vent heating
system and interconnecting wiring and plumbing.
c. Fuel Transfer Pumps .
A submerged,
electrically-operated fuel transfer pump is located in
a. Engine Driven Boost Pumps.
each inboard wing tank. Fuel level in the nacelle tank is
automatically maintained by gravity feed from the wing
tanks. However, approximately 28 gallons (182 pounds)
in each of the inboard wing tanks will not gravity feed.
CAUTION
This fuel is moved by the fuel transfer pumps. These
transfer pumps are energized and de-energized by a fuel
quantity sensor located in each nacelle tank (when the
Engine operation using only the
transfer pump switches are in the ON position).
engine-driven
primary
(high
Whenever the nacelle tank quantity drops to 8 gallons
pressure) fuel pump without auxiliary
(52 pounds), the transfer pump is automatically
fuel pump or engine-driven boost
energized and begins transfer of fuel from the wing tanks
pump fuel pressure is limited to 10
to the nacelle tank. Fuel transfer continues until the fuel
cumulative hours. This condition is
quantity in the nacelle tank reaches 24 gallons (156
indicated by either R or L FUEL FAIL
pounds). The fuel transfer pumps are protected by two
lights. All time in this category shall
5-ampere circuit breakers placarded TRANSFER PUMP,
be entered on DA Form 2408-13 for
located on the fuel system circuit breaker panel
the
attention
of
maintenance
personnel.
d. Fuel Gaging System. Four fuel quantity gages
A gear-driven boost pump, mounted on each engine
are mounted on the fuel management panel (fig. 2-12).
supplies fuel under pressure to the inlet of the engine-
All gages are calibrated in quarters of total tank capacity.
driven primary high-pressure pump. Either the engine-
Two gages indicate quantity of each fuel system: one
driven boost pump or auxiliary fuel pump is capable of
gage indicates fuel quantity of the nacelle tank and the
supplying sufficient pressure to the engine-driven
other indicates fuel quantity of the four interconnected
primary high pressure pump and thus maintain normal
wing tanks. Refer to table 2-1 for usable fuel, capacity
engine operation.
and weight. The fuel gages are protected by two 5-
ampere circuit breakers placarded QTY IND, located on
NOTE
the fuel system circuit breaker panel (fig. 2-12).
Boost pump failure is indicated by
steady illumination of either the L
management panel is located on the cockpit sidewall, on
FUEL FAIL or R FUEL FAIL light on
the left side of the pilot. It contains the fuel gages,
the annunciator panel, and the
auxiliary fuel pump switches, transfer pump switches,
simultaneous
flashing
of
both
transfer test light, crossfeed valve switch, firewall shutoff
MASTER CAUTION lights. Refer to
valve switches, and nine circuit breakers protecting the
fuel system.
b. Auxiliary
Fuel
Pumps .
A
submerged,
2-21
