TM 55-1510-215-10
(1) Transfer pump manual operation. While
PUMP switch to OFF.
sufficient fuel remains in the wing tanks, the pilot may
use manual control to refill the nacelle tanks to capacity.
2. When the gage of the affected tank
Refilling must be conducted with the TRANSFER PUMP
indicates a quantity below 24 gallons (156 pound), reset
switch on, and by placing TRANSFER TEST switch at L
the TRANSFER PUMP switch to ON. This will reset the
or R position (whichever applies). If the TRANSFER
automatic level control between the limits of 24-57
TEST switch is held at the L or R setting momentarily,
gallons (156-370 pounds).
then released, the initiated fuel transfer will be shut off
by either the 24 or 57 gallon (156 or 370.5 pound) float
(3) Transfer pump operational check . When
switch position, whichever the rising fuel level
engines are running, transfer pump operation must be
encounters first. If the TRANSFER TEST switch is
checked by a method which does not depend on sound.
manually retained in the ON position fuel transfer will
Another factor is that transfer may be already underway
continue until the switch is released. In this instance, the
when the pilot decides to conduct the transfer check. He
transfer pump shutoff circuits on the 24 and 57 gallon
cannot hear pumps running, and if transfer is in
(156 and 370.5 pound) float switches are bypassed, and
progress, the associated FUEL XFR annunciator light
if enough fuel is present in the wing tanks, the nacelle
will not flash, due to pressure within the transfer line.
tank may be overfilled, resulting in excess fuel flowing
For fuel transfer pump operational check procedure,
through the vent lines back into the wing tanks. A safe
refer to chapter 8.
continuous transfer loop is thus established but is not a
recommended procedure. Unless a nacelle tank is full to
b. Operation with failed engine-driven boost pump
capacity whenever a TRANSFER PUMP switch is turned
or auxiliary pump. Two pumps in each fuel system
ON, after an OFF period, the affected pump will start an
provide inlet head pressure to the engine-driven primary
immediate transfer cycle. Transfer will continue until fuel
high-pressure fuel pump and if crossfeed is used, a third
within the receiving tank rises enough to actuate a float-
pump, the auxiliary fuel pump from the opposite system,
switching position which was not already exceeded by
will supply the required pressure. A triple failure, which
the fuel level when the TRANSFER PUMP switch was
is highly unlikely, would result in the engine-driven
placed ON. If fuel quantity before the start of transfer
primary pump operating without inlet head pressure.
was between 8-24 gallons (52-156 pound), transfer
Should this situation occur, the affected engine can
power will be cut of at the 24 gallon (156 pound) float-
continue to operate from its own fuel supply on its
switching level. However, if quantity within a nacelle
engine-driven primary high-pressure fuel pump, but only
tank is above the 24 gallon (156 pound) switching level,
for a 10-hour period due to the limitation on the primary
when the TRANSFER PUMP switch is turned ON, a
pump. The total time that the engine-driven primary
transfer will initiate, continuing to fill the tank until the top
high-pressure pump is operated without fuel being
float-switching position of 57 gallons (370.5 pounds) is
supplied under pressure from the engine-driven boost
reached.
pump or an auxiliary pump shall be entered on DA Form
2408-13.
(2) Top nacelle fuel quantity sensor failure
(continuously full nacelle tank). If fuel transfer into a
2-37. Ferry Fuel System.
nacelle tank should not be terminated by actuation of the
top level quantity sensor, over-fill fuel will flow back into
CAUTION
the wing tanks through vent lines. Operation would
stabilize into a continuous fuel transfer loop.
A
Do not use AVGAS in the ferry fuel
continuously full nacelle tank, monitored on the gage,
system. It has not been tested using
would indicate this condition and can be corrected by
AVGAS. Flow rates will be less, and
using the following procedure:
consequently ferry fuel pump may
not be able to keep up with engine
1. Reset the appropriat e TRANSFER
demand.
2-28 Change 10
