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level, uncovers gravity transfer line (C) and allows air
to be drawn into the sump tank. Continued zero- or
low-g (lesst han 0.5) maneuversw ill aggravateth is condition
and increase the probability of air ingestion. Ifair
enters the boost pump and engine feed line, the fuel
pressure light will illuminate. If the maneuver is continued,
the left AB will blow out and subsequenlte ft-engine
flameout can occur. Right-engine flameout can
follow after left-engine flameout because engine feed
crossfeed operation will reduce the effective output of
the right boost pump. Aircraft deceleration can further
interrupt fuel transfer from cell No. 2 to the right sump
through the gravity transfer line (D, Figure 2-33). Once
initiated, this sequence can occur rapidly and is independent
of total fuel state.
pi-G-1
. During zero- or negative-g flight, the oil
pressure light will normally illuminate
and activate the master caution light. Subsequent
illumination of a fuel pressure
light may go unnoticed, allowing the pilot
to continue the maneuver to the point of
AB blowout and engine flameout.
e In the presence of a fuel pressure light,
fuel demand must be reduced and positive
g restored to prevent possible engine
flameout.
2.14.3.3 Fuel Shutoff Handles. Individual engine
fuel feed shutoff valves in the IeA and right feed lines at
the point of nacelle penetration are connected by control
cables to the FUEL SHUT OFF handles on the pilot
instrument panel. During normal operation, the handles
should remain pushed in so that fuel flow to the engine
fuel feed system is unrestricted. If a fire is detected in
the engine nacelle, the pilot should pull (approximately
3 or 4 inches) the FUEL SHUT OFF handle on the
affected side to stop the supply of fuel to the engine.
Securing the engine at high power settings
using the FUEL SHUTOFF handles may result
in damage to the aircraft fuel system.
2-49 ORIGINAL
NAVAIR 01.Fl4AAD-1
Figure 2-33. Forward Fuselage Fuel Transfer
Note
Engine tlameout will occur approximately 4
aaxmls after the FUEL SHUT OFF handle(s)
ispulledwiththethrottle(s)atMIL.Withlow~~
power settings!t,im e to tlameoutw ill increase
(appmximately 30 seconds at IDLE).
2.14.4 Fuel Transfer
2.14.4.1 Motive Flow Transfer. With the exception
of the external tanks, which utilize bleed air, all fuel
transfer is accomplished by gravity and motive flow. In
motive flow, a relatively small amount of pressurized
fuel moves at high speed through ejector pumps, using
the venturi effect to induce flow of the transfer fuel. The
ejector pumps have no rotating parts or power requirements
other than motive flow.
Like other elements of the fuel transfer system, motive
flow transferi s initially segregatedto right and left.
The motive flow pump driven by the right engine provides
motive flow and pressure to drive the right boost
pump and to run the ejector transfer pumps in the forward
fuselage and right wing. The motive flow pump
driven by the left engine provides motive flow and pressure
to drive the left boost pump and runs the ejector
transfer pumps in the aft fuselage and left wing.
The path ofthe motive flow fuel is essentiallyt he same
for either side. Fuel 6om the engine feed line is pressurized
by theengiwdrivenmotive flow pumpandinitially muted
through the boost pump turbine. The motive flow fuel is
then routedt hroughi ts respectivetr ansfers ystem.A s the
pressurizedf uel passest hroughe ach ejectorp ump, it induces
transfer fuel to flow along with the motive flow fuel.
This combinationo f fuel eventuallyi s transferredin to the
respectivew ing box-beamt ank.
There are four valves that control motive flow
transfer:
1. Motive flow isolation valve - Normally closed,
but when the low-level thermistor in cell Nos. 2 or
5 is uncovered or the FEED switch is out of
NORM, the valve is commanded open, providing
a path for motive flow fuel from a normally operating
side to cross over and power a malfunctioning
opposite side.
2. Forward fuselage motive flow shutoff valve -
Normally open except when the R FUEL PRESS
caution light is illuminated or the FEED switch is
in AFT. When the valve is closed, all motive flow
transfer in the forward fuselage is shut off. If the
valve is closed because of the R FUEL PRESS
caution light, positioning the FEED switch to
FWD will open the valve.
ORIGINAL Z-50
3. AFT fuselage motive flow shutoff valve - Normally
open except when the L FUEL PRESS caution
light is illuminated or the FEED switch is in
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F-14D 飞行手册 Flight Manual 1(82)
