parallel. The harness mounts on the turbine frame
aft of the turbine rotor.
FUEL FLOW SYSTEMS
Fuel flow indicating systems provide a con-
tinuous indication of the rate of fuel delivery to
the engine. The rate of flow is in pounds per hour.
In some systems, the indicator also shows the
amount of fuel remaining in the tanks. A typical
flowmeter consists of two units--a transmitter
and an indicator. The measurements are trans-
mitted electrically to the panel-mounted indicator.
Thus, use of electrical transmission ends the need
for a direct fuel-filled line from the engine to the
instrument panel. This minimizes the chance of
fire and reduces mechanical failure rate.
The fuel flowmeter system is quite similar
to other synchro systems discussed in Navy
Electricity and Electronics Training Series
(NEETS) course. The following discussion
describes a typical fuel flow indicating system
to acquaint you with flowmeters in general.
However, you should always refer to the manuals
for the particular system you are maintaining.
Fuel Flow Transmitter
Figure 6-53 shows a cutaway view of a fuel
Figure 6-53.-Cutaway view of a fuel flow transmitter.
flow transmitter. It is a two-in-one unit--a
fuel-measuring mechanism (or meter) and a
synchro transmitter. You can separate these parts
the bar magnet. The two magnets send vane
from one another for maintenance purposes, but
movement, caused by the fuel flow, to the synchro
they join as a single assembly for installation.
rotor. This action results in a corresponding
The fuel enters the inlet port of the transmitter
movement of the rotor. Therefore, the angular
and flows against the vane (callout 1), causing the
displacement of the vane in relation to the fuel
vane to swing. The spiral fuel chamber design
chamber housing determines the synchro rotor
allows the distance between the vane and chamber
movement with respect to the stator.
wall to become increasingly larger as fuel flow
The fuel flow transmitter has a relief valve,
increases. A calibrated hairspring (callout 2)
which automatically opens and bypasses the
retards the motion of the vane. The vane ceases
instrument when the fuel flow exceeds the capacity
motion when the forces exerted on it by the
of the instrument. At such time, only part of the
hairspring and by the fuel are equal.
fuel flows through the metering portion. As the
The rotor shaft of the synchro transmitter
pressure across the instrument falls below the
(callout 3) connects to a bar magnet (callout 4).
value at which the relief valve opens, the valve
Attached to the vane shaft is a ring magnet
closes. This lets the flowmeter again operate
(callout 5). The ring magnet moves as the vane
normally. The transmitter unit location is in the
shaft moves. The transmitter mounting frame is
fuel line between the fuel pump and fuel nozzle.
between the bar magnet and the ring magnet,
forming a liquid-tight seal. This is the seal between
Fuel Flow Indicator
the fuel-metering section of the mechanism and
the synchro. However, the bar magnet moves in
The fuel flowmeter indicator is located on the
unison with the ring magnet because the two
instrument panel. It is a remote-indicating
magnets are magnetically coupled. The south pole
instrument. This indicator consists of a synchro
of the ring magnet is opposite the north pole of
