C. The turbine of the fuel flow transmitter is mechanically independent from the impeller. The turbine incorporates straight through vanes that straighten the fuel flow. As the fuel flow is straightened, the swirling motion of the fuel rotates the turbine against restraining springs. The extent of turbine rotation depends on rate of fuel flow.
D. The turbine is directly connected to a permanent magnet which is positioned with respect to the angle of rotation of the turbine. A coil surrounds the permanent magnet in the fuel flow transmitter and 115 volts ac current is introduced to this coil. The fuel flow transmitter produces an output signal which is proportional to fuel flow.
E. A coil in the fuel flow indicator picks up the output signal from the fuel flow transmitter. The fuel flow indicator coil is energized by the 115 volts ac current to stabilize the pointer. The permanent magnet in the fuel flow indicator takes a position corresponding to the position of the permanent magnet in the fuel flow transmitter. The fuel flow indicator permanent magnet is directly connected to the pointer. The pointer gives a visual indication of fuel flow on the dial face of the fuel flow indicator.
500
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5C8
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CONTINUED FROM PRECEDING PAGE
B
OK - With interchanged indicator, replace old indicator.
NOT OK - Repair wiring and wrap chaffed area with Teflon tape.
500
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AB
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FUEL FLOW INDICATING SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
AP N471GB and N472GB GJ B-2509 and B-2510 DL ALL EXCEPT N236WA thru N245WA, N373DL thru N383DL,
N4569N, N4571M, EI-BOM, and EI-BON
1. General
A. The function of the fuel flow indicating system is to provide a visual indication of the fuel consumption rate in pounds per hour and fuel consumed for each engine.
B. The fuel flow indicating system consists of a fuel flow power supply, two fuel flow transmitters, two fuel flow rate/fuel consumed indicators, and a fuel consumed reset switch. The fuel flow transmitter is located on the forward left side of each engine. Two flow rate/fuel consumed indicators and a fuel consumed reset switch are on the center instrument panel. The fuel flow power supply is located on the E3-3 electronic equipment rack (Fig. 1).
C. When the system is energized the fuel flow power supply furnishes constant frequency 2-phase power for driving the two fuel flow transmitters. Each transmitter senses the mass rate of fuel flowing to its respective engine and generates an electrical signal proportional to this flow. The electrical signals are transmitted to the indicators which show the rate of fuel consumption, in pounds per hour, and the fuel consumed, in pounds, by their respective engines.
D. The fuel flow rate is indicated by graduations around the circular face of the dial. The total fuel consumed is indicated on the digital readout counter in the center of the indicator.
E. The fuel flow reset switch permits the digital readout counters to be set back to zero.
2. Fuel Flow Power Supply
A. The fuel flow power supply furnishes a constant 8-cycle frequency power source for the fuel flow transmitters. The power supply is a solid-state device with no internal moving parts. The power supply transforms 115-volt, 400-cycle input to 63-volt, 8-cycle output. Only one power supply is required to furnish power to both transmitters.
3. Fuel Flow Transmitter
A. There are two fuel flow transmitters in the fuel flow indicating system. One transmitter is located on each engine.
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H62482
Fuel Flow Indicating System Component Location 529
73-31-01 Figure 1 Feb 15/71
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Fuel flows through the transmitter which sense the mass rate of fuel flow. The transmitter transmits an electrical signal to the fuel flow indicator which varies with the fuel flow rate.
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