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 FUEL FLOW INDICATORS  ú ú C02 Page 3 ú Nov 12/00
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L58222
////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
SEE C
MAN SET
N1
120 120 102 102 84 84
6 6
FLIGHT COMPARTMENT
EGT
FF/FU
X1000
60 60

PULL
51 51
PULL
TO

TO
3
SET 42 42 SET
N2
3 3
N1 N1
PUSH FUEL USEDKGPH KG RESET
FF/FU
X1000 120 120 111 111 PULL
102 102
PULL TO
93 93
TO
2
SET 874 874 SET
5 5
6 6
N1 N1
PUSH FUEL USEDPPH LB RESET
PRIMARY ENGINE DISPLAY UNIT
2
INDICATORS READING IN POUNDS
C
3
INDICATORS READING IN KILOGRAMS
Fuel Flow Indicator Location
Figure 2 (Sheet 2)

B10820
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 FUEL FLOW INDICATORS (EIS)  ú ú C03 Page 4 ú Nov 12/00
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CFM56 ENGINES
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(3)  
Fuel then flows to a spring restrained turbine. The turbine moves radially as the fuel passes through it. The turbine has a signal blade which protrudes back to the rotor. A stop pulse is induced each time the second magnet on the spinning rotor passes the signal blade.

 (4)  
The time interval between the start and stop pulses is measured by the fuel flow indicator and converted to a fuel flow rate. The resulting fuel flow is displayed on the fuel flow indicator found on the bottom of the pilots' center instrument panel.

OUTER TURBINE

Fuel Flow Transmitter Flow Diagram
Figure 3

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 ALL  ú ú C02 Page 5 ú Nov 15/92
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////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
(5)  
The fuel flow/used indicator gives a continuous indication of fuel flow rate (FFR). To do this, the indicator uses the start and stop pulses from the fuel flow transmitter.

 (6)  
Analog Fuel Flow Indicators

 (a)  
Primary function of the indicator is to process the time interval between the start and stop pulses which is proportional to the flow rate and display coarse and fine indication of FFR using pointer/dial and light emitting diode (LED) numeric display.

 (b)  
Secondary functions of the fuel flow indicator are as follows:

 1)  Integrate fuel flow rate and by selection of the FUEL switch to display fuel used by means of the LED numeric display. The display reverts to fuel flow rate display when the switch is released. The LED numeric display may be reset to indicate zero fuel used by setting the selector switch to the RESET position. When the selector switch is in the center position the LED numeric display indicates fuel flow rate.
 2)  Accept an external 28 v dc voltage from a test unit which causes all diodes in the LED display to illuminate.
 3)  Provide a dc voltage proportional to the fuel flow rate indicated by the indicator pointer/LED display to supply the fuel flow data to the data recording and reporting systems if installed.
 4)  Indicate a failure or low voltage of the 28 v dc supply by means of blanking the LED display and driving the indicator pointer to below the zero scale mark on the dial.
 5)  Indicate excessive servo system error by means of blanking the LED display.
 (7)  Digital Fuel Flow Indicators on the Primary Engine Display
 (a)  
Primary function of the indicator is to process the time interval between the start and stop pulses which is proportional to the flow rate and display coarse and fine indication of FFR using an LED dial and numeric display.

 (b)  
Secondary functions of the indicator are as follows:
　
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