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MAINTENANCE MANUAL
Pressure Fueling System
Figure 1
H42221
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MAINTENANCE MANUAL
FUEL TANK LEFT MAIN CENTER FUEL TANK FUEL TANK RIGHT MAIN TANK SURGE
SENSOR FUEL LEVEL BSEE DOOR AIRPLANE CENTERLINE SENSOR BSEE FUEL LEVEL
ELECTRICAL SYSTEMS CARD FILE, P50
ASEE ELECTRICAL SYSTEMS CARD FILE, P50 SENSOR FUEL LEVEL (EXAMPLE) EJECTOR CONNECTOR ELECTRICAL A CONTROL CARD OF THE FUEL LEVEL SENSOR ELECTRICAL SYSTEMS CARD FILE, P50
ELECTRICAL CONNECTOR
REAR SPAR
FWD INBD
B FUEL LEVEL SENSOR
Figure 2 Pressure Fueling Overfill Protection Components
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MAINTENANCE MANUAL
(1)
A fuel level sensor attaches to the rear spar of each surge tank. The fuel level sensor has a probe with a small piezo-electric element sealed in the probe and an electrical connector. The probe, which extends into the fuel tank, and the element form an electromechanical circuit. This circuit sets up acoustic vibrations in the probe when 28v dc from the control card for the fuel level sensor energizes the element. With fuel around the probe the circuit frequency decreases. The control card monitors changes in frequency and controls the fueling shutoff valves accordingly.
B.
Control Card for the Fuel Level Sensor
(1)
A contral card for the fuel level sensor is installed in the electrical systems card file, P50, in the electrical/electronics bay. The control card supplies control logic to protect the fuel system from overfilling during fueling. The control card operates on 28v dc power and supplies drive signals to each fuel level sensor. The fuel level sensors supply frequency outputs back to the control card which controls the refueling valve relays. The frequency level that the control card senses determines whether the control card logic interrupts power to the refueling valve relays.
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