(1)  
A fuel boost pump removal check valve mounts to the inlet port of each main tank fuel boost pump and each center tank override pump. The check valve, a spring loaded closed poppet valve, prevents fuel drainage through the boost pump housing when the motor/impeller unit is removed. Removal of the motor/impeller unit allows the spring to seal the poppet against the seat to close the fuel path. Reinstallation of the fuel boost pump forces the poppet open against the spring to open the fuel flow path.

 G.
Main Tank Fuel Boost Pump Bypass Valve (Fig. 6)

 (1)  
If the fuel boost pumps fail, the two bypass valves of the fuel boost pumps let suction fuel feed to the engines. The bypass valves contain a filter screen and a check valve body with a hinged flapper. One bypass valve connects to the engine fuel feed manifold for each engine.

 H.
Automatic Sumping Jet Pump (Fig. 7)

 (1)  
An automatic sumping jet pump at each aft fuel boost pump inlet, in the main fuel tanks, will scavenge water when the aft boost pump operates. An automatic sumping jet pump at each override pump inlet, in the center fuel tank, will scavenge water when the override pumps operate.

 (2)  
Each jet pump scavenges water from the low point of its respective fuel tank. The jet pump consists of a housing and a jet nozzle. The housing has three ports: a motive port, an induced port and a discharge port. The motive port connects to the boost pump primer discharge port. The induced port connects to an inlet screen sealed to the lower surface of the fuel tank. The discharge port is open to the boost pump inlet.

 (3)  
The operating boost pump pressurizes the motive port of the jet pump. Flow through the jet nozzle draws fuel and scavenged water through the inlet screen to the induced port and out through discharge port.

 I.
Fuel Scavenge System (Fig. 7A)

 (1)  
A fuel scavenge ejector pump in the center tank provides scavenging whenever the left main tank is below half full. The fuel scavenge system is controlled by a float operated shutoff valve in the left main tank that opens when the tank drops below half full.

 (2)  
The ejector pump consists of a housing with three ports: a motive port, an induced port, and a discharge port. The motive port connects to the left forward main boost pump primer discharge port. The induced port connects to an inlet screen sealed to the lower surface of the center fuel tank. The discharge port is connected by tubing to the float operated shutoff valve in the left main tank.

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 28-22-00
 ALL  ú ú 11 Page 11 ú May 20/98
　
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本文鏈接地址：757 AMM 飛機維護手冊 燃油 CHAPTER 28 - FUEL 2(100)