The air release valve has:
 -
a valve body

 -
a diaphragm and vent valve assembly

 -
a rubber check valve

 -an annular float.
 The body of the air release valve has a mounting flange at the bottom and the rubber check valve at the top. Internally the valve has three chambers, which are:
 -
a vent chamber

 -
a diaphragm chamber

 -
a float chamber.

 The float chamber contains an annular float. The openings in the bottom of the chamber let in the fuel and the air. A small opening at the top of the float chamber connects to the diaphragm-chamber. The vent valve (attached to the center of the diaphragm) closes the vent port between the float chamber and the vent chamber. The valve has these conditions of operation:
 -
the stable or suction condition

 -
the air in fuel condition

 -
the bled-of-air condition.

 1EFF : ALL 1 28-21-00Page 50 1 1 May 01/05R 1 1 1CES 1

 Air Release Valve Figure 014
 1EFF : 1 1R 1CES  ALL  1 11 1 28-21-00 Page 51 May 01/05

 Stable or suction condition.
 When the pressure in the valve is equal to (or less than) the pressure in
 the fuel tank, the rubber check valve closes (to seal the valve).

 Air-in-fuel condition.
 If air (which is caught in the fuel pipe) goes into the float chamber,
 the float falls. This opens the opening to the diaphragm chamber. During
 the fuel pump operation this air becomes pressurized which causes:

 (1)
 the diaphragm/vent valve assembly to move to the open position

 (2)
 the rubber check valve to open

 (3)
 the air to bleed from the valve (and thus from the fuel pipe).

 Bled-of-air condition.
 When the fuel goes into the float chamber:

 (1)
 the float lifts and seals the opening to the diaphragm chamber

 (2)
 the diaphragm/vent valve assembly moves to the closed position

 (3)
 the rubber check valve closes to seal the valve.

 1EFF : ALL 1 28-21-00Page 52 1 1 May 01/05R 1 1 1CES 1

 7. Operation/Control and Indicating
________________________________

R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 (Ref. Fig. 002, 004)
 **ON A/C 301-399,
 (Ref. Fig. 004A)
 **ON A/C ALL
 (Ref. Fig. 005)
 **ON A/C 001-049, 051-099, 101-105, 151-154, 201-207,
 (Ref. Fig. 006)

R **ON A/C 106-149, 155-199, 208-299, 401-499,
 (Ref. Fig. 006A)

R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 The wing tank pumps of the main fuel pump system are manually controlled. The FLSCUs normally control the center tank pumps automatically. For the system to operate it is necessary to:
 -energize the 115AC BUS (101XP), (103XP), (202XP) and (204XP), and the 28VDC BUS (101PP), (103PP), (202PP), (204PP) and (401PP)
 -close the circuit breakers 1QA, 2QA, 3QA, 4QA, 7QA, 8QA, 9QA, 10QA, 11QA, 12QA, 29QA, 30QA, 31QA, 32QA, 47QA and 55QA.
 The main fuel pump system has six main pumps. The main fuel pump system is divided into two sub-systems (LH/RH). Each sub-system has three main pumps that supply fuel to their related engine. The circuit for each sub-system contains (and connects to) the same type of equipment. As the other sub-system is the same, only the operation of the No. 1 sub-system/circuit (LH) is given here.
 1EFF : ALL 1 28-21-00Page 53 1 1 Aug 01/05 1 1 1CES 1 **ON A/C 301-399,

 The main fuel pump system is manually controlled. For the system to operate it is necessary to:
 8. Not Applicable
______________
 -energize the 115AC BUS (101XP), (103XP), (202XP) and (204XP), and the 28VDC BUS (101PP), (103PP), (202PP), (204PP) and (401PP)
 -close the circuit breakers 1QA, 2QA, 3QA, 4QA, 7QA, 8QA, 9QA, 10QA, 11QA, 12QA and 55QA.
 The main fuel pump system has four main pumps. The main fuel pump system is divided into two sub-systems (LH/RH). Each sub-system has two main pumps that supply fuel to their related engine. The circuit for each sub-system contains (and connects to) the same type of equipment. As the other sub-system is the same, only the operation of the No. 1 sub-system/circuit (LH) is given here.
 **ON A/C ALL
 A. Operation

R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 In normal conditions the two pumps in the wing tank or the related pump in the center tank supply an engine. But, one pump can supply the necessary fuel for an engine.
　
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