Pressure Fueling System Flow Diagram  5C8 
28-21-0  Figure 2  Aug 01/96 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

3.  Fueling Receptacle Manifold
A.  The fueling receptacle manifold is mounted on the forward surface of the wing front spar and is the collection and distribution center for the pressure fueling system (Fig. 1). The manifold consists of a cast aluminum unit having one inlet and four outlet ports. The inlet port is connected to the fueling receptacle. The inboard outlet port is connected to the crossfeed line and the three outboard outlet ports are connected to the fueling lines.
4.  Fueling Power Control Switch
A.  The fueling power control switch (Fig. 1) automatically provides 28-volt dc electric power to the fueling shutoff valve switches when the fueling station access door is opened. Closing the door removes electric power from the valve switches which allows the fueling valves to close in case the switches were inadvertently left in the valve open position after fueling. The fueling power control switch is located at the forward, outboard corner of the fueling station and consists of a fixed sensor (magnetic switch) and movable actuator (magnet) which moves with the hinged fueling station access door. For positive switch actuation/deactuation the air gap adjustment between the sensor and the actuator magnet is important (Ref 28-21-81).
5.  Fueling Shutoff Valve
A.  Three fueling shutoff valves are mounted in the fueling receptacle manifold to provide the means for controlling fuel distribution to fuel tanks No. 1, 2 and center during refueling (Fig. 1). Each valve is an electric, solenoid-actuated, shutoff valve. The valve is spring loaded to the closed position with a manual override pushbutton. The manual override pushbutton on the valve solenoid provides a manual method of opening the valve when the valve is not energized or dc power is not available.
B.  The valves are operated by 28-volt dc power and are controlled by the float switch when a full tank is sensed, or by individual switches on the fueling panel for fueling control at any fuel level. Valve position lights mounted on the fueling panel are illuminated any time the valve is open (Fig. 3).
6.  Fueling Control Panel
A.  The fueling control panel P15 is located in the fueling bay and contains all the controls required for operation of the pressure fueling system (Fig. 1). Components mounted on the panel are fueling quantity indicators, fueling shutoff valve switches, fueling shutoff valve OPEN indicator lights and fueling quantity indicator test switches. Three illumination lights mounted on each side of the control panel and outboard of the fueling receptacle provide illumination for the fueling bay.
5A8 
Oct 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  28-21-0 Page 5 

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Pressure Fueling System Circuit  5C8 
28-21-0  Figure 3 (Sheet 1)  Aug 01/96 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

B.  The fueling quantity indicators provide an indication of fuel quantity in individual tanks. They act as repeaters and receive their signals from the corresponding fuel quantity indicators on the center instrument panel (Ref 28-41-0, Fuel Quantity Indicating System). The test gage switches provide a means of checking if the indicators are operating. Placing switch to TEST GAGE(S) position will cause the pointer of an operating indicator to move toward zero or display. On all airplanes, the tank No. 1, 2, and center tank test switch may be placed to AUX or ALTN FUELING POWER CONTROL to bypass the fueling power control switch whenever it becomes inoperative.  
C.  The fueling shutoff valve switches control the operation of the shutoff valves. If the switches for the main and center wing tanks are unintentionally left in the OPEN position after fueling is completed, closing the fueling bay door automatically removes electrical power from the switches causing the fueling valves to move to the closed position. Valve-open lights mounted adjacent to the shutoff valve switches are illuminated any time the respective fueling shutoff valve is open. 
7.  Fueling Float Switch
A.  Fueling float switches, one for each fuel tank, prevent the fuel tanks from being overfilled. During pressure fueling, with a shutoff valve switch in the OPEN position and the fuel tank less than full, the float switch closes the fueling circuit to open the valve and illuminate the light. When the No. 1, center or No. 2 float switch senses a full fuel tank, power is discontinued to the fueling shutoff valve and the valve open light, to close the shutoff valve and to extinguish the light. 
　
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