(b)  
Wait for one hour.

(c)  
Examine and make sure there is no fuel leakage at the front spar where you installed the bulkhead fitting for the engine fuel feed line.

(d)  
Examine and make sure there is no fuel leakage at the access panel you opened to get access.

(15)
Install the left (right) access panels 6212, 6301, 6241 (6512, 6401, 6541) you opened to get access to the dry side of the bulkhead fitting (AMM 12-31-61/201, AMM 12-31-71/201).

501 
28-22-142 Page 406  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 01/03 

DEFUELING - DESCRIPTION AND OPERATION
1. General
A.  The fuel system is designed to permit complete or partial defueling of any or all tanks, or to allow fuel transfer to one or both other tanks while the airplane is on the ground. To accomplish defueling or fuel transfer, portions of the pressure fueling, engine fuel feed, and defueling systems are used in combination.
B.  Most rapid defueling of one or more tanks is accomplished by attaching a fuel truck hose nozzle to the fueling station (right wing) receptacle, positioning appropriate fuel system valves, and operating the fuel truck defueling pumps and the respective airplane fuel tank boost pumps. Fuel remaining in the tanks (unusable, trapped) after the pumps cease drawing fuel, is drained into containers by opening the sump drain valves (Ref 12-11-0, Fuel Servicing).
2.  Defueling Valve
A.  The defueling valve (Fig. 1) is a manually operated, semisubmerged, slide-type shutoff valve which controls fuel flow from the engine fuel feed line to the pressure fueling receptacle. It is mounted on the wing front spar of the right wing. The actuating handle of the defueling valve is such that its access door cannot be closed while the valve is in the open position. As with other valves in the fuel system, the defueling valve mechanism can be removed without defueling a tank.
B.  The defueling valve consist of the following major assemblies; actuator handle assembly, gate assembly, and the port adapter assembly.
(1)  
Actuator handle assembly.

(a)  The actuator handle assembly consists of an actuating handle, two spring-loaded balls, and a splined output shaft. The splined output shaft provides a means for the actuating handle to actuate the gate assembly. The two spring-loaded balls drop into detents and lock the actuating handle in the ful1 open or closed position. The actuating handle assembly is bolted to the gate assembly and can be replaced as an independent unit.

(2)  
Gate Assembly

(a)  The gate assembly consists of a housing, a splined input shaft, a valve actuating arm, a sliding gate, and gate seals. One end of the valve actuating arm is attached to the splined input shaft. The other end of the arm carries a roller which engages in a slot in the end of the sliding gate. Spring-loaded seals, held in carriers attached to the housing, provide fuel line seals on both sides of the sliding gate: Other seals, at the housing mounting flange and the splined input shaft, seal the unit against external fuel leaks. The gate assembly is attached to the airplane by nuts installed on double ended bolts attaching the port adapter assembly to the airplane. Removing the nuts allows the gate assembly to be removed without disturbing the port adapter assembly or fuel lines (Fig. 1).

(3)  
Port Adapter Assembly

544 
Nov 01/74  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  28-23-0 Page 1 

 Defueling Valve  500 
28-23-0  Figure 1  Nov 15/67 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

(a)  The port adapter assembly consists of a housing and a thermal relief valve. The assembly, which is mounted inside the fuel tank, provides the mounting surfaces for the fuel lines and a fuel tight enclosure for the gate assembly. A thermal relief valve vents excessive pressure inside the valve body back into the fuel tank.
500 
Aug 15/68  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  28-23-0 Page 3 

DEFUELING - MAINTENANCE PRACTICES
1. General
A.  The following paragraphs cover the steps necessary to defuel the fuel tanks, transfer fuel from tank to tank and the precautions which must be observed during defueling. Standard precautions in effect at the airport, or as required by the airline, must be observed during al1 defueling operations to avoid fire and accidents.
CAUTION:  DO NOT OPERATE HYDRAULIC SYSTEM A OR B IF DEFUELING TANK NO. 1 OR NO. 2, RESPECTIVELY, BELOW APPROXIMATELY 1675 POUNDS (250
　
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