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MAINTENANCE MANUAL
JETTISON TRANSFER VALVE (REF 28-31-00)
(REF 28-31-00) PUMP OVERRIDE/JETTISON CENTER WING TANK
FWD
INBD CONTROL UNIT REFUEL VALVE CENTER WING TANK REAR SPAR
G (DRY SIDE)
NOTE:RIGHT SIDE SHOWN; LEFT SIDE SIMILAR.
Pressure Fueling System Component Location
Figure 1 (Sheet 4)
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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MAINTENANCE MANUAL
3. Refueling Manifold (Fig. 1)
__________________
A. The refueling manifold distributes fuel to all tanks during a pressure fueling operation. The manifold consists of two crossover manifolds and a main distribution manifold; the main distribution manifold is also used as the fuel jettison manifold. The crossover manifolds extend from the fueling receptacles at the front spar through outboard main tanks to the main distribution manifold. The main distribution manifold is routed inside the fuel tank area with solenoid-controlled refuel valves installed in each tank. Multiple outlet tube manifolds are installed at the main tank refuel valves to provide equal distribution of fuel in each tank.
4. Manifold Drain Valve (Fig. 1)
____________________
A. The manifold drain valves are located at low points in the refueling manifold to drain residual fuel into the inboard main tanks. Two valves are installed in the main distribution manifold, one in main tank No. 2 and one in main tank No. 3. The valve is a double-acting check valve that will prevent flow in either direction under certain conditions.
B. When the manifold is pressurized, a spring-loaded piston inside the valve is forced against a seat. When pressure is removed from the manifold, spring pressure will open the valve and allow fuel to drain from the manifold when the fuel level in the tank falls below the valve. A reverse flow through the valve is prevented by a flapper assembly inside the valve that is spring loaded closed when the manifold is fully drained.
C. The time for the manifold drains to remove the pressure from the
refuel/jettison manifold is 1.5 hours.
5. Refuel Valve (Fig. 1 and 2)
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A. The refuel valves allow fuel to flow from the refueling manifold into the tanks. Each shutoff valve assembly consists of two units, a solenoid-operated control unit mounted externally on the tank and a valve unit mounted inside the tank. The two units are connected through an opening in the tank wall. The valve assembly consists of a spring-loaded poppet valve, a diaphragm that controls the poppet valve, a solenoid-actuated pilot valve, and fuel passages for diaphragm control. Also included is a valve position switch actuated by the diaphragm that illuminates a light on the fueling control panel when the valve is open. Manual override of the valve is provided in the event of valve failure during a fueling operation.
B. When fuel pressure in the manifold is applied to the inlet port of the valve, pressure flows through a passage to the solenoid side of the diaphragm (a passage through the shaft connects cavities on each side of the diaphragm). Actuating the solenoid-controlled pilot valve opens a larger outlet passage on the tank side of the diaphragm, allowing the difference in fuel pressure to move the diaphragm in a direction that forces the poppet to open. To close the valve with pressure in the manifold, the solenoid valve is closed. With the flow stopped, pressure is equalized on both sides of the diaphragm thus allowing the spring-loaded poppet to close. Spring pressure holds the poppet closed when pressure is removed from the manifold.
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