Engine Bleed Air/Starting Systems

There are 4 valves for each motor that route 14th stage bleed air to a 2 cross-ship shut of valves.

The six valves are powered by SEDC
The pressure gause is powered by MEAC No.1 Instrument bus

A slow pressure buildup, that is of no concern, regardless of how high
the pressure goes. A rapid pressure rise may indicate a serious leak or
broken duct

Ground air Check Valve(1)
Engine Starter(4)
Fuselage Shutoff Valve(2)
14th stage check Vave (4)
Bleed air valves(4)
Star Air Solenoid (4)

W.E.B.O.C.E.

Wing de-ice
Engine starting
Bomb bay heat
Oil cooler augmentation
Close 10th and 5th state at 94%
Engine anti-ice

-Located on the engine accessory section
-Contains three switches that actuate at approximately 16, 65, and 94 % RPM.

Energizes the ignition relay SEDC

1. Energizes the igniter plugs (cans 2 and 5).
2. Energizes the paralleling valve solenoid allowing the primary and secondary pumps to operate in parallel
during the starting sequence (16 to 65 percent rpm).
3. Energizes the fuel manifold drain solenoid.
If prime is selected, the enrichment valve solenoid energizes

Deenergizes the ignition relay SEDC

1. Deenergizes the igniter plugs.
2. Deenergizes the paralleling valve solenoid that puts the primary and secondary pumps in series.
3. Deenergizes the fuel manifold drain valve solenoid, but the drain valve itself remains closed because of fuel
pressure.

Above 94 percent, the temperature datum control system switches from start limiting to temperature limiting

Controls 5th and 10th stage bleed-air to reduce compressor back pressure and starter overload during start up.

are held open below 94 percent rpm by compressor air pressure from their respective stage. At 94 percent, the
speed‐sensitive valve ports 14th‐stage bleed air to close the 5th and 10th stage bleed‐air ports.