engate rapido
Bleed air comes from the 9th and 5th stages of the engine high stage

compressors. At low engine speed, the pneumatic system uses 9th stage

bleed air. 5th stage air is not sufficient for pneumatic system demands at low

engine speeds.

At low engine speed the high stage regulators and high stage valves control

the pressure of the engine bleed air.

At low engine speed the 5th stage check valves prevent reverse flow. At

high engine speed the high stage valves close and the 5th stage check

valves open to supply bleed air to the pressure regulating shutoff valves.

The air conditioning bleed air controls panel has engine bleed switches to

control the pressure regulating shutoff valves. Also, there are BLEED TRIP

OFF lights to show overpressure or overtemperature.

The bleed air regulators and pressure regulator and shutoff valves control

the flow of engine bleed air to the pneumatic manifold. The bleed air

regulators have overpressure switches to prevent overpressure conditions

and turn on the BLEED TRIP OFF lights.

The 450F (232C) thermostats make the pressure regulating and shutoff

valves move towards closed when the temperature gets to 450F (232C).

The air conditioning accessory unit (ACAU) is an interface between the air

conditioning bleed air controls panel and the pressure regulating shutoff

valves.

The 490F (254C) overheat switches turn on the BLEED TRIP OFF lights

and close the pressure regulating shutoff valves. This prevents overheat

damage to the pneumatic manifold and user systems.