737 MAX Flight Crew Operations Manual
Air Systems -
Bleed Air System Description
MN-FLT-OH-201
2.20.3
APU Bleed Air Valve
The APU bleed air valve permits APU bleed air to flow to the bleed air duct. The
valve closes automatically when the APU is shut down. The APU bleed air valve
is DC controlled and pressure operated.
With both the APU and engine bleed air valves open, and the engines operating at
idle thrust, there is a possibility of APU bleed air backpressuring the 10th stage
modulating and shutoff valve. This would cause the 10th stage valve to close.
DUAL BLEED Light
The DUAL BLEED light illuminates whenever the APU bleed air valve is open
and the position of the engine bleed air switches and isolation valve would permit
possible backpressure of the APU. Therefore, thrust must be limited to idle with
the DUAL BLEED light illuminated.
March 1, 2021
