737 MAX Flight Crew Operations Manual
Air Systems
Chapter 2
Bleed Air System Description
Section 20
MN-FLT-OH-201
2.20.1
20 Bleed Air System Description
Bleed Air System Description
File Highlight
Introduction
Air for the bleed air system can be supplied by the engines, APU, or an external
air cart/source. The APU or external cart supplies air to the bleed air duct prior to
engine start. After engine start, air for the bleed air system is normally supplied by
the engines.
The following systems rely on the bleed air system for operation:
• Air conditioning/pressurization
• Wing and engine thermal anti-icing
• Engine starting
• Hydraulic reservoirs pressurization
• Water tank pressurization
• Nitrogen generation system
Switches on the air conditioning panel operate the APU and engine bleed air
supply system.
Engine Bleed System Supply
Engine bleed air is obtained from the 4th and 10th stages of the compressor
section. When 4th stage low pressure bleed air is insufficient for the bleed air
system requirements, the high stage valve modulates open to maintain adequate
bleed air pressure. During takeoff, climb, and most cruise conditions, low pressure
bleed air from the 4th stage is adequate and the high stage valve remains closed.
Engine Bleed Air Valves
The engine bleed air valve acts as a pressure regulator and shutoff valve. With the
engine bleed air switch ON, the valve is DC activated and pressure operated. The
valve maintains proper system operating pressure and reduces bleed air outflow in
response to high bleed air temperature.
March 1, 2021
