MD-11 Flight Crew Operations Manual
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Air Chapter Air
Description and Operation Section 10
Air.10.1
Air.10 Air-Description and Operation
General
Three air systems provide the pneumatics required for:
• Engine Start.
• Thrust Reversers
• Air Conditioning.
• Pressurization.
• Anti-ice.
• Avionics Cooling.
• Galley and Lavatory Ventilation (Passenger Configuration).
• Cargo Compartment Heating/Ventilation.
• Potable Water Pressurization (Refer to Water and Waste Chapter).
• Cargo Loading System.
The normal source of pneumatics for each of the three air systems is its associated
engine. The three systems normally operate independently, but may be
interconnected through two isolation valves, if fewer than three engine bleed air
sources are available. The valve(s), ISOL 1-2 and ISOL 1-3, identify the air
systems that are interconnected.
When engine air is not available, the following alternate sources may be used:
1. The APU.
2. External air (ground).
3. Any other operating engine.
Each air system manifold is pressurized by engine compressor air.
For GE engines:
• 8th stage air is low stage heated air and is the main source for normal
operation.
• 14th stage air is high stage heated air and is used during airfoil anti-ice
operation and to compensate for low power settings, such as during idle
descent.
• 11th stage air is used for engine anti-ice protection and is routed directly
to the engine cowl.
Pneumatics and air conditioning automatically turn off as engine thrust increases
for takeoff. Air conditioning remains on, except when airfoil anti-ice is selected
prior to takeoff, if the required entry has been made through the Flight
Management System (FMS).
October 02, 2006
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