MD-11 Flight Crew Operations Manual
k
Air -
Description and Operation
Air.10.10
Pneumatic System Management
A Pressure Regulator Valve (PRV) on each engine pneumatic system controls
bleed air from that engine. With engines running, only one bleed system may feed
a single pneumatic manifold.
The ESC normally keeps all pneumatic systems isolated. However, when one or
more systems are tied together, the PSC closes the high stage valve. If the ESC is
also in auto, the PRV closes to prevent reverse flow.
With pneumatic supply from the APU or from a ground external source, the ESC
opens the isolation valves to allow pressure into all three manifolds.
The PSC enters a Reverse Flow Check (RFC) mode when pneumatics are supplied
by a ground cart. All high stage valves are commanded closed until the cart is
removed.
The PSC senses cart removal when system pressure in all three manifolds falls
below 11 psig for at least 20 seconds. System pressure returns to normal within
one minute following cart removal.
Air Conditioning System Management
Each air conditioning pack may be operated by bleed air from its respective
engine, from another engine, from the APU, or from external pneumatics.
Normally, each engine supplies its respective pack.
The packs cannot use air from the APU if exhaust air from engines 1 or 3 is
entering the APU air intake.
When the APU is supplying pneumatics to manifold 2 with engines 1 or 3 running,
packs using pneumatics from manifold 2 are commanded off.
Pressurization Control System
The pressurization control system controls cabin altitude throughout the flight,
provides gentle pressurization changes enroute, and depressurization during the
landing.
Additional ESC Control Functions
The trim air system, the recirculation fan system, and the equipment cooling fans
are managed automatically by the ESC.
ESC Automatic Operations - Abnormal
The ESC automatic operations include management of the following abnormal
situations:
• Monitors MFDS - The ESC reconfigures a failed manifold system to shut
off hot air flow. Verifies the failed manifold and restores operative
manifolds initially shut down in response to the failure detection.
Automatically tests the MFDS before each flight.
October 02, 2006
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