MD-11 Flight Crew Operations Manual
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Electrical -
Description and Operation
Elec.10.2
APU Generator
The APU generator is installed in the tail section and provides electrical power for
ground operations. The APU also serves as a supplemental electrical power source
when required in certain flight phases.
The APU generator does not have a CSD. The APU is governed to drive the
generator at the correct speed.
External Power
The main external power receptacle is on the ground power panel near the nose of
the aircraft. It connects external power onto the ac generator buses through the Bus
Tie Relay-External Power (BTR-EP), the External Power Relay (EPR) and
associated Bus Tie Relays (BTR). Main external power will not power the galley
buses.
Additionally, on passenger aircraft, a galley external power receptacle (on ground
power panel) connects external power onto the galley buses through galley
transfer relays (GTR) 1, 2, and 3.
AC Distribution
Three independent ac generator buses distribute power to the aircraft ac buses and
Transformer Rectifier (TR) units. Each IDG assumes the loads on its respective ac
generator bus through its own independent supply network.
Paralleling of the ac generator buses is accomplished automatically through the ac
tie bus. This allows assumption of electrical loads by any functioning IDG.
The APU generator can power any of the ac buses through its own independent
supply network.
A time limited emergency ac source is available to the left emergency ac bus
through the battery/inverter combination. The ADG may be used to power the left
and right ac/dc bus, the battery bus and the battery charger.
The ac generator buses and the ac ground service bus supply most of the centrally
located and/or high current loads (hydraulic pumps, most fuel pumps, ac buses,
and galley power). Power for lower current, non-centrally located loads and
essential loads is supplied through the three ac buses, cabin ac buses, ground
service buses, and the two ac emergency buses.
Instrument buses supply their respective component loads.
The ac ground service bus distributes power to those components essential to
ground servicing operations. The APU generator or main external power can be
connected to the ac ground service bus without energizing any of the other ac
generator buses. This allows ground servicing of the aircraft without having to
energize the whole electrical power distribution system. The ac ground service bus
is powered by ac generator bus 2 in flight.
October 02, 2006
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