787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Electrical -
System Description
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 6.20.9
Electrical Load Management
The 787 electrical system dynamically manages electrical loads. Using electronic
controllers, the system can automatically cycle on or off loads for efficient use of
available airplane power.
The Bus Power Control Unit (BPCU) provides flight deck control/indication,
power transfer functions, and overall load management and protection. In the
event of a BPCU failure, a second BPCU assumes all functions.
Modes of Operation
By using electronic controllers to selectively energize individual loads on
different buses, the airplane can operate a group of loads together as an electrical
operating mode.
Note: The lists of loads energized by the following modes contain high priority
equipment for the type of operation being conducted. These lists are
considered a general guideline, and are not intended to be all-inclusive.
Some of these loads may be shed depending on power availability.
These modes are defined as follows:
“Towing Power” mode – When the TOWING POWER switch is selected to ON
(with the main BATTERY switch OFF). The main and APU batteries energize
only the equipment essential for towing operations. (Refer to Towing Power Panel
in Chapter 6, Section 10, for additional information.) Significant loads energized
by this mode include:
Note: Radio communication systems are not energized in the towing power
mode.
• captain’s ACP
• captain’s flight interphone
• flight deck dome lights
• aisle stand flood lights
• navigation lights
• brakes
February 15, 2010
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