737 MAX Flight Crew Operations Manual
Electrical -
System Description
6.20.4
MN-FLT-OH-201
Flight Deck Auxiliary Power System
1B401 - 1B785, 1B801 - 1J594
The system is composed of a power converter and AC outlets on the P6 and P18
panels to provide power for Flight Deck Personal Electronic Devices (PEDs). A
protective device is a part of the safety aspect of the outlets to prevent tampering
with foreign objects. PEDs that are plugged into the Flight Deck Auxiliary Power
outlets must be fully inserted into the outlet with the prongs of the plug inserted
simultaneously to activate the protective device. If a plug is not inserted correctly,
electrical power will not be present at the outlet and the plug will need to be
removed and reinserted.
Note:
Plugs installed before power up will need to be removed and reinserted to
achieve electrical power.
Automatic Load Shedding (Engine Generators)
For single generator operation, the system is designed to shed electrical load
incrementally based on actual load sensing. The galleys and main bus on transfer
bus 2 are shed first; if an overload is still sensed, the galleys and main bus on
transfer bus 1 are shed; if overload still exists, the IFE buses are shed. When
configuration changes to more source capacity (two generator operation),
automatic load restoration of the IFE/PASS buses takes place; restoration of galley
and main bus power requires reset of the CAB/UTIL switch. Manual restoration
of galley and main bus power can be attempted by moving the CAB/UTIL Power
Switch to OFF, then back ON.
APU Automatic Load Shedding
In flight, if the APU is the only source of electrical power, all galley buses and
main buses are automatically shed. If electrical load still exceeds design limits,
both IFE buses are also automatically shed. On the ground, the APU attempts to
carry a full electrical load. If an overload condition is sensed, the APU sheds
galley buses and main buses until the load is within limits. Manual restoration of
galley and main bus power can be attempted by moving the CAB/UTIL Power
Switch to OFF, then back ON.
March 1, 2021
