During the APU start cycle, the APU EGT indication may fluctuate from 0 deg.C to 1100 deg.C prior to normal EGT rise and the LOW OIL PRESSURE light may cycle on and off several times. These indications have no adverse effect on starting the APU. It is not necessary to monitor EGT during start.
The APU starts, operates and can supply electrical power alone up to:
Of the four lights located on the APU control panel, which light will NOT cause an automatic shutdown of the APU when it illuminates?
The APU can supply both transfer busses:
The APU is capable of supplying bleed air for both air conditioning packs:
The blue APU MAINT light means that:
During APU operation, fuel is automatically heated to prevent icing:
In flight, if the APU is the only source of electrical power, all galley busses are automatically shed. If electrical load still exceeds design limits, both main busses automatically shed until the load is within design limits. On the ground, the APU attempts to carry a full electrical load. If an overload condition is sensed, the APU sheds galley busses first, and then both main busses until the load is within limits.
Pulling up the APU fire warning switch:
The APU start cycle may take up to:
Automatic shutdown occurs in the event of EGT exceedance.
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If the APU GEN OFF BUS light fails to illuminate by the end of the start cycle:
The APU OVERSPEED light illuminates when:
If light is illuminated when APU switch is placed to OFF, light extinguishes after 5 minutes (light is disarmed when the APU switch is in OFF position).
Electrical power to start the APU comes from:
With AC power available, the starter generator uses AC power to start the APU. With no AC power, the starter generator uses battery power to start the APU.
APU cooling air:
The APU may be used as a pneumatic source up to:
It is recommennded to operate the APU for _____ before using it as a bleed air source.
This one minute stabilization is recommended to extend the service life of the APU.
THe APU will shutdown on the ground if:
When the APU is started using battery power only, there is no indication on the electrical metering panel that the APU generator has come on line and is ready to be selected. Both the frequency and voltage readings are zero until the APU generator is placed on line.
Moving the battery switch to OFF automatically shuts down the APU.
! Because of power loss to the Electronic Control Unit (ECU)
If the APU is the only source of electrical power:
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APU operation requires the following:
When the APU is started using battery power only, there is a normal indication on the electrical metering panel that the APU generator has come on line and is ready to be selected.
When the APU is started using battery power only, there is a NO indication on the electrical metering panel that the APU generator has come on line and is ready to be selected. Both the frequency and voltage readings are zero until the APU generator is placed on line.
The APU Electronics Control Unit (ECU) provides:
The APU may be used as an electrical and pneumatic source simultaneously up to:
The APU switch OFF position has an automatic shutdown delay of: