The APU starter engages when:
Starter selection is automatic.
The APU has attended and unattended operating modes. The attended mode operates when an engine is being started. The unattended mode operates when the airplane is in flight.
The attended mode operates when either engine is starting or running, or when the airplane is in flight. The unattended mode operates in all other configurations on the ground.
The APU is started by:
Either starter can be powered by forward external power or an engine generator.
When the APU Selector is selected to ON:
The APU air inlet door is located on the upper right side of the tail cone, aft of the APU firewall. The APU air inlet door supplies:
When the APU selector is rotated to OFF, the APU controller (APUC) initiates a normal shutdown sequence. The APU continues running in a _____ cooldown cycle.
The EICAS memo message APU COOLDOWN is displayed.
During in-flight starts, once the APU is running, it is recommended to run the APU until the oil temperature stabilizes.
This helps oil flow to the bearings and prevent accelerated deterioration due to thermal shock.
If the start fails, the APU shuts down automatically. The "APU" EICAS advisory message is displayed.
In this condition, the EICAS advisory message APU SHUTDOWN is displayed. Moving the APU selector from ON to OFF clears the message and resets the shutdown system to enable a restart attempt.
What does this APU FAULT amber light indicate?
When the APU reaches starter cutout speed (approximately 50% rpm), the starter disengages and ignition is turned off.
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APU Automatic Start - In flight, if three or more engine generators go offline, the APU automatically starts, regardless of APU selector position.
When the automatic start condition is no longer valid, the APU can be shut down by positioning the selector to ON, then OFF. When the automatic start condition is valid, the APU can only be shut down by pulling the APU fire switch.
If starting the APU from an unpowered airplane (battery switch recently moved to ON), the APUC waits until the common core system (CCS) applications are available before proceeding with the start.
If demand pumps are turned on during an APU start:
The common core system (CCS) fire detection and fuel management applications are not necessary to start the APU but when available they are visible on the CDU on the lower display unit.
The CCS fire detection and fuel management applications are necessary to start the APU and are available when the CDU page is visible on the lower display unit.
During the APU Attended mode:
The attended mode operates when either engine is starting or running, or when the airplane is in flight. There is no cooldown period. The EICAS advisory message, APU SHUTDOWN, displays.
When the APU shutdown cooldown period finishes, an ______.This shuts off fuel and the APU shuts down.
The APU controller (APUC) then commands the APU spar valve to close and the CCS fuel management application turns off fuel pumps as applicable. At 15% rpm, the APUC commands the air inlet door to close and the normal shutdown sequence is complete.
If AC power is not available or no AC pump pressurizes the left fuel manifold, the DC pump in the left main tank provides APU fuel.
The DC pump continues to run until either the APU is shut down or an AC pump supplies fuel pressure.
The APU battery powers:
When the APU START selector is moved to ON:
The main airplane battery powers the:
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When the APU Selector is selected to OFF:
The EICAS memo message APU RUNNING is displayed, and the APU is ready to power the airplane when:
At any time during the APU shutdown cooldown period, the APU may be returned to its running condition by placing the APU selector back to ON.
The APU is designed to be started with no pumps operating when on the ground or in-flight up to:
With DC power available and the APU selector in the ON position, the left aft fuel pump is commanded on regardless of flight deck switch position.
Ian Abbott
With AC power available and the APU selector in the ON position, the left aft fuel pump is commanded on regardless of flight deck switch position.
The _____ commands the APU air inlet door to open.
The B787 APU generates only electricity and it has no bleed system.
If an engine is shutdown during the APU start:
The APU battery is designed to support two consecutive start attempts. If the APU fails to start after the second attempt, a _____ cooling period must be observed before a third attempt is made.
APU fuel is supplied from the left fuel manifold by:
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The APU supplies electrical power which is available throughout the airplane operating envelope.
