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Flashcards in APU Deck (12):

During APU start is it normal to see the right battery switch OFF?

Yes. During APU start the right battery contactor opens.


With the APU switch OFF is it normal to see APU indications on the EICAS portion of the MFD?

NO. call MX


Why is there a 9000 foot field elevation limit for staring the left engine with the APU?

Ducting is longer from the APU bleed valve to the left engine and you may not get adequate air pressure to that side.


Why is the APU certified to operate at FL370 even though you cant use electrics or pneumatics at that altitude?

If the APU starter failed after the APU was started, you could leave the APU running and still be able to climb to altitude without having to shut down the APU. Then if needed the APU could be used on descent and landing.


What are the APU starter limits?

3 Starts with 1 minute cooling intervals, then 20 minutes of cooling.
2 more starts may be attempted, then 40 minutes cooling.


Where does the APU get its fuel from?

Right Collector Tank.


Can you operate the APU during de/anti icing?

NO. it is prohibited.


Can you take off with APU SHUTDOWN CAS message

NO. inspection required


What is the primary function of the APU

to provide power to the gear box GENERATOR


What controls all aspects of APU operation?

the ECU


Does the APU have automatic shutdown and fire extinguishing capability?

YES. on the ground ONLY


Pressing the APU FIRE switch/light does what?

Shuts off/Turns off fuel, electrics, pneumatics, arms the bottle and ECU commands the APU to shut down.

**ALL aspects of APU operation are controlled by the Electronic Control Unit (ECU)