APU

Question 0

After starting the APU, how long should you delay before selecting the BL AIR switch to ON?

Answer 0

Wait two minutes after APU RUN advisory light illuminates before selecting APU BL AIR switch on.
FSM 3.2.4
“A warm-up period of 2-5 minutes with no load or generator-only load is recommended when the APU is first started.
FSM 7.9.3 (Supplementary Normal Procedures)

Question 1

What battery switches must be on in order to provide APU fire protection?

Answer 1

All of them: The Main, Aux and Standby Batteries, and the BATTERY MASTER.

FSM 3.2.3 & 3.19.4

Question 2

Is the APU fire protection system automatic or manual?

Answer 2

Automatic.

(And all of the battery switches must be on in order to provide APU fire detection: The Main, Stand-by and Aux, and the Battery Master).
SDM 4-9, and FSM 3.2.3 & 3.19.4

Question 3

Can we operate the APU during deicing?

Answer 3

Yes, but the APU Bleed Air must be selected off.

FSM 1.8.3

Question 4

What will happen if you conduct the APU FIRE TEST with the APU running?

Answer 4

The APU will shutdown.

SDM 4-11

Question 5

Where does the APU get its fuel?

Answer 5

From the left wing collector bay, through an APU fuel shutoff valve.

SDM 4-6

Question 6

After landing, when should the APU be started if needed?

Answer 6

During the FO parking flow. Do not start the APU until Park Brake is Set and MAIN BUS TIE is selected.

FSM 3.19.5

Question 7

What kind of electrical power does the APU generator provide?

Answer 7

28 volt DC (ground operations only).

SDM 4-1

Question 8

What action is required after two unsuccessful APU start attempts?

Answer 8

Maintenance action is required prior to the next start attempt.

1. 60 seconds on ……………………… 5 minutes off
2. 60 seconds on ……………………… Maintenance action required.
   FSM 1.8.3

Question 9

Can we operate the APU during pressure refueling?

Answer 9

Yes (But cannot START the APU during pressure refueling).

FSM 1.8.3

Question 10

Are there any restrictions to operating the APU with passengers on board?

Answer 10

Yes, it must be attended.
“The APU shall not be operated unattended with passengers on board.”

FSM 1.8.3

Question 11

Is it permitted to operate the APU while over-wing (gravity) refueling?

Answer 11

No.

FSM 1.8.3

Question 12

What are the APU ambient temperature limits?

Answer 12

Upper: +50C or ISA + 35 C, whichever is lower
Lower: -54C
Note: prior to start, at temperatures below -35C, the APU must be preheated.
FSM 1.8.3 and Bulletin 13-13