APU

Question 1

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

Answer 1

APU fire protection requires the Batteries and BATTERY MASTER to remain selected ON.

FSM 3.2.3

Question 2

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

Answer 2

NOTE: Wait two minutes after APU RUN advisory light illuminates before selecting APU BL AIR switch ON.

FSM 3.2.4

Question 3

What are the APU ambient temperature limits?

Answer 3

APU ambient temperature limitations
(Upper) +50°C or ISA+35°C, whichever is lower. M (Lower) -54°C. M

FSM BULLETIN 13-13

Question 4

Is the APU fire protection system automatic or manual?

Answer 4

The APU has a fully automatic fire detection and extinguishing system.

SDM 4-9

Question 5

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

Answer 5

No

Question 6

Can we operate the APU during deicing?

Answer 6

The APU Bleed Air shall be selected off when the aircraft is being deiced/anti-iced. QX

FSM 1.8.3

Question 7

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

Answer 7

APU shall not be operated unattended with passengers on board. M

FSM 1.8.3

Question 8

Can we operate the APU during pressure refueling?

Answer 8

Yes

Question 9

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

Answer 9

Pushing the FIRE TEST pushbutton with the APU operating will cause the APU to shutdown.

SDM 4-11

Question 10

Where does the APU get its fuel?

Answer 10

APU fuel is supplied from the left wing collector bay through an APU fuel shutoff valve.

SDM 4-6

Question 11

After landing when should the APU be started if needed?

Answer 11

During FO parking flow

Question 12

What kind of electrical power does the APU generator provide?

Answer 12

The APU consists of a gas turbine engine driving a DC Starter-Generator (air-cooled, 400 amp) which provides 28 volt DC power to the electrical system during ground operations.

SDM 4-1

Question 13

What action is required after two unsuccessful APU start attempts?

Answer 13

APU starter cranking limits: M Start Max. Time On Followed By

1 60 seconds 5 minutes off
2 60 seconds Maintenance action required

NOTE: Including the time taken for maintenance action following the second start attempt, a minimum of 30 minutes must elapse prior to the next start attempt.

FSM 1.8.3