APU

Question 1

From which tank does the APU draw fuel?

Answer 1

• left side of the fuel manifold
  when the AC fuel pumps are operating.
• If the AC and DC fuel pumps are not
  operating, fuel is suction fed from the No. 1 tank.

Question 2

Where is the APU door located?

Answer 2

Right side of fuselage

Question 3

Is battery required to start the APU and why?

Answer 3

Electrical power to start the APU comes from No. 1 transfer bus or the airplane
battery. 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.

Question 4

How do you know when APU is ready for electrical/bleed loading?

Answer 4

APU GEN OFF BUS light illuminates.

Question 5

What is the recommended wait period before bleed loading after starting APU?

Answer 5

2 minutes

Question 6

How many packs can the APU run inflight/ ground?

Answer 6

The APU supplies bleed air for both air conditioning packs on the ground or one
pack in flight.

Question 7

When APU demands are high during engine start, what will be prioritized? Electrical or bleed?

Answer 7

During engine starting, electrical load shedding occurs prior to reducing bleed air.

Question 8

Times APU will shutdown automatically

Answer 8

Automatic shutdown protection is provided for overspeed conditions, low oil pressure, high
oil temperature, APU fire, fuel control unit failure, EGT exceedance, and other system faults monitored by the ECU

Question 9

What APU fire protection is available on the ground/ in air?

Answer 9

On ground - In the event a fire is detected in the APU when the airplane is on the ground and the engines are shutdown, the APU fire extinguishing system will automatically
discharge the APU fire bottle 10 seconds after detection
In Air or engine running - Fire switch/ bottle

Question 10

When the switch placed in the OFF position how long does the APU run for?

Answer 10

1 minute