APU Questions

Question 1

What kind of APU is on the aircraft?

Answer 1

Sundstrand APS 2300

Question 2

Describe the APU?

Answer 2

• Constant speed
• Single stage impeller with a 2 stage axial flow turbine
• Independent oil system

Question 3

What controls the APU?

Answer 3

• A dedicated FADEC system

Question 4

What battery is used for the APU start?

Answer 4

• BATT 2 powers the starter

- BATT 1 powers the FADEC and EICAS for monitoring

Question 5

What is the fuel source for the APU?

Answer 5

• Right fuel tank

- Left fuel tank through the crossed valve

Question 6

What fuel pump is used for APU start?

Answer 6

• Batteries ON only DC fuel pump in right tank
• AC powered airplane ACMP 2
• Right engine running ejector fuel pump

Question 7

Will the APU shutdown automatically if speed and acceleration rate isn’t reached in starting cycle time?

Answer 7

• Yes

Question 8

What does moving the APU start switch to OFF do?

Answer 8

• Initiates normal APU shutdown
• 1 Minute cool down
• No pneumatics (electrics only for 1 minute)

Question 9

Can the APU shutdown be cancelled?

Answer 9

• Yes, by moving the START switch back to ON before the 1 minute cool down is over how is the APU shutdown immediately.
• APU emergency stop button
• No 1 minute cool down period

Question 10

What will happen if batteries are turned OFF during the 1 minute cool down period?

Answer 10

• APU will shut down immediately

Question 11

When will automatic shutdown of the APU occur?

Answer 11

• Ground
  
  • Overspeed
  • Underspeed
  • FADEC critical fault
  • Fire
  • Overheat
  • Low Oil pressure
• Flight
  
  • Overspeed
  • Underspeed
  • FADEC critical fault

Question 12

Can the APU be started after a critical fault?

Answer 12

• NO