Apu

Question 1

What are the start sources of the APU and which do we normally use?

Answer 1

T/R (util bus 4 powered)
APU battery: Normal

Question 2

Can the APU be operated in flight

Answer 2

Yes
Operated to 20,000ft
Only start on the ground

Question 3

APU electrical or Bleed available in flight?

Answer 3

Electrical - NO
Bleed - yes, one pack, 15,000ft

Question 4

What components powered by APU battery?

Answer 4

APU controller
DC Fuel Pump
APU inlet door
DC electrical starter
APU fire detection system

Question 5

What components are powered by main battery?

Answer 5

APU fire extinguisher
APU fuel valve
Standby power APU controller
(Note: during APU battery start, DC electrical starter is powered by APU battery why all other APU functions are powered by main battery

Question 6

What powers the APU starter during the battery start sequence

Answer 6

APU start T/R whenever util bus 4 is powered (either external or internal AC power source through synchronous bus)
No util bus 4 then 24V APU batt (norm)

Question 7

T/R overheat with start source in T/R

Answer 7

Transferred to battery and start continues

Question 8

T/R failure besides overheat

Answer 8

• Does not provide automatic switching
• moving APU start source to BATTERY removes T/R from circuit and allows start

Question 9

When does EICAS memo message APU running display?

Answer 9

APU RPM >95%

Question 10

Describe the APU shutdown sequence

Answer 10

Select APU selector to - OFF
- closes APU bleed valve
- initiates 60 sec cool down
- end of cool down APU shuts off

Question 11

What would happen if the battery switch is positioned to off prior to completion of the APU cooldown period?

Answer 11

APU shuts down immediately

Question 12

How long should you wait before turning off the APU selector is rotated to OFF why?

Answer 12

2 minutes
Fire Detection capability available

Question 13

What would cause the APU to shut down automatically!

Answer 13

Limit exceedance
Fire detected