APU

Question 0

What is the function of the APU surve control valve (SCV)?

Answer 0

Reduces APU surge potential

Question 1

APU bleed air is controlled by modulating what?

Answer 1

APU LCV

Question 2

When is the surge control valve commanded open (SCV)?

Answer 2

When the APU is supplying electrical loads above 17,000 feet

Question 3

Under high demand what takes APU priority?

Answer 3

APU electrical loads over pneumatic loads

Question 4

Max APU operating altitude

Answer 4

41,000 feet

Question 5

Max starting altitude

Answer 5

37,000 feet

Question 6

Main engine and ECS operation limited to what altitude?

Answer 6

25,000 feet

Question 7

What controls and monitors all facets of the APU operation?

Answer 7

APU electronic control unit (ECU)

Question 8

APU door position speed

Answer 8

220 KIAS if door is open and APU not operating

Question 9

How is the APU door operated?

Answer 9

Electrically by the ECU

Question 10

Where is the APU door position displayed?

Answer 10

EICAS status page

Question 11

Where does the APU receive fuel from?

Answer 11

Left collector tank

Question 12

When will the APU starter disengage

Answer 12

Between 46-60% rpm, dependent on altitude

Question 13

Battery voltage required for an APU start?

Answer 13

22 volts in both batteries

Question 14

At what RPM will the ECS inhibit start?

Answer 14

7% RPM on ground

12% RPM inflight

Question 15

What is the purpose of the internal bypass valve?

Answer 15

Allows the APU to continue to run if the APU pump fails

Question 16

When will the APU AVAIL light illuminate?

Answer 16

99% RPM plus 2 seconds

Question 17

APU OVERSPEED warning is displayed when?

Answer 17

When RPM exceeds 106%

Question 18

Max permissible load on the APU generator?

Answer 18

40 KVA

Question 19

What does the main battery power during an APU start?

Answer 19

APU ECU

Question 20

What does the APU battery power during a start?

Answer 20

The 28v DC electric start motor

Question 21

When does the APU ignition turn off during a start?

Answer 21

95% rpm

Question 22

What happens when the PWR FUEL switchlight is pressed?

Answer 22

• ECU is powered
• APU IN BITE
• APU fuel pump activates
• APU gauges appear
• Fuel SOV opens
• APU air inlet door opens

Question 23

Can the APU supply bleed air for anti-icing?

Answer 23

No

Question 24

Can the APU bleed air and another source of bleed air be used at the same time?

Answer 24

No

Question 25

How many squibs does the APU fire bottle have?

Answer 25

1