Section 06 - APU

Question 1

Assume all bus switches in AUTO, APU engine running, AUX PWR switch ON, and BATT 1 & 2 switches ON. If the battery switches were selected to OFF, what would happen to the APU?

Answer 1

There would be no change in APU operation.

Question 2

Below what altitude is the APU guaranteed to start no later than the second start attempt?

Answer 2

15,000ft

Question 3

What would happen if APU air is selected on immediately after APU start?

Answer 3

The APU air would turn on immediately

Question 4

Normal shutdown of the APU is accomplished by pushing what switch?

Answer 4

The APU OVSP-STOP switch

Question 5

Selecting what APU switch to the off position will close the APU fuel shutoff valve immediately?

Answer 5

The APU Master switch

Question 6

Prior to starting the APU, how can the position of the right engine lower cowl door be checked?

Answer 6

Visually, or using the indicator light on the APU panel (if installed)

Question 7

What is the minimum fuel temperature required prior to APU start?

Answer 7

Above -30ºC

Question 8

If necessary, how can the batteries be warmed most effectively prior to APU start?

Answer 8

Use an external AC power cart to charge and warm the batteries

Question 9

What is the minimum acceptable battery voltage prior to APU start?

Answer 9

22 volts DC

Question 10

After APU start, when will the APU generator power the electrical buses?

Answer 10

When the AUX PWR switch is selected ON

Question 11

How is an APU start manually terminated?

Answer 11

Depress the APU OVSP-STOP switch, which trillers the over speed circuit, resulting in an immediate start abort

Question 12

Would an APU DIRE message cause the APU to shutdown in-flight or on the ground?

Answer 12

Both on the ground and in-flight

Question 13

Can the APU provide pressurization in flight?

Answer 13

No

Question 14

If an APU start attempt on the battery power fails, how long a wait is required in order to try a second attempt?

Answer 14

No waiting is required until it fails a third attempt, then 1 hour

Question 15

If an APU start attempt on external DC power fails, how long a wait is required in order to try a second attempt?

Answer 15

15 minutes

Question 16

From where does the APU receive its fuel?

Answer 16

From the motive flow line to the left fuel ejector

Question 17

How long is the recommended wait for turning on APU air after the APU is started?

Answer 17

2 minutes

Question 18

After a normal or automatic shutdown of the APU, what must be done in order to re-start the APU

Answer 18

Cycle the APU master switch to OFF, then ON

Question 19

What is indicated by the red “OIL PRESSURE LOW” light on the APU control panel?

Answer 19

The APU inlet door is fully open

Question 20

During APU shutdown, when is it acceptable to turn off the APU master switch?

Answer 20

After the APU RPM is less than 10%

Question 21

When is a specific APU inspection required in regard to normal operation of the APU?

Answer 21

An inspection is required if the APU is operated above 30,000 feet for more than 1 hour per flight, or on more than 5 occasions (not required for aircraft with the 36-150G APU)

Question 22

What is the maximum permissible APU EGT?

Answer 22

• Up to 60% RPM during the start: 988°C
• 60% to 100% during the start: 821 °C to 732°C (linear decrease)
• Running: 732°C

Question 23

What is the maximum permissible APU EGT {36-150G)?

Answer 23

• Up to 50% RPM during the start: 973°C
• 51 % to 87% during the start: 973°C to 732°C (linear decrease)
• 87% to 100% during the start: 732°C
• Running: 732°C

Question 24

What are the APU starting limits?

Answer 24

• With aircraft batteries: 30 seconds per start, 3 attempts, then 20 minutes cool down
• With external DC power: 15 seconds per start, 2 attempts, then 20 minutes cool down

Question 25

The APU has just been started, Five minutes later, a red “APU FIRE” CAS message illuminates. The fire warning bell is also ringing. Describe the emergency procedure associated with this condition.

Answer 25

• APU Overspeed Test Button - PRESS
• APU Master Switch - OFF
• APU Fire Extinguisher - PRESS
• After 1 minute, APU Fire Test - PRESS

Question 26

The APU “HIGH OIL TEMP” light has illuminated. Describe the abnormal procedures associated with this condition.

Answer 26

No action is required. The APU will initiate an automatic shutdown