APU

Question 1

What monitors APU start / shutdown, speed and temp, fuel flow and APU bleed air?

Answer 1

ECB
Electronic Control Box

Question 1

Which fuel line does the APU feed from? How many kilos/hour?

Answer 1

Left fuel line
100-120 kg/h (less at altitude)

Question 2

What to the APU inlet guide vanes do? How are they moved?

Answer 2

Control bleed air flow
Fuel pressure-powered actuator, ECB controlled.

Question 3

When does the ECB command 99% and 100% power?

Answer 3

99% when ambient temp between -18ºC and +35ºC, otherwise 100%.

Question 4

How long is the cool down if bleed has been used?

When does the APU flap close?

Answer 4

60-120 sec

7%

Question 5

APU Start:
When is the starter energised?
When does the ignition come on?
When is the starter de-energised?
When does the ON light show?
When does AVAIL show?

Answer 5

Starter energised when flap open

Ignition on 1.5 sec after starter

Starter de-energised @ N 60%

ON light- 2 sec after 95% (or at 99.5%)

AVAIL- 95%

Question 6

When does the APU N% turn amber and red?

Answer 6

Amber: 102%
Red: 107%

Question 7

When does the APU EGT show amber and red?
What are the maximum EGT temperatures?

Answer 7

Amber- 33ºC below max
Red- at max

Starting max: 1090ºC (1120ºC over FL350)

Running 675ºC

Question 8

How long must one wait after 3 consecutive failed starts?

Answer 8

60 min

Question 9

When can one not start an APU during fueling? When must it be shut down?

Answer 9

If after failed start or automatic shutdown.

Must be shut down normally after a fuel spill

Question 10

APU Envelope
Max altitude? For bleed?
Max altitude on batteries?
Min/Max aerodrome altitude?

Bleed Envelope
For engine start?
Single / Dual pack?

Answer 10

Max alt - FL410 (FL250 for bleed)
Batteries FL250
Aerodrome elev: 14500 to -2000 ft

Engine start FL200
Single pack FL225
Dual pack F150
Not permitted for WAI