APU PANEL (AND START SWITCH)

Question 1

MAINT Light

Answer 1

Illuminated (blue):

• APU maintenance problem exists
• APU may still be operated
• (light disarmed when APU OFF)
• Can be from low oil qty

Question 2

LOW OIL PRESSURE - APU

Answer 2

Illuminated (Amber):

• on during APU start (until press normal)
• Low Oil press after start cycle complete (auto shutdown in approx 20 seconds)
• if light is illuminated after APU switch is placed to OFF - it goes out after 5 minutes
• disarmed - when APU switch is OFF
• illuminated MC and APU lights

Question 3

FAULT Light (APU)

Answer 3

Illuminated (Amber):

• malfunction that triggered an automatic shutdown
• if light is ON when APU switch is turned OFF - will stay on for 5 minutes
• disarmed when APU switch is OFF (except for failure of APU fuel valve to close)
• triggers a MC and APU light
• illuminates at shutdown when:
  
  • overspeed protection lost
  • APU fuel valve fails to close
  • APU inlet door fails to close
  • FIRE
  • ECU failure
  • DC power loss
  • high oil temp
  • inlet overheat
  • loss of EGT
  • loss of speed
  • no acceleration
  • no flame
  • oil filter
  • overtemp
  • sensor failure
  • underspeed
• if fuel SOV does not close in required time, the FAULT light comes on and STAYS on until APU is started again OR the Batt Switch is turned OFF

Question 4

OVERSPEED Light

Answer 4

Illuminated (Amber):

• APU rpm exceeded (auto shutdown)
• failed self-test during shutdown
• if light ON when APU switch turned OFF - stays on for 5 minutes
• disarmed when APU switch OFF
• maintenance must reset this light

Question 5

EGT Indicator

Answer 5

• displays APU EGT
• remains powered for 5 minutes after shutdown
• no limitations on gauge
• EGT increases when bleed air valve opens

Question 6

APU Switch

Answer 6

Notes.

• the BATTERY MUST BE ON before starting the APU
• if AC power available turn on left main boost pump (gives pressurized fuel to APU - make APU start better)

OFF:

• normal position when not running
• if APU is running and you turn it OFF:
  
  • Trips APU Generator off the buses (if connected) - turns off [APU GEN OFF BUS] light
  • Closes APU Bleed Air Valve
  • APU continues to run for 60 seconds (cooling)
• APU air inlet door AUTOMATICALLY closes after shutdown
• when APU speed decreases sufficiently the fuel valve also close (if it doesnt close the [FAULT] light will go on approx 30 seconds later
• can IMMEDIATLY shutdown APU by pulling APU FIRE SWITCH - no cooldown period

ON:

• Normal position when APU running

START (Momentary)

• initiates APU start sequence

Question 7

What are the auto-shutdowns of the APU? (1sp)

Answer 7

5 Auto Shutdowns.

any of the 3 lights amber light

(low oil pressure, fault, overspeed)

APU Fire

Battery Switch Off (in flt or gnd)

Question 8

How long does it take for the APU door to open and close? (1sp)

Answer 8

20 seconds (1sp)

20 to open an 20s to close

Question 9

How long do you have to wait to open the APU bleed valve? (1sp)

Answer 9

60 seconds (1sp)

Question 10

1sp - how long does it take to start the APU at sea level

Answer 10

from 60 - 120 seconds (based on altitude)