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DASH 8 > APU > Flashcards

APU Flashcards

1
Q

Fuel Burn

A

120 lbs/hr

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2
Q

Can it power the De-Ice?

A

No, bleed air goes to De-Ice system, but to provide 18 PSI for the rear outflow valve. Helps the plane to not pressurise on the ground.

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3
Q

DC Load Remains >1 after start?

A

APU starter has possibly welded shut. Aircraft needs to be shutdown.

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4
Q

Gen Info?

A

Constant Speed, Gas Turbine.

Installed next to A/C packs.

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5
Q

Elec Power for Start?

A

RHS 28V DC bus, from main or external power.

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6
Q

Fuel Supply?

A

LHS Tank, from the collector bay

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7
Q

ESU?

A

Electronic sequence unit, controls the APU start/running etc.

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8
Q

Start Circuit?

A

Armed when fuel pressure is sufficient for start (sensed by ESU)

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9
Q

APU Bleed Air

A 
De-ice system,
Air Conditioning (allow APU to run for 1 min prior to on)
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10
Q

Start Bypass Valve

A

Controls pressure during start, it prevents compressor overpressure by bleeding off excess air.

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11
Q

Starter Limitations

A

2 mins between retries (5 mins for Skips)
Try 1: 1 min on, 2 mins off
Try 2: 1 min on, 2 mins off
Try 3, 1 min on, 30 mins off.

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12
Q

Starter/Generator - Electrical output

A
  • Operates ALL DC, Fixed Freq AC and charges both batteries.
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13
Q

Start/Gen - Engine Starts

A

Can assist up to 300 amp limit.

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14
Q

When does starter cutout during start.

A

70% RPM (GCU signals starter to cutout, starter light goes out, ignition de-energised).

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15
Q

What happens at 90% RPM during APU start.

A
  • ESU signals FCU for auto RPM governing
  • Arms bleed air and gen systems
  • Starter light out, run light on.
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16
Q

GCU Functions

A
  • Provides voltage reg, contractor control and auto fault protection to starter/gen.
17
Q

Bus Logic?

A

The DC logic relays close the main bus ties, and close the secondary to main bus ties. All DC buses are then tied to the APU.

18
Q

Limitations (Big List)

A
  • Ground use only
  • Fire detection test must be conducted before 1st flight of day
  • APU off before takeoff
  • Max operational temp is 51 degree
  • Same fuel as A/C
  • During Px refuelling, flight crew/eng must be in cockpit
  • Not on during grav refuelling.
19
Q

Rear Bay Overtemp

A
  • 2 temp sensors, one above and forward, one above and aft, of the APU.
  • Operates at 121 degrees.
  • Auto shutdown initiated and RBY OHT light on APU panel.
20
Q

ESU monitoring

A

Detects high EGT, high oil temp, low oil press, under/over speed. ESU will autoshutdown the APU.

21
Q

Gen Fault?

A

If detected GCU will remove DC gen from R main feeder bus, and open the main to secondary bus tie.
Gen light goes on, warn light on, with APU caution light and master caution light on.

22
Q

APU Overspeed

A

If detected the ESU illuminates:

  • FLR on APU PWR Switch
  • APU Caution Light
  • Master Caution Switch Light
  • Normal APU S/Down initiates.
23
Q

Duct/Pack O/Temp - System & What Happens

A
  • Fire loop around exhaust and APU shroud
  • Fully automatic extinguish system
  • Discharges under APU for compartment fire, and inside APU shroud for internal fire.
  • ESU initiates automatic shutdown.
24
Q

ESU Fire Shutdown Indications

A
  • Red fire warning light on O/Head panel
  • APU caution light on
  • Master warning and caution lights on.
25
Q

Extinguisher discharge delay

A

15 seconds after fire detected (to allow APU to shutdown and fuel to be used/drain)
If the discharge fails, there is a manual release available, powered from the battery bus, orange BTL light indicated problem.

26
Q

APU fire test switch lights up

A

Fire, Fault, BTL, Fuel Valve Closed, Master Warn/Caution light

27
Q

APU Compartment Vent

A

Fully automatic

  • Opens at 94 degrees for oil temp, 66 degree for rear bay temp
  • Cools APU and allows RBay cooling
  • Blower pulls in air through rear bay, through the oil cooler and out the exhaust ports.

DASH 8 (9 decks)

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