CRJ 200 APU Sample Questions

• What factors determine the position of the APU intake door?

  The position is determined by the ECU and is based on aircraft altitude and true airspeed.

• What is the purpose of the screened duct on the left rear fuselage?

  Air is drawn in through the screen by an APU gearbox driven fan to provide APU oil cooling and ventilation of the APU enclosure.

• How will the APU receive fuel should the XFLOW/APU pump fail?

  The APU will receive fuel via the APU negative gravity relief valve, which is pressurized by the right engine fuel feed manifold.

• What accessories are mounted on the APU gearbox?

  The AC generator, fuel control unit (FCU), oil cooling fan, DC electric starter, and oil pump.

• Where is the APU air intake located?

  The intake is located on the upper left rear side of the fuselage.

• How many positions does the APU intake door have?

  It has three positions, open, mid, or closed.

• What can be done if the APU door actuator fails and the door is not operable?

  Maintenance can mechanically position the door to any of the three positions. This allows the aircraft to be dispatched.

  Limitations are that the APU must be operating or if not operating the airspeed is limited to 300 KIAS.

• What is the limitation if the APU intake door is failed open or if the door position is unknown?

  The airspeed is restricted to 300 KIAS or the APU must remain running then there will not be a restriction.

• How is the APU lubricated?

  The APU has a self-contained lubrication system. There is a gearbox mounted oil pump, oil cooler assembly, and an integral oil tank.

• Where does the APU normally get fuel?

  The APU receives fuel from both wing tanks by the APU/XFLOW pump.

• How many pounds an hour does the APU burn?

  Approximately 120 pounds an hour with electrical and bleed air loading.

• What is the purpose of the XFLOW/APU pump in the operation of the APU?

  This pump draws fuel from both wing tanks and sends the fuel to the APU.

• What is the purpose of the APU fuel feed shutoff valve (SOV)?

  It is used to control the fuel supply to the APU.

• How is the APU SOV opened?

  By pressing the PWR FUEL switch light on the APU control panel.