Systems: APU & Powerplant Flashcards
What does turning APU master knob to the ON position do?
energizes the FADEC
commands the fuel shutoff valve to open
enables APU indication and alarms on EICAS
Where is the APU located?
tailcone of the aircraft, aft of a firewall
How does the APU receive its fuel?
Normally, tank #2.
Can receive fuel from tank 1 if crossfeed is selected to LOW2 and electric fuel pump for engine #1 is ON
What controls the start and normal ops of the APU?
its own FADEC
Which electrical busses can the APU energize as the sole source of electrical power?
In flight: all of the main busses, except the shed busses
On the ground: all of the busses, providing the shed bus switch is in the OVRD position
What is the max altitude for an APU start?
FL300
What is the max altitude for APU operation?
FL370
What are the max cool-down periods before subsequent APU start attempts?
after 1st attempt - 1 minute
after 2nd attempt - 1 minute
after 3rd attempt - 30 minutes
How is a fire detected in the APU?
by its own dedicated fire loop
How is a fire extinguished in the APU?
by its own dedicated extinguishing bottle
Explain how the APU fire bottle works
The APU, without pilot intervention, will automatically shut down after 10 seconds due to any heat-related malfunction on the ground. In flight, the APU will NOT shutdown automatically for a heat-related malfunction.
It is important to understand that this automatic occurrence of the APU shutdown on the ground is just a shutdown, and not an automatic deployment of the APU fire bottle. The APU fire bottle can only be discharged by the pilots via a dedicated extinguishing button on the overhead panel.
What is the max electrical load of the APU generator?
400 amps up to FL300
300 amps above FL300
What are the minimum battery temperatures and voltages for APU start?
-20 degrees C and 23.5 volts
At 23.5 volts and higher, the APU may be started off the batteries alone. Between 19v and 23.5v, the APU must be started with a gourd power unit. At 19v and lower, the battery must be removed from the airplane to be recharged. When battery starting the APU, it’s important that Battery 1 AND Battery 2’s respective temperature and voltages are noted. Even though Battery #2 is responsible for starting the SPU, both batteries receive a charge when the APU generator comes online. If either of the batteries is lower than the prescribed limits, the crew runs the risk of thermal runaway of the main batteries. Under most circumstances, it is advantageous to start the APU off of a GPU, since this practice does not place any load on the aircraft’s electrical system during APU start.
What type of engines do we have on our aircraft
Rolls Royce AE3007 A1E
What are the 3 pilot selectable thrust modes for takeoff?
ALT/TO - reduced thrust, lowest level
T/O - full thrust, medium level
E/TO - extended thrust, highest level
What two stages are bleed air tapped from?
9th and 14th
When does the high-stage valve open automatically to allow 14th stage bleed air to run the system?
low thrust settings
cross-bleed starts
pneumatic anti-ice is activated
How is the accessory gear box powered?
the accessory gear box is powered via a tower shaft that is connected to the high-pressure turbine (N2)
if there is adequate N2 rotation, generators should be running, engine-driven hydraulic/fuel/oil pumps should be working
What components are located on the accessory gear box?
FAGHOP
engine-driven fuel, hydraulic, and oil pumps
2 engine-driven generators
permanent magnet alternators
air turbine starter
What are the 3 sources of air for engine start?
APU bleed air
Cross-bleed air (requires 83% N2 on operating engine)
External air
What is the preferred source of air for an engine start?
APU bleed air
What is the FPMU and what does it do? What operates it?
The FPMU controls and supplies fuel to the engine nozzles at correct pressure and flow rate for engine start, correct engine operation, engine stop and also controls the compressor variable geometry vanes. The FPMU for each engine operates under the full authority of the FADEC.
How does the fuel shutoff valve work?
The fuel shutoff valves in the belly are only activated (fuel cutoff) by pulling either of the T-handles. For each engine, there is a separate latching shutoff valve (controlled by the Start/Stop switch) that shuts off fuel immediately prior to the engine, if Start/Stop is placed in Stop position.
What are the 2 ways that pilots can shut off fuel to the engines?
The Start/Stop selectors to Stop cuts fuel off right at the engine.
The T-handle closes the fuel-shutoff valve in the belly. In only the T-handle is pulled, the engine may run for up to a minute before shutting down. This is not desirable if an immediate engine shut-down is wanted (engine fire).
