Engines and APU Flashcards
What are the primary engines indicators?
N1 and EGT
What are the secondary engine indications?
N2, fuel flow, oil pressure, oil temperature, oil quantity, and engine vibration
What does the EEC do?
Electronic Engine Control (EEC) monitors autothrottle and flight crew inputs through the thrust levers to control the engines.
Describe EEC normal mode.
Sets thrust by controlling N1 based on thrust lever position
Describe EEC alternate mode.
Soft vs Hard
In the alternate mode, the EEC schedules N1 as a function of thrust lever position.
Soft mode - switch normal and EEC mode is alternate
Hard mode - the switch position is ALTN, the EEC mode is alternate
Thrust protection is not provided in the alternate mode and maximum rated thrust is reached at a thrust lever position less than full forward.
How does overspeed protection work?
If N1 or N2 approaches overspeed, the EEC commands reduced fuel flow.
EICAS advisory message ENG RPM LIMITED (L or R) is provided
Describe the flow of oil to the engine
- Oil is pressurized by an engine–driven oil pump.
- From the pump, the oil flows through the oil filter. If the oil filter becomes clogged, then oil bypasses the oil filter and the EICAS advisory message ENG OIL FILTER (L, R) is displayed.
- Then oil flows through the fuel/oil heat exchangers and
- Then through the backup generator oil/oil heat exchanger
- Then flows to the engine main bearings, gears, and accessory drives.
- A scavenge pump returns the oil to the reservoir.
What is the minimum oil quantity and limitations?
No minimum oil quantity or limitations
What is the purpose of the airborne vibration monitoring system?
Primarily intended for engine condition monitoring, but it is also a useful tool for isolating and determining corrective action for engine anomalies.
APU bleed air is available at what altitudes?
At or Below 22,000’
Explain the APU start system.
What is the starter motor duty cycle?
Has an air turbine and electrical starter.
Air turbine starter has priority.
Gets fuel from the left manifold from the AC pump when AC power is available. From the DC pump when AC power isn’t available.
3 starts is a 60 min period for each motor.
What are the 2 modes of the APU?
Explain them
Attended and unattended.
Attended when either engine is running or starting and in flight.
Unattended all other times on the ground
When will the APU automatically start?
In flight, if both AC transfer busses lose power, the APU automatically starts, regardless of APU selector position.
The APU can be shut down by positioning the selector to ON, then OFF.
What causes the APU to shutdown automatically in the attended mode?
- APU fire/inlet over temperature
- overspeed/loss of overspeed protection
- APU controller failure
- speed droop.
What causes the APU to shutdown automatically in the unattended mode?
- APU fire/inlet overtemperature
- overspeed/loss of overspeed protection
- high EGT
- low oil pressure
- high oil temperature
- generator oil filter approaching bypass
- intake door failure
- APU controller failure
- speed droop
- no combustion on start
- no acceleration on start.