Powerplant Flashcards
The N2 section consists of a ___ stage axial flow compressor connected to a ___ stage high pressure turbine.
10 stage
2 stage
FADEC stands for:
Full authority Digital Engine Control
What is the maximum normal takeoff thrust rating for CRJ 900?
13,600
Describe how the engine operates through the stages:
Suck, Squeeze, Bang, Blow
What percentage of air is bypass and what percent is core air?
80% bypass, 20 % core (5:1 ratio)
What is different about the first four stages of N2 compressor section?
VG system regulates inlet guide vanes and starter vanes for first four stages.
(SYS 22-3)
Describe function and actuation of variable geometry system:
Uses high pressure fuel to actuate stator vanes guide vanes through mechanical linkages.
Maintains compressor aerodynamic performance and stall margin by changing path of air to simulate lowering AoA.
(SYS 22-3)
How is the position of the variable geometry system controlled?
Programmed by FADEC.
Describe the function of the operability valve:
Additional compressor airflow control. Extracts bleed air to offload compressor during engine starts and high aerodynamic load. Also relieves pressure during surges.
How is the operability valve controlled?
FADEC uses high pressure fuel from the FMU (Fuel metering unit) to hydraulically activate it.
What components are on the accessory gearbox?
3-2-1
3 Pumps:
1. Engine Lubrication
2. Engine Fuel
3. Hydrualic
2 Electric:
4. FADEC alternator
5. IDG
1 ATS:
6. Air Turbine Starter
From which compressor stages do we receive bleed air and what is the purpose of the bleed air?
6th or 10th.
- Air conditioning / pressurization
- Engine Starting
- Wing/cowl anti ice
How many igniters are in the combustion section and what are their power sources?
2 Igniters:
Ignition A = AC ESS Bus
Ignition B = BATT Bus through Inverter
How can Battery Bus be the power source of Ignition B when both igniters use AC power?
Static inverter converts DC to AC
During a battery start, Ignition A is the active ignition. How will you be able to start the engine?
FADEC transfers to Ignition B after 15 seconds
What happens when Continuous Ignition is selected? When is it required?
Both A and B Igniters are energized.
- Contaminated RWYs
- Moderate/Heavy Turbulence
- Moderate/Heavy Rain
- Vicinity of thunderstorms
When will FADEC automatically engage continuous ignition?
- Engine flame out
- Turbulent airflow detected when close to a stall at high AoA
Where is the probe located that gives us ITT information (Inter turbine temperature)?
Between high and low pressure turbines
When will the FADEC receive power from its own alternator and when will it rely on aircraft electrical power?
N2 above 50% = FADEC Alt
N2 below 50% = Aircraft
How many channels does the FADEC computer have? What happens if one channel fails?
2 Channels.
Status message for loss of redundancy shows up.
When does the FADEC automatically switch channels during normal operations?
Every second engine start at 7% N2.
Both channels activate during overspeed to actuate the SOV in attempt to reduce RPM.
When will FADEC command a shutdown of the engines?
- Thrust lever placed at shutoff position
- Overspeed
- Hung or Hot start
How are the thrust levers connected to the FMU (Fuel metering unit)
Wired electrically
What would occur if the L or R FADEC failed completely?
Unsure what will happen since “brain” is lost
