Engines - Propeller System Flashcards
How does the PVM control prop blade angle?
Metering engine oil to one side of the pitch change mechanism in the hub to reduce blade angle (fine) which is opposed by a constant oil pressure supplied to the mechanism to increase blade angle (coarse)
What happens if the supply of oil pressure to the PVM is lost?
Pitch lock feature prevents aerodynamic loads from reducing blade angle more than 1 degree and prop speed increasing more than 2% from the point of oil pressure loss
What controls blade angle in the ground beta range?
Fuel governing mode
EEC automatically increases fuel flow to maintain a minimum prop speed approx 70.8% Np
What does the Signal Conditioning Unit do?
Supplies torque data from a sensor on each engine
Sensor measures torque on the power turbine shaft
When is autofeather triggered?
When an armed AFU detects a failure of its associated engine by a decrease of torque below approx 18%
What is the auxiliary pressure pump for?
Runs for a set time to provide adequate time for prop feathering
How is feather mode initiated?
- by placing condition lever in the feather position
- by a feather solenoid valve which is opened by the auto feather system
What does a LO PITCH light indicate?
Low blade angle
CCAS also triggered
Triggered when actual blade angle is less than the normal flight idle blade angle
Illuminates during ground ops below Flight Idle
When is differential pressure measured?
Across the engine oil filter to detect a restricted or blocked filter
Across the fuel filter to detect a restricted or blocked filter
Across the reduction gearbox scavenge filter to detect a restricted or blocked recut ion gearbox scavenge filter
What does the Np gauge indicate?
Propeller RPM as sensed by a speed sensor on the reduction gearbox
Values are indicated as % of the max
What does the red radial indicate on the Np guage?
Max RPM 1200
What does the green arc indicate on the Np guage?
Normal operating band of 70.8% to 100%
What does the amber arc indicate on the Np guage?
Caution range that is to be avoided
41.6% to 65%
What will the Np guage show during a test?
It will read 115%, marked by a blue dot
What does the Nh gauge indicate?
High pressure gas generator RPM as a % of the max
Value is sensed by a speed sensor on the accessory gearbox
What does the red radial on the Nh guage indicate?
The max normal operation speed of 102.7%
What does the green arc indicate on the Nh gauge?
Normal operating and starting band of 62 to 102.7%
What is the Nl value?
The low pressure gas generator RPM as a %, sensed by a speed sensor in the LP compressor housing
What are the Nl coloured sectors?
Green represents 62 to 104.2% and the red radial indicates the max permissible value of 104.2%
What does the ITT gauge indicate?
The ITT temp sensed by thermocouple sensors between the LP turbine and the power turbine
When does an amber light illuminate on the ITT gauge?
When the max operating limit of 800 degrees is exceeded
Will trigger CCAS alert
In hotel mode will illuminate when ITT temp exceeds 715 degrees
What do the red markers mean on the ITT gauge?
Red mark - max operating limit of 765 degrees during normal ops
Red dot with H - max temp in hotel mode of 715 degrees
Red dashes - max uptrim operating limit of 800 degrees
Red dot with S - max starting limit for a 5s period of 950 degrees
Red point - max temp limit during a 20s period of 840 degrees
What does the amber section mean on the ITT gauge?
Caution range from 765 to 800 degrees
What does the green arc indicate on the ITT gauge?
The normal operating range of 300 to 765 degrees
What will you see on a ITT gauge test?
Will indicate 1150 degrees, shown by a blue dot
What do the two sensors on the reduction gear box of each engine do?
One sensor supplies low torque signal to the AFU
One sensor supplies torque information to the EEC
What does it mean if the torque indicator shows amber triple 0?
The EEC torque sensor has failed
What does it mean if the torque indicator shows three dashes?
The associated EEC is unable to control the associated handling bleed valve
Handling bleed valve will be closed
What does it mean if LAB is displayed on the torque indicator?
The wrong EEC has been installed
What does the red radial indicator show on the torque sensor?
Red radial - The normal max torque of 100%
Red dashed line - max uptrim torque of 106.3%
Red dot - max torque value of 120%
What does the green arc mean on the torque indicator?
Indicates the normal operating band of 0 to 100%
What will a test on the torque indicator show?
It will read 115%, indicated by a blue dot
What does the amber triangle mean on the torque indicator?
The target torque value calculated by the FDAU, based on selection made on the pwr mgt panel
If TO is selected, the target indicator will show the reserve take off torque value
When will the FAULT light illuminate on the pwr mgt panel?
When both channels of a PEC are lost
What happens when you press the FAULT PEC button?
The associated PEC will be deactivated and the Np will be blocked at 102% whenever power is sufficient
What is the CRANK position used for on the eng start panel?
Motors the engine only and ignition is deactivated
Used in case the engine needs to be cleared of fuel fumes
What will happen when the start button is pressed on battery power?
The start contactir will close and connect the starter generator to the main battery
What is the Nh during start up?
The HP spool is driven by the starter generator to a speed of approx 20% Nh
When is fuel introduced during start up?
At 10% Nh by placing condition lever out of the FUEL SO position
When will the starter disengage during start?
45% Nh starter will disengage adn ignition is deactivated
ON light on start pb extinguishes
Why will a FAULT light illuminate?
- starter generator remaining engaged after 45% Nh
- failure of associated GCU during start
- on right engine, prop brake on while the gust lock is not engaged
What happens when manual ignition is selected?
Both igniters will be on continuously
