15.14 Flashcards
Where is the hottest temperature
Directly behind the combustion chamber is where the gas hits the HPT
Called (TIT)
Temperature of TIT
Higher then 1400 degrees C
What has a direct relationship to the TIT
EGT
(Max can be 600-900 degrees C )
Where is EGT taken from
Between high and low pressure turbine or behind the low pressure turbine
What part of the engine is temperature taken from
First stage turbine inlet guide vanes
What component measures temperature
Thermocouples
How are thermocouples placed
Around the permitter of the engine turbine casing or exhaust duct
What are the parts of the dual thermocouple
Two electrically independent junctions within a single probe
What are primary indicators
Performance indications which monitor performance and set thrust for flight phases
What are secondary indications
System indications which measure operation of the engine and detect malfunctions
What is engine trend monitoring
Done on ground to detect engine problems at an early stage
Uses parameters recorded by ACMS
What is the ACMS
Aircraft condition monitoring system
What two parameters give us thrust
Rotational speed of the fan , N1
Engine pressure ratio
What does the oil system monitor
Oil quantity
Oil pressure
Oil temperature
3 analyses of engine trend monitoring
Thermodynamic - pressure and temperature along gas flow path
Mechanic dynamic - failure in rotors
Oil consumption
What is compared to get epr
Engine turbine discharge pressure to the pressure of the ram air at the inlet of the engine
What does the amber or redline show for EPR
Maximum thrust available
What’s the blue circle in an epr indication
Actual throttle position
What’s flexible take off
Standard take off thrust setting used on airbus
Boeing is (assumed temperature derate)
When is full thrust (TOGA) used
Wet/icy condition or short runway / hot and high
What pressure does oil pressure indicator show
Engine oil pump discharge pressure
Oil pressure transmitters
Bourdon tube type
Strain gauge
Shape and material of bourdon tube
C shaped or helical with oval cross section
Made of copper , brass , aluminium or nickel alloy (money)
How does a strain gauge work
When object undergoes strain resistance changes proportionally
Shape and material of strain gauge
Small rectangular shape
Made of foil , metal wire or semiconductor materials
How does a low oil pressure switch work
When pressure is below a limit switch closes and signal sent to computer as a warning
What are the two types of oil temperature sensor
Resistance temperature detector
Thermocouple ( 2 dissimilar metals )
How is cavitation caused
High fuel pump demand
What kind of warning do fuel sensors give
Impeding blockage and risk of cavitation
When an auxiliary pump on an aircraft is off how is pressure created
Pressure created by the engine driven pump
What warning switch is used on turbine powered aircraft
Low pressure warning switch at the outlet of each fuel boost pump
Where is the announciator for each switch located
Adjacent to the boost on/off switch on fuel panel in flight deck
What two indications for fuel flow is there
Actual fuel flow
Fuel used since engine start
(Indicated in kg , lbs , tons)
What’s measured on synchronous mass flow
Deflection angle
How does motorless mass flow generate acceleration
Fuel flow
How is rotor speed indicated
Percentage of 100% design speed
Rotor speed indication main parts
Sensor
Data transmission
Indication
What are the other names for a variable reluctance sensor
Magnetic reluctance sensor
Magnetic pickup
How does a variable reluctance sensor work
Detects change in a magnet and ferromagnetic target
What affect does the target have to do with the magnet and air gap
As the target moves closer to the magnet the air gap decreases which reduces magnetic reluctance and vice versa
How does a tachometer generator work
Generates 3 phase ac voltage which is sent to the FADEC to generate speed signal
Why is the tachometer called dedicated engine
Supplies electrical power to the computer
3 types of rotor speed indication
Clock type scale
Moving vertical bar
Classical electromechanical indicator
What colour is the over speed indicator line
Red
If engine exceeds for the duration of the overspeed it’s recorded and initiates report from engine trend monitoring
What does vibration indicate
Rotor imbalance
What the range of vibration units
0-6
How many vibration sensors
1 or 2
What’s the vibration computer called
Engine vibration monitoring unit (EVMU)
What do accelerometers do
Measure the radial acceleration of the rotor system
Where are the 2 vibration sensors located
Compressor area and turbine area
What’s the electromagnetic accelerometer
Magnet with two springs
When vibration occurs the coil moves up and down with the sensor housing
How does a piezoelectric crystal sensor work
Voltage is generated when you apply a force to the crystal
What’s shown when n1 or n2 speed signal fails
Broadband (BB) vibration
What does a electrical torque meter system consist of
Torque meter assembly
Phase detector
Indicator
How is a hydraulic torque meter operated
By engine oil metered through a valve that is controlled by a helical ring gear that moves in response to the applied torque
Why is a power assurance test needed
Check that the engine can accelerate and decelerate to and from idle with a given epr within a specific time period
During a power assurance test which way is the plane placed
Into the wind with chucks in front and behind the wheels
How quickly should the engine accelerate and decelerate during a power assurance test
Accelerate to given speed - 7s or less
Decelerate to idle - 8s or less
After n1 operating above 70% how do you shut down
Run at idle for 10m to decrease engine temp and safely shutdown the engine
Where is low pressure sensor in the fuel system
After the outlet from the low pressure filter
