15.14 Engine Indication Systems Flashcards
What are the 2 relevant temperatures of the engine?
Exhaust Gas Temperature (EGT)
Turbine Inlet Temperature (TIT)
Why are EGT measured?
To prevent thermal damage.
Indicate if a limit is exceeded.
Where is EGT measured?
At a colder location between HPT and LPT or directly behind LPT.
What is TIT?
The highest temperature directly behind combustion chamber.
What temperature is physically measured.
Only EGT, TIT is calculated using EGT.
How does an EGT indicator show average temp?
Using individual thermocouples.
What is the scale range of an EGT indicator?
0-1200 C
What happens when TIT is high?
An over temp warning light will illuminate.
What are engine thrust indications divided into?
Performance/ primary.
System/secondary.
Engine trend maintenance.
As Thrust can’t be measured directly, what are the 2 indications of equivalent value?
Engine Pressure Ratio (EPR).
N1 (fan) speed.
What is the purpose of system indication?
To monitor correct system operation.
When is engine trend monitoring done?
On ground to detect engine problems.
What 3 analyses are done for trend monitoring?
Thermodynamic,
Mechanic dynamic,
Oil consumption.
What is EPR?
A measured of thrust being developed.
How is EPR measured?
Comparing RAM air at engine inlet and exhaust.
What does a AMBER + RED indication mean on an EPR display?
Maximum thrust available.
What does the blue circle indicator on the EPR display mean?
It corresponds to the actual throttle position.
What is Flexible take off?
The standard take off thrust.
What do Boeing call Flexible take off?
Assumed temperature derate.
What does oil pressure indicate?
The pressure of engine oil pump discharge.
What are the 2 oil pressure indicator types?
Bourden tube.
Strain gauge.
The strain gauge indicator uses what configuration?
Wheatstone bridge configuration.
What principle does a strain gauge indicator use?
Strain causes a proportional resistance change.
What is the low oil pressure switch connected to?
Oil supply line and oil tank vent line.
Where is a low oil pressure switch connected to?
Flight warning computer.
What does an oil temperature sensor use?
Resistance Temperature Detector (RTD)
Thermocouples.
Where is oil temperature measured?
At the oil pump entrance.
What does an over temperature warning produce?
A visual and audible warning.
Where is the low pressure sensor located?
At the LP filter outlet.
Where is a differential pressure sensor fitted?
Across the filter.
What do light reciprocating engine aircraft use to measure fuel pressure?
A direct reading Bourden tube pressure gauge.
Where is the fuel pressure gauge connected?
To the inlet of the fuel metering device.
What does a pressure warning signal produce?
It illuminates a warning light using simple pressure sensing switches and an audible warning.
What 2 indications are used to measure fuel flow?
Actual fuel flow to engine,
Fuel used since engine was started.
What is fuel indicated in?
Weight.
Kg, tons, lbs.
What is fuel flow calculated by?
The FADEC system.
What does a fuel flow transmitter measure and where?
Mass flow between FCU and fuel nozzles.
What are the 2 fuel flow transmitters used?
Synchronous mass flow.
Motorless mass flow.
What do the impeller, motor and turbine do in a synchronous mass flow transmitter?
Impeller turns with the electric motor.
Motor accelerates fuel through the transmitter.
Turbine measures deflection angle against a spring.
How does a motorless mass flow transmitter accelerate fuel?
Using the fuel itself and a small turbine.
How is the deflection angle measured in a motorless mass flow transmitter?
Using 2 coils in combination with 4 permanent magnets.
How can turbine engine speed be measured?
Variable reluctance sensor = measures N1
Tachometer generator type = measures N2
How does a variable reluctance sensor measure turbine engine speed?
By detecting a change in magnetic flux.
In a variable reluctance sensor, a speed probe is positioned on compressor casing in line with what?
A phonic wheel or actual fan blades.
What makes up a tachometer generator ?
A permanent magnet driven by a gearbox.
What does the permanent magnet do in a tachometer generator?
It generates 3 phases AC voltage with a frequency that is proportional to speed input.
What is another purpose of the Permanent Magnet Generator?
It also tells the pilot ether the engine is turning in the correct direction.
What are the 3 types of rotor speed indicators?
Clock type.
Moving vertical bar.
Electromechanical.
What is vibration measured in?
Units from 0 to 6.
What is the vibration monitoring computer called?
Engine Vibration Monitoring Unit (EVMU)
What does an accelerometer measure?
Radial acceleration of rotor system.
Where are the 2 accelerometers located?
In the compressor area and in the turbine area.
What are the 2 types of accelerometers?
Electromagnetic
Piezoelectric crystal.
How does the piezoelectric crystal accelerometer work?
It generates a voltage when a force is applied to the crystal.
In vibration indication, if a speed signal fails, what does rotor identification show?
Broadband (BB) vibration.
What are the 2 types of torque meters?
Electric or hydraulic.
How does an electric torque meter work?
A twist in the shaft is measured by the difference between 2 shafts.
How does a hydraulic torque meter work?
A helical gear moves in response to applied torque.
What is a critical power test?
A power assurance test.
What does a power assurance test check?
If the engine can accelerate to Engine Pressure Ratio in a specific time and decelerate in a specific time.
How long must an engine operate at idle for before a power assurance test?
5 mins.
After what conditions must the engine be left to cool down and for how long?
After operation for 8s above 70% power.
Leave for 10 mins.
