15.14 engine indication systems Flashcards
what does EGT stand for?
exhaust gas temperature
where do we measure EGT?
between high and low pressure turbine or directly behind the low pressure turbine
what is TIT and why cant it be measured ?
turbine inlet temp
its too hot so is measured from the EGT
what is the temperature indication range for the EGT instrument?
0- 1200 degrees c
what are the three types of engine indications?
-performance indications
-system indications
-engine trend monitoring
what is another name given for system indications?
secondary indications
where might engine trend monitoring be shown?
not typically in the flight deck usually for maintenance purposes
what is EPR?
engine pressure ratio, the difference between inlet airspeed and outlet
what are examples other performance indicators?
EPR, N2, N1, N3 if applicable, Turbine inlet temp measured from EGT, fuel flow.
what is another way that thrust could be represented ?
speed of fan rotation or (N1)
what may be included in engine system indications?
engine vibration, oil quantity, oil temp and oil pressure.
what are the main parameters measured for engine trend monitoring?
The thermodynamic analysis
The mechanic-dynamic analysis
The oil consumption analysis
how is EPR shown?
analogue and/ or digital value
what indications will be shown on a typical EPR display?
-blue circle shows position of actual throttle
-green line shows throttle level when autopilot is engaged
-red line shows max available thrust
what is the purpose of FLEX take off or assumed temp derate?
it uses an assumed temperature thrust reduction to prevent engine wear
where is oil pressure measured?
after the oil pump
how is oil pressure measured?
A Bourdon tube can be either c-shaped or helical, with. When the pressure enters the tube, the pressure acts to change the oval to a circular cross section. This causes the tube to move – opening the c-shape The deflection can be measured on a scale
what is another way that oil pressure can be measured
a strain gauge operating with a Wheatstone bridge, when no strain is applied the bridge is balanced meaning voltage difference is zero
what is the function of the oil pressure switch?
operating on a diaphragm measuring pressure principle it gives a decrease in pressure activates the switch indicating a drop in oil pressure to the cockpit
what is the most commonly used types of engine oil temperature sensor?
the Resistance Temperature Detector (RTD) or Thermocouple. An RTD is a sensor made of a temperature-sensitive resistor, while a thermocouple consists of two dissimilar metal wires joined together
what is the largest concern with cold fuel?
ice build up
what type of fuel temperature sensor is used?
resistance type electric fuel temperature sender in the main fuel tank
how can temperature of fuel be adjusted?
low fuel temperature can be corrected with the use of a fuel heater
what are the two indications given by the fuel flow indicators?
the actual fuel flow to the engines
The fuel used since the engine was started
what is fuel quantity indicated in?
kg, lbs or tons
what fundamental law of physics is fuel flow always based on?
Force = Mass x Acceleration
what are the most common types of fuel flow transmitters available today?
Synchronous mass flow and motorless mass flow
how does the synchronous mass flow transmitters function?
the fuel mass turns a turbine against a spring and the deflection angle is measured. To get the force the fuel must be accelerated. This is achieved by an impeller that rotates continuously, driven by an electric motor
how does a motorless mass flow transmitter function?
They use the fuel itself to generate acceleration. In this transmitter type, the fuel flow turns a small turbine. The rotating turbine also drives a drum and an impeller, which is located inside the drum. Both are coupled by a spring.
The fuel drives the turbine, drum, and impeller with a speed that is proportional to the volume of fuel
what are engine speeds expressed as?
a percent of top speed
how does the variable reluctance sensor function?
a type of electromagnetic sensor which detects a change in the magnetic flux between a magnet and ferromagnetic target the frequency of this is measured
how does a tachometer generator function?
The tachometer generator has a permanent magnet that is driven by the gearbox with a speed that is proportional to the N2 rotor speed. The rotating magnetic field generates a 3-phase AC voltage with a frequency that is proportional to the input speed
what are the types of speed indication displays?
A display with a clock-type scale
A display with a moving vertical bar
The classical electromechanical indicator
what is vibration typically measured in?
numbers 0-6
what is the EVMU?
Engine Vibration Monitoring Unit
what is typically used to measure engine vibration?
accelerometers -
The electromagnetic accelerometer
The piezoelectric-crystal type sensor
how does the piezoelectric-crystal function?
A piezoelectric crystal generates a voltage when you apply a force to the crystal In this sensor, the force is applied by an inertia mass, which presses the crystal against the base plate when the sensor is accelerated
what will occur if the N1 or N2 speed signal fails for vibration monitoring?
BB will be shown which is broadband
why are toque meters used to measure power being outputted by turboshaft engines?
its not possible to measure with turbine gas temperature and engine RPM
what is the structure of a typical torque meter?
to concentric shafts one is a datum shaft only connected to engine output the twist of the other shaft is measured as it is proportional to torque
what is the structure of a hydraulic torque meter?
helical ring gear moving in response to applied torque
what is a critical test to be performed after engine maintenance?
power assurance test which consists of running the aircraft from 0 to full power and back in a set amount of time
after start up on a power assurance test how long should the engine be left to idle?
5 minutes
after engine operation above 70 % of N1 how long should the engine be left cool at idle on a power assurance test?
10 minutes
