15.14 Flashcards
Where is the highest temperature in an engine?
Directly behind the combustion chamber at the High pressure turbine (TIT)
Where is EGT measured?
Between the high and low pressure turbine/ directly behind the low pressure turbine
What are the temperatures (including the EGT relative too)
Gasses entering the first stage turbine inlet vanes
What is used to measure the temperature, and where are they placed?
Thermocouples near the turbine exit by the exhaust
What do the EGT’s show?
The average temperature from the thermocouples
How are EGT’s sealed?
Hermetically
TIT indicating system shows information how?
A visual indication on the instrument panel
Because numerous thermocouples are used to find TIT, what must you do?
Find an average
Dual thermocouples contain two electrical junctions for what two purposes?
One to send signals to the flight deck and the other to provide signals to control and monitoring systems
What happens when the TIT reaches a predetermined limit?
An over temperature warning light in the indicator illuminates
What do digital indicators not use?
Resistance-type or servo-driven thermocouples
What are the three groups engine indications can be split into?
Performance Indications
System indications
Engine trend monitoring
What are performance indications also known as? And what are they for?
Primary indicators and they are used to monitor the performance and limits of the engine.
What can you do with performance indications?
Set thrust for different flight phases
What are system indications also known as?
Secondary indications
What are system indications used for?
Monitor the operation (such as fuel and oil) and detect malfunctions quickly
What is engine trend monitoring?
It is done on the ground to detect engine problems early.
What does engine trend monitoring use?
ACMS (Aircraft condition monitoring system)
Which of the three indications do not show up on the flight deck?
Engine trend monitor
Where are engine indications shown in the flight deck?
ECAM at the top
Engine performance indicators are used to do what?
Monitor and set engine thrust
What are the two values used to measure thrust because you can’t measure it directly?
EPR (Engine pressure ratio)
The rotational speed of fan N1
What is another performance indicator ?
Engine rotor speed for each rotor system (N1 N2 N3)
What are two examples of engine performance indicators?
Exhaust gas temperature and fuel flow indications
Where does the computer send the data to?
The indicators or display system. (Use it to control the engine)
What are engine system indications used to monitor?
Correct operation
What does the engine vibration indication show?
Imbalances that occurs in rotating parts of the engine
What do engine trend monitoring systems prevent?
Engine problems during flight/engine reductions
The engine data is analysed by a computer system that does what?
Find any parameters that indicate a trend towards a limit
(thermo-dynamic, mechanic
-dynamic, oil consumption)
What does thermodynamic show?
Checks the pressure and temperature
What does mechanic dynamic show?
Failures in the rotor system
What does the oil consumption analysis generate?
An alert when the oil consumption is exceeded
How are EPR indications shown?
Analogue or digital
The EPR function has the same command as what?
The N1 command
What does an AMBER or RED line show?
The EPR for maximum thrust
What does the blue circle show on an EPR display?
The actual throttle position
What is Flexible Take Off, ‘FLEX’?
Standard take off thrust setting used on Airbus
When is TOGA used?
On a contaminated(wet/icy) runway or if performance changes (short runway)
What Is TOGA?
Full thrust
What do FLUX take-off settings use?
why?
An assumed temperature thrust reduction
To prolong engine life
What term do Boeing use?
Assumed temperature derate
Why is the oil supply system monitored?
To guard against engine failure from inadequate lubrication and cooling?
What does the oil pressure indicator usually show in regards to the engine oil?
The engine oil pump discharge pressure
What are the 2 types of oil pressure transmitters?
Borden tube
Strain gauge
What shape is the Borden tube?
C-shaped or helical with an oval cross section
When the pressure enters the tube what happens to the cross-section of the Borden tube?
It becomes circular extending the helix
What does the extension of the helix cause?
Indicator needle to deflect which is proportional to the pressure exerted
What can a Borden tube have to provide an electrical representation of the pressure?
A potentiometer
What does a string gauge measure?
Mechanical strainer deflation
What principle do strain gauges work off of?
When an object undergoes stain the resistance changes proportionally
What does a strain gauge look like?
Small and rectangular, made of metallic foil for electrical properties
What is a strain gauge designed in a specific pattern to maximise?
Sensitivity to strain
What is the most common arrangement for a strain gauge?
Wheatstone bridge configuration
What is a Wheatstone bridge configuration?
Grid like pattern with several active arms and a central section when the strain is applied
What do the active arms do?
Detect the strain, and change their resistance accordingly
What happens when strain is applied to a strain gauge?
The object deforms and its length changes
What causes an alter in the electrical resistance of the strain gauge?
The change in active arms length
What happens when no strain is applied to the object?
The Wheatstone bridge is balanced, meaning the voltage is 0
When the bridge becomes unbalanced therefore creating a voltage difference, what initially occurred?
When strain is applied to the object
What must you do the output voltage of the Wheatstone bridge?
You must filter it
What is the low oil pressure switch used for?
Initiate a low oil pressure warning
Where is the low pressure switch connected to?
The oil supply line and oil tank vent line
What happens to the low oil pressure switch when oil pressure decreases below the limit?
It closes, a signal is sent to the flight warning computer and a warning message appears in the flight deck
What is an oil Inlet temperature indicator used to do?
Indicate the temperature of the oil as it enters the oil pressure pump
What is the primary component responsible for measuring the oil temperature?
The oil temperature sensor which is designed to respond to changes in temperate and convert the information into electrical signals
What is the most common type of oil temperature sensor?
The resistance temperature detector (RTD) or thermocouple
What is an RTD made up of?
A temperature sensitive resistor
What happens when the oil temperature exceeds operational limits?
The pilots get an over temperature warning
What happens during an over temperature warning?
Can be visual and audible
Where is the Low pressure sensor positioned?
After the outlet for the low pressure filter
Where can low fuel pressure originate from?
Cavitation caused by high fuel pump demand
What type of sensor is located on the fuel filter?
Differential pressure sensor
What do differential pressure sensors give warning of?
Impending blockage and cavitation
How is a warning of low pressure fuel displayed?
As a warning lamp or EICAS message
What type of pressure gauge do light recoporricating engines use?
Bourdan tube
What is the pressure gauge connected to?
The fuel inlet of the fuel metreing device
What do more complicated aircraft have located at the fuel inlet of the fuel metering device?
A sensor that sends electrical signals to flight deck
What does the gauge indicate when the auxiliary pump is switched off?
The pressure created by the engine driven pump
What type of engine may use a differential fuel pressure gauge?
Complex and large aircraft
What happens to the contacts of the switch when the fuel pressure is insufficient?
They close which sends a current flow to the annunciator or waning light in the flight deck
Where are low pressure warning switches located?
At the outlet of each fuel boost pump
Where is the annunciator for each switch positioned?
Adjacent to the boost pump on/off switch
Where is ice likely to form due to low fuel temperature?
Filters
Fuel system
What type of aircraft use a resistance type electric fuel temperature sender?
High performance
What can low fuel temperature be corrected with?
Fuel heater
What does viscosity differences at varying fuel temperatures affect?
Fuel flow sensing accuracy
How can you correct viscosity differences affecting fuel flow sensing accuracy?
Thought the use of computers
The fuel flow indicating system provides what 2 different indications?
Actual fuel flow to the engines and the fuel used since the engines were started
Why does each flow indicator show identical fuel flow?
Because the engines have the same power setting
What does the fuel flow transmitter measure?
The mass flow of the fuel between the fuel control unit and the fuel nozzles
What do all fuel flow transmitter types measure?
The force applied by the mass of fuel
What are the 2 types of flow meters?
Synchronous and motorless
What is measured in synchronous mass flow?
The deflection angle (a turbine is turned against the spring)
In synchronous mass flow to get the force, what. just you do to the fuel?
You must accelerate it
How do you accelerate the fuel?
By an impeller that is driven by an electric motor continuously
What do motorless mass flow not need?
An electric motor with a power supply
What do motorless mass flow use to accelerate the fuel?
The fuel itsel
What does the fuel flow turn in a motorless mass flow?
A turbine
What does the rotating turbine drive?
The drum and impeller coupled by a spring
When the impeller magnet is delayed, what else is also delayed?
Impeller coils
What does the FADEC calculate in motorless mass flow?
The time between the 2 pulses, which is proportional to the mass flow
What does interrogation of the fuel flow value give?
The required fuel used
What is N1 for?
Low-pressure rotor
What is N2 for?
High-pressure rotor
When is a N3 indication used?
When there is 3 rotors
What are engine rotor speeds expressed as?
A percentage of a 100% design speed
What are the 2 types of sensors used to measure rotor speed?
Tachometer
Variable reluctance type
What is another name for a variable reluctance type sensor?
A magnetic reluctance type sensor or magnetic pickup
Where is a tachometer generator type usually located?
On the gearbox
How does a variable reluctance sensor work?
Magnetic flux, between a magnet and a ferromagnetic target (magnetic reluctance)
Where is the speed probe positioned?
On the compressor casing with a phonic wheel or fan blade
what changes in the speed probe when the spool rotates?
Probe or sensor head is altered
What causes magnetic flux to vary when passing through the sensor?
Magnetic reluctance
What is directly proportional to the rate of change ofd magnetic flux?
Induced voltage
What must happen to the induced voltage before it can be an output?
It must be amplified
What does the tachometer rotating magnetic field generate?
A three phase AC voltage
What is the permanent magnet in a tachometer driven by?
The gearbox
Because the permanent magnet in the Tachometer is driven by the engine gearbox, what is the speed directly proportional to?
N2
What does the Tachometer send the 3 phase AC voltage to?
FADEC which is used to dictate super
What does the Tachometer send the 3 phase AC voltage to?
FADEC which is used to dictate super
Why is the Tachometer also called the dedicated generator or control alternator?
Because it also supplies electrical power to the generator
The speed probe or Tachometer can also send a warning to the flight deck that tells the pilot what two things?
That the engine is turning
And what direction it is turning in
The speed probe or Tachometer can also send a warning to the flight deck that tells the pilot what two things?
That the engine is turning
And what direction it is turning in
When is it important for the pilot to know the engine is spinning and its direction?
During start up as it is used to tell the Pilot when to open the HP fuel cock
What value do all three indications show?
N1
What does the red line on the speed indicator show?
Over speed
What occurs if the rotor speed N1 goes over the over speed red line?
It is recorded via the engine trend monitoring
What occurs if the rotor speed N1 goes over the over speed red line?
It is recorded via the engine trend monitoring
What does vibration show?
An imbalance in the rotor
What do the vibration units vary to?
0-6
What is another name for the computer that collects and filters engine vibration data?
The EVMU (Engine vibration monitoring unit)
The vibration sensors are accelerometers that measure what type of acceleration?
Radial
Where are the two accelerometers sensors placed in the engine?
One on the N1 compressor
The second in the turbine area
What are the two types of accelerometers used in an engine to measure vibration?
Piezoelectric-crystal type
Electromagnetic
What is the electromagnetic sensor?
Permanent magnetic held in place by two springs. When vibration occurs, the coil moves up and down
What is the electromagnetic sensor?
Permanent magnetic held in place by two springs. When vibration occurs, the coil moves up and down
How does a piezoelectric crystal work?
You apply a force to the crystal which pushes it against the base plate
What is the vibration indication controlled by?
Engine vibration monitoring unit
What is shown on the rotor identifier if the N1 or N2 rotor speed fails?
Broadband vibration
What does the vibration have to be more than for it to automatically show up on the secondary display?
4
What does the vibration have to be more than for it to automatically show up on the secondary display?
4
When the engine is shutdown, what will the vibration and performance page show?
0.00
What performs a balance calculation that corrects the engine high vibration?
The engine balancing system
What performs a balance calculation that corrects the engine high vibration?
The engine balancing system
What does the solution of the engine balancing system identify?
The balance weights that are required to be removed and replaced on the LPT blades
What does the solution of the engine balancing system identify?
The balance weights that are required to be removed and replaced on the LPT blades or engine spinner
Are torque meters electric or hydraulic?
Both
What do torquemeters measure?
Torque being delivered to the propellor or rotor
How many concentric shafts do torque meters comprise of?
2
How many concentric shafts do torque meters comprise of?
2
What does the inner shaft connect?
The drive from the engine to the gear box
What does the outer shaft connect?
The engine output only
What is on both shafts? And what does this induce?
Toothed gears and permanent magnets
EMF forces
When happens to the output shaft when the torque is applied and increase?
Twists
What operates the torque meters?
Engine oil pressure metered through a valve
What is the most importantly thing a torque meter does?
Set power settings
What is the most importantly thing a torque meter does?
Set power settings
What is the Power assurance test?
To check the engine can go from idle to a given engine power ratio within a specific time and back to idle in a specific time
What must you ensure when doing a power assurance check?
Engine must be positioned in run up enclosure/position
Facing into the wind
Chocks plages
What must you ensure when doing a power assurance check?
Engine must be positioned in run up enclosure/position
Facing into the wind
Chocks plages
During a power assurance check, how long must you hold the engines at idle for?
5 minutes
During a power assurance check, how long must you hold the engines at idle for?
5 minutes
What must you identify before running a power assurance check?
EPR for that day
What must be switched off to ensure the engines can accelerate correctly?
Anti ice and engine bleed valve
What must be switched off to ensure the engines can accelerate correctly?
Anti ice and engine bleed valve
How long must it take you to reach EPR, hold it there for and then decrease back to idle?
30 seconds
After engine operation above 70% N1 how long must you operate the engine at idle for?
10 minutes to decrease the engine temp safely shut down the engine
What are the units used to measure fuel?
Kg or tonnes
