15.14 Engine Indication Systems Flashcards
What do all gas turbine engines require?
An exhaust gas temperature (EGT) indication
Where would a low pressure sensor for fuel be positioned?
After the outlet for the low pressure filter
Why could low fuel pressure occur ?
Can originate from cavitation caused by high fuel pump demand
What is an exhaust gas temperature monitor for?
To monitor the high temps experienced by the turbine engines to prevent thermal damage and indicate when a limit is exceeded
What are fuel pressure sensors on filters used for ?
To give warning of an impending filter blockage and risk of cavitation
Where will an indication for low fuel pressure be displayed?
As a warning lamp or as an EICAS status message
There must be an indication that the fuel system is delivering to where ?
That there is flow to the fuel metering device
Where is the highest temperature on an engine?
Directly behind the combustion chamber where hot gas hits the high pressure turbine
There must be an indication that the fuel system is delivered to where ?
What is the highest temperature on an engine called?
Turbine inlet temperature (TIT)
Where is the exhaust gas temperature measured?
In a much colder location either between the high and low pressure turbine or directly behind the low pressure turbine
What do light aircraft use to read fuel pressure ?
A direct reading bourdon tube pressure gauge
What should a direct reading bourdon tube pressure gauge be connected to ?
A fuel line
What are the 5 relative temperatures used to monitor temperature?
Exhaust Gas Temperature (EGT), Turbine Inlet Temperature (TIT), Turbine Gas Temperature (TGT), Interstage Turbine Temperature (ITT), and Turbine Outlet Temperature (TOT)
How may modern complex aircraft read fuel pressure ?
Using a pressure transducer which sends electric signals to the flight deck
What makes up an electrical torque meter system
Torque meter assembly, a phase detector and an indicator
Where are temperature thermocouples placed?
Inserted at the turbine discharge, the temperature provides a relative indication of the temperature at the inlet
If an aircraft is equipped with an auxiliary pump, what does the fuel pressure gauge indicate ?
The auxiliary pump pressure until the engine is started, then the gauge will indicate pressure created by the EDP
Several thermocouples are usually used, spaced at intervals, where are these?
Around the perimeter of the engine exhaust duct near the turbine exit
What does the EGT indicator show in the flight deck?
Average temperature measured by the individual thermocouples
What does the EGT indicator show in the flight deck?
Average temperature measured by the individual thermocouples
Complex reciprocating engined aircraft may use a differential fuel pressure gauge, what are the two values this gauge compares ?
Fuel inlet pressure to air inlet pressure at the fuel metering device
What do the temperature scales range from?
0°C to 1200°C
When an aircraft has sensors that output signals, where is this data processes for display?
Instrument gauge microprocessor or a computer
What is twist in the drive shaft from the engine to the gearbox proportional to in a torque meter
Torque
What does a turbine inlet temperature system provide?
A TIT indicating system provides a visual indication at the instrument panel of the temperature of gases entering the turbine
What does an electric torque meter use to measure torque
Magnet
What happens to the contacts of a pressure sensing switch when there is low fuel pressure ?
Contacts create a circuit as there is insufficient pressure to hold them open, causing lights or annunciations to switch on
What do turbine powered aircraft use to indicate low fuel pressure ?
A low pressure switch at the outlet of each fuel boost pump
What do dual thermocouples consist of?
Dual thermocouples exist containing two electrically independent junctions within a single probe
Why should fuel temperature be monitored ?
Allows indication to the flight crew when temperature is causing ice to form in the fuel system and especially filters
Engine indications are used to monitor the parameters of the engine and its systems. What are the three groups?
Performance indications - also named primary indications- are used to monitor the performance and the limits of the engine and to set the thrust for the different flight phases
System indications - also called secondary indications- are used to monitor the operation of engine systems such as the oil or fuel system. They are also used to detect malfunctions quickly.
Engine trend monitoring - not usually shown in the flight deck, is done on the ground to detect engine problems at an early stage. It uses engine parameters that are automatically recorded by the Aircraft Condition Monitoring System (ACMS)
What is the most common fuel temperature sensor for large High performance turbine aircraft ?
Resistance type electric fuel temperature sender in the main tank
What are the two ways of measuring engine thrust?
Rotational speed of the fan called N1, engine pressure ratio (EPR)
How does a hydraulic torque meter work?
Uses engine oil pressure controlled by a gear in response to applied torque. This year moves a piston which controls the oil pressure flow
Where are the signals from the resistance type electric fuel temperature sender sent to ?
A ratiometer gauge or through a computer for processing and digital display
What are the other engine performance indications?
Engine rotor speed indication for each rotor system
Exhaust gas temperature (EGT)
Fuel flow indication
What is the pressure in the hydraulic torque meter equal to
Torque in the shaft
How can low fuel temperature be corrected ?
Use of a fuel heater
What are used to measure the other performance indications?
N1, N2 and N3 if available
What are the secondary engine indications?
Used to monitor the operation of the engine systems
What are the indications for the oil system?
More to the oil quantity, oil pressure and oil temperature
How can viscosity of fuel due to temperature effect readings and how can it be accounted for ?
Viscosity affects fuel flow sensing accuracy which can be accounted and corrected by flow processing calculations in a computer
What does the engine vibration indication show?
Any imbalance that occurs in the rotating parts of
Before doing a power assurance test what must be done
Engine should be idled for 5 minutes
What are the two indications of fuel flow for the flight crew ?
-actual fuel flow for the engines
-the fuel used since the engine was started
What does monitoring fuel flow tell us ?
The performance and economic operation of the engines
If engines have the same power settings what should the fuel flow indication be ?
The same
There are also these warnings and cautions you displayed on the ECAM/EICAS page when it comes to do with oil
When an indication exceeds a limit
When the system detects a low oil pressure
When a filter becomes clogged
When an unlocked thrust reverser is detected
What should be done before an engine test run to ensure the engine accelerates correctly
Engine anti ice and bleed air switches are off
What does the engine trend monitoring do?
Monitoring to alert the operator to problems at early stages, this prevents large performance reductions
Once fuel flow is sensed, calculations need to be done, what computer does these calculations ?
FADEC system computers
A transmitted engine data is analysed by a computer system to find any parameters that indicate a trend towards a limit. What are the three analysis?
Thermodynamic analysis, mechanic dynamic analysis, oil consumption analysis
What and where do fuel flow transmitters measure ?
Mass flow between the fuel control unit and the fuel nozzles
A transmitted engine data is analysed by a computer system to find any parameters that indicate a trend towards a limit. What are the three analysis?
Thermodynamic analysis, mechanic dynamic analysis, oil consumption analysis
What does the thermodynamic analysis do?
The thermodynamic analysis checks the pressures and temperatures along the gas flow path
What does the mechanic dynamic analysis do?
The mechanic-dynamic analysis mainly checks for failures in the rotor system
What does the mechanic dynamic analysis do?
The mechanic-dynamic analysis mainly checks for failures in the rotor system
What does the oil consumption analysis do?
The oil consumption analysis generates an alert when the oil consumption exceeds a certain level
What is the general fundamental that fuel flow transmitters work on ?
Force= mass x acceleration
What is the thrust of an engine limited to?
What the engine can safely tolerate yet must be adequate for the safe operation of the aircraft
What does the engine pressure ratio gauge compare?
Compare the engine turbine discharge pressure to the pressure of the ram air at the inlet of the engine
What is the actual engine pressure ratio indication shown by?
An analog and/or a digital value
What are the two other indications shown on the engine pressure ratio display?
An AMBER or RED line that shows the EPR for the maximum available thrust
A BLUE circle that shows the EPR that corresponds to the actual throttle position
What are the 2 most common types of fuel flow transmitters?
Synchronous mass flow and motor-less mass flow
What is flexible takeoff?
Flexible Take-Off, “FLEX”, is the standard take-off thrust setting used on Airbus aircraft, unless departing a contaminated (wet/icy) runway or if performance constraints (short runway or hot and high) exist, in which case TOGA (full thrust) is used
What is measured in a synchronous mass flow transmitter type ?
Fuel mass turns a turbine agains a spring, its angle of deflection is measured
How do you guard against failure resulting from inadequate lubrication?
Monitor oil supply system, the oil pressure indicator usually shows the engine oil pump discharge pressure
What are the two main types of oil pressure transmitter?
Bourdon tube type and strain gauge type
What must be done for the fuel to gain the correct force to move the turbine in a synchronous mass flow type transmitter and how is this achieved ?
Fuel must be accelerated, achieved by an impeller that roadster continuously, driven by an E motor
What is a bourdon tube?
A Bourdon tube can be either c-shaped or helical, with an oval cross section
How does a Borden tube work?
When the pressure media enters the tube, the pressure acts to change the oval towards a circular cross section
What is a strange gauge used for?
Used to measure mechanical strain or deformation
When there is fuel flow inside a motor less mass flow, how is flow indicated ?
When there is fuel flow, the impeller magnet is delayed by an angle in proportion to the fuel mass. When this happens the pulse from the impeller child is also delayed.
How does a strain gauge work?
Works on the principal that when an object undergo strain, is resistance changes proportionally
When there is fuel flow inside a motor less mass flow, how is flow indicated ?
When there is fuel flow, the impeller magnet is delayed by an angle in proportion to the fuel mass. When this happens the pulse from the impeller child is also delayed.
What does the strain gauge look like?
The gauge is typically composed of a grid-like pattern with several active arms and a central section where the strain is applied
What does FADEC use to compute mass flow from a motor less mass flow transmitter type ?
Time between the two pulses, which is proportional to mass fuel flow
What is the most common arrangement of strange gauge?
The most common arrangement is the Wheatstone bridge configuration
What is the most common arrangement of strange gauge?
The most common arrangement is the Wheatstone bridge configuration
How do they measure the resistance change accurately?
Often use in a wheat stone bridge circuit
What are the engine rotor speed indications expressed as ?
A percentage of a 100% design speed
What are the three main parts for rotor speed indication ?
The sensor
The data transmission
The indication
What can lead to a voltage difference between output terminals?
When strain is applied to the object and the resistance of the strain gauge changes, the bridge becomes unbalanced
What is the unbalanced voltage output from the Wheatstone bridge if proportional to what?
Amount of strain experienced by the object
What is the unbalanced voltage output from the Wheatstone bridge if proportional to what?
Amount of strain experienced by the object
What are the two types of sensors used to measure engine speed ?
Variable reluctance sensor
Tachometer generator
What is the oil pressure warning connected to?
The pressure switch is also connected to the oil supply line and the oil tank vent line
What happens if the oil pressure decreases below the limit?
the low oil pressure switch closes, a signal is sent to the flight warning computer and a warning message appears on the display unit in the flight deck
What concept does the variable reluctance sensor use ?
Magnetic reluctance
What unit is engine vibration measured in
0-6
What does it depend on for the engine oil to lubricate and cool?
The temperature of the oil as well as the amount of oil supplied to the main component areas
How many vibration sensors are there
One or two
What is responsible for measuring the engine oil temperature?
The oil temperature sensor
What is responsible for measuring the engine oil temperature?
The oil temperature sensor
What is the tachometer mounted to ?
The engine gearbox
What is the most common type of oil temperature sensor used on aircraft?
Resistance temperature detector or thermocouple
What computer receives vibration sensor signals
Engine vibration monitoring unit (EVMU)
What is a resistance temperature detector and thermocouple made from?
A sensor made of a temperature sensitive resistor, while a thermocouple consist of two dissimilar metal wires joined together
What measures engine vibrations
Accelerometers
What can the over temperature warning be?
Visual and audible to immediately alert the flight crew to the potential issue
How does the tachometer read speed ?
Generator speed is proportional to N2 speed. Generator creates a 3-phase AC which is sent to FADEC where it is used to calculate the speed signal
What are the two types of accelerometer used in engines
Electromagnetic (N2)
Piezoelectric-crystal (N1)
What else is the tachometer generator used do create ?
Electrical power to the computer and is therefore also called dedicated generator of control alternator
What else is the tachometer generator used do create ?
Electrical power to the computer and is therefore also called dedicated generator of control alternator
What happens if N1 and N2 speed signals fails
Shows BroadBand (BB) vibration.
What are the regrew different types of rotor speed indication ?
- a display with a clock type scale
- a display with a moving vertical bar
- the classical electromechanical indicator
What is indicated by a red line limit on speed indicators?
The maximum permitted rotor speed
