Module 15.14 Engine indication systems Flashcards
Where is EGT measure from?
After the HP turbine or after the LP turbine
Why do we take the Exhaust Gas Temperature (EGT)?
As we want to know the Turbine Inlet Temperature (TIT) but the 1st nozzle guide vane is too hot to measure temperature at the point
TIT is not easy to read as it can be above what temperature?
1400℃
What improves the accuracy of the calculations of TIT?
Placing the EGT sensor after the HP turbine
What does the EGT indicator in the flight deck show?
The average temperature measured by the thermocouples
What does the instrument scale range from?
0 to 1200℃
What are dual thermocouples?
Two electrically independent junctions within a single probe
Digital flight deck instrumentation does not use what to give temperature information to the crew?
- Resistance type indicators
- Adjusted servo-driven thermocouples
What does EPR stand for?
Engine Pressure Ratio
What are the two types of engine performance indicators?
- N1, rotational speed of the fan
- Engine Pressure Ratio (EPR)
They give an equivalent value
Engine indication can be divided into what 3 groups?
- Performance indications
- System indications
- Engine trend indications
What are the primary indications?
- N1
- EPR
- N2/N3
- EGT
- Fuel Flow (FF)
What warnings and cautions are displayed on the EICAS/ECAM?
- Indication exceeds limit
- Low oil pressure
- Clogged filter
- Unlocked thrust reverser
What are the 3 types of analysis done?
- Thermodynamic
- Mechanic dynamic
- Oil consumption
What does EPR compare?
Compares engine turbine discharge pressure to the pressure of the ram air at the inlet
What does the blue circle represent on the EPR display?
EPR compared to the throttle position
What does the amber/red represent on the EPR display?
Max available thrust
What is the purpose of Flexible Take Off/Assumed Temperature Derate?
Uses an assumed temperature thrust reduction to preserve wear and prolong life
Where is oil pressure measured?
After the pump
What happens to the bourdon tube profile as pressure enters the tube?
Oval to a circle
What is the most common arrangement of a strain gauge?
Wheatstone bridge configuration
What does a strain gauge measure?
Change in resistance
When there is no strain, what is the voltage across the Wheatstone bridge?
0, balanced
What is the oil pressure switch connected to?
- Oil supply line
- Oil tank vent line
Where does the oil pressure signal get sent to?
Flight warning computer
What are the most common type of temperature sensors?
- Resistance temperature detector
- Thermocouple
Where is oil temperature measured?
As oil enters the pump
Where is the low pressure sensor in the fuel system?
After the LP pump
What sensor is fitted across the filter?
Differential pressure
What aircraft utilise bourdon tubes?
Small reciprocating aircraft
What is sued alongside the gauge indications for warnings?
Visual and audible warnings
Low fuel pressure warning lights are illuminated using what?
Simple pressure sensing switches
When do the switch contacts close?
When there is not enough pressure to hold open the diaphragm
Where is the low pressure warning switch usually located?
Outlet of the fuel boost pump
How can low fuel temperature be corrected?
Fuel heater if equipped
The fuel temperature can be integrated into what?
The fuel flow processing calculations
What two indications does the fuel flow indication system display?
- Actual fuel flow to the engines
- Fuel used by the engines since the start
What is required to generate fuel flow and fuel used indications?
Fuel flow transmitters
What law do the fuel flow transmitters utilise?
Newton’s 2nd law
What do all transmitters measure?
Force applied by the mass of fuel
What are the types of flow meters?
- Synchronous mass flow
- Motorless mass flow
What measures the force in the synchronous mass flow meter?
Fuel mass turns a turbine against a spring, deflection angle corresponds to the force
In a motorless mass flow meter, what is used to generate acceleration?
Turbine driven by fuel itself
What does the rotating turbine drive? (motorless)
Drum and impeller
How are the drum and impeller coupled?
By a spring
What are the 2 types of turbine engine speed sensor?
- Variable reluctance
- Tachometer generator
Where is the variable reluctance probe placed?
- On the fan blades
- Phonic wheel
What spool is a variable reluctance sensor on?
N1
Tachometer generator frequency is proportional to what?
N2 rotor speed
The 3 phase generator output of the tachometer supplies power to what?
FADEC computer
What are the 3 types of rotor speed indication?
- Clock type scale
- Moving vertical bar
- Electromechanical indicator
If the engine speed exceeds the N1 redline limit what is initiated?
Generation of a report from engine trend monitoring
How is the vibration indication given?
Units from 0 to 6
What does EVMU stand for?
Engine Vibration Monitoring Unit
Where are the sensors on each engine located?
- Compressor area
- Turbine area
What are 2 accelerometer types used to measure vibrations?
- Electromagnetic accelerometer
- Piezoelectric crystal type sensor
If N1 or N2 speed signal is lost what will be shown?
BroadBand (BB)
The computerised engine fan balancing system helps to do what?
Change or decrease vibration
Torque meters give engine power in what engines?
Turboshaft
How do torque meters measure torque?
- Electrically
- Hydraulically
How is a reading obtained on a torque meter?
Concentric shafts. Twist between the inner and outer shaft, the twist is proportional to the torque
How is an electric torque reading produced?
Relative movement between teeth and magnet
How do hydraulic torque meters give a reading?
Movement opens a valve. Oil pressure is proportional to the torque
What is the purpose of the power assurance test?
Check engine can accelerate and decelerate in a certain time
How long should the engine be held at idle for initially?
5 mins
If above 70% N1 is achieved during the test, how long post test must the engine be run at idle?
10 mins
What switches should be set too off in a power assurance test?
Anti-ice and bleed air
How is N2 rotor speed found?
Output from a Permanent Magnet Generator
