M15.21 Operation and Monitoring Flashcards
What are the circumstances when maintenance personnel are required to operate a gas turbine engine?
- Confirming a flight crew reported fault
- Post-maintenance basic engine or aircraft system checkout
- Deterioration of engine performance
- Aircraft control linkage wear
- Moving an aircraft from one maintenance location to another
- To taxi-check an aircraft system
What types of engines do the engine operating procedures apply to?
- Turbofan
- Turboprop
- Turboshaft
- Auxiliary Power Units (APU)
What must be checked before any engine start?
The engine air inlet must be checked to confirm free movement of the compressor and turbine assembly, and that the engine run-up area is clean and free of Foreign Object Debris (FOD)
How is a turbofan engine controlled?
By one control thrust lever for each engine
What must be ensured before starting the engine?
- Undercarriage is down and locked
- Engine oil levels are satisfactory
- All panels are secure
- Sufficient fuel for the ground run
- Intakes and exhausts are inspected for foreign objects and damage
What is the appropriate fire extinguisher needed during engine ground running?
CO2 fire extinguisher
What must be done during engine start monitoring?
- Engine speed indicator (tachometer)
- Oil pressure
- Exhaust Gas Temperature (EGT)
What is the recommended cool-down time before shutting down an engine that has been operated at high power levels?
5 minutes at idle power
What does the Engine Pressure Ratio (EPR) indicate?
The thrust output of the engine
What are the indications used for engine monitoring?
- Engine Pressure Ratio (EPR)
- Rotor speed, N1 and N2 (and N3)
- Fuel Flow (FF)
- Exhaust Gas Temperature (EGT)
What is the purpose of torque monitoring systems in turbo-prop or turbo-shaft engines?
- Indicate power developed by the engine
- Automatically operate the propeller feathering system
- Assist in the automatic operation of a water injection system
- Limit engine power output
- Balance power output between engines
What is the function of the Aircraft Condition Monitoring System (ACMS)?
To record operating parameters and generate reports for engine trend monitoring
What is the purpose of oil analysis in engine monitoring?
To provide information about the condition of the engine by identifying wear particles in the oil
What is the Spectrometric Oil Analysis Program (SOAP)?
A process used to detect wear particles in engine oil
What are the four primary groups of magnetic particles?
- Swarf
- Magnetic fines
- Metal flakes
- Chip
Fill in the blank: The ___________ must be checked to confirm sufficient fuel for the ground run.
fuel tanks
True or False: It is acceptable to start the engine without ensuring that the areas in front and behind the aircraft are clear.
False
What is the purpose of the torque meter in a turbo-prop or turbo-shaft engine?
To provide continuous indication of the horsepower output of the engine
What is required to identify metal particles in engine oil?
Spectrometric Oil Analysis Program (SOAP)
What must be established with the ground crew before starting the engine?
Communications for clearance and safety confirmation
What is the significance of monitoring Exhaust Gas Temperature (EGT)?
To recognize and prevent overheating conditions
What happens if the EGT exceeds the red line?
Immediate inspections of the critical engine are required
What is the role of the Data Management Unit (DMU)?
To record and compile ACMS reports
What should be done if abnormal deteriorations in engine efficiency are detected?
Schedule engine removal before the defect fully develops
What is a common method for identifying ferrous particles?
Using a magnet to separate ferrous from non-ferrous particles
What is the purpose of engine and gearbox inspections?
To assess the condition of the engine and gearbox, usually at regular intervals or after specific events like heavy landings or lightning strikes.
Inspections can also aid in troubleshooting issues.
Name the four primary groups of magnetic particles.
- Swarf
- Magnetic fines
- Metal flakes
- Chip
These groups help categorize the types of contamination in engine components.
What is swarf?
Unwanted material caused by machining engine components, which can remain in the engine/gearbox after assembly.
How do magnetic fines appear on an MCD?
As black sludge when oil is present.
They originate from worn areas in the engine/gearbox.
What do metal flakes indicate in an engine?
They come from ball bearings, roller bearings, bearing tracks, and gear teeth, and their shape can indicate the source.
Describe gear teeth flakes.
They are shiny, irregularly shaped flakes that can resemble solder splashes.
What are chips in the context of engine components?
Thick flakes or pieces of metal with one smooth machined surface.
What is a boroscope inspection?
An internal visual inspection of the engine using a rigid boroscope, flexible fibrescope, or electronic imaging video probe.
Why is vibration monitoring important in gas turbine engines?
Because changes in vibration levels may indicate impending failure that could otherwise go unnoticed.
What do modern engines use to monitor vibration?
Piezoelectric accelerometers.
What sections is a turbine engine divided into for inspection purposes?
- Cold section (Compressor Section)
- Hot section (Turbine and Combustion Section)
This division aids in focused maintenance procedures.
What can cause damage to compressor blades?
Foreign object matter entering the turbine engine air intakes.
What is the effect of dirt accumulation on compressor blades?
It reduces the aerodynamic efficiency of the blades, resulting in deterioration in engine performance.
What are the allowable limits for minor damage to compressor blades?
Damage can be repaired if it can be removed without exceeding the limits set by the engine manufacturer.
What tools are recommended for reworking damage on compressor blades?
Hand tools such as files or emery cloth.
Power tools should not be used for buffing.
What is Foreign Object Damage (FOD)?
Damage caused by foreign objects entering the engine, which can degrade performance and shorten engine life.
List some typical causes of blade damage.
- Loose objects entering the engine
- Foreign Object Damage (FOD)
- Excessive heat levels
- Corrosive agents
These causes can lead to various types of damage.
What is the definition of ‘blend’ in the context of blade repair?
Smooth repair of ragged edges or surface to match the contour of the surrounding area.
What is the significance of inspecting the combustion section of a turbine engine?
Inspection and cleaning are crucial for prolonging service life.
How should cracks in turbine blades be detected?
Primarily through visual inspection, possibly supplemented by structural inspection techniques like dye penetrant methods.
What must be considered when replacing turbine blades?
Moment-weight limitations as specified in the engine manufacturer’s technical instructions.
What is the recommended method for cleaning fuel nozzles?
Washing with a cleaning fluid approved by the engine manufacturer and using a soft bristle brush.
What is the purpose of a desalination wash?
To remove salt contamination from the compressor to maintain engine efficiency.
What should be done before starting a turbine engine?
Inspect the engine inlet ducts to ensure no Foreign Object Damage (FOD) items are left.
What types of materials can be used for temporary marking during assembly?
- Layout dye or chalk for gas path exposed parts
- Wax marking pencil for non-gas path parts
Avoid using materials that may cause corrosion.
What is the risk associated with tools left inside an aircraft?
They can interfere with safe flight by jamming controls or shorting electrical connections.
What is Tool FOD?
A serious hazard caused by tools left inside the aircraft following maintenance.
What can Tool FOD interfere with?
Safe flight operations, including control cables and electrical connections.
Give examples of FOD.
- Aircraft parts
- Rocks
- Broken pavement
- Ramp equipment
- Parts from ground vehicles
- Rubbish on ramp/runway
- Ice on wings/propellers/intakes
- Bird strikes
- Dust/ash in air intakes
- Tools and metal shavings left inside aircraft
What does airport operations do regarding FOD?
Regularly inspect and clear the runways of aircraft FOD.
What can happen to jet engines from FOD?
They can suffer major damage from even small objects being sucked into the engine.
What type of test must all manufactured engines pass?
A test involving firing a frozen chicken into a running jet engine.
What is the requirement for engines after the bird strike test?
The engine must not cause significant damage to the rest of the aircraft.
What was Boeing’s solution for early B737s to avoid FOD?
A gravel runway kit with gravel deflectors and screens on landing gear.
What do vortex dissipation devices do?
Reduce airflow into the engine from the bottom to decrease the likelihood of sucking up gravel.
True or False: The engine must remain operational after the bird strike test.
False.
