ENGINE MONITORING Flashcards
When can Engine trimming be carried out?
Once the engine is running.
How can the condition of an engine be determined?
By analysis of the engine oil.
What is the process of oil analysis?
SOAP (spectrographic oil analysis program)
How is metal identified during oil analysis?
Measuring the colour and intensity
What types of boroscope are there?
Rigid, flexible, fibrescope, electronic imaging video probe
How is vibration monitored on modern engines?
Piezoelectric accelerometer measured I inches per second (ips) or (mm/s)
Where are piezoelectric accelerometers places on engines?
Fan or LP casing
Turbine casing
In general terms, what does hard time and on conditioning monitoring require?
Involve actions preventing failure
What is hard time monitoring?
Preventative action which involves removal of items at specific intervals.
(Landings, cyclic loads, calendar etc)
What is the period of time which the engine can be installed on the aircraft for?
Time between overhaul
What is on-condition monitoring?
Preventative action which involves inspection or check at specified periods.
What is scheduled servicing?
Based on flying hours, periodic recurring checks
What is un-scheduled servicing?
Covers work due to malfunction, scheduled maintenance or occurrences such as heavy landing
What is condition monitoring?
Not a preventative process, info on operational experience is gained to prevent inflight shutdown, secondary down time
What are the three main methods for condition monitoring?
- Flight deck indication (oil pressure, EGT, RPM)
- In flight recorders (intergrated data systems automatic recording)
- Ground indication (internal view points, magnetic chip detectors, oil filters, soap tests)
Why is FOD a major problem to engines which use titanium?
Can cause hard rubs, titanium may reach ignition temp. Aerodynamic imbalance (vibration, stalls and surge)
What will placing a protective mat on the intake protect?
Acoustic panelling
How can feeling for restriction or rubbing of the compressor be inspected?
Rotating manually by hand
If non-metallic damage is found on an engine which is repairable, where should be inspected and how?
Boroscope later stages of the compressor
How is ‘broken’ described?
Separation of a part by force in two or more pieces?
How Is ‘battered’ described?
Damage caused to a part that is constantly hit
How is ‘bending’ described?
Angular change from initial shape or contour, usually lateral forces.
How is ‘bowed’ described?
A curve which changes the surfaces initial shape or contour. Usually heat or lateral force
How is ‘brinelled’ described?
Circular surface damage on bearing races. Usually constant shock loads applied to bearing
How is ‘burned’ described?
Complete structural failure due to hot temperatures
How is ‘carboned’ (coked) described?
Quantity of carbon particles collected on the surface of the material
How is ‘cracked’ described?
Linear opening that can be easily seen and cause the material to break
How Is ‘curled’ described?
A rounded fold in the material such as a blade tip that has rubbed against the engine casing
How is ‘dent’ described?
Damage to surface when hit. Material distorted not removed.
How is a ‘deposit described?’
Particles of a material collected on a part
How Is a ‘nick’ described?
A small cut on the surface or edge of a part.
How is ‘overheat’ described?
Part become too hot seen as change in colour or condition
How is ‘peeling’ described?
When the surface finish breaks away
How is ‘pitted’ described?
Small irregular holes in the surface of a material caused by corrosion or electrical discharge
How is ‘scratched’ described?
Small surface cut caused by sharpe object
How is ‘skidding’ described?
Surface damage to balls, and races of bearings. Seen as Matt silver effect on surface (causes by intermittent loading)
How is ‘spalled’ described?
Rough broken area on the surface of a material. Usually caused by cracks or inclusions when a load is applied
What is the main source of compressor contamination?
Salt water.
Wash with fresh water with engine running over the starter
What is performance recovery washing?
Emulsion type surface cleaning under same conditions as desalination wash.
(Turbine also benefits, life extend)
How can centrifugal compressors be cleaned?
Injection of abrasive grit
Doesn’t clears turbine stage
How can fan blades be cleaned?
Spraying coke into eye of fan while rotating
Or hand cleaned using proprietary solvent.
What should be used if cleaning the engine in cold conditions?
Isopropyl alcohol used as an anti-freeze method as ethanol can damage titanium.
What is needed to achieve accurate trim data?
OAT and barometric pressure/airfield altitude.
What is engine trimming for?
Engine performance testing.
How must all engine adjustments be carried out at?
Idle rpm
How long should the engine be cooled down for at idle before shutting down?
3 minutes.
How is engine trim increased?
Turning adjuster on FCU (fuel control unit) anti clockwise.
What engine monitoring categories are there?
System
Performance
Condition
How is EPR measured?
Ratio of pressure at engine inlet to the exhaust gas pressure.
(Gives indication of thrust)
How is N1 measured?
% related to 100% design speed.
What are idle speeds controlled to?
N2 value.
When is fuel flow indications important?
Engine start
Fuel consumption during flight.
How do centrifugal compressor engines measure engine power?
Comparing the relationship between engine rpm and jet pipe temp.
How much thrust is produced by the fan on large fan engines?
90-95%
What are torque monitoring systems used to indicate?
Indicate power developed by a turbo prop or turbo shaft engines.
Is engine torque proportional to horsepower?
Yes.
How is torque displayed in the cockpit?
Torque oil pressure
Torque percentage
(With a torque meter)
What are the most commonly used sensing systems for torque meters?
Hydro mechanical
Electronic
What is the engine data recording performed by?
Aircraft condition monitoring system (ACMS)
Data transmitted to the Data Management Unit (DMU)
What does the DMU do?
Records the data and compiles to ACMS reports.
Sent to ground or printed via data link.
