15.21

Question 1

What are some circumstances where maintenance personnel are required to operate a GTE

Answer 1

• 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

Question 2

What should be done prior to positioning aircraft for ground engine operation

Answer 2

Check tech log to see if ac is servucabelfor ground run
Inform atc
Check engine oil levels and sufficient fuel for engines to run on ground
Position ac into the wind
Ensure area around ac is clear

Question 3

Why should both engines be run at same time when doing engine runs

Answer 3

To prevent asymmetry

Question 4

Why should engine power not be increased above idle on ground

Answer 4

As the more the engine is heated and cooled down the shorter it’s operational life will become

Question 5

What’s trimming

Answer 5

A term applied to idle speed, variable throttle settings and max thrust adjustment during engine performance testing

Question 6

What’s required to get accurate trim data

Answer 6

OAT and barometric pressure/airfield altitude is measured

Question 7

When must all engine adjustments be carried out during ground run

Answer 7

At idle rpm

Question 8

Why’s idle trim adjusted

Answer 8

To ensure that the engine idles at lowest rpm

Question 9

What should be used as the reference point when carrying out acceleration checks

Answer 9

The oldest engine to ensure all engine accelerate at same rate

Question 10

On completion of an engine ground run how long should the engine idle for

Answer 10

3 mins
Before closing HP cock

Question 11

What can an n1 indication on high bypass engines also be used as

Answer 11

A thrust indication

Question 12

What does the fuel flow indication do

Answer 12

Shows amount of fuel consumption during flight and used for trend monitoring

Question 13

What’s exhaust gas’s temp indication used for

Answer 13

To recognise ans prevent critical condition of overheat

Question 14

How do centrifugal compressor engines measure engine power
Why can’t axial flow compressors use this

Answer 14

By comparing relationship between engine rpm and jet pipe temp

As there’s no relationship between engine rpm and thrust

Question 15

What percentage of thrust is produced by fan in large fan engine

Answer 15

90-95%

Question 16

What simple and easy method was produced to calculate thrust

Answer 16

EPR (engine pressure ratio)

Question 17

What are the torque monitoring systems used to indicate to flight deck

Answer 17

Power developed by a turbo prop or turbo shaft engine

Question 18

What are The two most commonly used torque sensing units

Answer 18

Hydro mechanical , which concerts oil pressure to a torque signal
Electronic , converts the twist of power output shaft into torque signal

Question 19

What performs the data recording on ac ans what is the data transmitted to

Answer 19

ACMS ANS DMU

Question 20

What’s important about the refitting of access plugs for a bore scope inspection

Answer 20

Must be duplicate inspected

Question 21

What type of vibration monitors do modern engines use to detect engine vibration

Answer 21

Piezoelectric accelerometers

Question 22

What does hard time and on condition maintenance concern compared with condition monitoring

Answer 22

Preventing failure

Question 23

What’s hard time

Answer 23

Prevantatuvw process that involves removal of items for overhaul or replacement at specified intervals.

Question 24

What’s on condition

Answer 24

On-condition is a preventative process which involves the inspection, test or check of a particular item at specified periods to ensure it can stay in service

Question 25

What’s condition monitoring

Answer 25

Condition monitoring is not a preventative process, but one in which information gained from operational experience is collected, analysed and interpreted on a continuing basis as a means of implementing corrective procedures.

Question 26

What are three methods of condition monitoring

Answer 26

Flight deck indicators
In flight recorders
Ground indicators

Question 27

What will aerodynamic imbalances cause

Answer 27

Stalls, surges, vibration

Question 28

What should be done before inspecting for fod

Answer 28

Disable stating and ignition circuit by removing starting and ignition fuses and flagging circuit breakers
Cockpit placarded

Question 29

What can happen if there’s an accumulation of contamination on compressor ans turbine section

Answer 29

Reduces efficiency

Question 30

What form does contamination form in the turbine section

Answer 30

Sulfidation

Question 31

How’s the compressor washes? Is this isn’t successful what other way is there of washing

Answer 31

Desalination
Performance recovery wash

Question 32

What’s the more vigorous cleaning method of CENTRIFUGAL compressor engines

Answer 32

Injection of an abrasive grit

Question 33

What other abrasive material can be sprayed into fan eye to clean it

Answer 33

Coke