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Powerplant O&P > Turbine Engines > Flashcards

Turbine Engines Flashcards

1
Q

What is meant by trimming a turbine engine?

A

Adjusting the fuel control so the engine develops the correct idle and trim speed RPM

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2
Q

What type of equipment should be used to determine that a turbine engine is performing up to the standards specified by the engine manufacturer?

A

A JetCal analyzer/trimmer has all of the instrumentation and cables to determine the EGT, EPR, and other parameters specified by the engine manufacturer

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3
Q

What is meant by a hot-section inspection?

A

An inspection of the hot section of a turbine. The hot section includes the combustors, the turbine, and the exhaust system

An inspection of the combustors, turbine, and exhaust system

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4
Q

What is meant by on-condition maintenance of a turbine engine?

A

The monitoring of the engine performance at regular intervals and determining when maintenance is required based on certain operating parameters specified by the engine manufacture

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5
Q

What checks of a turbine engine are necessary to verify preflight condition?

Delete

A
  1. Inspect the cowling and all air inlet areas and attachment of the engine to the airframe
  2. Inspect the inlet guide vanes and the first stage of the compressor or fan blades
  3. Check for unusual noise when the compressor is rotated
  4. Inspect the rear turbine and exhaust system
  5. Check the quantity of the lubricating oil for the engine and the constant-speed drive unit
  6. Check the ignition system for operation by listening for the sparks
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6
Q

Explain the main difference and advantage of turbofan over turbojet engines

A

A turbofan engine uses a fan to bypass some air around the engine core and to provide thrust. The advantage is that this provides additional thrust without increasing fuel flow

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7
Q

Name the major components in a gas turbine engine

A
  1. Air inlet
  2. Compressor section
  3. Combustion section
  4. Turbine section
  5. Exhaust section
  6. Gearbox
  7. Accessory section
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8
Q

What determines the amount of airflow through a turbine engine?

A
  1. Forward speed of the aircraft
  2. Compressor speed
  3. Air density
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9
Q

Name the two types of compressors commonly used in turbine engines

A
  1. Axial
  2. Centrifugal
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10
Q

Name two different methods for attaching turbine engine rotor blades to the rotor disks

A
  1. Dovetail
  2. Bulb
  3. Fir tree
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11
Q

What is a split compressor system?

A

(Also called dual or twin spool compressors) These are connected to the turbine section with two rotor shafts, one inside of the other

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12
Q

What are the different types of combustion chambers used in turbine engines?

A
  1. Can
  2. Annular
  3. Can-annular
  4. Reverse flow annular
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13
Q

What prevents the combustion chambers from burning?

A

Cooling air along the inside of the liner

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14
Q

What is the purpose of the interconnecting tubes attached between can-type combustion chambers?

A

For flame propagation during start

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15
Q

What functions do axial flow turbine nozzles perform?

A

They direct the mass airflow to drive the turbine rotor at a specific angle

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16
Q

How is thermal stress relieved on a turbine disc?

A

By directing bleed air onto the face of the disk, or by grooves cut into the disk

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17
Q

What are carbon seals used for in turbine engines?

A

They are used as oil seals for the rotor shaft bearings

18
Q

What is shaft horsepower?

A

It is an indication of the torque developed by a turboprop or turboshaft engine

19
Q

What is the purpose of an APU

A

They provide ground electrical and pneumatic power for aircraft systems when the engines are not running. Many APUs may also be used as an emergency source of inflight electrical power

20
Q

Name the main components of a typical APU

A
  1. A small power turbine for power and bleed air
  2. An electrical generator
21
Q

When is the greatest demand placed on an APU

A

When supplying bleeding air

22
Q

How is an APU generally started?

A

With its own electrical starter and battery power

23
Q

Where does the APU get its fuel supply?

A

From one of the aircraft’s main fuel tanks

24
Q

At what speed does a gas turbine APU operate and how is this speed maintained?

A

At or near its rated speed regardless of electrical or pneumatic loads imposed. The APU fuel control automatically adjusts the fuel flow to maintain the rated speed

25
Q

What is used to prevent a heavily loaded APU from exceeding its maximum EGT?

A

A load control valve modulates the pneumatic load to keep EGTs within limits

26
Q

How is an APU shut down and why is this procedure used?

A

After the APU is unloaded by closing the bleed air valve, it’s typically run for three minutes to allow the EGT to cool and stabilize.

If a heavily loaded APU is abruptly shut down without any cooling down period, damage could occur as a result of thermal shock

27
Q

What powers are the variable inlet guide vanes used on some APUs to regulate compressor intake airflow?

A

Fuel Pressure

28
Q

What is fan blade shingling?

A

When the midspan shrouds overlap the fan blade

29
Q

When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?

A

Any rubbing sound or other unusual noises from the engine

30
Q

Why are compressor washes performed and what methods are commonly used?

A

Fluid and abrasive grit wash are commonly used to remove contaminants from the compressor section and improve engine performance

31
Q

How can you tell if a turbofan or turbojet engine is out of trim?

A

There will be a high EGT at the target EPR for takeoff power

32
Q

Name the different types of compressor blade damage that may be found during inspection

A
  1. Dents
  2. Cracks
  3. Galling
  4. Pitting
  5. Scratches
  6. Burrs
  7. Burns
  8. Gouges
33
Q

What kind of markers can be used to mark the parts in hot and cold sections during repair?

A
  1. Layout dye
  2. Felt tip marker
  3. Chalk
34
Q

How does relative humidity affect turbine engines?

A

It has a negligible effect

35
Q

What criteria determines replacement of life limited turbine engine components?

A

Cycles, hours and/or calendar time

36
Q

If turbine blades are removed from a turbine disc, why should they be reinstalled in the same location?

A

To maintain the balance of the turbine wheel

37
Q

How are gas turbine engine tachometers calibrated?

A

In percent RPM

38
Q

On a turbine engine, what is the engine pressure ratio and what does it indicate?

A

It is the ratio between the inlet pressure and turbine exhaust pressure and is used to indicate the thrust developed by the engine

39
Q

On a turbine engine, what does exhaust gas temperature (EGT) indicate and how is it obtained?

A

EGT is the average temperature of the turbine discharge gasses and is obtained by thermocouples placed near the turbine exit

40
Q

Can the EGT system on a turbine engine be checked without running the engine?

A

Yes, by checking the resistance of the thermocouples and circuits

Powerplant O&P (11 decks)

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