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M15 > 15.16 Turboprop Engines > Flashcards

15.16 Turboprop Engines Flashcards

1
Q

What is a turboprop engine known as?

A

A gas generator/ producer engine.

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2
Q

How can a gas coupled/ free power turbine be identified?

A

There are no mechanical connections between the gas generator and the free power turbine.

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3
Q

What are the advantages of a gas couple/ free power turbine?

A

Vibration isn’t directly transmitted to the gas generator.

Engine is easier to start.

Propellor can be held at low rpm=low noise + blade erosion.

Propellor brake can be used during loading= engine can be used as an APU.

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4
Q

How does a gear/direct coupled turbine differ from a free power turbine?

A

It has extra turbine discs.

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5
Q

What does the gear/direct coupled turbine do?

A

Transmitter increased power forwards.

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6
Q

In a gear/ direct coupled turbine, because the propeller is driven by the engine what is necessary?

A

Complex integrated propeller control system.

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7
Q

How is constant speed achieved in a gear/ direct coupled turbine?

A

Propeller pitch and fuel flow are coordinated.

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8
Q

For small reductions, what gears are used?

A

Spur gears.

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9
Q

For larger high torque reductions, what gears are used?

A

Epicyclic gears.

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10
Q

How is oil viscosity different than a turbo jet engine?

A

It is higher, due to heavier loads been imposed on gears.

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11
Q

What are the 2 main types of reduction gears?

A

Parallel spur.

Epicyclical.

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12
Q

What are the advantage and disadvantage of straight cut parallel gears?

A

+ Lowest friction losses

  • But noisy.
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13
Q

When may heavy duty bearings be required?

A

When torque changes create high loading on gear teeth.

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14
Q

What are the advantages of helical parallel gears?

A

Allow gradual onset of torque changes,

Quieter

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15
Q

What is the disadvantage of helical parallel gear?

A

Less efficient power transmission.

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16
Q

What is an annulus also known as?

A

Ring gear.

17
Q

In a fixed annulus system, which way does the propeller spin?

A

Same direction as power turbine shaft.

18
Q

In a rotating annulus system, which way does the propeller spin?

A

Oppositely to the power turbine shaft.

19
Q

What is flight range known as?

A

Alpha range.

20
Q

What is ground handling range known as?

A

Beta range.

21
Q

When is the feathering system used?

A

When an engine shut downs in flight.

22
Q

Can propellers be unfeathered in flight?

A

Yes, to restart the engine.

23
Q

Where is single lever control used ?

A

On gear coupled engines.

24
Q

What makes up a single lever control?

A

An integrated fuel and propeller control unit.

And a PCU.

25
Q

Where is Dual lever control used?

A

With free power turbines.

26
Q

What is the purpose of the thrust lever?

A

Schedules fuel flow.

27
Q

What is the BETA/ ground operating propeller angle range?

A

+20 to -20 degrees.

28
Q

Where is the propeller lever operated?

A

In flight.

29
Q

What is the purpose of control locks?

A

Ensure control surfaces don’t flutter on ground with engines running.

30
Q

What system prevents propeller windmilling?

A

Automatic Drag Limiting System (ADLS)

31
Q

What is the feathering angle of ADLS?

A

90

32
Q

What is the purpose of ADLS?

A

Prevents propeller from driving engine in case of oil supply failure.

33
Q

What powers ADLS?

A

Feathering pump

34
Q

Where does the feathering pump get its oil supply from?

A

Draws oil from engine tank

35
Q

What are the 3 over speed safety devices?

A

Pitch locking.
Propeller over speed govenor.
Turbine shaft failure.

36
Q

What is the purpose of pitch locking?

A

Prevents propeller moving to a fine pitch angle.

37
Q

How does pitch locking work?

A

It moves under spring force when oil supply fails.

38
Q

What does the propeller over speed govenor do?

A

Dumps oil pressure to return if propeller speed exceeds 105%

39
Q

What happens in the event of turbine shaft failure?

A

Engine fuel supply is immediately shut down.

M15 (18 decks)

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