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M17 > 17.3* > Flashcards

17.3* Flashcards

1
Q

When is BETA range used?

A

When the pilot controls the pitch on the ground

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2
Q

When is ground fine pitch used?

A

Used for engine starting and discing braking

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3
Q

When is negative (reverse) pitch used?

A

For power on braking and manoeuvring

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4
Q

When is ALPHA range used?

A

Also known as constant speed range, propeller governor controls the pitch

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5
Q

When is max fine pitch used?

A

For rapid acceleration during take off - allowing for a shorter take off time

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6
Q

When is coarse (high) pitch used?

A

Used for high forward speed flight

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7
Q

On a single acting prop with a SINGLE engine, how does the prop pitch system work?

A

The oil pressure moves the blades in the direction of high (coarse) pitch and the spring moves the pitch to a low (fine pitch)

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8
Q

On a single acting prop with a MULTIPLE engine, how does the prop pitch system work?

A

Oil pressure moves the blades to the low (fine pitch where as the spring moves the pitch to the high (coarse) direction

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9
Q

What do double acting probs do?

A

They use oil pressure to change pitch in both ways

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10
Q

What is a propeller governor driven by?

A

It’s mounted on and driven by a reduction gearbox

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11
Q

When the propeller governor is in a neutral - on condition position, what is happening?

A

The speeder spring is equal to the centrifugal forces required to keep the flyweights in the vertical 0/ neutral position.
Which creates a hydualic lock - allowing no oil in.

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12
Q

In the under- speed condition, how are the flyweights positions and why?

A

The flyweights are positioned inwards, by the speeder spring pushing down on the pilot valve. This allows the oil trapped in the pitch cylinder to drain away and pitch to be changed

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13
Q

In the over - speed condition, how are the flyweights positioned and why?

A

The pilot requires a lower rpm, so control lever moves rearwards, this reduces tension on speeder spring which allows the pilot valve to come up. This then allows the oil to move into the pitch change cylinder and therefore change pitch to increase propeller brake moment and decrease RPM

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14
Q

What psi is the hydaulic oil at in a constant speed prop?

A

250psi

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15
Q

What psi is engine oil pressure at?

A

90 psi

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16
Q

In the event of the engine stopping in flight what must be done?

A

Must be selected to feathering to prevent windmilling

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17
Q

After a prop have be feathered in flight, if the pilot wants to rest the engine, what must be do?

A

The prop must be set to a fine (low) pitch

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18
Q

Some engines are equipped with an unfeathering accumulator, how does this work?

A

By moving the power lever to a higher RPM and releasing the pressure build up in the accumulator

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19
Q

When are centrifugal latches engaged and disengaged?

A

They are engaged By spring pressure at low RPM (700-1000 rpm) and disengaged when centrifugal forces are high as RPM increases

20
Q

Pg 71

A
21
Q

The efficiency of compressor and turbine depend on what?

A

The RPM

22
Q

Turboprops can only supply the power requires over a?

A

Small RPM range

23
Q

Turbo props are used where flight speeds do not exceed what?

A

450mph and economy is a large consideration

24
Q

What RPM are props only efficient at?

A

1000- 1200rpm

25
Q

Because the propeller has such a low rpm, what is needed for the engine?

A

A reduction gearbox usally epicyclic design

26
Q

What is the reduction ratio of a epicyclic reduction gearbox?

A

6:1 and 20:1

27
Q

What are the 3 turboprop engine arrangements?

A

. Direct connected
. Compounded
. Free power turbine

28
Q

How does a direct connected engine arrangement work?

A

The turbine drives the compressor through the reduction gearbox

29
Q

How does a compound engine arrangement work?

A

A twin spool layout where the HP turbine drives the HP compressor and LP turbine drives the LP compressor and the prop reduction gearbox

30
Q

How does a free power turbine engine arrangement work?

A

Compressor and prop are mounted on different shafts and driven by independent turbine. Has both a power and conditioning lever

31
Q

What is ESHP?

A

Equivalent shaft horsepower

32
Q

How do you get ESHP?

A

The sum of SHP and thrust - it indicates the total power a viable from the engine

33
Q

What does 1HP equal.

A

2.5lbs of thrust

34
Q

What % RPM do gas generators on turbo props run at?

A

Nearly 100% RPM

35
Q

What is ground fine pitch?

A

Known as discing position and is used for starting and initial acceleration. Done by a fixed adutment stop which allows the prop to take up the zero position

36
Q

When what does flight fine pitch stop do?

A

A retractable stop is used to limit the to fine (low) pitch avialable during flight

37
Q

When is the FFPS locked?

A

It’s locked in position automatically as power lever is advatanged to take off
. Has two positions ENGAGED and WITHDRAWN

38
Q

What does the hyduakic pitch lock ensure?

A

A spring operated valance which is designed to prevent the prop from moving finer pitch in the event of an operating oil supply faliure

39
Q

Why would feathering be selected?

A

It’s selected to prevent excessive drag and negative torque (windmilling) in the event of an engine faliure

40
Q

How is the operation of manual feathering achieved?

A

By selecting the feathering lever which is interconnected to the engine HP cock

41
Q

When would automatic feathering happen?

A

During take off and cruise

42
Q

What is the BETA range?

A

The range of blade angles which can be obtained when the aircraft is operating on the ground

43
Q

How does reverse pitch work?

A

The negative blade angles are combined with the engine power being produced, will force the airflow forwards - creating variable breaking force - reverse thrust

44
Q

How is the beta blade angle changed?

A

With power lever so angle between zero and flight idle (full reverse)

45
Q

The hydro mechanical PCU is designed to do what?

A

Mounted on the reduction gearbox, designed to control the pitch of the prop by directing oil to either side of the pitch change piston through a dual concentric beta tube

46
Q

What does PEC mean?

A

Prop electronic control unit

M17 (12 decks)

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