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Module 17 > 17.3 Propeller Pitch Control > Flashcards

17.3 Propeller Pitch Control Flashcards

1
Q

What are the two types or propellers

A

Pusher and pullers

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2
Q

What are the three ways of changing pitch if propellers

A

Hydraulic mechanical and electrical

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3
Q

What is disc braking

A

Propeller can be moved into a negative angle of attack (different to reverse pitch) gives more drag helping slow aircraft

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4
Q

What is power on braking

A

Making a reverse pitch with blade and increasing power creates reverse thrust force slowing the aircraft

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5
Q

What’s is BETA range

A

Pilot controls the pitch on the ground

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6
Q

What is reverse (negative) pitch

A

Used for power-on braking and manoeuvring

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7
Q

What is ground fine pitch

A

Used for engine starting and discing braking

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8
Q

What is ALPHA range

A

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

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9
Q

What is MAX fine pitch

A

Used for rapid acceleration during take-off, allowing a shorter take-off run

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10
Q

What is high (coarse) pitch

A

Used for high forward speed

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11
Q

What are the two mechanisms of pitch change

A

Moving piston and moving cylinder

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12
Q

What is a moving piston mechanism

A

Have a piston moving forwards and backwards powered by using oil in each chamber

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13
Q

What is moving cylinder mechanism

A

Cylinder attached to prop and oil and weight turns the cylinder moving the propeller (used on smaller aircraft)

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14
Q

What is a single acting propeller for single engine aircraft

A

Oil pressure moves blades in direction of high (coarse) and a spring moves it to low pitch

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15
Q

What is a single acting propeller for multi engine aircraft

A

Oil pressure moves blades in low (fine) pitch and springs move blades towards high (coarse) pitch

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16
Q

What does centrifugal force do to the pitch of a blade

A

Turns naturally to low (fine) pitch as a result of the distribution of the blade mass

17
Q

What are double acting propellers

A

Able to change pitch in both directions (with pitch oil)

18
Q

What does a propeller governed do

A

Engine RPM sensing device and oil pump, responds to change in engine RPM by directing oil to hydraulic cylinder causing blade angle change

19
Q

How is the spring in the propeller governed adjusted

A

By pilot using propeller control lever (conditioning lever)

20
Q

What can a single acting constant speed propeller control do

A

Turn pitch of propeller to negative using oil not CTM

21
Q

How does an electrical control pitch change mechanism work

A

Uses electrical power to supply power to oil which moves a servo piston and moving blade pitch

22
Q

What is used to change pitch angle in the modern day

A

Electronic control

23
Q

How does the electronic control work

A

Use ARINC digital control to drive torque motor and change the pitch of the blades

24
Q

Which electric system uses oil

A

Electrical system NOT electronic system

25
Q

What is automatic feathering

A

Automatically feathers during take off and cruise. In case of engine failure the centrifugal flyweights are automatically overridden and the electric feathering pump will run

26
Q

What is a second feature of the auto feather system during an engine failure

A

Power up engine trim to compensate for loss

27
Q

When does Up trim trigger

A

When torque of local engine falls below 25%

28
Q

What do some feathering systems have to provide reserve pressure

A

Accumulator

29
Q

What does a centrifugal latch do

A

Locks piston in fine pitch position when engine is not rotating to prevent load on the starter system

30
Q

What is a CSU

A

constant speed unit (primary propeller governer)

31
Q

When does the CSU work to prevent over speed

A

102-103%

32
Q

When does the propeller overspeed governor operate

A

104-106%

33
Q

What is the last method of defence to prevent overspeed

A

Flyweights inside the main propeller governer open a bleed air link this slows fuel flow to the engine and slows propeller speed. Operates at 106-107%

Module 17 (6 decks)

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