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Props And Rotors > Propellers > Flashcards

Propellers Flashcards

1
Q

Purpose of a propeller

A

To convert engine power into thrust

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2
Q

How does propeller produce thrust

A

Bernoullis theorem

Cold jet principle (newton’s third law)

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3
Q

Where does thrust act

A

Along the longitudinal axis of the aircraft

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4
Q

How does torque act in relation to a blade

A

At right angles to the propellers longitudinal axis

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5
Q

Describe centrifugal force in relation to propellers

A

The forces acting outwards, down thr longitudinal axis, pulling the blades out the hub

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6
Q

What’s the greatest force on a propeller

A

Centrifugal force

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7
Q

Describe thrust bending and why it happens

A

Thrust bending is when the tips of the blades bend forward when roating producing thrust. This is due to the lifting force and the flexibility of the blade that causes this forward arc

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8
Q

Describe torque bending

A

The reaction force opposing the blades moving through the air, opposite to their rotational path

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9
Q

Explain aerodynamic twisting moment

A

The moment that the blade courses the pitch due to the aerodynamic force applied infrastructure of the point of rotation

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10
Q

Define centrifugal twisting moment

A

The fining of pitch due to the weight force being in front of the point of rotation therefore the force reduces the blades angle

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11
Q

Name 6 parts of a blade

A 
Butt
Shank
Face
Back
Leading edge
Trailing edge
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12
Q

Define plane of rotation

A

Plane perpendicular to the shaft, as which the blades rotate

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13
Q

2 types of blade stations

A

Normal - measured from the centre of rotation, used to specify points on the blade

Master - used in maintenance to check blade angles, known point.

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14
Q

In relation to a angle of attack with a propeller, if the aircraft is moving faster the angle of attack is…

A

Smaller.

Rotational velocity and thrust are two main variables that impact AoA

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15
Q

Define geometric pitch

A

The distance measured in inches a propeller will move through a solid with no impacts over one revolution.

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16
Q

Define effective pitch

A

The actual distance measured in inches that a blade will move in one revolution

17
Q

Define slip

A

The difference between geometric pitch and effective pitch. How efficient a propeller is. Most range from 75 to 85% efficient

18
Q

What is torque reaction

A

Reaction force to the rotation of a propeller.

19
Q

Define on speed

A

When a propeller is moving at the “correct”, set speed

20
Q

Define windmilling

A

A propeller spinning in the wind, which can create drag

21
Q

Outline feathering

A

When the blade is set extremely course to be in a position of lest air resistance. This setting also stops windmilling

22
Q

Define reversing

A

When the propeller is in negative pitch, however the propeller still spins in the same direction. This is used to slow down, or move backwards when on the ground

23
Q

5 Safety features in relation to propellers

A 
Negative torque system, NTS
De coupling
Auto feathering
Pitch lock
Propeller brake
24
Q

Outline a front spinner

A

An aerodynamic fairing that covers the prop hub and reduces drag

25
Q

5 Parts of a propeller fairings and hub assyembly

A 
Front spinner
Barrel assy (front and rear)
Rear spinner
After body
Control assy
26
Q

2 parts of a Control assyembly and thier purposes

A

Valve assy - is the brains such as housing the governor

Control assyembly- is the muscle, and holds the pumps, and back up pumps to allow pitch control

27
Q

Outline cones and retention nut

A

The front and rear cone are squeezed together by the retention nut which locks the barrel assy

28
Q

Purposes of blade cuffs

A

Improve the airflow around shanks

Increases the flow or cooling air to the engine nacelle

29
Q

3 types of propeller

A

Variable pitch
Ground adjusted
Fixed pitch

30
Q

3 things the governor does

A

Boost pressure of engine oil
Controls amount of oil flowing to propeller
Senses rotational speed of propeller

31
Q

3 basic components of a governor

A

Fly weights
Pilot valve
Pump

32
Q

Purpose of fly weights

A

Senses rotational speed

33
Q

How much does the boost pump increase pressure

A

180 to 300psi, has a spring loaded relief valve to release excess pressure

34
Q

What valve is the pilot valve

A

Shuttle valve

35
Q

2 types of propeller anti/de ice

A

Fluid and electrical

Props And Rotors (3 decks)

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