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Propellers > Propellers Theroy > Flashcards

Propellers Theroy Flashcards

1
Q

How is an airplanes thrust produced

A

By accelerating a mass of air

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2
Q

What are the two two types of propeller theory’s

A

Momentum theory
Blade element theory

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3
Q

What is momentum theroy

A

A pressure difference between the face and back of the blade

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4
Q

What is the blade element theory

A

Each blade is made up of an infinite number or sections with a distance from the axis of the prop

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5
Q

What are the sections of the blade

A

Blade face
Blade back
Plane of rotation which is a line running horizontally through the middle
Chord line that runs the length of the blade
Leading edge
Trailing edge
Axis of rotation
Blade angle

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6
Q

What is propeller pitch

A

The angle between the chord line and the plane of rotation

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7
Q

What are the three types of pitches

A

Geometric
Effective
Slip

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8
Q

What is geometric pitch

A

Theoretically if a prop turned on revolution through a solid that is the distance

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9
Q

What is effective pitch

A

Actual distance a propeller advances. Through the air in one revolution

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10
Q

What’s the difference between the geometric and effective pitch

A

Slick

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11
Q

What is the angle of attack

A

The acute angle between the chord line and the relative wind

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12
Q

What is centrifugal force

A

Puts the greatest stress on a prop tries to pull the blades out of the hub

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13
Q

What is thrust bending force

A

This force tries to bend the blades forward and is greatest near the tip of the blade

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14
Q

What is torque bending force

A

Tries to bend the prop blade in its plane of rotation opposite of the direction of rotation

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15
Q

What is aerodynamic twisting force

A

The force that tries to increase blade angle

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16
Q

What is centrifugal twisting force

A

Force acting on the longitudinal axis of a prop tries to rotate the prop to a low pitch position

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17
Q

What is asymmetrical loading

A

The loading in which a prop disk produces thrust more on one side of the blade

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18
Q

The asymmetrical loading has a what

A

Critical engine

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19
Q

What are the different types of props

A

Fixed pitch
Ground adjustible
Controllable pitch

20
Q

How does fixed pitch aircraft operate

A

They have different blades with diff ent blade angles that allow them for cruise and take off

21
Q

How do ground adjustible props work

A

By setting the blade angle with a universal prop protractor and rotating till the right angle the tightening the blade clamps

22
Q

What are the types of controllable pitch props

A

Two position propellers

23
Q

What are the two types of constant speed propellers

A

Counterweight
Non counterweight

24
Q

How do counterweighted props work

A

By pushing oil on a piston to move the blades into low pitch position
And the centrifugal force moves the blades back into the high pitch position

25
Q

How do no counter weight props work

A

It uses a spring and centrifugal twist to move it into the decreased pitch position and it uses oil pressure to move it into the increased pitch potion

26
Q

What are the major components of the propeller governor

A

The speeder spring that supplies the pressure for the flyweight assembly

The spur gear type govenor oil pump that increases the pressure to the prop

The pilot valve that controls where the oil flows

27
Q

What component can be adjusted to set the blade angle pitch

A

High RPM adjustment stop screw

28
Q

What are the three conditions of a propeller governor

A

Over speed
On speed
Under speed

29
Q

Where does oil flow when the counterweighted prop is at an overrated condition

A

Flows back into the oil pan

30
Q

Where does oil flow when an counterweighted prop is at an under speed condition

A

Into the propeller

31
Q

Where does oil flow on an non counterweighted prop in an over speed condition

A

Into the propeller

32
Q

Where does oil flow in an non counterweighted prop in an under speed condition

A

Into the oil sump

33
Q

What is the basic principle behind feathering constant speed props

A

Pressing an feathering button which will rotate the blades from low pitch to high pitch to extreme high pitch

34
Q

What are the different types of feathering constant speed props

A

Hamilton standard hydrostatic

35
Q

How does a Hamilton standard hydro magic control an under speed condition

A

Engine oil pressure overcomes governor oil pressure and is helped by centrifugal twisting moment so the blades move into a low pitch position so the engine can speed up

36
Q

How does a hdh control an over speed condition

A

High pressure from the governor pump is pushing the piston outward to move the blade into a high pitch position to slow the blade down

37
Q

What is already on the oil container to prevent engine oil draining out and not being able to feather the prop

A

The standpipe at the bottom of the oil container

38
Q

How does a hartzell steel hub operate

A

Same basic principles as the non feathering counterweight prop it uses oil pressure and and a govenor

39
Q

How does the hartzell steel hub feather the prop

A

By moving the governor control into the full aft position. This drains the oil out of the prop and the counterweights use centrifugal force to move them into the feather position

40
Q

How do you un feather a hartzell prop

A

Moving the governor control into its normal range and the oil pump with turn the prop into low pitch position once it rotates

41
Q

How does some hartzell feather their prop

A

By the use of an accumulator and it stores oil under pressure to allow for a faster switch

42
Q

What is used in a hartzell system to prevent the prop from feathering each time there is an engine shut down

A

High pitch stop plate which prevents the prop from going full feathered unless it is spinning

43
Q

How do McCauley constant speed props work different from others

A

They use a counterweight and a spring to assist in feathering

44
Q

How does the McCauley feather the prop

A

By moving the governor control into the aft position which raises the piolet valve and allows oil back into the sump. Centrifugal force holds the high pitch and the spring rotate the prop into the feathered position

45
Q

How does a McCauley prop unfeather their props

A

By the use of an accumulator to move the blades into the unfeathered position. The prop lever has to be controlled back to its normal conditions to go into the normal position

Propellers (1 decks)

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