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Mod 17: Propellers > Kevin Questions > Flashcards

Kevin Questions Flashcards

1
Q

The blades are said to be feathered when?

A

They are very coarse i.e 88 degrees

almost 90 degrees

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2
Q

The term ‘Spinner’ is applied to what?

A

Applied to a component that fits over the prop hub which can be either ‘‘skull cap’’ or ‘‘full spinner’’

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3
Q

In a double acting propeller, where is oil pressure used?

A

Oil is used in governor oil (increase blade angle) and engine oil (decrease blade angle + CTM)

Hydromatic propeller = double acting propeller

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4
Q

When are the blades set to be feathered?

A

When the blade angle has been turned on edge to the airflow.

(when engine is shutdown to prevent drag/yaw)

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5
Q

The term spinner is applied to what?

A

A streamlined covering over the propellor hub.

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6
Q

A ground fine pitch stop is removed when?

A

A ground fine pitch stop is removed on the ground.

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7
Q

Low torque sencing is used for what?

A

Low torque sencing is used for iniating auto feathering.

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8
Q

When is super fine pitch used?

A

During engine starting to reduce propellor torque loading on the starter motor.

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9
Q

If a propellor is in fine pitch and then it moves to the feather position what will it pass through?

A

Coarse position.

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10
Q

A double acting prop has oil where?

A

Oil on both side of the piston

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11
Q

During normal prop operation the oil pressure for the governer is provided by what pump?

A

By a boost pump in the governer.

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12
Q

Oil for an on-speed conditon passes through which pitch line?

Coarse pitch line

Fine pitch line

Neither of the lines

A

Neither of the lines

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13
Q

Releving the compresive force on the governer valve spring causes the blades to:

Become more course

Become more fine

Remain Hydraulicly Locked

A

Releving the compresive force on the governer valve spring causes the blades to become more course

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14
Q

If a spur gear pump in a single acting propellor governer failled what would happen?

Blades will become more course

Blades will become more fine

Blades will rotate to the feathered positon

A

Blades will rotate to the feathered positon

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15
Q

The hydromatic variable pitch propellor is operated on what principle?

The oil pressure moving in a pistion

An electrical motor moving a gear segment

A Venturi

A

The oil pressure moving in a pistion

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16
Q

The minimum % seating on a propellor rear cone should be:

70%

90%

95%

A

70%

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17
Q

A rotating propellor imparts rearward motion to what?

Small mass of air at high velocity

Large mass of air at Low velocity

Small mass of air at low velocity

A

Large mass of air at Low velocity

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18
Q

A prop is feathered when the blades are what degree to the plane of rotation?

90°

0°

-20°

A

90°

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19
Q

A constant speed unit governer works on what principle?

Manual selection through a gear box

Centrifugal twisting moments

Spring pressure acting agaisnt centrifugal force

A

Spring pressure acting agaisnt centrifugal force

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20
Q

A constant RPM advance per revolution depends on what?

The angle of advance

The fwd speed

The HP of the engine

A

The fwd speed (true air speed)

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21
Q

The thrust face of a prop is on which side?

Rear face/ flat side

Front face/ Curved Side

The root to which the gear segment is fitted

A

Front face/ Curved Side

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22
Q

The purpose of the pitch change cams is to

Convert linear motion to rotary motion

Convert rotary motion to linear motion

Prevent windmilling

A

Convert linear motion to rotary motion

23
Q

A fixed pitch propellor is usually at what angle for take off?

Too coarse an angle for take off

Too fine an angle for take off

The optimum angle for take off

A

The optimum angle for take off

24
Q

If a blade angle is increased, does that mean it becomes

finer

courser

No effect on the blade

A

Courser

25
Q

What is the chord line of a propellor?

A line joining the tips of the blades

A line joining the leading and trailing edges

A line joining the tip to the root

A

A line joining the leading and trailing edges

26
Q

Deffine propellor blade angle

A

The angle between the chord line and the plane of rotation.

27
Q

In which areas are repairs not permitted on propellors?

A

In the inner 1/3 of a blade

28
Q

The centrifugal twisting moment turns the blade in what direction?

Towards coarse

Towards Fine pitch

Towards Negative pitch

A

Towards the fine pitch

(Reducing th eblade angle)

29
Q

Where is the greatest load felt on a propellor?

A

In around the propellor hub.

30
Q

Define a constant speed propellor is one which

Maintains constant aircraft speed

The blade pitch remains contant

The propellors pitch angle is altered to maintain the rotational speed

A

The propellors pitch angle is altered to maintain the rotational speed

31
Q

The purpose of a propellor is to convert ______ ______ to ________ ________

A

The purpose of a propellor is to convert engine power to useful thrust

32
Q

What is the greatest force acting on a propellor?

A

Centrifugal force

33
Q

What force tries to bend a propellor blade forward?

A

Thrust

34
Q

The distance a propellor advances in one revolution is called what?

A

The effictive pitch is the distance a propellor advances in one revolution.

35
Q

What is the optimum blade angle for a fixed pitch propellor?

A

2°- 4°

36
Q

What force on a propellor blade turns the blade to a fine pitch?

A

CTM (Centrifugal Twisting Moment)

37
Q

The blade angle at the root is larger/smaller than at the tip?

A

Larger/Greater

38
Q

What is the purpose of a blade cuff?

A

To increase the flow of the cooling air into the nacelle.

39
Q

The thrust developed by a propellor is IAW with which of Newtons Laws?

A

Both 2nd and 3rd (Think 2nd is more correct)

2nd Law: F=MA, thrust is equal to the mass of the air times the acceleration of the air.

3rd Law: For every action there is an equal and opposite reaction. If mass of air is accelerated in one direction by the propeller, then an equal force tries to move the propeller in the opposite direction.

40
Q

When the blades are set to a low angle what happens the load on the engine?

A

The load on the engine decreases

41
Q

What is the purpose of a reversing angle on a propellor?

A

To reduce ground roll when landing.

42
Q

Define geometric pitch (Propellor pitch)

A

Geometric pitch is the theoretical distance the prop will move forward per one revolution.

(effective pitch = geometric pitch - slip)

43
Q

Propellor torque is the resistance offered by a propellor to what?

A

rotation

44
Q

Define aerodynamic twisting moment.

A

Tries to twist a blade to a higher angle by aerodynamic action. This results from the centre of rotation at the blade being at the mid point of the chord line while the centre of lift is more towards the leading edge of the blade.

This tends to cause an increase in blade angle

45
Q

What is the purpose of blade twist?

Reduce the AOA at the root

To even out thrust distribution throughout the prop

To ensure the prop tip speed doesn’t exceed Mach 1

A

To even out thrust distribution throughout the prop

(But also To ensure the prop tip speed doesn’t exceed Mach 1)

46
Q

Where are blade stations measured from where?

A

The centre of the hub.

47
Q

The thrust produced by a rotating prop is the result of an area of what type of pressure and where is that pressure?

Decreased pressure behind the propellor blades

Decreased pressure immediatly infront of the prop blades

Increased pressure infront of the prop blades

A

Decreased pressure immediatly infront of the prop blades

48
Q

If propellor RPM increases what happens to the centrifugal twisting moment on the blades?

A

The CTM increases

49
Q

The resultant airflow over a prop depends on what?

A

The RPM + FWD velocity

50
Q

Reverse thrust occurs when a propellor blade does what?

A

When blades rotate to a negative angle

51
Q

A propellor mounted forward of the engine is known as what type of a propellor ?

Hydromatic

Tractor

Pusher

A

tractor

(propeller behind is a pusher)

52
Q

Disadvantages of using wood for propellors?

Difficult to manufacture

Easy damaged + Difficult to repair

Has a low strenght to weight ratio

A

Wood has a low strenght to weight ratio

53
Q

Propellor torque is the resistance offered to the propellor to which

The changing pitch

The rotation

The feathering

A

Propellor torque is the resistance offered to the propellor to the rotation

Mod 17: Propellers (10 decks)

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