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M17 Propeller > Fundamentlas > Flashcards

Fundamentlas Flashcards

1
Q

What is windmilling

A

Airspeed turns propeller and turns engine with a negative AoA & torque value

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2
Q

As angle of attack changes what else does

A

Thrust produced

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3
Q

What’s the window for efficiency for angle of attack

A

Small

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4
Q

What happens when brake moments become large

A

Blade angle moved into reverse pitch

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5
Q

Where is leading edge in feathered position

A

Presented into oncoming airflow

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6
Q

What direction does partial force work in

A

Direction of rotation and drives propeller

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7
Q

What drag increases in windmilling propeller

A

Increases aircraft drag considerably

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8
Q

What position reduces increased aircraft drag

A

Feathered

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9
Q

What is slip

A

Geometric pitch minus effective pitch

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10
Q

How is slip given

A

% of geometric pitch

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11
Q

What is bottom of the blade called

A

Butt

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12
Q

How does aerofoil produce lift

A

aerodynamic action

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13
Q

What happens to AoA during constant pitch

A

Decreases and becomes negative due to an airspeed increase or decrease in rotational speed

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14
Q

Is damage permitted in the blade root area

A

No damage or repair work

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15
Q

What makes decibel levels go down

A

As blades are added

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16
Q

What does a propeller do

A

Convert engine torque into thrust

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17
Q

What does a propeller accelerate

A

Large mass of air slowly rearwards

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18
Q

When is turboprop most effective

A

Low speed (subsonic region)

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19
Q

What is plane angle perpendicular to

A

Engine

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20
Q

What is blade angle

A

Angle between chord line and plane of rotation

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21
Q

AoA + what = blade angle

A

Helix angle

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22
Q

In a fixed pitch propeller what is blade angle

A

Angle of incidence

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23
Q

Where is blade angle measured from

A

Blade face

24
Q

What % of prop radius is blade reference station for blade angle

A

50-75%

25
Q

What is Angle of attack (AoA)

A

Angle between profile chord line and relative airflow

26
Q

What do you add to make RAF ( relative airflow )

A

Vector of airspeed velocity + propeller rotational velocity

27
Q

What does increase airspeed do to helix angle and AoA

A

Helix angle increases & AoA decreases

28
Q

What is a fixed pitch propeller limited to

A

Good take off/climb & cruise

Also towing

29
Q

What does an increase in propeller rpm do to helix angle and AoA

A

Decrease helix angle & increase AoA (for more thrust)

30
Q

At constant speed what is the sum of propeller break moment & engine torque

A

Zero

31
Q

At a constant pitch what happens in regards to airspeed and AoA

A

Airspeed increase or rotational speed decreases while AoA will decrease and be negative

32
Q

How does root loses occur

A

It is rounded for strength which causes loses in aerodynamic efficiency

33
Q

What cases tip loses

A

Tip vortices and induced drag at high rotational speeds and compressibility effect

34
Q

What does washout do

A

Maintains constant AoA at different rotational speeds along blade

35
Q

How is the leading edge twisted for washout

A

Downwards from root to tip

36
Q

What is pitch distribution

A

Blade angle is smaller the further away for centre axis which keeps constant AoA

37
Q

What is geometric pitch

A

Blade angle = pitch , in one rotation propeller moved forward axial by geometric pitch

38
Q

What is effective pitch

A

1 revolution the aircraft moves forward by effective pitch

39
Q

What is propeller thrust related to

A

Engine output power

40
Q

What is normal propeller efficiency range

A

80-90%

41
Q

What angle is aerodynamic twist moment

A

High blade angle

42
Q

What angle is centrifugal twist movement

A

Low blade angle

43
Q

What are 2 causes of vibration

A

Engine and gearbox & aerodynamic loads

44
Q

What’s the effect of vibration

A

Structural failure

45
Q

How is vibration reduced

A

aerofoil and tip design being correct

46
Q

Where are highest vibration loads felt

A

80% of blade length

47
Q

What’s the most attractive way to have the best power absorption

A

Increase number of blades

48
Q

How do aircraft wings compensate for roll

A

Generate more lift on the downside

49
Q

When is twist effect compensated and what for

A

Cruise speed & compensate for yaw

50
Q

How is yaw compensated

A

Vertical stabiliser mounted obliquely 1 degree or 2 to longitudinal axis

51
Q

When does a spiralling rotation to slipstream occur

A

High rotational speed of aircraft propeller

52
Q

How does pilot compensate for gyroscopic effect

A

Rudder and elevator offset at takeoff

53
Q

what is the critical engine

A

Engine that creates smaller yaw moment should the other engine fail

54
Q

What does the propeller do if the critical engine fails

A

Propellers turn both inboard downwards (opposite direction) to decrease yaw moment

55
Q

How do we reduce decibel levels on a propeller

A

Add more blades

M17 Propeller (7 decks)

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