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M17 > 17.1* > Flashcards

17.1* Flashcards

1
Q

Explain what acceleration of air mass is?

A

The change in velocity in front of and behind the propellor plane which occurs as a result of the air flowing around the propeller blade aerofoil

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2
Q

What is the angle of attack?

A

The angle between the profile chord line and the relative airflow towards it

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3
Q

What is another word for blade angle?

A

Beta

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4
Q

What is another word for angle of attack?

A

Alpha

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5
Q

What happens if RPM increases?

A

The rotational speed will increase and this causes an increase in the angle of attack

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6
Q

What happens if airspeed increases

A

This causes a decrease in the angle of attack, decarese in braking moment and increase in helix angle

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7
Q

A change in airspeed or rotational velocity always results in a change to what?

A

The relative airflow direction and velocity

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8
Q

What is geometric pitch?

A

The distance a propeller should advance in one revolution - ideal

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9
Q

What is effective pitch?

A

The distance a propeller actually advances in one revolution - reality

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10
Q

What is propeller slip?

A

The difference between the geometric and effective pitch. Essentially the loss of efficiently.

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11
Q

What does the slip normally vary from?

A

50-90% but always a %

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12
Q

What is the normal % of propeller efficient ranges?

A

80-90% 0.8-0.9

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13
Q

What does ATM stand for?

A

Aerodynamic twisting moments

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14
Q

What does ATM do to the blade?

A

Try’s to turn the blade to a more coarse angle (higher) - due to the centre of pressure being forward of the blade’s centre of rotation

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15
Q

What does CTM stand for?

A

Centrifugal twisting moment

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16
Q

What does CTM do to the blade?

A

It tries to make the blade more fine (low) - due to the mass of the blade is thrown out from the centre of rotation

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17
Q

What is the direct correlation of CTM and ATM?

A

CTM will always try and oppose ATM and CTM will always be greater so wins

18
Q

What is the direct correlation between CTM and ATM?

A

CTM is always trying to oppose ATM but CTM is always stronger and wins

19
Q

What are the 5 static loads that a blade experiences?

A

. Centrifugal loads
. Thrust bending force
. Torque bending force
. Aerodynamic twisting force
. Centrifugal twisting moment

20
Q

Where are all static loads felt?

A

At the blade root

21
Q

What is significant about the blade root IAW maintenance?

A

There can be no damage or repairs

22
Q

What is the dynamic load felt by the blades?

23
Q

At what point on the blade feels the most vibration?

A

At 80% of the blade length - called the outer nodal point

24
Q

What is the basic vibration frequency range for a metal propeller blade?

25
What is the basic vibration frequency range for a wooden propeller blade?
60Hz
26
What range just the aircraft travel as fast as possible through to avoid major vibration?
The red range - 2050 - 2200RPM
27
What is the maximum number of blades normally used on a prop?
8 - however more powerful aircraft need more blades
28
What is the biggest static load?
Centrifugal loads
29
What does the prop do to produce thrust?
Converts torque to thrust
30
What law does torque reaction depend on?
Newtons 3rd law - every action has an equal and a reaction
31
What does newtons 3rd law cause regarding a prop aircraft whist in flight?
The propeller is turning in one direction, and an equal force is trying to turn the aircraft in the opposite direction. Which acts in the aircraft’s longitudinal axis, causing it to roll
32
What does newtons 3rd law cause regarding a prop aircraft whist take off or on ground?
Causes an additional turning moment in the vertical axis, that results in yaw.
33
How is the yaw moment in take off corrected?
By the rudder or rudder trim
34
At high speeds the propeller gives on a spiralling rotation to slipstream, what is another name for this?
Twisted propeller wash
35
How can twisted propeller wash around the vertical stab be compensated for?
The vertical stabiliser is mounted obliquely 1 - 2 degrees to the aircraft’s longitudinal axis - however, only suitable for one speed (cruise)
36
What is toqruq reaction?
It try’s to turn the aircraft to the left side as more weight is placed on the left landing gear
37
How is gyroscopic effect compensated for?
As it causes a pitching and yaw moment, use the elevator or rudder
38
Critical engine?
The one that produces the least amount of yaw
39
When is p factor present (asymmetric loading)
In climb
40
How can you treat the torque effect?
By offsetting the engine

M17 (12 decks)

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