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I think that
it is important that you understand the term Angle of Attack.
Angle of
Attack is only relevant to R/C helicopter pilots that have 3D
capable helicopters. To get some practical understanding what Angle
of Attack means, do the following. Next time you drive in a car, put
your hand outside into the relative wind. You have to go at least
120 kilometres per hour to experience the term Angle of Attack
fully.
You will notice
that when your hand is pointing straight into the relative airflow,
your hand produces zero lift. This means that the Angle of Attack
equals zero degrees.
Twist your hand
upwards, and you will notice that your hand tends to move up. You
have just increased the Angle of Attack positively relative to the
airflow. If you increase the Angle of Attack of your hand even more,
you will find the lifting force to increase. Now you can clearly
feel that with increase in A of A, more lift is produced.
Twist your hand
downwards, and you will notice that your hand wants to move down.
You have just decreased the Angle of Attack negatively relative to
the airflow. If you decrease the Angle of Attack of your hand more,
you will find the negative lifting force to increase. Now you can
clearly feel that with decrease in A of A, more negative lift is
produced.
This scenario
can be compared to the rotational rotor blades of a helicopter. I
hope you have a better understanding of the term Angle of Attack.
This is how 3D R/C helicopters are capable to fly upside down. When
you start 3D flying with your helicopter, you will notice how
important positive and negative pitch are with aerobatic maneuvers.
Angle of
attack is an aerodynamic angle and is illustrated here:
It is defined
as the angle between the airfoil chord and its direction of motion
relative to the air (resultant relative wind). Several factors may
cause rotor blade angle of attack to change. Some are controlled by
the R/C pilot and some occur automatically due to the rotor system
design. R/C pilots are able to adjust angle of attack by moving the
cyclic and collective pitch controls.
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