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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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