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The primary flight
controls on any aeroplane are:
Pitch : Roll :
Yaw : Throttle
The following
descriptions give an explanation of the effect of each control in isolation,
for a theoretical aircraft. Obviously in flight, control are operated together,
and there are also secondary effects of controls to consider.
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Pitch
Pitch changes
raise or lower the nose of the aircraft. This effect is caused by the operation
of the elevator. As the elevator is raised, the force of the
airflow pushes the tail down, rotating the aircraft about the balance point and
raising the nose. |
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Roll
Roll is a
rotation around the long axis of the fuselage. This effect is caused by the
operation of the ailerons. To roll left, the left aileron is
raised and the right aileron lowered. The combined effects of the airflow on
the controls lifts the right wing and lowers the left wing. The operation is
reversed to roll right. |
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Yaw
Yaw is a
horizontal rotation around the vertical axis of the aircraft, and is initiated
by the rudder. If the rudder is deflected left, the pressure
from the airflow pushes the back around and the aircraft rotates around the
vertical axis. Right rudder makes it rotate in the opposite direction. In the
absence of any other control inputs, the aircraft will carry on the original
direction of flight but with a sideways motion; it will only turn as a
consequence of the secondary effects of controls. |
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Throttle
Controls the
amount of power the engine produces. Contrary to what you may see at the flying
field, most models are not required to be flown around at full throttle all the
time!
Opening the throttle will cause the aircraft to speed up, thus
creating more lift, resulting in a climb. Closing it will cause the aircraft to
slow down, reducing the lift and hence making the aircraft
descend. |
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Now you have seen how
the control surfaces affect the flight path of the model, you can read about
Secondary effects of controls
None of these controls
actually work in isolation, whenever a control is applied, there are always
secondary effects which influence the reaction of the aircraft.
Pitch - elevator:
If the elevator is
used to pitch the nose of the aircraft up, this has the secondary effect of
increasing the angle of attack of the wing and so more lift is generated which
will make the aircraft climb, however at the same time the change of attitude
will increase the drag of the aircraft which will tend to slow it down and
cause it to descend. So, provided the engine output remains the same, the
secondary effects of the elevator are to control the speed of the
aircraft.
Roll - aileron:
 If the stick is moved to the left the aircraft will bank to the left.
As the lift always acts at 90º to the wing, and weight always acts
straight down, the resultant imbalance of forces causes the aircraft to
sideslip to the left.
 This sideslip causes a flow of air
towards the fuselage sides. As there will be more area behind the Centre of
Gravity than in front of it, the resultant force will tend to rotate the
aircraft causing it to yaw.
Yaw - rudder:
Application of the
rudder causes the model to yaw from side to side. This yaw means that the wing
on the outside of the turn is moving faster through the air, while the inside
wing moves slower. This speed change generates more lift from the outside wing
and less from the inner, causing the aircraft to roll in the direction of the
turn. The application of rudder then, causes first a yaw, followed by a roll.
It is this secondary effect that allows aileron-less rudder only models to be
controlled. |
