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|GREAT ELECTRONIC PROJECTS FOR R/C
|BIPLANE BALANCE POINT CALCULATOR BY FRED HAUCK
airplanes and they control the model in exactly the same way.
The four primary controls of an rc airplane are throttle, elevator, ailerons and
rudder. The elevator, ailerons and rudder are known as control surfaces and the
picture below shows where these main controls are located on a fairly typical 4
channel rc 'sport' airplane....
Above: location of ailerons, elevators and rudder on an rc airplane.
Which controls do what?
Now you know where the primary rc plane controls are located, let's take a look
at each one...
Throttle controls the speed of the engine and hence how fast or slow the
On a glow plug (or petrol) rc airplane engine the throttle works the same as any
internal combustion engine throttle, by changing the amount of fuel and air that
enters the combustion chamber of the engine. The carburettor is operated by a
single servo connected to the Venturi of the carb, which opens and closes (thus
changing the fuel/air mixture) in response to your throttle stick movements on
On an electric rc airplane the throttle is usually referred to as motor power rather
than throttle. Very basic electric rc planes (I.e. Toy ones) might not have
proportional control to motor power but just a simple on/off switch instead.
Electric airplanes that do have control to motor power have an electronic speed
control, or ESC, that controls power to the motor in direct response to your Tx
In the air throttle/motor power not only controls the forward speed of the
airplane but also, more importantly, the rate of climb and descent, because
different amounts of lift are generated at different airspeeds. For example, if
your landing approach path is too low you can make the airplane rise slightly
without changing speed much, simply by opening the throttle instead of using
up elevator. Conversely, closing the throttle will cause the airplane to sink
before the speed reduces.
Using throttle/motor power in this way is the correct way to fly your rc airplane,
but many pilots use the elevator to control altitude and rates of climb and
The elevators are the hinged section of the tailplane, or horizontal stabiliser, at
the very rear of the airplane. Elevators control the horizontal pitch attitude of the
airplane, in other words whether the nose of the plane points upwards or
When elevators are in the up position (upward deflection) the nose of the
airplane is forced to point upwards, and with the elevators deflected
downwards then the nose is forced downwards.
It's worth noting that a plane can still fly level with a very nose-up attitude (I.e.
Not climbing) but a nose-down pitch attitude will almost always result in the
plane entering a dive, thanks to our friend gravity!
Very basic rc airplanes might not have elevator control; motor control may be
the primary way of controlling altitude.
Elevators are used in conjunction with rudder and/or ailerons when making a
Not all rc airplane controls include ailerons, in fact the majority of 3 channel
radio control airplanes use rudder instead. But where fitted, ailerons control the
roll of the airplane about its longitudinal axis (imagine a straight line running
through the centre of the fuselage, from nose to tail).
Ailerons work in pairs and are found on the trailing (rear) edge of the wing, and
they work opposite to each other I.e. When one aileron moves up, the other one
moves down and vice versa.
Ailerons work by changing the amount of lift generation over the wing. As an
aileron moves upwards so it disrupts the smooth airflow over the wing surface
and so lift is reduced slightly on that wing. Over on the other wing the aileron
moves downwards and increases lift slightly. As a result, the airplane tilts and
hence rolls towards the side that's experiencing less lift.
When up elevator is applied at the same time as ailerons, the airplane is pulled
round in to a banked turn; the ailerons cause the plane to roll and the up
elevator causes the nose to pitch round in that direction.
Ailerons are used in all aerobatic maneuvers that involve a rolling motion.
The rudder is the hinged section of the fin, or vertical stabiliser, at the rear of the
It's used for directional control by changing the yaw of the airplane and works
in the correct sense I.e. Moving the rudder to the left causes the airplane to turn
left and vice versa.
Applying rudder makes the nose of the airplane point to the left or right, but
rudder alone does not make the airplane roll like ailerons do. It's actually the
dihedral, or the upward 'V' angle of the wing when viewed from the front, that
makes the plane roll when rudder is applied; a plane with very little or no
dihedral will have a much flatter turn when rudder is applied.
Rudder is also very important on the ground, it's the one control that will keep
your rc airplane tracking straight during a take off run or landing roll if your
plane isn't fitted with a steerable nose or tail wheel.
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|ORANGE RX 710 TEST BY ART MANSFIELD