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D6 - RADIO - I have 2
servos to control the ailerons on my helicopter, but my
radio only provides a setting for one of them - what goes on
This is a
question that often confuses new pilots.
originates form the fact that all RC radio systems started life out
as controllers for fixed wing aircraft (planks). Planks do not
have a pitch control as such, as they do not need it.
helicopters came along, there was an obvious need for another
controlled channel to let the pilot control the angle of the main
rotor blades, at least for Collective Pitch (CP) helicopters.
So what does
any CP helicopter need ?
1 - An
elevator servo/channel to control the pitch of the helicopter (nose
2 - An aileron
servo/channel to control the roll of the helicopter ('Wings
3 - A throttle
channel to control the speed of the motor (and therefore head speed)
4 - A rudder
servo/channel to control the yaw of the helicopter (Nose left/right)
5 - A gyro
gain control channel to control the way the gyro operates
6 - A Pitch
servo/channel to control the pitch of the main rotor blades
independently of the throttle setting.
So, if we try
to match these to the names the channels on a receiver (Rx) are
given most often we get the following :
Ch 1 -
Ch 2 -
Ch 3 -
Ch 4 -
Ch 5 -
Ch 6 - Aux
Ch 7 - Aux
So what works
for the pitch control we so badly need ? Well, most radios provide
this control on Ch 6, commonly named AUX1, or sometimes Pitch.
OK you say,
fair enough, but my swash plate has 2 servos connected one to each
side of the swash plate, and both are used for aileron
control. Which one goes where ?
Now it starts
to get more complicated. There are two different types of
swash plate system used by RC CP helicopters. The original method
was/is called "mechanical" mixing, while the other is
called "electronic" mixing. These are even known as
mCCPM and eCCPM. The mechanical mixing uses a 90 degree swash
plate arrangement for the servo connections, whilst CCPM uses 120
The problem is
that when the radio is using CCPM (Cyclic Control Pitch Management)
to "mix" the operation of all the servos that attach to
the swash plate, as far as it is concerned, both of those aileron
servos have to operate in OPPOSITE directions for Aileron control,
but in the SAME direction for pitch control. That is where
CCPM comes in, and in most cases, it assumes that the aileron servo
mounted on the left side of the helicopter is the one connected to
the AILERON channel (CH 1),while the other one needs to be mounted
on the right. WARNING - This setup is not cast in stone,
and maybe the opposite way around on some helicopters.
So for CCPM
systems, all you really have to remember is that the servo that is
connected to the Aileron (Ch 1) will be "in charge" of
aileron movement, while the servo connected to the AUX1/Pitch (Ch 6)
will be working in conjunction with Ch 1 to handle AILERON and
PITCH. All swash plate servos have to work TOGETHER to achieve
the required swash plate movements.
For non CCPM
it is far more simple, as the AUX1/Pitch control ONLY the pitch
control, which is always handled by one single servo alone, and the
aileron control is handled by one other servo. In other words, each
servo performs exactly one task all by itself, and does not work in
conjunction with the other swash plate servos.
THIS DESCRIPTION HELPS ... ?
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