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This is how it works ...
With the servos arranged at 120° the swashplate ac-
tuation system looks like this:
6
3
Servos 2 and 6 are involved in moving the swashplate
in all directions as they are arranged neither in the
direction of flight nor at right-angles to it.
When the swashplate is to be tilted at 90° to the direc-
tion of flight (ROLL), only servos 2 and 6 are required
to move. This means that the ROLL input must be
switched off in the mixer for servo 3.
One other important point regarding
PITCH-AXIS and ROLL:
When you move the PITCH-AXIS stick the swashplate
should tilt forward or back only. It should not move at
all in the vertical direction, otherwise the result would
be an unwanted collective pitch input.
For this reason servos 2 and 6 need to move through
a smaller travel than servo 3. A little simple mathe-
matics is required to calculate how great the travel
has to be.
We will assume that servo 3 is set up to produce
100% PITCH-AXIS travel. For servo 2 the necessary
travel is calculated using the following formula:
Travel in % = cos (60°) * 100
Your pocket calculator will tell you that the cosine of
60° is 0.5. The PITCH-AXIS input for servo 2 must
therefore be set to 50%.
Servo 6 is located at the 300° point. The cosine value
is also 0.5, and the PITCH-AXIS input must therefore
also be set to 50%.
Direction of
flight
2
- 19 -
For ROLL the mixer input to servos 2 and 6 has to be
changed. In this case the following formula applies:
Travel in % = sin (60°) * 100
The sine of 60° is 0.86. The ROLL input for servos 2
and 6 must therefore be set to 86%. In the corre-
sponding base types (9. Trainer 120° and Heli 120°)
the default setting is 83%, but as the two inputs are
the same, the discrepancy is not significant.
How the mixers work
The following sections are intended to clarify how the
various helicopter mixers are used and which inputs
they employ.
We can differentiate between three types of mixer:
1. Ready-made mixers
HEAD-MIX, HEIMHEAD, DYN. THROTTLE
2. Auxiliary mixers
COLLECTIVE PITCH MIX, TAIL ROTOR, HELI-
THROTTLE
3. Free mixers
SERVOMIX and MULTIMIX
The type and number of mixer inputs for ready-made
mixers cannot be altered, but the values of the inputs
are variable.
The composition and type of mixer inputs for auxiliary
mixers can also not be changed. The values of the
inputs are flight mode dependent, and can be
changed in the curve adjustment menus on the
transmitter control side.
Free mixers, as the name suggests, can be set up
and adjusted exactly as you wish. If one of the ready-
made mixers (or the auxiliary mixers) is „almost" right
for your application you can even use it as the mixer
input for a free mixer. In the base types we use this
method for TAIL-MIX. There the auxiliary mixer TAIL
ROTOR is mixed with YAW and passed to the tail
rotor servo.
NFIK/ZAU
This mixer is used if the swashplate of your helicopter
is actuated by 3 or 4 servos (CPM rotor head). The
mixer combines all three control functions to generate
the signals for the swashplate system servos. These
are:
1
V-ROLL
2
V-PITCH-AXIS
3
COL:PITCH-MIX
The V prefix to ROLL and PITCH-AXIS stands for
„virtual", and this indicates that these two inputs are
already prepared for „virtual" rotation of the swash-
plate. Setting up and adjusting swashplate rotation is
carried out in the menu for adjusting the ROLL and
PITCH-AXIS transmitter controls. Swashplate rotation
is pre-set to 0° and can be set to different values for
all flight modes!
The menu for setting virtual swashplate rotation looks
like this:
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