Setting the SWASH AFR / Pitch & Cyclic Pitch
This setting is for managing the swashplate mixing. It is
typically used to limit the amount of travel the swashplate moves,
and therefore control the maximum amount of pitch. As stated before,
the TREX clones are capable of setting a pitch level to over 14
degrees. More than 12 degrees can stress the entire drive train. AFR
settings are for the cyclic servos. These are Channel 1, 2 & 6.
The values than can be applied are in the range of -100% to +100%.
The AFR settings go beyond limiting the amount of pitch. To
explain it, I have inserted an article from “dkshema” on
the Run Ryder forum http://rc.runryder.com
Author: dkshema, Cedar Rapids, IA
- http://www.slyster.com/heli/mix.html
If you were flying a standard mix,
non-CCPM helicopter, if you needed more
or less aileron or
elevator CYCLIC movement of the swashplate, you would
adjust the
ENDPOINTS/ATV for the AILERON or ELEVATOR channel. If you needed
more
or less collective PITCH, you'd adjust the ATV/Endpoints for
the
collective pitch channel. If you needed to REVERSE the servo
movement for
one or all three of these channels, you would do the
reversing in the
REVERSE menu of your TX, for the channel that
needed to be switched.
-----
But, since you have a heli whose
swashplate is setup for 120 degree CCPM
control, it requires that
three servos work in unison to move the swashplate
correctly. The
individual control adjustments take on new meaning, as you
have to
deal with the electronic mixing that is occurring in the
radio.
-----
The electronic mixing requires a few things to
work differently in your
transmitter. First, the channel reversing
function in your TX ONLY affects
one of the three servos, not the
action of all three. The channel reversing
feature in your TX ONLY
allows you to get the three servos moving correctly,
with respect
to each other, and has nothing to do with them moving correctly
with
respect to the function they are controlling.
For instance,
for aileron control, two servos need to move in opposite
directions,
one up, one down. The third servo does nothing. But if your
servo
reversing switches are in the wrong position, those two servos
may
both move up, or both move down. Fix THAT using the reverse
function for ONE
of the TWO servos.
Elevator requires that
two servos move up (or down) in unison, while the
third moves
opposite (generally the elevator servo). IF all three move UP
(or
down), you reverse the elevator channel.
Collective requires
that all three move up, or down in unison. Generally, if
you get
the elevator and aileron channels moving correctly with respect
to
each other, the collective takes care of itself.
BUT --
you may find that although the servos move correctly with respect
to
each other, they may move opposite of the direction required
for the
FUNCTION.
This is where the SWASH MIX/SWASH AFR
menu comes into play. By simply
changing the SIGN of the aileron,
elevator, and/or pitch function, you
reverse that function instead
of messing with the channel reversing stuff.
-----
The
ATV/Endpoints no longer adjust the travel of the FUNCTION, they
only
adjust the travel of an individual servo. So, if you find
your swashplate
level at mid collective/zero degrees, but that it
tilts as it goes full up
or full down, you use the individual
endpoint/ATV settings to correct the
movement of the individual
servo that is moving too far, or not enough. You
don't affect the
other two servos in this manner.
-----
The SWASH
MIX/SWASH AFR menu is also where you control how much
total
collective travel you get (full stop to stop) with the SIZE
of the pitch
number, and how much aileron and elevator CYCLIC
pitch you get by adjusting
the SIZE of the AILE and ELEV numbers
in the swash mix menu.
-----
Finally, the numbers in
the swash mix menu do NOTHING to center the
swashplate in its
travel range for that zero degree setting.
This is
accomplished by making sure your servo arms are where they
are
supposed to be AT NEUTRAL (generally horizontal, parallel to
the ground
unless your pushrods have some weird geometry). When
you have all three
SERVO ARMS properly positioned at NEUTRAL
(mid-stick on both sticks), you
adjust the pushrods controlling
the swashplate to get the swash not only
level, but in the center
of its overall travel range.
When you have accomplished THAT,
you then adjust the pitch links up on the
head generally to get
all mixing arms level, and ZERO degrees pitch in
BOTH
blades.
-----
Barracuda mentions the idea of
setting your pitch curve to a big FLAT LINE
at 50%. I picked this
idea up from Ron Lund's Heliproz South website. If you
have a
5-point pitch curve radio, set points 2, 3, and 4 at 50%, and point
1
at 0, point 5 at 100.
In doing so, as long as the
collective stick is anywhere between points 2
and 4, the servos
will be centered (neutral) and you can make your pushrods
to level
the swash, and center it in its overall travel range. You can set
the
rest of the pushrods to level the various mixing arms, and to set
ZERO
degrees pitch in both blades.
Finally, you can go to
points 0 and/or 100 to set the overall pitch travel
using the
PITCH number in the SWASH MIX/AFR menu.
-----
To figure
out what the AILE and ELEV numbers "should" be, use your
pitch
gauge to figure out what your cyclic pitch is.
If you
turn the head so that the flybar is perpendicular to the sides of
the
heli (main blades -- one in front, the other over and parallel
to the tail
boom), set your collective stick to the ZERO degree
setting, you can measure
CYCLIC PITCH values for the AILERON
function.
Put the pitch gauge on the MR blade sticking out
front, about mid-way on the
blade. MOVE THE AILERON stick side to
side. Go full LEFT (or right) and
measure the amount of pitch from
ZERO degrees that the blade moves. Adjust
the AILERON number in
the SWASH MIX/AFR menu to get +/- 6 or 7 degrees of
aileron
cyclic.
Turn the head 90 degrees, keeping the collective at
the ZERO degrees pitch
setting. The flybar is now over and
parallel to the tail boom, and sticking
out in front, the MR
blades are perpendicular to the sides of the heli.
This time,
move the ELEVATOR stick to its full extreme, measuring the amount
of
pitch the MR blades get as you do. This time, set the ELEV number in
the
SWASH MIX/AFR menu to get that same +/- 6 or 7 degrees of
cyclic.
For the FS-CT6A radio, the AFR settings per channel can be a
little confusing. A lot of new pilots get End Points and AFR settings
mixed up. I will speak to End Points in a moment, but lets consider
what the AFR settings do. They provide scale SWASH MIX/AFR menu to get that same +/- 6 or 7 degrees of cyclic.
For the FS-CT6A radio, the AFR settings per channel can be a little confusing. A
lot of new pilots get End Points and AFR settings mixed up. I will speak to End
Points in a moment, but lets consider what the AFR settings do. They provide
scale settings to the collective mixing processor. When you set an AFR channel
to 50% (for example) the collective signal will make a calculation that will
limit that collective input to only 50% travel, but more than that, it will
create an internal linear curve (scale) for that 50%. Basically, it tells the
controller that instead of 30 degrees of motion for the servo at full stick, it
should only move the servo motor 15 degrees at full stick. Now this is where it
gets different than an end point. The new scale will divide that 15 degrees
across the total stick movement, spreading it out evenly. It changes the speed
and distance and direction the collective moves. Notice I did not say channel.
End points effect individual servos, whereas AFR effects all cyclic servos.
The channel labels in the swashplate AFR settings are misleading.
Channel 1 - effects CYCLIC Aileron/Pitch for the Left and Right servos. Only effects the right and left servos, and causes them to move in opposite directions
Channel 2 - effects CYCLIC Elevator. Adjusts forward and reverse flight. Acts on all three servos. Elevator servo moves opposite from the Aileron and Pitch servos.
Channel 6 - effects COLLECTIVE pitch. Adjusts maximum pitch. Acts on all three servos. Moves all three servos in the same direction.
To experiment, set all of the AFR settings to 0 (zero).
Watch the graph in the software. With all set to 0% you will notice that your right stick has 0% control... nothing moves.
Also the left stick only controls the motor CH3 and the rudder CH4.
Now increase just the CH1 AFR setting to 80%.
Watch the graph. Notice that the CH1 and CH6 servos can now be controlled with the right stick, but only left and right. They only
move 80% of their full travel (that is what we set it to). This is for banking left or right, but not going forward or reverse. Notice that if you move the right stick Up and Down, nothing
happens. Also, the Left stick still does not control anything.
Now change the CH2 AFR setting. Put in 80% - This allows us to control forward and reverse.
Now the right stick Up and Down work on all three servos. CH1, CH2 & CH6 (Aileron, Elevator & Pitch)
Notice your left stick still does nothing....Lets take care of that now.
Change the CH6 AFR setting to 80%. Now your left stick will cause all three servos to move. This controls the total amount of
pitch (how far the swashplate moves). With a pitch gauge, you can measure the
pitch of the blades with the flybar level, the left stick all the way up, and
keep lowering the AFR CH6 setting until you get 9 degrees of pitch. When you get
better at flying, you can increase the number to get more pitch to play with.
I was using + positive 80% numbers in these settings, but that may not be correct for your setup. Here is what you do.Hook up your helicopter and set throttle hold switch
so that the motor will not move.
Use you right stick and move right. The servo on the right should go down, and the servo on the left should go Up. If the opposite is
happening, then change the +80 to a -80 for CH1 AFR settings. That will reverse
it.Now for CH2 AFR, move the right stick Up. The two
side servos should move down, and the rear of the swashplate should move Up
(forward flight). If it is opposite, then change the CH2 AFR to a -80. See how
that works? Finally, we move to CH6 AFR settings. If when you
move the Left stick UP, the swashplate should go Up and stay level. If it is
opposite, then change the CH6 AFR setting to -80.
Only use Endpoints to prevent binding or servo horn to gear
contact, and then keep the collective channel endpoints the same
value so they maintain the same rate/scale.
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