3. Installing the Gyro
3.1. Direction of Gyro Action
The correct direction of gyro action is obviously important. Otherwise the heli will go into an
uncontrolled spin. As regards the electronics, the gyro action is determined by three factors, the
parameters
Gyro Orientation
and
Servo Direction
in the GA250-OW, as well as the
normal/reverse setting for rudder in your transmitter. Their correct adjustment can be achieved
by strictly going through step by step the following recipe. This should be done on the
workbench (with throttle hold, and main blades removed):
1) Set the parameter
Gyro Orientation
according to whether the gyro is installed with the top
face showing up (Gyro Orientation = upside up) or down (Gyro Orientation = upside down).
2) Set the parameter
Servo Direction
such that by moving by hand the tail to the left and right
the tail rotor shows the correct counter action.
3) Finally set the direction of the rudder stick in your transmitter (normal/reverse) such that
moving the rudder stick leads to the correct action of the tail blades.
Comment
: If your heli starts spinning although these steps were strictly followed, then the
mechanics is not set up correctly. For instance, the tail rotor may spin in the wrong direction.
Tip #1
: It can be helpful to set the gyro into heading hold mode, since then the reaction of the
tail blades is most easily observed.
Tip #2
: For TRex-type helicopters, the following video may be helpful for accomplishing steps
(2) and (3):
http://www.youtube.com/watch?feature=player_embedded&v=QvI-nW9XcvU
(the
movie is in German, but it should be self explanatory).
3.2. Servo End Points
The next step is to adjust the servo end points such that the tail bridge doesn't bind (maybe you
want to leave 0.5 mm space) but on the other hand the maximal travel range is available to the
gyro.
Servo End Right
determines the maximal travel range for the rudder stick moved to the
right, and
Servo End Left
that for the rudder stick moved to the left.
It seems that some folks adjust the servo end points according to their desired piro rates. For
some gyros this may be an appropriate strategy, but it's not for the GA250-OW. With the
GA250-OW the piro rate is exclusively determined by the rudder signal, and should be adjusted
by the range-limit and/or dual-rate functions in the transmitter. The piro rate could also be
adjusted via the parameter
Rudd Rate
, which does exactly the same as range-limit/dual-rate in
the transmitter. In fact,
Rudd Rate
just multiplies to the adjustments in the transmitter.
3.3. Servo Midpoint
The "correct" adjustment of the neutral (hover) servo horn position is an issue of much
discussion and controversy. The arguments go from "servo mid doesn't matter at all in HH
mode" to "servo mid hast to be adjusted in rate mode for proper gyro operation". Both arguments
are both true and incorrect. The GA250-OW isn't different to other gyros in this point, and you
may follow whatever procedure you like. I recommend the following canonical procedure:
1) Set all rudder trimmings etc on the transmitter to zero and/or mid.
2) Mount the servo horn on the tail servo such as to come closest to a 90° orientation. Try
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