Specifications

MUST be plugged into a receiver channel.
There isn't good documentation for the gain setting available, so the following information is
what I have personally deduced from my own observations, which may not be completely cor-
rect.
The gain setting seems to control how much the tail is allowed to drift before the gyro will cor-
rect the position. It is basically a "fussiness" value. A low gain allows the tail to drift of about 2
or 3 degrees in either direction before the gyro will correct the position. A high gain allows a
drift of less than 0.5 degrees.
There are two factors which limit the maximum gain setting:
For a heli with a tail servo, the limiting factors are the tail servo resolution and the amount of
slop in the tail rotor pitch control mechanism.
If the tail servo resolution is low, then the gain setting must be fairly low to prevent wag.
For a heli with a tail motor ESC, the limiting factors are the tail motor ESC's throttle resolution
and the inertia of the tail motor and tail rotor.
Imagine a tail servo or tail motor ESC with an extremely low resolution; let's say only 9 steps
between the low and high endpoints. So, any position between 0 and 9% is truncated to 0%,
any position between 10% and 19% is truncated to 10%, etc.
Imagine that hovering requires a tail channel position of 57%. However, the tail servo or tail
motor ESC has limited resolution and can only be at 50% or 60%.
If the gyro gain is set very high, then the gyro will be very fussy about the tail position, and will
keep changing the tail position. This will cause tail wag.
If the gyro gain is set fairly low, then the gyro will be less fussy about the tail position and will
allow some drift before correcting the tail position. This reduces or eliminates the tail wag.
If the tail rotor pitch control mechanism has a lot of slop, then the gyro will need to move the
tail servo past the slop in either direction before the tail pitch will change.
If the gyro gain is set to a high value, then the gyro will be fussy and will try to move the tail
servo often. This will cause wag.
If the gyro gain is set to a low value, then the gyro will be less fussy about the tail position and
won't care about small changes in tail position, and this will decrease or eliminate wag.
Many guides recommend the gain value be set as high as possible without causing wag, but
this causes the servo to wear more quickly. I recommend this value be set to a slightly lower
value than the maximum possible value to reduce servo or tail motor wear.
If your transmitter o supports the GY mode (Futaba 8U, 9C, 7C, etc) then you can set the
mode to either heading hold (AVC) or yaw rate (NOR). If your transmitter does not support the
GY mode, then you can set the mode with this formula:
For heading hold mode, take the 50 and add the heading hold gain percentage divided by two,
and this is the percentage of the travel you should use for the transmitter's gyro gain channel.
For example, to set heading hold with 60% gain, then this would be (60 / 2) + 50 = 80% of full
travel.
For yaw rate mode, take 50 and subtract the yaw rate gain divided by two and this is the per-
Technical Appendix
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