Power up and set the gyro to rate mode. Center the trim. (Note: Your heli should fly straight in this configuration before you take this measurement.) With a pair of calipers, measure the space between the slider and the tail box. This measurement does not change if you are only swapping the servo. Changes to the main blades, tail blades, curves, pulleys etc will require you to manually recenter your servo and take a new measurement.
The correct measurement for my King is 3.1mm. In the photo, I had just swapped the tail servo and it needs adjustment.
I'm sure the old pros know about this but I've never seen it mentioned anywhere.
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"...the helicopter symbolizes the victory of ingenuity over common sense."
HBK2, SG-90 cyclic, S3114 tail, Dynam 25A, KA400H motor, Telebee ATV, AR6100e
EXI 450, HXT-900 cyclic, S3114 tail, Hobbywing 40A , Scorpion 8, Telebee ATV, AR6200
