190-01115-01 G3X™/G3X Touch™ Avionics Installation Manual
Rev. AV Page A-4
9)
Roll Servo Gain
Tuning
The autopilot should now be engaged and roughly holding the aircraft straight and
level. The autopilot should be in PIT/ROL mode commanding a roll attitude of zero
degrees and a pitch attitude that roughly holds altitude for the given power setting.
First we will tune the Roll servo. The Roll servo has a single gain it uses to fly all
lateral modes of the aircraft including ROL, HDG, GPS, LOC, VOR, and LVL.
The goal when tuning the roll servo gain is to have the gain large enough so the AP
can quickly and accurately control the aircraft, but have the gain small enough so
the AP doesn’t become overly aggressive to control deflections or turbulence.
To tune the roll servo gain, allow the aircraft to settle in its steady state, then use the
control stick to quickly over-power the servo and displace the aircraft from the
desired roll angle. The pilot should push the stick to the right or the left for roughly
one second and then release the stick.
After releasing the control stick see the AP response by watching the control stick.
The desired response is called a “dead beat response”. As the stick returns to
neutral, it will just move into position and stop “dead” without cycling back and forth.
As you increase the gain above the dead stick response, you will see the stick
“bounce” or “cycle” once, twice, or even three times.
The recommended roll gain setting is one half the gain value that causes a “three
cycle response” to a quick control stick input. So if a gain setting of 2.0 caused a
three cycle response, the roll gain would be set to 1.0.
Use the following table to find the dead beat, one, two, and three cycle response
points if possible. Then set the roll gain to one half the value it was set to that
created the three cycle response.
WARNING
Increase the roll servo gain slowly to make sure the AP does not
become overly aggressive and be prepared to disconnect the AP.
Table A-1 Flight Test Outline
Task Description
Roll Servo Gain Response Cycles
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