Garmin G3X - Page 756

190-01115-01 G3X™/G3X Touch™ Avionics Installation Manual
Rev. AV Page A-5
10)
Pitch Servo Gain
Tuning
Pitch gain tuning is done the same way the Roll gain tuning was done.
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.
Now we will tune the Pitch servo. The Pitch servo has multiple gains for the various
vertical modes, but all vertical modes are based on the basic PIT mode. PIT mode
is completely controlled by the single pitch servo gain.
The goal when tuning the pitch 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 pitch 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 pitch angle. The pilot should pull or push the stick to up or down 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 pitch 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 pitch gain would be set to 1.0.
Use the table below 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 pitch 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
Pitch Servo Gain Response Cycles