View Full Version : GPSS VS?

Bayou Bert
04-02-2019, 06:23 AM
I continue to have issues with my Vision 385. Since I posted a couple
of weeks ago, I have installed the new version, stronger black motor
pitch servo. I flew with it yesterday and it is not as trim sensitive as
the old servo, good so far.
BUT something is still not right with either the AP or EFIS.
I have learned to zero the VS on the AP so that the EFIS/650/AP
can talk together.
Yesterday on take off I dialed in altitude on AP and then in EFIS entered
same altitude in HD/Alt mode, zeroed the VS in the AP and it captured
the altitude and just after it leveled off it aggressively started to climb.
Whoa, turned of AP then on again, showing GPSS VS and all was good.
Then I let the AP fly the RNAV35 at KREG, home port. Flew the procedure
turn great, lined up on right heading to airport. After IAF it steps down
from 2K to 1.7K to FAF. I stepped down, AP did great, then about 1 mile
from FAF, glide slope just starting down from top of display, the AP aggressively dived the plane. Let it go for a second but it appeared to be
still pushing I turned off AP and recovered at 900 feet.

So, thought everything was good, then the dive. I am building a big
no trust in the AP and that won't work on a real approach.
Suggestions appreciated. Didn't even call TT, sure they are at FNS.

04-02-2019, 07:09 AM
I know with mine if I am not trimmed out properly I will get an aggressive push.

04-02-2019, 07:38 AM
I have a Garmin 307 auto pilot and it was doing the same thing. Garmin sent me an auto pilot tuning guide. This was totally separate of installation and the manuals. I followed it step by step and my auto pilot works great now.
I imagine you have the same issue, it has to do with your settings.I would get ahold of the manufacture they will have a guide to tune it.

04-02-2019, 09:55 AM
If I remember correctly, you have a GRT HX for EIFS, right?

If so, have you changed/modified the servo gains and torque? I can't remember if GRT has torque setting but definitely it has gains and those need to be modified.

Also, the out of trim most likely would not do this as it will give an indication of trim needed and it will only apply more force on the servo.