Aspen PFD - adjusting GPSS gain in maintenance mode for STEC-30

[DXB]

My Aspen Pro Max has always been too sluggish in initiating turns in GPSS mode when driving my STEC-30 autopilot.  It it anticipates the turn per instruction from the GTN-650 but still overshoots and then turns back to re-intercept the course.  My internet “research” indicates there’s a GPSS gain setting that can be adjusted on the Aspen in “maintenance mode.” Supposedly the gain scale is 1.0 to 2.0, with 1.0 being the default but 1.5 to 1.75 being recommended for STEC autopilots. Does anyone here have any guidance on this issue and how to accomplish this adjustment? Thank you in advance!

[LANCECASPER]

On 2/27/2024 at 12:52 PM, DXB said:

My Aspen Pro Max has always been too sluggish in initiating turns in GPSS mode when driving my STEC-30 autopilot.  It it anticipates the turn per instruction from the GTN-650 but still overshoots and then turns back to re-intercept the course.  My internet “research” indicates there’s a GPSS gain setting that can be adjusted on the Aspen in “maintenance mode.” Supposedly the gain scale is 1.0 to 2.0, with 1.0 being the default but 1.5 to 1.75 being recommended for STEC autopilots. Does anyone here have any guidance on this issue and how to accomplish this adjustment? Thank you in advance!

I hope you get it adjusted the way you like it, but since STec is rate based rather than attitude based you might find that it is still sluggish and then overshoots. I had an STec 55X 24 years ago and while monitoring it fly the ILS I re-named it the STurn 55X. On the next airplane I had an STec 550, which wasn't any better. 

I did bring the first airplane up to Mineral Wells and they made some adjustments which helped a little, but having a King autopilot before, that flew on rails, the STec was a little disappointing. A big advantage though is that since it gets info from the turn coordinator if you lose the attitude indicator your autopilot doesn't disconnect.