I operate a 2005 SR22 and we’re having problems with the STEC 55X. It tends to hold the airplane in a 3 degree bank when tracking a course, holds the heading 5 degrees to the right of where the heading bug is set, blows through an Localizer when it’s supposed to intercept it, and frequently rolls past an assigned heading without attempting to capture it. The avionics shop sent in the AP unit and STEC said the “computer was bad and it they repaired it.” The AP test fine on the ground, but when flown behaves the same way it did before we had work done. Has anyone had something similar happen?
There is a set up procedure after installation of the Stec 55X autopilot. Good chance you need some adjustments done to your unit. I would get ahold of Dave Featherston at NexAir Avionics he should be able to help you out, or steer you in the right direction…
A little closer to home for you is Muncie Aviation. They are not a Cirrus center, but they did some autopilot work for me and I was quite pleased with them. They really know S-Tec.
Bruce, thanks for the advice. My shop called Muncie for several days and left voice messages each day for the Avionics lead. He never returned the calls. My shop wants to now start getting into the servos.
Shane, I had my STEC doing similar crazy things several years ago. Turns out the bungee for the rudder aileron interconnect was frayed on one side. Replaced the bungee and all was fine. Might not be your issue but worth ruling out. This was after I had wasted $500 getting my DG overhauled. The rudder aileron interconnect bungee did not seem to affect trim in hand flying (not that I could notice anyway), but the autopilot sure did not like it.