55x auto pilot problem

[Topper]

I have a 310Q With a 55x and the step turn coordinator. It commands a less than standard rate turn when following the heading bug. We recently upgraded from a King HSI to an Aspen. We hoped that during this upgrade, that problem would be solved. Still the same, maybe worse. When in gpss mode, the auto pilot will command a standard rate turn and follow the course. I timed a 90 degree turn and it was right around 30 seconds.

I timed a turn following the heading bug, I would consistently keep he bug 90 degrees left of course keeping it in a turn. It would start what appears to be std rate but would shallow out some, hard to tell with the wind bouncing around. I timed the turn and only made about a 180 in a little over 2 minutes. I assumed the turn coordinator was fine since it would make a perfect gpss turn but was told I can't count on that. We pulled the TC and had it bench tested at Mid Continent. They adjusted it slightly, but not likely enough to make a difference. Going to install it Wednesday and test fly. Everyone from Stec to Aspen is scratching their heads. I had the 55x head unit bench tested as well. We also tested the voltage out of the Aspen and it is as expected (not to mention we had a similar problem with the king HSI). Not much left to test, hoping this group has some ideas.

Thanks,
Jim

 

[Cruiser]

did you change the Stec 55x setup to the Aspen configuration?
Is there a difference in response to the GPSS from Aspen vs. the GPSS in the 55x?

 

[Topper]

The aspen is set up to emulate the King HSI that it replaced. I don't have the gpss option on the aspen (my understanding is that it can be set up either way but for some reason it is better to get the gpss from the stec).

I put the turn coordinator back in today and it is better, but still not right, did a 180 in 90 seconds. Here is the weird part, keeping the heading bug about 90 degrees ahead of the turn would produce close to a standard rate turn, but still less than std. If I cranked it to maybe 110 degrees ahead of the turn, the bank would shallow considerably. According to Aspen, anything more than 30 degrees off will send full voltage (15 volts) to the autopilot which as I understand it will look at the turn coordinator and command a standard rate turn. Once it gets to 30 degrees, it sends .5 volts less per degree to slow the turn down. It takes forever for it to go from say 5 degrees to following the heading bug.

Dropped it off at the shop and waiting for them to call when they pull it in, going to check voltage out of the aspen with everything plugged in. If voltages a good, I am guess I will have to send the 55x to Stec. Tulsa is close, maybe should make a trip to Autopilots Central.

 

[Topper]

Update, I think we have it figured out. Configuration error in the aspen setup. In the middle of replacing a prop boot and can’t test fly until late tomorrow or Saturday. Based on voltage checks I think it will work properly. Update after I fly.