Altimatic III roll sensitivity

[Kevin Weidner]

Hello,

We have been having some troubles with our Altimatic III lately. First, we had trouble with it intermittently tracking a nav source. It would act sluggish, then start working normally sometimes. Then we had a total failure of the roll servo. We took it to Muncie, IN for 3 days and had the airspeed controller, coupler, amplifier, and roll motor replaced or serviced. After all of this, they (Rocky Paul was the one working on it) thought it was finished, and sent us home. We noticed that the roll was very sensitive and seemed to over correct when turning or tracking anything, and just figured it needed an adjustment. The other issue was that the pitch control switch was now intermittent (it had never had an issue before). We knew this before we left, and they took the switch apart several times with no improvement. The electric trim works when it is pushed in, but the switch has to be just right to engage the pitch servo.

So, we called them when we got home and scheduled an appointment for the roll adjustment. They did not have time for the switch that day. However, on the way there that day, the roll completely gave up the ghost again, just as it had done before the first appointment. So when we got there, they said the amplifier was messed up, and put yet a different one in, which checked out good on the bench. This change of the amplifier made the roll work again, but just like it had the day we went home, which is very sensitive. They told us not to turn it on again until they work on it again.

So, after all that background information, here are my two questions; does anyone here have any experience with a problem like this, where the roll is over sensitive, and appears to be damaging the amplifier?

Second, does anyone know where we can locate a good used pitch switch for the controller? Rocky told us that there is no such thing as a 'new' switch for this system, so we may be looking for a good used one if they cannot get it working better the next time we are there.

Thank you for your time.

[Kristin Winter]

What is the pitch switch? I have some extra control heads, though I don't know if they work right on not as I haven't tested them.

[Kevin Weidner]

The pitch switch I am referring to is the push button on the lower right corner of the control head, which engages/disengages the pitch function of the autopilot. (looks just like the ROLL, HDG, and ALT switches)

[Kristin Winter]

OK! Now I get it. I think I have an entire spare control head that I don't think I need to save for Maggie. If you don't find a switch, shoot me an email at kristin_winter at comcast dot net.

Have you tried Autopilot Central in Tulsa for parts?

[Kevin Weidner]

We left the airplane over in Muncie last week, and they did end up getting it fixed. It turned out to be a strand of braiding on a wire shielding was touching one of the other pins behind the attitude gyro, and this was causing a bad ground, which made the roll 'hunt' for a level indication.

They also seem to have fixed the pitch switch for now. They were fairly confident that it would hold up, but we will find out in time I guess.

Hopefully we can get 5-10 years of good service out of the autopilot now without any trouble.