Autopilots

[side241]

I have a 400A in my T377C. The thnig has worked on navigation, but alt. hold never really worked well. I just attributed the alt. hold problem on simply being the best technology offered in 1968 (but maybe I'm wrong, please advise). But recently, it started to only hold a course intermitantly, because the center manual turn knob seems to not release control of the rolling axis even though the knob is pushed in. For a while, if I jiggled the knob the AP would navigate again, but not anymore. I live close to SoCal, anybody have any recommendations on having it repaired? I fly single pilot IFR often, and would love a reliable AP, but it seems S-Tec did not get an STC for the TURBO 337C, just every other model of 337. All input appreciated,
Ben

[Ernie Martin]

I have the same unit in my Skymaster and everything works perfect, including altitude hold. I'm an engineer who spent 20 years in the hi-tech space business and I have been very pleasantly surprised at how well it works.

Others may disagree, but here's my suggestion: try to get the unit repaired. In the end I think you will be satisfied with the results and, if you do it right and depending on what's wrong, I think it will cost far less than installing a new S-tec unit.

Part of the problem is finding someone who knows these units. If you can't find such a person near you, the units can be removed from the aircraft and sent to one of several companies which have the needed expertise. I say "units" because I believe there are two main boxes, the one with controls under the panel and a larger box (with most of the electronics) typically overhead, behind the headliner above the rear seats. In addition, there are other elements of the system throughout the aircraft, such as a servo and gear unit in one of the booms. But if you reach a knowledgeable person, he/she should be able to diagnose the problem and tell you what units to send for repairs.

If you choose to go this route, do some "Search" on this message board to see if the name of some of these companies appear. I have the name of a retired fellow who is an expert on these systems. By phone he advised me and my A&P on the repairs needed when my 400A had a problem. He might be able to suggest companies. I can look for his phone number if it would help.

Ernie

[kevin]

I agree completely with Ernie. My 400B worked perfectly, altitude hold included. Autopilots Central, in Oklahoma City, is a good place to start for expertise with this equipment, spare parts, overhaul, etc.

Kevin

[KyleTownsend]

We have the 400A as well. After having it worked on a couple of times in the past 5 years, it works great most of the time. The other 5%, it doesn't seem to work at all.

Anyway, Autopilot Central in Oklahoma is well known as an expert on these systems. I see them recommended more than anyone else, and this is who we used. They did a good job. It wasn't cheap.

I believe there is another shop in Illinois that is considered highly skilled in working on the 400 series. I could probably find the name if you want it.

I believe I have heard mention of a shop in CA that works on these, but the name escapes me. I would suggest talking to Tom Carr or Tom Rogers at Cessna Pilots Association. I am sure they would be able to recommend someone.

At the risk of repeating something you already know, it is very important to have the airplane level and properly trimmed before engaging altitude hold. If it still doesn't work, then you've got a problem.

I think we have reached the point where, the next time the AP really starts acting up, it's time for a S-Tec. We have spent enough on repairs to make a major down payment on a new system already.

Good luck!

[Pete Somers]

The 400A is a very good autopilot, but like everything requires some TLC.

The problem with the turn control is the micro- switch that needs adjusting so that it goes into the recess on the cam attached to the turn control.

Your ALT hold problem is either the Autotrim is not working or the pitch servo is not working.
Does the A/P pitch sync ok when switched (ie does the white pitch wheel run and then stop and the pitch should eng ).

The ALT hold should work from a climb or descent, as long as the autotrim and pitch servos are servicable.

Spares units are avialable from Airwich Avionics, at Wichita.

Let me know if you need any help.

Pete Somers

[JediNein]

Greetings,

You're in the right state!

Get ahold of Ron Hitchcock at Executive Autopilots in Sacramento. The number is 916-399-5969. Tell them that Bridgette sent you.

Usually, they like to see the entire airplane for a test flight. They look at:
Control Cable tension
Pully lubrication
Autopilot Computer functioning (they usually have a spare for the flight)
Cable connections
and a lot of other things are on their troubleshooting checklist.

Ron will also give you the straight scoop on if it is better to repair or replace the 400A. I observed Ron turn down a planned 55X installation in favor of repairing a 400B in a T210 recently. The 400B problem was a dying computer. Remove, replace, tweak, and the autopilot and aircraft owner have been happy since.

Good luck and let us know how it goes.

Fly SAFE!
Jedi Nein