Auto Pilot (420A)

[SkyMac]

Hi everyone

Just sorting through my last remaining bug after the extensive rebuild, and it is proving to be a troublesome little thing. Hard to believe it has been 2 years since it returned to the skies and 103hrs later, yes I'm still smiling!

Need some help, I have been methodically working through the entire autopilot system and struggling to rectify the pitch control.

On the ground the entire auto pilot works fine in every function through every test following the manual for post installation and the pilots guide for pre-operations check prior to flight.

Now once in the air and in level flight, turning on the autopilot it tracks following the heading bug without issue, however within 3 to 4 seconds the pitch will automatically engage and climb the aircraft and continue to pull the yoke backwards, if I apply pressure to the yoke and push forward after some resitsance the autopilot will go into down pitch and continue to push the yoke forward.

Now I have checked all wiring, actuators, reset actuators as per the post installation checks, and as mentioned completed all on ground checks.

Any thoughts? (besides buying an new system) as I want to keep it original.

The other issue is limited experience left in Australia to work on these systems, one last remaining thing to check is the pitch sensors in the A/H (G519A). This is where I need some more help, I will be in the USA in two weeks, is there an avionics shop that can test these pitch sensors I can send it to whilst there?

To wrap this up, I have been 2 years without it as the plane once trimmed is very stable. But it would be nice to have it fully operational.

Let me share a recent photo of some flying over a bit of our high country.

[Jerry De Santis]

Prior to turning the autopilot on, do you set the autopilot vertical trim? On my 400a I preset vertical trim by turning the vertical trim all the way up to the stop, than 5.5 turns down on the vertical trim wheel.

Jerry
N34EC

[SkyMac]

Thanks Jerry

No I have not done that, I will give it a run on the weekend to see what happens. Many thanks for replying.

Dave

[hharney]

Dave
Autopilots Central may still work on these, they are in Tulsa, OK https://www.autopilotcentral.com/index.php/contact-us/

Also I think Jerry said he uses Muncie Aviation in Muncie, IN
https://www.muncieaviation.com/avionics

[kilr4d]

I do the same as Jerry and center the pitch command wheel before turning on the A/P...5.5 turns from either stop.

Strongly recommend you reach out to Jake at Bevan-Rabell. They just IRAN'ed my A/P computers and I'm quite pleased. Jake knows those legacy Cessna components very well. https://bevanaviation.com/

Also Bob Weber at Webair Consulting. http://www.webairconsulting.com/

[SkyMac]

Thanks John

Before trying, yours and Jerry’s suggestion I wanted to rule out the G519A A/H. So I swapped out the A/H with one from a working system last Sunday, same result.

So this weekend I will try the suggestions, the last thing before pulling the computer and bringing it to the USA with me next week.

Appreciate all the support,

Dave

[hharney]

Originally Posted by kilr4d

Strongly recommend you reach out to Jake at Bevan-Rabell. They just IRAN'ed my A/P computers and I'm quite pleased. Jake knows those legacy Cessna components very well. https://bevanaviation.com/

John

You sent your computer into BR? The box up in the attic? What did they do?

[kilr4d]

Originally Posted by hharney

John

You sent your computer into BR? The box up in the attic? What did they do?

Autopilot box up in the headliner:

ACTION: The unit was checked for any applicable ad's before repairing the component.
Inspected and function tested ca-530a flight computer. Found unit to be out of alignment for all modes. Performed factory alignment on unit under test. Verified unit responds to all input commands. Repaired unit i/a/w mfg maintenance manual, unit is operating within mfg specs.

Autopilot control head from the center stack:

ACTION: The unit was checked for any applicable ad's before repairing the component.
Inspected and function tested c-530a control head. Found unit to have loose roll detent pin, aligned pin for roll null. Adjusted roll/trim nulls to mfg specs. Cleaned pitch sync motor drive and inspected drive motors for wear. Verified unit responds to all input commands. Repaired unit i/a/w mfg maintenance manual, unit is operating within mfg specs.

Total bill was less than $1K.