Century IIB Autopilot Calibration

[agjolly]

I am having problems with my Century IIB (single axis) autopilot.  It works well in HDG mode.  When I switch the radio coupler to any of the NAV modes the autopilot initiates an immediate right turn even with the CDI deflected left.  Has anyone else had this problem?  I was reviewing the ground/flight calibration procedure in the Century II&III manual (pages attached).  I can understand the instructions all of the way through except in one area.  It seems there is a step missing around paragraph (10) of page 6-5.  I would think the radio coupler would need to be in one of the NAV positions (probably OMNI).  It appears from the procedures that the radio coupler is in HDG mode at this point and I believe it would just be tracking heading and the left deflected CDI wouldn't have any effect on the heading computation of the autopilot.  Am I correct in thinking that the procedure should include OMNI (or some other NAV) mode at this point? 

If there is anyone that has experience with the Century IIB calibration, I would welcome your input.  Anyone else that would have any ideas, I would welcome those also.

   

Edited February 15, 2016 by agjolly

[N201MKTurbo]

First, if it is that bad it is probably a bad connection not an adjustment error. 

Does it do the same thing with all the nav sources?

Does it do the same thing with the nav sources powered off? 

Does it do the same thing in all the nav modes? 

The first thing I would do is reseat all the connectors on the radio coupler.

If it only does it in nav mode and not in heading or attitude mode, your problem is not in the amplifier, so don't mess with any of the adjustments on it.

If heading mode works, then most of the radio coupler works.

It is most likely the +left, +right signals from the nav source. One of them is not connected.

if you have a switch to select nav 1 or nav 2, it is a prime suspect.

 

[cnoe]

It doesn't sound like an adjustment problem to me either. The AI and DG are also tied into that system and can affect system performance. Absolutely before making adjustments use some contact cleaner and reseat the connectors. FWIW a $500 overhaul of my AI solved all my Century IIB problems.

I also agree that the adjustment procedure is somewhat counterintuitive.

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[Steve Dawson]

  On 2/15/2016 at 2:47 PM, cnoe said:

It doesn't sound like an adjustment problem to me either. The AI and DG are also tied into that system and can affect system performance. Absolutely before making adjustments use some contact cleaner and reseat the connectors. FWIW a $500 overhaul of my AI solved all my Century IIB problems.

I also agree that the adjustment procedure is somewhat counterintuitive.

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This is very similar to what happened with my CIIB. I'd check all your connections first then your DG and AI. My cost was $500 also.

[agjolly]

  On 2/15/2016 at 4:50 AM, N201MKTurbo said:

First, if it is that bad it is probably a bad connection not an adjustment error. 

Does it do the same thing with all the nav sources?

Does it do the same thing with the nav sources powered off? 

Does it do the same thing in all the nav modes? 

The first thing I would do is reseat all the connectors on the radio coupler.

If it only does it in nav mode and not in heading or attitude mode, your problem is not in the amplifier, so don't mess with any of the adjustments on it.

If heading mode works, then most of the radio coupler works.

It is most likely the +left, +right signals from the nav source. One of them is not connected.

if you have a switch to select nav 1 or nav 2, it is a prime suspect.

 

Expand  

It does the same thing on all NAV modes (even BC) and both sources (G430 and KX170B).

I haven't tried it with the NAV sources off, I will do this next flight.

I have reseated the connections on the coupler several times.  I haven't reseated the connections on the source relay (assuming it has connections and not directly wired, I will try this also).  

I do have a NAV 1/2 switch but it's a booger to get to.  This will be a near future check if the other checks don't provide a fix.

Thanks for the feedback.

 

[agjolly]

  On 2/15/2016 at 2:47 PM, cnoe said:

It doesn't sound like an adjustment problem to me either. The AI and DG are also tied into that system and can affect system performance. Absolutely before making adjustments use some contact cleaner and reseat the connectors. FWIW a $500 overhaul of my AI solved all my Century IIB problems.

I also agree that the adjustment procedure is somewhat counterintuitive.

Sent from my iPad using Tapatalk

Expand  

I have reseated connections on the radio coupler several times.  I will try reseating all connections that I can find before next flight.  I'm having trouble believing that my AI and DG are suspect since it flys great in Wing Level (only) or HDG mode.  It only acts up when in the NAV modes.  What were the symptoms in your plane that the AI overhaul fixed?

Thanks for the reply!

[cnoe]

Yeah, different symptoms for sure but wanted to reiterate M201MKT's post that it doesn't sound like an adjustment issue. Mine wouldn't adjust to wings-level with the roll knob centered and tracked a bit off center on the indicators. I hear that Autopilots Central in Tulsa is very good with the old Centuries if it comes to that.

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[jetdriven]

Have autopilots central check out the radio coupler. 

[flybylatham]

I just came across this post, was wondering if you ever resolved your radio coupler issue? Having a very similar issue with mine in my J. 

[carusoam]

It’s only been six years since @agjolly checked in last... 

So I invited him to join us for the follow-up discussion... 

See if his email is still attached to his MS account...

Best regards,

-a-

[joepilotmooney]

Century 2B problems - I am having similar issues, my unit tracks good some days, some days bad. Old analog equipment I think will do that, depending on temp, etc.? All the way home last time it was off 1/2 to one full dot off, but at least tracked steady like that. Anyone think it's worth it to overhaul these units somehow, or??

[N201MKTurbo]

  On 7/13/2021 at 10:15 PM, joepilotmooney said:

Century 2B problems - I am having similar issues, my unit tracks good some days, some days bad. Old analog equipment I think will do that, depending on temp, etc.? All the way home last time it was off 1/2 to one full dot off, but at least tracked steady like that. Anyone think it's worth it to overhaul these units somehow, or??

Expand  

If you have a cross wind it will do that. If you move the heading bug into the wind, it will usually take out the error.

[OR75]

start with something more basic before overhauling ....

The connector in the back of the console needs to be seated correctly. The frame/box that houses it makes the "bite" of the connector very "weak" . i would check that first