200A Navomatic

OkieAviator

OkieAviator

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OkieAviator
I have this 200A Navomatic wing leveler installed in my plane. Here's a picture of the thing. I've read through some old documentation I found on the internet to try to see if it works but I'm not having any luck. I turn the A/P switch to on.. press Dir Hold and nothing happens. The only time I see anything is if I switch from Nav 2 to Nav 1, then both the CDI go full deflection to the left and up. But nothing after that.

Looking in the log book I can't find anything about the servos being removed or really anything about this device. I'm speculating it's all in there but really don't know.

So my multi part question is for someone who has used this, is there a better way to test this? Going off the assumption that it's broke should I just slap an inop sticker on it until I get it removed at a future date? Lastly where would the servos for the ailerons be if they're in the plane? For reference it's a 1977 172N.
 

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I haven't found too much information out there on the 200A. I have one in my cardinal, and the POH is about all I can find. I did find a site on repairing the 300A, and it made mention that the 200A is just about worthless. I can get mine to hold the wings level, and I can get it to do a turn using the knob. But nav track and nav capture seem to be a bit too much to ask.

It looks like you have replaced the VOR indicator. That may be the issue with yours. Also, do you still have the original turn coordinator? The 200A gets its information from the those, not the DG. So if you don't have original or compatible units, then the 200A isn't getting any information for it to do its job.
 
I'm guessing it's the original turn coordinator. It's hard to see in the picture but it's the old dog house style kind not the little airplane picture kind.

I read on the 300A info about it linking to the turn coordinator. So do you just hit A/P on, Dir Hold and it starts working?
 

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OkieAviator said:
I'm guessing it's the original turn coordinator. It's hard to see in the picture but it's the old dog house style kind not the little airplane picture kind.

I read on the 300A info about it linking to the turn coordinator. So do you just hit A/P on, Dir Hold and it starts working?
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On mine, yes. Actually, re-reading the POH, there are a few steps, and you have to push the turn knob in for direction hold.

On your CDI, does it have the back course light? That will be a big clue as to whether its compatible or not. There is a back course button on the autopilot. When you push it, it will turn on an amber light next to the letters BC on the CDI if its the original, and the course indicator will now reverse sense (yes, I mean that) so that when you are on the back course you don't have to switch up mental interpretation of what the CDI is telling you to do. Whether the AP is on or not is irrelevant to whether the back course button will cause the CDI to reverse sense.
 
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Here are the relevant pages from my POH. This give a good description of the system design, and how to use it.
 

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OkieAviator said:
I'm guessing it's the original turn coordinator.
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That doesn't look like the correct turn coordinator. That's a turn and bank indicator.


And going back to your original photo, those are bendix king indicators, not the original Cessna indicators.
 
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Thanks. Going to print out those pages for the next time I fly. If I can't get it working I'll just placard it as broken and never touch it again. Not really worth installing a new AP of any axis on the plane.
 
OkieAviator said:
Thanks. Going to print out those pages for the next time I fly. If I can't get it working I'll just placard it as broken and never touch it again. Not really worth installing a new AP of any axis on the plane.
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Good luck. Let me know how it goes. Honestly, I think you are going to have difficulty because of the replaced turn coordinator and CDIs. But you won't know until you try.
 
PPC1052 said:
On your CDI, does it have the back course light? That will be a big clue as to whether its compatible or not. There is a back course button on the autopilot. When you push it, it will turn on an amber light next to the letters BC on the CDI if its the original, and the course indicator will now reverse sense (yes, I mean that) so that when you are on the back course you don't have to switch up mental interpretation of what the CDI is telling you to do. Whether the AP is on or not is irrelevant to whether the back course button will cause the CDI to reverse sense.
Click to expand...

One little caveat to this-- the back course light only illuminates if you are tuned into an ILS/localizer, and you push the back course button. It will not illuminate if you are on a VOR frequency when you push the back course button.
 
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It is also possible that the sheer pin in the servo broke. If the same as the 300A, that is about a $70 part and about an hour of labor to fix.

Jeff
 
OkieAviator said:
Where are the servos located?
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Should be the right wing, behind an inspection panel.

The sheer pin can be a really PITA to change. Should be a 20 minute job, but it takes an hour, in our experience.

Also the pin weighs about a third of a gram, so by weight, it could be the most expensive part on the plane. :eek:
 
That mtnflyers is a good article and where I was getting my information from mostly. Thanks for the lead on the autopilotcentral and the servo location. I know exactly where that access panel is.

I'll take a look and see if it's still there, if it is then I'll debate on getting it fixed. I flew last night and messed with it with no response.
 
I agree with PPC, there ought to be a G300A turn coordinator in that system (which looks like a run of the mill turn coordinator on its face).
 
flyingron said:
I agree with PPC, there ought to be a G300A turn coordinator in that system (which looks like a run of the mill turn coordinator on its face).
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On some systems the AP turn coordinator can be located remotely. Any chance, it was moved? In my Mooney, some of the hardware is located in the avionics bay in the back, other stuff is behind the panel (like my Aspen ACU). Might be worthwhile to see if they did something silly.
 
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Marauder said:
On some systems the AP turn coordinator can be located remotely. Any chance, it was moved? In my Mooney, some of the hardware is located in the avionics bay in the back, other stuff is behind the panel (like my Aspen ACU). Might be worthwhile to see if they did something silly.
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You are correct that almost anything could have happened. But I think it is highly unlikely. I don't know why you would move the original turn coordinator to some remote and hidden location just so that you can put in a more rudimentary turn and bank indicator in the panel. If it was function such that you could even still get it to talk to the autopilot, why move it? My guess is the original compatible turn coordinator died and was replaced with something cheap and available.
 
PPC1052 said:
My guess is the original compatible turn coordinator died and was replaced with something cheap and available.
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That is probably more accurate. I'll see if I can find an entry in the log books, I need to scan them anyhow.
 
I don't if you had any luck with this, but after re-reading the manual, and trying to get my 200A to nav capture, it actually seemed to work. :yikes: The issue I now have is that my turn coordinator give a smooth indication. The wings on the little plane often rock back and forth a little more dramatically than should be reflective of my actual changes in my rate of turn. I suspect my turn coordinator could use a cleaning/overhaul. It works, for the most part, but it just rocks a lot. The result is that on at least one occasion, it seemed to be causing the AP to rock the wings back and forth rather than simply hold the wings level.
 
PPC1052 said:
Here are the relevant pages from my POH. This give a good description of the system design, and how to use it.
Click to expand...

Thanks for this post - I've been searching for details on the 200 as it's installed in a 172 I'm about to start flying and wanted to have more of a clue than I did. Much obliged!
 
J Scott said:
Thanks for this post - I've been searching for details on the 200 as it's installed in a 172 I'm about to start flying and wanted to have more of a clue than I did. Much obliged!
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Glad to help. Read the manual carefully and make sure to read each step. There is much about its operation that is not at all intuitive. In particular, read steps 7 and 8 on NAV CAPTURE to make sure you understand it. In short, even on a good day, the 200A needs a lot of help.

One gotcha is the Back Course button. If pushed, it will cause the compatible indicators to reverse sense on localizers, EVEN IF THE AUTO PILOT IS TURNED OFF.

Also another gotcha, which may or my not apply to you, depending on whether you still have the original audio panel, is the sensitivity switch ("HI SENS"). The autopilot instructions tell you to push it in for NAV CAPTURE, and and to leave it engaged for localizer tracking, and leave it out for VOR tracking. High sensitivity "on" for the localizer. Ok, fine. Makes sense. But on the original ARC audio panel (which we still have installed), there is also a sensitivity switch ("HI/LO/TEST"). On that switch, they tell you to put the switch on "HI" for VOR tracking, and "LO" for ILS/LOC tracking. Ugg. I can never remember which one is supposed to be high for VOR because they are the exact opposite.
 
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Taking notes - I will be exercising the 200 fully in CAVU before counting on it in the soup. Thanks again!
 
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