Bartman

Century IIb not following new IFD 440 in NAV mode

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Ok so after delays and weather issues I finally got my plane back.  My installation required panel work so we installed the new tray and this was not a slide in replacement. I love the IFD 440, IFD 100, AXP322 and the Skytrax 100, but now I have an autopilot issue. Previously the Century IIb would track the 430W in NAV mode.  Now it does great in HDG mode like it always did, but does not follow the IFD440 GPS signal in NAV mode.  I do not and did not have GPSS, but it followed the HSI output from the 430W without fail. It did not make turns, and basically followed what I set on the KCS 55A (kinda like HDG mode), but compensated for wind and drew straight lines for hundreds of miles. 

I read that the Century IIb would follow output from the 430W without GPSS and I think that's what I had, but sometimes required increasing the CDI output signal strength from the 430W.  I do not have a GPSS switch on the panel.  Now there is resistance in the yoke like it is trying to follow something, but definitely not on course and IIRC just gently deviates to the right every time. I spoke with Avidyne support who were very helpful and we went thru the settings pages on the IFD440.  They were happy with everything and referred me back to the installer. I can go back thru the adjustments on the radio coupler, but the fact it follows HDG well tells me that's not it.  I'd say it is a connection, need to clean and reseat the connector pins, some setting on the IFD, new wiring error or connection, or a gain adjument for CDI output. My gut feeling is since the yoke has resistance and feels like it's trying to follow something then it's some kinda CDI output gain setting.

I'm out of town for work for the week and can't get the plane to the installer so I thought I'd see what you guys think. 

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Those two spliced lateral deviation wires did not survive the install.  

Having it track in Hdg mode means the radio coupler, amplifier and servos are all functioning in some capacity.  That’s why you have resistance.  

Fortunately it’s only two wires.  You could even test it by taking test leads and using the HSI pins to connect to the radio coupler.   Then use the 430 as a CDI/HSI and see if it tracks on the ground.   

Your installer should probably tackle this one as part of warranty work. 

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I had a similar issue with my 540 and STEC 30 ended up bringing it back to the shop and they fixed it not sure what they did though.

 

 

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You guys are awesome !

I remember the Avidyne support representative said something about the two parallel wires may be the problem and an easy fix, but I had no idea what he was talking about. Sounds like the 2 parallel wires he was referring to are the Lat Dev L+R wires in the diagram and as Rich and Brad stated above. 

Ill pass this info along and am sure it will speed up the process. 

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1 hour ago, Bartman said:

You guys are awesome !

I remember the Avidyne support representative said something about the two parallel wires may be the problem and an easy fix, but I had no idea what he was talking about. Sounds like the 2 parallel wires he was referring to are the Lat Dev L+R wires in the diagram and as Rich and Brad stated above. 

Ill pass this info along and am sure it will speed up the process. 

Actually, its the Main +Right and Main+Left

 

OOPS, my bad. That's what they call them on the autopilot side of the chart.

Edited by N201MKTurbo

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On Wednesday, March 21, 2018 at 9:58 AM, Stanton R said:

You might have a NAV1 /NAV2 switch and it is in the NAV2 position

Very good thought and thanks for the suggestion.

As it turns out I do have a Nav 1/ Nav 2 switch but it made no difference.  Come to think of it I suppose that could be an issue if they didn't hook that part back up correctly.  I will have access to the plane all of next week and hopefully get this figured out.

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In retrospect although I did require some panel work to remove the old transponder and a CD player that came with the PMA 7000, I regret allowing them to pull the old 430W tray.  I should have done the slide in replacement on that, and just have the remote transponder installed and CD player and old KT76A trays removed and called it a day.

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Ok so after some delays I finally got it to the shop. As it turns out they did not remove the 430w tray and did not put in a new Avidyne tray. That means they did not have to re-wire the trays or anything like that so no wires to get crossed or messed up. I have tested numerous times over the past couple of months and could not get it to follow anything in NAV mode including GPS, ILS, LOC but works fine on HDG mode. It felt like it coupled, but didn't really follow anything and just slowly drifted to the right every time. This week they tested on the ground and said it worked on the test equipment, but when they did test flight said it was turning in the opposite direction and said it did the same when they tested again on the ground turning in the opposite direction. They want to send the control console and radio coupler to a specialty shop for rebuild and said not very expensive but didn't indicate a price. 

1. Does this sound right ?

2. Is it worth the money and effort ?

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On 3/23/2018 at 11:55 AM, Bartman said:

Very good thought and thanks for the suggestion.

As it turns out I do have a Nav 1/ Nav 2 switch but it made no difference.  Come to think of it I suppose that could be an issue if they didn't hook that part back up correctly.  I will have access to the plane all of next week and hopefully get this figured out.

My shop deleted my NAV1/NAV2 switch because it doesn't exist in the diagram that Rich posted above.  I'm still not happy about that.   

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Final thread resolution time. 

My Century IIb worked great before my IFD 440 upgrade and everyone thought it was the parallel wires for righ and left deviation. The avionics guys at KIOB checked that and no joy. We considered replacing all the wiring, but before that we sent the autopilot radio coupler and control head to Bevan Rabell and got it back earlier this week. Fellow Mooney pilot @Jkeene02 had to go there for transponder issues so we picked up Thursday. Bevan Rabell found some minor issues but the biggest thing they found I was told is the sensitivity adjustment (roll threshold) was way way high. It worked perfect with the GNS430W and no adjustments were made to the autopilot during or after installation of the IFD440. After installation of the refurbished radio coupler and control head it follows NAV 1 and NAV 2 GPS, VOR, and ILS all rock solid and straight as an arrow. The thinking is maybe the sensitivity was jacked way up to work with the 430W or maybe there was a problem with the GNS430W, but was too high for the IFD 440. Anyway, I am pleased with the work from KY Airmotive at KIOB, Bevan Rabell charges were minimal, the old Century IIb is now once again draws straight lines and Bartman is happy.

Hope this PIREP helps someone else. 

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