MidContinent CDI vibrating needle issue

DesertNomad

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DesertNomad
I picked up my plane with new G5s today.

Previously I had a 750 hooked to a MD200-706 and a GNC255 hooked to a GI-106A. I removed the GI-106A and connected the MD200-706 to the CGN255 because the 750 is now connected to the G5.

I am either seeing a weird parallax issue, reflection or my MD200-706 needle is vibrating at a high frequency fore and aft. The needle is clear when it is centered, but if I look at it from off-center it gets blurry. It did this with two different VORs.

A video is here:

http://www.xericdesign.com/archive/CDI-Video.mp4

Is this supposed to be like this? I have had this instrument for just over a year and don't recall it being like this. I got it at last annual in late October 2017. When I dropped off my plane at my shop in late September 2018, it was not like this (at least I don't think so). I just picked it up today and flew it from Portland to Reno.

Naturally, it is 6 weeks out of warranty now... except it has been in the shop since before the warranty expired.

Thoughts?
 
Does it change with engine RPM?

That's something I need to check. I plan to test it on the ground today without the engine running. I normally fly at 2300rpm and have never seen this before. It was doing it at cruise.
 
That's something I need to check. I plan to test it on the ground today without the engine running. I normally fly at 2300rpm and have never seen this before. It was doing it at cruise.

My guess would be that the G5 installation significantly changed the instrument panel's harmonics. Maybe jut changing how the wires are tied up would stop it.
 
Works fine n the ground with the engine off. I'll fly it in a couple days.
 
So dead on, its good but from the side angle, vibrating. So the needle is vibrating fore and aft, not side to side the way I see it. Call MICO and ask them if they have ever seen this. Looks like a disaster waiting to happen.
 
So dead on, its good but from the side angle, vibrating. So the needle is vibrating fore and aft, not side to side the way I see it. Call MICO and ask them if they have ever seen this. Looks like a disaster waiting to happen.

Yup - fore and aft. They have never seen this issue but I am in touch with someone there to run some tests since they know the instrument better than anyone.
 
Does it change with engine RPM?

Yes.

I flew it today and found that it starts vibrating at about 2280rpm, peaks at 2330 and stops at 2350. Since I normally fly at 2300, it is a bit of an issue. I have asked my shop and MidContinent about it.
 
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Swapped the instrument - no change.

Re-balanced the prop (down to 0.04 on the meter) and the problem range moved from 2260-2360rpm to 2220-2320rpm.

Today we’re trying the old GI106A.
 
I'd probably put a shim between the instrument and the panel and retest
 
I have tried touching the panel in different places with no change. The GI6A also vibrates but in more of an up/down and not as severe.
 
Progress as it is stable out of the panel so it seems the old vacuum gyros aided in dampening it. A&P working on a solution. There are sunken holes to screw the instrument in so not sure about a shim or rubber gasket since the vibration would be transferred through the screws.

Maybe the vacuum hoses used to provide a damper connecting the firewall to the gyros??
 
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Progress as it is stable out of the panel so it seems the old vacuum gyros aided in dampening it. A&P working on a solution. There are sunken holes to screw the instrument in so not sure about a shim or rubber gasket since the vibration would be transferred through the screws.

Maybe the vacuum hoses used to provide a damper connecting the firewall to the gyros??

Screw it./.... Buy a G5 HSI.
 
OOOOOhhhh.... A triple G5 in the works! Sometimes ya jes gotta let it go. Ya know..? Accept change. I dare ya to put in another G5.
 
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