Dying attitude indicator?

cowman

cowman

Final Approach
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Cowman
So some quick background, this AI is a sigmatek and I had it rebuilt after it tumbled in flight ~200 hours ago. It is a typical vaccum powered AI.

A few flights ago I noticed after shutdown that it was spinning at a high speed.. looked like a front-load washing machine on spin-cycle. On the next startup it appeared tumbled but righted it's self by the time I completed my run-up.

I've had several flights then and it's been normal on some and on others doesn't start working for a minute or two after initial startup. Yesterday I it was really bad, I thought it was done. On startup it did nothing.. and the bank indicator lines(The part that normally remains fixed in place) had rotated almost 90 degrees over and it wasn't moving at all. I thought it was toast but around the time of takeoff again it had righted it's self and was working normally.

I'm assuming I need to contact the avionics shop and get it looked at but I'm just wondering if there's anything I could try beforehand. I've got a long cross country trip coming up in 2 weeks and I don't want to depart with an inop instrument. Suction gauge reads normal, HI is functioning normally so I'm thinking it has to just be in the AI.
 
Drop a G5 in and be done with it.
 
I'm also anti-vacuum so G5 or Dynon D-10a would be easy bets, although I don't remember what Cowman is flying in.
 
I wish I had a G5 or Dynon as well since I had to overhaul my AI a hundred hours ago. I also have an electric HSI, so I could get rid of the whole vacuum system. However, I have to keep my vacuum AI to run the piper autopilot.
 
rolivi said:
Stay tuned... Two or three good options are in the certification process.
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I don't want to hijack the thread, but what products are there in the certification process?
 
I don't have an autopilot but I have a very long multi-leg Vfr cross country trip planned in 2 weeks. I've really got to decide if I want to fly it with a questionable AI or try to get something done.... preferably something my regular A&P can do at my home field within that timeframe.
 
cowman said:
I don't have an autopilot but I have a very long multi-leg Vfr cross country trip planned in 2 weeks. I've really got to decide if I want to fly it with a questionable AI or try to get something done.... preferably something my regular A&P can do at my home field within that timeframe.
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I'm sorry I have no advice. When mine went bad, it would show that I was in a turn when I was straight and level. I am guessing that it could be a real problem if it tumbling. I bet mine would have started to tumble if I had continued to fly.
The only suggestion I have is to preheat the cabin if you are in a cool climate. That seems to make a marginal AI work for a little while longer.
 
Two thoughts: Is there a filter on the AI or between it and the vacuum source that could be clogged? If so, check it.
If it's a VFR trip, take a cover for the AI and cover it if it goes bad. You've got a TC or T&B, right? And it's not required for VFR flight...

John
 
cowman said:
I don't have an autopilot but I have a very long multi-leg Vfr cross country trip planned in 2 weeks. I've really got to decide if I want to fly it with a questionable AI or try to get something done.... preferably something my regular A&P can do at my home field within that timeframe.
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Former cub pilot. I would not worry about it!

You do want to cover it. In the highly unlikely event that you fly into clouds inadvertently, it will be easier to keep wings level by using the turn coordinator if the bad gyro is covered.
 
Makes sense, I lost the AI on my second cross country as a student and yeah it's really not an important thing to have VFR. I guess I'm more bothered by the idea of departing on such a long distance trip without having everything 100%.

I guess we'll run with it and see how it goes.
 
Thanks Cowman. My backup AI started bouncing around yesterday. And my wife is scheduled to take her IFR checkride in a couple of weeks.
 
Welp, after a flight to the south I was able to determine that temperature is a factor, in warm weather it worked perfectly... came back to the cold and it started acting up again. Always returns to functional shortly after takeoff....

Then another thing went happened, on my way home the DG started spinning like crazy. That eventually stopped but it's been of pretty questionable utility since... doesn't really hold it's calibration very well if at all.

I'm wondering if I have a vacuum issue or just two failing instruments. Annual is due so I guess I'll add it to the list of issues.
 
Is the DG on vacuum and working OK? If it is that might rule out the vacuum issue unless you have a problem with the vacuum line to the AI. But to my uneducated mind it seems to be a problem with the AI.
 
My DG started spinning shortly after landing at DNN. After shutdown, and a sody pop, it had plenty of time to spin down.
When I fired up, and took off, it was working just fine. had no episodes since. But I expect it's on it's last leg.
 
We had to replace our AI, then the vacuum pump went out a month or so later. I have heard about the vacuum pump going down causing the instruments downstream to go out first. Not sure if that happened to us or if was just dumb luck. Just thought I would throw that in. Watch the vacuum pump...
 
Maybe put a new Aspen in it? That is what I would do if funds permitted to get rid of the old instruments.
 
Code90 said:
We had to replace our AI, then the vacuum pump went out a month or so later. I have heard about the vacuum pump going down causing the instruments downstream to go out first. Not sure if that happened to us or if was just dumb luck. Just thought I would throw that in. Watch the vacuum pump...
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There is a filter to prevent that normally. When my AI started to die, I ordered a factory refurbished one from Spruce and swap it out, no down time.
 
Welp, our AI is waiting to get replaced. (I think I posted in this thread before) As mentioned before it would wobble on start up and then straighten out within 30 secs. Or a minute. Got in the plane with my instructor and it wobbled for a couple minutes.... then went completely TU. We decided we would do some partial panel IFR things to make the most of our time. Halfway through an approach it righted itself.
One of the partners called our mechanic. He's ordering another AI to swap with ours. Still waiting to hear when that will happen. Will have to be before my commercial checkride for sure.
 
Mine was acting slow and took a LONG time to stabilize. Didn't trust it in IMC so I ordered an OH'd unit from AQI and all in the world is good now.
 
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