Jumping Attitude Indicator

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planeviz

Pre-Flight
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Jan 19, 2012
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Dave G
Has anyone experienced the AI behavior in the linked video? It has been doing this for quite some time now but I have not seen one fail like this before (i.e., if it is indicating a pending failure). This is an overhauled unit I bought in 2008. When the old one failed it did so in the traditional, roll-over, manner.

The plane passed its IFR check less than a year ago and the DG is stable so thinking it's not the vacuum system. Anyone seen this before?

Jerky attitude indicator
 
Huh... Never noticed mine doing that but then again I don't think I've looked at it really close in turbulence - could this simply be an aircraft vibration issue?
 
That's engine/prop vibration. Hard on radios and gyros. Get a dynamic balance done and it will go away. There should be a shop with a balancer close by somewhere.

When I was looking after flight-school airplanes we bought a Vibrex balancer. Something like $4K, but there are cheaper units out there now. A machine like that soon pays for itself in saved gyro and radio work.

Dan
 
Gyros will do this if they're in need of overhaul too. Mine was doing this but, when I started really getting in the clouds for real, this was unacceptable. I got an overhauled unit from AQI ($500) and it's rock solid now. I think AQI does MOHes on AIs for about 350 or so.
 
I had one which just came from an shop on an overhaul exchange do just that. Sent it back. They apologized and sent my original one after they overhauled it. No futher problems. If I had one which just started doing that out of the blue, I'd send it out for overhaul.
 
I was flying (from the right seat) a six place Bonanza on an Angel Flight last weekend and the AI was way off. I was straight and level, but in a bank according to the AI. The TC said I was straight and level, and our eyes said so too. It went back to normal after roughly an hour, we have no idea what happened.
 
I've seen some do that. They've always been the ones with that little curved piece in the bottom like that one. Maybe those are more susceptible to vibration. Ones with a full field "ball" don't ever seem to do it.

I like the dynamic balance idea.

If that doesn't clear it up, at today's overhaul prices and gas prices, you can overhaul a gyro for slightly under the price of two 100LL fill-ups.

One of the only positives about a "steam gauge" panel these days.
 
kimberlyanne546 said:
I was flying (from the right seat) a six place Bonanza on an Angel Flight last weekend and the AI was way off. I was straight and level, but in a bank according to the AI. The TC said I was straight and level, and our eyes said so too. It went back to normal after roughly an hour, we have no idea what happened.
Click to expand...

That one is failing or the aircraft has a vacuum problem.

Next look should have been at the suction gauge.

Filters clogged, loose vacuum hose, cracked vacuum hose, failing vacuum pump (those usually fail instantly and fully though)...

My experience with significantly "leaning" AIs is that they'll roll over and die in the next 10 hours or so, if it's the instrument. Fun to watch, VMC. Not so much fun IMC, I would imagine from recent training.
 
denverpilot said:
I've seen some do that. They've always been the ones with that little curved piece in the bottom like that one. Maybe those are more susceptible to vibration. Ones with a full field "ball" don't ever seem to do it.

I like the dynamic balance idea.

If that doesn't clear it up, at today's overhaul prices and gas prices, you can overhaul a gyro for slightly under the price of two 100LL fill-ups.

One of the only positives about a "steam gauge" panel these days.
Click to expand...

I just looked at KSUN, a fill up in my 150HP cherokee would be more than a gyro overhaul :(
 
bartmc said:
I just looked at KSUN, a fill up in my 150HP cherokee would be more than a gyro overhaul :(
Click to expand...

TacAir at APA has Jet-A on their billboard for more than $2/gal less than 100LL goes for at their Self Serve.

Too bad a 182 turbine conversion price or a diesel wouldn't cover the spread. ;)
 
Thanks for the feedback. Will ask about balancing since the annual is next month. If that and a new vacuum pump (at nearly 500 hours now) don't fix it I will replace it.
 
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