Attitude Indicator Overhaul

Banjo33

Banjo33

Line Up and Wait
Joined
Sep 21, 2011
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903
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Southern Indiana
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Display name:
Banjo33
I have an AI that was starting to lean randomly back in 2019. Sent it into one of the recommended/popular shops for overhaul. It came back working better but started to lean randomly again a few months later, so I sent it back to the same shop for a warranty repair. 5 months later, it's doing it again. I can send it back to the same shop, but they want me to pay for a new overhaul (it's well-outside of the original warranty window now...but they've offered to give me a 10% discount). This AI is my standyby (I'm running a G5 as primary now), but it's needed to drive my attitude-based autopilot. Are AI overhauls generally successful and this shop has done a poor job thus far? Is there a point where it makes more sense to go with an "exchange" unit or splurge for a "new" one? I'd like to get it right the first (third?) time as lack of a trustworthy autopilot over the last 2 years has affected the utilization of my plane. Just trying to decide where my money's best spent.
 
What's your suction reading on your vacuum system? Mine was pulling too much vacuum and burned through several gyros. Rather than trying to fix the antiquated system I just removed it.
 
Mtns2Skies said:
What's your suction reading on your vacuum system? Mine was pulling too much vacuum and burned through several gyros. Rather than trying to fix the antiquated system I just removed it.
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It's set right on 5.1" on both a digital and analog instrument.

Too much vacuum burned them up? How high were they?
 
Can your AP not use the G5?
 
Helpful if you give more information. KI-256 are junk from the get go, and very few shops know how to overhaul/repair them.
 
WDD said:
Can your AP not use the G5?
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G5 cannot supply attitude information to attitude based autopilots. However, the GI275 does have that capability for some autopilots.
 
How is the G5 able to drive the Garmin GFC 500 autopilot in that case?

I probably am not up to speed on how autopilots work. Don’t all autopilots have to have attitude information from an attitude indicator of some sorts? Or do a lot of them have their own internal attitude capability?
 
WDD said:
How is the G5 able to drive the Garmin GFC 500 autopilot in that case?

I probably am not up to speed on how autopilots work. Don’t all autopilots have to have attitude information from an attitude indicator of some sorts? Or do a lot of them have their own internal attitude capability?
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Because Garmin unlocked that functionality for their autopilots, but not the legacies.

It’s a 52D67.

APs are either (generally) attitude-based (Attitude Indicator) or rate-based (turn and bank).

GI275 will run it and so will an Aspen, but I have a G5 and am happy with it.
 
What if you moved the G5 to back up and got a G275 for your primary to drive the AP? Cost more than fixing the old AI, but you’d be done with paying to keep a vacuum driven AI working
 
WDD said:
How is the G5 able to drive the Garmin GFC 500 autopilot in that case?
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It's an all digital interface. Attitude based autopilots usually use an analog attitude input.
WDD said:
I probably am not up to speed on how autopilots work. Don’t all autopilots have to have attitude information from an attitude indicator of some sorts?
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No. Some are rate based and get the info from a turn coordinator.
WDD said:
Or do a lot of them have their own internal attitude capability?
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The most recent ones either have their own AHRS (e.g. Trio) or are tied into an AHRS (e.g. GFC500)
 
Sounds to me like you have dust polluting the AI. Assuming you replace filters as recommended, old hoses deteriorate and rubber dust gets whisked into the system. Maybe be a leak allowing dirt to enter system.

Another issue is a bad regulator, which also results from dust in the system.
 
I'd overhaul exchange, removes the offending core out of the causality loop.
 
asicer said:
Some are rate based and get the info from a turn coordinator. The most recent ones either have their own AHRS (e.g. Trio) or are tied into an AHRS (e.g. GFC500)
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TC, yep, was drawing a blank on the name, lol.

Clip4 said:
Sounds to me like you have dust polluting the AI. Assuming you replace filters as recommended, old hoses deteriorate and rubber dust gets whisked into the system. Maybe be a leak allowing dirt to enter system.

Another issue is a bad regulator, which also results from dust in the system.
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I change the filters at every annual and we’ve verified no leaks in the system. The hoses are all in good condition, but if it were dust, wouldn’t the overhauler tell that me the instrument was contaminated after having to redo an overhaul within 6 months of the first?
 
Banjo33 said:
TC, yep, was drawing a blank on the name, lol.



I change the filters at every annual and we’ve verified no leaks in the system. The hoses are all in good condition, but if it were dust, wouldn’t the overhauler tell that me the instrument was contaminated after having to redo an overhaul within 6 months of the first?
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They might. It is common to look at the bearings under magnification to see if there is dust. Also just because the hoses look good doesn’t mean they are. If they are 10 years old they probably need replaced.
 
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