Attitude indicator failures on fresh overhauls?

MN_Flyer

MN_Flyer

Pre-takeoff checklist
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MN_Flyer
Quick question for you guys.....

I had a Piper Arrow that was on the ground for about a month for an avionics upgrade and then an annual inspection. After the annual, the attitude indicator decided that it would intermittently indicate a climbing left turn while in level flight. The suction gauge indicated 5 inches of vacuum and the DG would still respond properly. This also happened when using alternate vacuum. I had an overhauled instrument installed and the new instrument was indicating a left turn in level flight occasionally. The avionics shop decided that it must have been a bad overhaul. They installed yet another AI and a couple new hoses just in case. This one occasionally shows about a 15 degree left turn while in level flight. I had my maintenance guy look over the entire vacuum system and he discovered no issues. He consulted McDonald who overhauled the two replacement instruments and they suggested that we replace the instrument.... again.

Is this a common problem with overhauled attitude indicators? Is there any way the shop can bench test an AI for this type of intermittent problem? My mechanic says that he has inspected the entire vacuum system and found no issues. It just seems strange that a bad instrument can be intermittent like this.

Thanks in advance for any words of wisdom that you guys may have,
Dan
 
This doesn't really relate to your situation but it's a story about troubleshooting a bad attitude indicator that carries a lesson.

This was a B-747 100 that was parked outside the maintenance hangar. It was noted that the Captains AI was indicating a slight climb while the FO's was level. So, suspecting a bad instrument the first step was to swap the two and see if the problem followed. It did, the Captain's instrument continued to display a climb when put in the FO's spot and the FO's showed level in the Captain's position.

So a new instrument was ordered and when installed it did the same thing, showed a climb. At this point management got involved and the entire troubleshooting process fell apart. Gyros were swapped back and forth, replaced, wires were rung out, the instrument was replaced for a second time. All to no avail, the problem persisted.

To make a long story short - it was the FO's AI that was bad, the one that was indicating level, because the airplane was parked at a slightly nose high attitude (the nose wheel was on a ramp services access cover)

Again, not related and sorry for deviating off topic but your issue just reminded me of it and I thought it would be an interesting story.
 
I had a similar situation with our 1973 Arrow II. The attitude indicator showed a slight (3 degree) left turn in level flight, not a big deal but very annoying in IMC. We have had it adjusted and later rebuilt, yet it continues to do the same. We are going to replace it with something completely new, which is the topic for another post.
 
Speaking of overhauling AIs, I have a good working unit, that just needs the glass replaced (foggy). any suggetions on a reputable shop?
 
I've had bad luck with Airparts of Lockhaven. And they have bad attitude, too.
 
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