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Attitude Indicator Failure
We (my DOM/IA and I) have now pulled the AI out and I'll probably just take it over to the Part 145 Instruments & Avionics shop on the field for overhaul. I did look on Spruce to see what a newer generation AI would cost - tho in my case the AI drives my Altimatic III autopilot so it would need to be compatible. As it stands I'm betting a simple overhaul is probably the best option.
It's funny... I was not really shocked by the failure at all because on the same morning I'd a couple times thought the AI looked ever so slightly off by showing wings level when the wings were ever so slightly banked. Then the autopilot (Altimatic III) wanted to turn off course slightly when the AI was level and the aircraft was already perfectly on course (i.e. - why turn?). These oddities were so slight and subtle that I wasn't convinced I was seeing it correctly so I just kept a close eye on it.
Another interesting point... on the last few flights my autopilot has been "porpoising" in altitude hold mode. It's always been finicky about setting the altitude with the fussy pre-select knob but once set it would always hold quite well. Last few flights I've been hand-flying at least the altitude hold because of the porpoising. Yesterday I searched the forums and saw a post from Pat commenting on her C2000 porpoising when the AI was on the way out (if I recall the post correctly).
Anyway... any thoughts or feedback on this topic from those who have been down this road before would be appreciated.
Best Regards,
- Charles
Charles Schefer- Posts: 563
- Joined: Mon Mar 12, 2012 7:09 pm
Re: Attitude Indicator Failure
Patricia Jayne (Pat) Keefer ICS 08899
PA-39 #10 Texas
N3322G- ICS member
- Posts: 1911
- Joined: Thu May 08, 2008 1:58 pm
- Location: Fort Worth, Texas area
Re: Attitude Indicator Failure
Same thing happened on my single with same autopilot several years ago.
Nothing to do but overhaul or replace.
Don
Don Nelson- ICS member
- Posts: 312
- Joined: Mon Nov 10, 2003 5:57 pm
- Location: Burlington, Washington; KBVS
Re: Attitude Indicator Failure
Richard Lanning- Posts: 65
- Joined: Tue Apr 15, 2014 11:08 pm
- Location: South Florida
Re: Attitude Indicator Failure
The vacuum pump is new and the relief valve was checked and set. The filters are the canister type right on the AI and I haven't been able to look at them. The only other instrument on the system is a DI and it is new.
I was planning on having it removed and inspected during the annual in a few months, and then probably replacing it unless there is something obvious. Too bad, really. It has a really nostalgic B17 look about it that suits the aircraft.
William Hughes- Posts: 97
- Joined: Mon Apr 21, 2014 9:23 pm
- Location: Saskatoon, SK
Re: Attitude Indicator Failure
Patricia Jayne (Pat) Keefer ICS 08899
PA-39 #10 Texas
N3322G- ICS member
- Posts: 1911
- Joined: Thu May 08, 2008 1:58 pm
- Location: Fort Worth, Texas area
Re: Attitude Indicator Failure
Tom told me that my unit was not an Edo-Aire unit (what he assumed I would have) but in AIM attitude indicator. He said all the Century AIs (whether via Edo-Aire or AIM) are extremely robust and well built. It was stamped 1993 (I think that's what he said) so it's obviously not the original but it did look old and dated. He said the AIM units are a little more involved to overhaul (vs Edo-Aire) but have the added advantage of having a built in filter in the back (which he showed me). My filter had carbon in it which he said was odd because that is more indicative of an AI that's been in a pressure system not a vacuum system. Vacuum pumps have carbon blades so if one fails in a pressure system the result is often carbon in the unit filter. It may be that this unit was in a pressure system before being put in my plane - all before I owned it.
It took a few days but Capital did a very nice job overhauling the unit. It has been completely rebuilt with a new, balanced pendulous mass, all new bearings and a new filter. They also offered to repaint the face which has made it look much more modern as you can see here (below). Not sure the sky blue should be "gloss" vs flat paint but nevertheless it looks very good. I've only ground tested it because I am doing other maintenance but I'll test fly in VMC later this week.
Total cost for the OH was $800.
- Charles