As a small addition to this thread I would like to say that I have over the years flown in excess of twenty five different R22 and R44 ships. A large number of these had an AI that would fall all over and that most of them would do it fairly quickly after erecting while still on the pad.
One maintanance guy said it was due to all the EOL's carried out in them in the training role and the general banging and bouncing of the airframe by students landing. Not sure if this is true but had to agree tha ships we did the majority of EOL's in did have the worst AI's.
The point being that when you are talking about the bottom end of the instrument equipment market ie. that fitted to an R22 compared to IFR S76 and its subsequent maintanance or lack off then it may well be that you can not believe your instruments.
Stay out of the cloud is the only sure way to gaurantee coming home.