ARTIFICIAL HORIZON PROBLEM ?
Not sure if I understand what is happening with my Artificial Horizon in my Vans RV6. It is a standard vacuum unit that is driven by the vacuum pump on the back of Lycoming 0-360 180 BHP. The vaccum gauge reads just over 5 in the cruise at 2200 to 2400 rpm. Twice recently when I have been flying at 2000 to 3000 feet in temperatures of about 6c to 12c, after about half an hour, I notice that it is starting to show a progressive nose down indication, then it slowly over about ten minutes starts to rolls over to the left and steep nose down. As soon as I land and am taxying the unit seems to be correct with a level nose up indication (taildraggerRV6).
This is the second time this has happened, but seems to be only at higher altitude ?? The reason I say this because, it happened on Sunday going over the Channel to LFAT luckily in clear visability, but on the way back I flew at 1500 to 1700ft and it seemed OK - maybe a bit sluggish - not sure. I have previously taken the AH out and put is on a test rig and it seems OK at all extreme angles and the bearings sounded OK according Bill Wunderlich whose test equipment we used, but it was only for a few minutes. So to summerise, why is it after half an hours flying and why at Altitude or is this all coincidences. Thanks John