I had a UMA with a leaking case also. It was a 4,000 FPM unit which was way too much anyway so I had them put on a new dial and case and recalibrate it for 2,000 FPM. They got it back pretty fast and only charged me something like $50.
I find my VSI to be very usefull. I usually start my descent planning about 50 miles out and depend on the VSI. I suspect that if yours was working you would use it a lot and not want to part with it. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Mark Langford Sent: Monday, February 20, 2006 10:03 PM To: KRnet Cc: Corvair engines for homebuilt aircraft Subject: KR> Re: Stall speeds. NetHeads, Several folks have asked if I've tried cabin air as my static source, and of course, I did that for several weeks, but there was no real difference in what I have now...it was just wrong in a different way. Today most sane people would've looked at the overcast drissly sky and said "no flying today", but as JFK would have said, "some say you can't fly, but I say why not?" Anyway, the ceiling was 3700' when I started out, so that's plenty of room to manuever, although I wouldn't do a stall that low. By the time I quit, it was down to 2700', and the terrain is mostly 900' around here. I stuck some 1/16" thick electrical tape 3/16" behind the static ports, and just about nailed it! At runway speeds in the neighborhood of 65 mph, I was only off by 4 mph, as opposed to 16 mph yesterday. At 2000' wide open, I was only off by 1 mph! Almost close enough for KR work, but not quite. I'll move them a little closer to the port and I'll be there. The good news is that the altimeter is only off by maybe 20' now, whereas it used to be off by 50'. The bad news is the VSI is still bonkers. After doing a little research on that tonight, I found an RV'er with exactly the same symptoms, and his UMA VSI was bad, because it had a case that leaked into (or out of) the cabin, causing errors similar to mine, and the same sort of never-ending descents that my VSI indicates. I assume the "calibrated orifice" is supposed to do that to some extent, but apparently mine's not as calibrated as it needs to be. I also have an UMA, and it was my UMA ASI that was off by 52% on my first flight (see http://home.hiwaay.net/~langford/airspeed_calibration/ ). Today I was straight and level doing speed tests and it told me I was descending at 1500 fpm! I guess I'll pull mine out to verify it's at fault, and cap off the line to see what happens with the ASI and altimeter without the VSI in the circuit. I'm sure it'll be another round of "port tuning" either way, but I wouldn't be a bit surprised if removing the dams doesn't get it close to right on! I'm not sure I even need a VSI, since it's useless and I don't look at it anyway. Maybe I'll put a nice tach in that hole, since Grand Rapids hasn't bothered to respond to my last two emails regarding the tooth counter interface that they said would make my EIS tach function actually work correctly. I've been waiting on that since early November. Of course I wouldn't have that problem if the EIS tach function worked properly to start with. It works OK as long as the temps are cold, but once it warms up, the tach indication is all over the place. The rest of the day was a real hoot though, as I did about 8 landings at 4 different airports, and had a whole lot of fun doing what amounts to "high speed low-level terrain avoidance flights" for the rest of the 2.4 hours. I wouldn't have landed then, except the rain was starting to make me worry about prop damage. I drove home with a huge smile on my face, and looking forward to my next fix. It was the best buzz I've had in years! The weather prognosticator painted a really dismal picture last week, showing 10 days of nothing but dark clouds and rain and snow coming out of them (I've never seen 10 straight days like that on the weather report before), but I've managed to fly for 5 of the last 7 days anyway. 138.5 hours and enjoying every schtinkin' minute of it. Life is good... Mark Langford, Harvest, AL see homebuilt airplane at http://www.N56ML.com email to N56ML "at" hiwaay.net _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
