Todd Thelin wrote: > Ultimately what I am trying to do is calculate the error in my airspeed > indicator, which I'm fairly sure is off by about 20 or 30 MPH at the > higher > Indicated Air Speeds, but appears to be much closer to accurate at traffic > pattern speeds.
At the risk of beathing this horse further, that's what I was trying to say earlier. When I do the four-way GPS thing on a calm day I write down both IAS and GPS speeds for each direction (after obtaining "steady state" for a minute or two in each direction). You can hardly go wrong if you're at the same IAS for all four readings, with the GPS speed varying by whatever small amount of wind you have. Then I average all four for both IAS (which should be the same) and GPS speeds and the error between the two falls right out in front of me. With my current airspeed indicator, I'm almost always within 1 mph of GPS speed at anything over about 90 mph, once TAS is calculated based on the IAS. Below that my ASI reads higher than actual, and by doing a four-way test at 80 mph, I have a pretty good idea how much it's off. I also checked the ASI calibration (see http://www.n56ml.com/airspeed_calibration/ ) throughout the normal flying range so I'd know if I had an instrument problem or a static/pitot problem. After you're sure you've got the calibration correct you can do something similar to see if either the static or pitot system leaks, while keeping the water out of the aircraft's lines, of course. Mark Langford N56ML "at" hiwaay.net website at http://www.N56ML.com --------------------------------------------------------
