I have an error in my indicated airspeed and was wondering if there is a way to put a permanent adjustment in the IAS. I am reading about 8-11 knots faster than I am really going and would like to adjust the D10 down. Is this possible in the menu set?
A better solution would be to find out where the error is coming from and fix it. There is a good possibility that the cause of the error is static source position error. If this is the cause, it will also be affecting your altimeter. A static source position error that gave a speed error of 10 kt error at 200 kt CAS would give an altimeter error of about 190 ft. If the speed where you see the error is 100 kt CAS, the corresponding altimeter error would be about 95 ft. You can find more info on measuring static source position error at
http://www.kilohotel.com/rv8/rvlinks/ssec.html.
Another possibility (if you are using the display TAS as a measure of airspeed accuracy) is that your OAT is reading too high, which would cause the TAS indication to be too high. But, it would take a very large OAT error to cause this much TAS error (about 30 deg C error at 200 kt would be required), so it is unlikely that this is the sole cause. It could be a contributor though.
A third possibility is simply that you might be using an inaccurate method to determine the errors in your airspeed system. Some folks come up with test methods, that might look good on the surface, but don't stand up to close scrutiny. For example, some folks believe that if you take the GPS ground speed on the four cardinal headings, and average them, that the average is equal to the TAS. In fact, this is only true if the wind is zero.
