207WF Posted February 12, 2013 Report Share Posted February 12, 2013 I had not done this in four years, and the accuracy of the airspeed indicators has changed. I flew a triangle course, 7nm each leg, twice around and recorded the data on each of the six legs after heading, altitude and airspeed had stabilized. I was at 3200 feet, OAT 15C with a density altitude of about 3700 feet. I flew at my normal cruise power setting, which is 5200 rpm (I have not checked how accurate the rpm is!). The wind aloft was light, indicated by a maximum groundspeed difference between any of the two legs of 9 knots. I assume that the average of my gps groundspeed over the six legs is my average true airspeed. Here are the data: Avg gps groundspeed = 115.0 knots avg flight design airspeed indication, round dial = 116.7 avg dynon airspeed indication, DA10 = 108.2 avg dynom computed TAS = 114.5 Using a whiz wheel, a correct average CAS would have been 109 knots. My flight design gauge has become more optimistic as it has aged, while the dynon has become less pessimistic and more accurate! I also confirmed what I had expected: getting my ailerons lined up with the flaps at -6 has added three knots to my true airspeed. (This is unlikely to be due to rpm error, as I saw that change over a one day interval.) WF Link to comment Share on other sites More sharing options...
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