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I live in the head of the Sequatchie Valley in mid-east Tennessee. It averages a few miles wide, 1000' deep, and runs arrow-straight for about 70 miles into northern Alabama. It runs south/southwest and thus is almost perpendicular to the usually prevailing westerly wind. It is one of the premier sites for ridge-soaring in the eastern U.S. I've spent many hours on the ridge in high performance sailplanes such as an ASW-20.
Today the wind was pretty steady out of the west and my wife and I were taking a "Valley Run" down the Valley in the 750. Once I got as far south as I wanted, I turned to run back up the Valley, and on a whim, settled-in a couple of hundred feet from the east ridge line. I could feel the "bump" come up under the right wing and knew the ridge was working. I was able to set the Jab 3300 at cruise rpm (2850) and motor up the ridge with the aid of the ridge lift at 107 kts. ground speed. What a kick!
I'm slats-off, 600 series tires, so a little cleaner than a stock 750. Usually see about 82 kts TAS @ 2850. The wind was reported at KCSV at 11 kts gusting to 19 kts and the wind was not perpendicular to the ridge, more of a quartering tailwind relative to me and the ridge. So let's say the constant wind speed was under-reported (the reporting station was about 20 miles away) and be really generous and say I was getting 15 kts from the wind. That would boot the ground speed up to 97 kts and I was showing 107 kts (123 mph !!!) on the GPS.
I can't give an exact angle of attack, but, just as we do in sailplanes, I definitely had to trim the nose down to maintain level flight, which of course accelerated my groundspeed. So all that is to guess I was getting the last 10 kts from the ridge lift?
But heck, that's nothing! In the ASW-20, I've hit 110 kts IAS in level flight on the same ridge, and that's with no engine! ;>)