Adam Day wrote: >>My question is does any on here have a KR based at high altitude or >>frequently go above 10,000 feet ? and if so what engine are you using and >>how the plane handles, climb and cruise with a given prop?<<
I do most of my flights at 9500-10500 feet, and I've been over 20,000' once, just to see where the ceiling was. It was still climbing, but not much. You really can't tell the difference in the way it handles at higher altitudes (within reason), as indicated airspeed appears the same to the pilot as it does to the plane, if that makes sense. As Jeff mentioned, diminished climb rate is the problem, but it's still better than a lot of spam cans. You probably wouldn't want to fly behind an 1835cc VW at those altitudes, just as a matter of safety (climb performance), but I'm sure somebody out there would disagree. I guess that's subjective, but you can hang numbers on the climb rate, and that does matter from a "return-to-the-field" standpoint. Altitude has an almost direct relationship with engine power, so at 8000' you start out with 75% engine power, not to mention reduced lift. There's a nice chart at http://www.cobham.com/media/83823/821-1.pdf that quantifies the pressure (and therefore performance) difference at altitude. I have a plastic water bottle that I opened at 17,000', emptied, and then resealed. After landing I noticed it looked like it'd been flattened. It had collapsed inward, and looks like 2/3 of the volume is gone from it now. That's a powerful reminder of the effects of high altitude. Note that I have an oxygen cylinder and use it, as does Joe Horton and some other high-flyers on this list. Joe could tell you a story about what happens when you run out of oxygen and don't realize it, but that might have to wait until a few beers and the campfire at the Gathering in September! One of the design parameters for the AS504x airfoil was the same lift coefficient as the RAF48, so if the wing area is the same on the new wing as the old one, lift should be the same. Lower drag is the "free lunch" benefit. Having over 1100 hours on the new wing, I highly recommend it as now "proven"... Mark Langford ML at N56ML.com website at http://www.N56ML.com --------------------------------------------------------
