The two limiting speeds for any subsonic aircraft is the stalling speed, where flight is no longer sustainable and the aircraft's top Mach speed, a speed relative to the local speed of sound. As you climb upward these two creep slowly close and closer, to eventually meetm and making subsonic flight impossible. But before it goes that bad you'll have a higher ground-speed if you go higher, a fact the jetliners take advantage of, of course! IC engines, like glow or ignition engines, fare badly as altitude increases, as they eventually get starved of oxygen. Those flying electric models at high altitude will notice faster flights and higher propeller revs and possibly longer endurance, but not much else to worry about. Any non turbo-charged engine will have to be continiously monitored and the needles readjusted if you plan to break any records :-)! So higher stalling speeds, higher cruise speed, and higher tops speed, if the model is a normal one. A very fast one might run into compressibilty problems at the top of Mount Everest, had you planned to take your Vindicator there :-)! Tord, Sweden -- If reply difficulties - use [EMAIL PROTECTED] Tord S. Eriksson, Ovralidsg.25:5, S-422 47 Hisings Backa, Sweden RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
