It has been modified by others for FSX if I recall correctly. That earlier release is no longer the best of SR-71 simulation aircraft. Jorgenandersen - you mention freeware in which case you are referring to the older 2003 SR-71 release. The older release has been replaced by the new 2008 SR-71 which has new features and procedures. I may not be wording this correctly but a new SR-71 was released in early 2007 to be followed a year later by the 2008 SR-71 for FSX which is for both DX9 and DX10. I believe it was in December 2003 that Alphasim released a payware SR-71 and I got it at once. At that time I was using a freeware SR-71. I've been using FS9 and now FSX for the SR-71 since summer 2003. You cannot argue with the price of freeware, but knowing the real thing would go over Mach 3 and 80,000 feet made me uninstall it.I am not Alphasim staff.
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I couldn't get it to go higher than just over 40,000 feet and speed fell off to the point of stalling at that altitude. Personally, I was not happy with the Alphasim SR-71. There's much more to it than that, but those are the basics. You start at 33,000 feet, start slowly descending to 30,000 and mach 1.2, and then you pitch up and off you go. To get the Alphasim SR-71 really moving, you need to have the aircraft configured for the climb well. To go mach 3 at altitudes like the airliners fly requires going thousands of MPH through the air, which no blackbird ever could do. I'm sure you're familiar with KTAS, KCAS, KEAS, KGS and KIAS, right? The real SR-71 did mach 3.2 at 80,000 feet, but was only pushing air aside like it was going 360KEAS because the air is so thin up there. You cannot argue with the price of freeware, but knowing the real thing would go over Mach 3 and 80,000 feet made me uninstall it.The Alphasim SR-71 is no joke-it's unforgiving to fly and will not climb to 80K and accelerate to mach 3 unless you fly it exactly like it needs to be flown in real life.