Originally Posted By: wfaulk
And, in fact, if there was a headwind that matched the plane's takeoff speed, it wouldn't move forward, but it would still leave the ground. (Theoretically. I'm sure that getting the wind to blow in that consistent a direction at that consistent a speed is virtually impossible. Maybe in a wind tunnel.)

Not so rare, actually. This is why light planes are tied down at airports. Airplanes take off and land into the wind, of course, so that less space is required. WWII aircraft carriers sailed full speed into the wind for aircraft launches for this very reason.

What's more, it's perfectly possible to have negative ground speed when flying into a headwind- all you need is a mountain pass to funnel the air up to high velocity (or higher than the flying speed of the aircraft).
I'm reminded of a story told by Richard Bach about flying a biplane across the country. I can't remember which book it was in- perhaps Nothing By Chance. He had to cross such a pass at low levels where the wind speed was less (wind speed is slower close to ground due to friction with the ground). He scared the heck out of a few drivers who happened to be on the road, but it was his only way through. At higher altitudes the wind drove him backwards. laugh
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