Tim,
Ok, I know you are having fun, but I am a little slow ----
The question remains, when is being airborne with forward speed not a flight?
Keith
I hesitate to answer because I'm not sure that I'm qualified, because I'm afraid it'll hijack David's thread, and because I'm afraid that I'll just feed an argument.
But, what the heck:
I think that this is a case that really highlights the fuzzy nature of any human language. I think it's more pertinent to ask yourself what the answer is to "yes, but is that
really flying?". If I put a rock in a trebuchet and let it fly, we say the rock is in flight. But if I clip a Piper Cub's wings to a 10 foot span, hook it to the sling of a trebuchet, and let it fly, can I enter it in a scale competition in it's nearly-wingless form on the basis of it having flown through the air?
More to the point, if I build a homebuilt airplane that is inherently unstable, or not powerful enough to rise it's own wingspan off the ground, or is otherwise incapable of rising off the ground at airport A, flying through the air in a safe and controlled manner, then landing at airport B so that I can buy a $100 hamburger, have I built an airplane that is capable of
really flying?
If I take said "airplane", and I manage to wrestle it off the ground a foot or two and then land it, without ever deviating from a straight flight path or leaving the confines of the airport, has it
really flown? Or is the flight only slightly more "real" than my hypothetical nearly wingless Piper Cub being flung by a trebuchet?
What about hovercraft, that "fly" inches above the ground without ever (necessarily) touching it? Are they "really flying"?
What about those Soviet ground-effects "airliners" that fly across huge lakes without ever being capable of getting more than a few tens of feet above the water? Are they "really flying"?
Or those weirdo Iranian "patrol seaplanes" that also can't get out of their own ground effects for any length of time? Are they "really flying"?
On the other hand, there are innumerable examples of machines that can be taken off from the surface in a safe and controlled manner, utilizing the reaction of the air against their flying surfaces, that can be flown in any arbitrary flight path (within their range and altitude capabilities), and landed safely from altitude back to the surface. These are
real aircraft, and no one is going to argue that what they are doing is
really flying.
For example, the Wright Flyers and other early machines did demonstrate that ability -- even though some of them were so rickety, underpowered, and inherently unstable that they stayed above ground by luck and phenomenal piloting ability. Those were "real airplanes" that "really flew", even if the FAA would never sign off on one even as a homebuilt.
So I would say that not only did the XF5U-1 not demonstrate "real" flight (because it was just a hop), but that you couldn't use it as a scale subject on that basis (pending, of course, a decision on what the rules really mean by someone in authority).
Had the thing taken off, climbed more than its wingspan above the ground, circled the airfield, then landed, I would definitely say that it really flew.