There are a lot of qualative judgements being made, like the pretty airplane, and debating the measurement of the radius gets somewhat esoteric. Wild Bill probably did come up with a plane that was capable of a five foot radius, but I am sure that the ship lacked the neccesary asthetics.
And they had other problems. Essentially all the compromises that where made to absolutely minimize the turn radius took away from other aspects of the flight. Like flying in a straight line reliably, and tracking in round maneuvers repeatably. A common misapprehension of the people concerned with the 5 foot turn radius spec was that it was frequently *the only thing they considered*. It became an obsession. The 5 foot radius was three words in a 5000 or so word document. The name of the event, for instance, was and is "Precision Aerobatics" - not, importantly, "Minimum Turn Radius Demonstration". Most of the airplanes dedicated to shooting for a 5 foot radius corner were also incapable of being flown precisely. A flaw that Bill and other recognized and attempted to solve with additional technology, like the exponential response control system, where they were trying to desensitize the airplane around neutral to make it possible to fly it consistently outside the corners.
Ultimately, it was an insoluble problem. If you managed to get a 5 foot radius, and any practical flying speed, the *time* required for a corner becomes so short that it was physically/neurologically
impossible to accurately control the exits in other than perfectly consistent conditions, because the feedback of your nerves is far to slow to respond to deviations. A perfect 5 foot radius corner takes a grand total of 100 milliseconds from start to finish at a typical 78 feet/second. If you hit the 5 foot radius but your 90 degree turn comes out 85 or 95 degrees at random,
you will lose every contest you enter, because it will cause the judge to quite correctly downgrade you for shape errors.
Moreover, if you can't immediately go from a perfectly straight line to the minimum radius - and you can't- the "lead-in" and "lead-out" from the corner will cause the effective radius to be much larger. That means you have to go from perfect level flight to near maximum deflection of the controls in a time much shorter than 100 milliseconds. This is also not physically possible. Making the controls soft around neutral just makes it worse, and the extra parabolic section of the corner taken to move the controls makes the corner
look much softer than its ultimate minimum radius. And all you are doing it trying to convince the judge that it is tight since no one is actually measuring it. Everything that we have done over the years, in fact, it to make the airplane MORE sensitive around neutral rather than less, to make it easier to abruptly go from a straight line to a radius. Do that, and you can't fly the extremely short-coupled gigantic tail volume and tail aspect ratio airplanes in level flight any more. It's essentially an impossible set of constraints.
Many times, the "pretty plane" accusers blame this on the excess weight caused by (quoting Bill) "many layers of lacquer buffed to a high sheen" but even if you made it weigh ZERO it doesn't solve any of the problems above. And even if you did manage it, that's only one tiny aspect of a huge set of rules.
That's why I said that I didn't think Bill actually liked stunt competition very much. Because to be successful at it, your goal is not to solve a series of engineering problems. Its to make it LOOK LIKE you are flying correctly in a subjective evaluation and convince someone to give you, with a second or two of eyeball evaluation, a high score. If you think it should be something else, and cannot accept that as it is, it will be a very frustrating event.
Brett
Topic: The Father of Modern Stunt (Read 7605 times)