Norman Vine wrote: > Unless runways aren't anywhere near as flat in reality as I was > trained to build them when I was in the Corp of Engineers I wouldn't > expect a difference of 1-2 meters in a horizontal direction to be more > then a couple of centimeters in the vertical. < ie dy/dx usually < > 1/100 >
Once more: ski jumps. I can assure you, without a shadow of doubt, that the deck of the Illustrious is nowhere near as flat as the runways you built in the army. :) And even so, it's not the *position* of the gear tip that is the problem, it is the *direction* of the compression vector. An 20 degree difference from vertical (not a terribly uncommon AoA for a jet touchdown, or bank angle for a stiff crosswind landing) can results in a translation of sin(20) (about 34%) of the gear length. The difference in spring force between a gear compressed by 34% and one that isn't compressed is very large. And again, it is true that under almost all circumstances we could just assume that gear compressed "down" regardless of aircraft orientation and get away with it. But we already make an even better assumption -- that the ground will be a flat plane. If you think about it, the assumptions are basically the same. All the circumstances where we'd get away with "down-only" gear compression are already handled just as well (or better*) by our existing "flat runway" assumption. Like I said, if we're going to do it, we should do it right. Andy * YASim can use the flat earth to compute a consistently flat runway for the gear to press against, for example. With a per-gear elevation like this, there would be no way to prevent the airplane from seeing a "stair-step" (really, escalator) configuration instead, which doesn't make any physical sense. -- Andrew J. Ross NextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com "Men go crazy in conflagrations. They only get better one by one." - Sting (misquoted) _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
