Bill Biggs asked: > The "optimum tail height" is achieved with the plane empty. The plane rarely flies empty.
> The minute you add a pilot the tail "droops". What if there are two large occupants? > Where is the gain? Is there an acceptable "window" for the static tail height? > Does load effect [sic] the landing characteristics? > This is why I wonder about the "tribal knowledge" thing Bill, Let me take these item by item. * The "optimum tail height" is achieved with the plane * empty. The plane rarely flies empty. The minute you * add a pilot the tail "droops". What if there are two * large occupants? That's a good observation. When we've talked about "tail low" we've been discussing it concerning an empty plane. I'm inclined to think that Fred Weick took this into account. However, he may have been figuring on two 180 lb. guys and full fuel. That weight for a man was on the high end back at the end of the depression. The *average* weight of men drafted for WW2 was only about 155. Our current 250 pounders are kind of like putting in an entire extra 1939 person into the plane. At least, we're putting the *extra* person in the pilot's seat, not in the aft baggage compartment. J If there's someone out there with the ambition, I'd appreciate a post showing how much the tail droops when two 180 lb. people get in the plane and how much it droops when two 250 lb. people get in the plane. * Where is the gain? Is there an acceptable "window" for the static tail height? I've not heard of wild landing complaints on planes that had tails within a couple (or maybe three) inches of design *level* specification. There's some tolerance. But, when the tail is up high enough for the window sill to be level on the ground, the crosswind characteristics are really, really good! I chose to bring my right-after-maintenance tail height up to the level-on-the-ground height (75" on my single-fork nose gear plane) and liked the results. * Does load effect the landing characteristics? Hum. I didn't see or feel any such difference. But, then, I was never at the *light* end of landing weights - not with me in the plane. * This is why I wonder about the "tribal knowledge" thing At this point, we don't have an engineering analysis. It could be said this is all "tribal knowledge." But it's "tribal knowledge" among college educated tribes-people with some scientific and mathematical training. We're not talking about illiterate, never-educated tribesmen. I do *not* recommend that you lower your tail to 71" and go out to fly in 25+ mph direct crosswinds on narrow runways. Sure, I'd use the resulting data, but I'd feel bad about the cost. I understand that it's proper to take a spoonful of salt with any statements by pilots, CFIs and airplane mechanics - look at what's been said about Ercoupes by many of those types for 67 years! Ed Burkhead http://edburkhead.com <http://edburkhead.com/> ed -at- edburkhead???.com (change -at- to @ and remove "???")
