Bill Biggs wrote: > Am I missing something? > > The spacers have no effect on the EXTENDED length of the gear. > The plane first touches with the gear extended and the "castoring > effect" takes place immediately. Then (unless you greased it on) > the donut-belvilles compress. At best the plane (oleo-donut) is in > the "level position" for only an instant somewhere in there.
Bill, Yep, you did miss something. We so often concentrate on the moment of touchdown - but the bad behavior that comes from a droopy tail mostly occurs after the castoring is done. When a Coupe is rolling along the runway, near touchdown speed (or even above "stall" or minimum flying speed), the plane should roll along nicely and stably on the ground. Coupes can do this, even at speeds well above minimum flying speed because the on-the-ground attitude is level and the wings are at a very low angle of attack. But, when the tail is low on the ground, the wings are at an excessive angle of attack. Thus, there's excessive lift for a plane rolling on the ground. Worse, because of dihedral, the upwind wing is at an even higher angle of attack. The result of a low on-the-ground tail is that the on-the-ground behavior is not stable, not acceptable and can even be dangerous. As I said yesterday, I used to hear stories about Coupes landing in strong crosswinds that had the upwind wing lift so high people were afraid they'd flip or they'd fear the other wingtip would touch (almost impossible) and their upwind main gear would lift and it'd be almost impossible to steer and they'd veer off the runway, maybe into other planes or runway lights or ditches or fences! These are things that occur after the touchdown, during the rollout (and sometimes, to a lesser extent, during the takeoff roll) in strong crosswind conditions. Coupes with the tail at the correct height, which thus have the plane level in pitch and thus have the wings at the designed low angle of attack behave well on the ground even in crosswinds that have grounded most other planes. I hope this is a better explanation. Does it seem clear, now? Ed Burkhead http://edburkhead.com ed -at- edburkhead???.com (change -at- to @ and remove "???")
