On Fri, 13 Dec 2002 10:09:06 -0800 Andy Ross <[EMAIL PROTECTED]> wrote:
Whatever convention we pick should be an easily explainable and identifiable from the *shape* of the airframe only. Not everyone has a POH handy, very few people have W&B or C.G. numbers, and even things like the centerline are subject to argument on some aircraft.
True.
*Very* true. I don't think anyone really thinks we should use the ground plane for anything other crashing into.Referencing the ground plane is especially bad, since the gear are going to compress differently depending on load.
Even for those of us who have access to the structural frame, it wouldn't be hard to bias our config file numbers to reflect an origin at the nose or farthest forward projection. The structural frame numbers are just nice to have and use (when you have them). The X-axis should probably be coincident with the thrust axis centerline for single engine props; for and for non-single-engine aircraft: coincident with a line through the tip of the nose of the fuselage and parallel to the fuselage as it sits "level" (not necessarily as it sits on the ground - think of the DC-3 - but perhaps as it is "level" in cruise, where one might expect the cabin floor to be roughly horizontal). In both cases the Z axis would extend out from the tip of the nose/prop, upward.I continue to like "the origin is at the tip of the nose". You'd have to look really, really hard to find an aircraft without an identifiable nose. And finding an aircraft author who doesn't understand the concept is literally impossible.
Jon
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