> That's the hard part. The POH and the TCDS give the standard origin > on the X axis (the weight and balance reference datum), and the origin > on the Y axis can be assumed to be the centreline of the plane, but > where do you put the Z origin? For a single, the thrustline of the > propeller might be a good choice;
Yes. > alternatively, the cabin floor at the firewall (right in front of the > rudder pedals) should work for any aircraft, ehhhhh ... > and the ground sort-of works, as long as you're consistent > about strut compression. yecch. > I'm not big on rules and standards, but we > could publish a list of friendly suggestions for all aero and 3D > modellers: > > 1. Put the X axis origin at the published weight-and-balance reference > datum. 1) Respect the manufacturer's structural coordinates, if known. If not, place the X axis origin at the published weight and balance reference datum. If not known, place the X axis origin at the tip of the aircraft nose or propeller hub - whichever is farther forward (not including probes or antennas). > 2. Put the Y axis origin at the centreline of the plane. Yes. > 3. Put the Z axis origin [where? the ground?]. Place the Z axis origin as specified by the manufacturer's structural coordinate system, if known. If not, place the Z axis origin at the tip of the nose or propeller hub that the X axis origin is located at. This would place the origin for the entire axial system at the nose or propeller hub. Maybe there should be a few sensible systems and we can specify which one is to be used. For the FDM, as is known, its the relative distances that need to be known, with the stipulation that the X axis is positive backwards, the Y axis is out the right wing, and the Z axis completes that using the RHR. Perhaps the above have problems, too, but it I agree that some kind of agreement should be reached. Jon
smime.p7s
Description: application/pkcs7-signature
