|
In modern terms what the original document said was the planes CG should be placed so that the entire aircraft has a positive static margin (as was said, the CG is ahead of the CP). Unfortunately, that is kind of a "DUH!" statement since it doesn't tell you where the CP is, how to calculate it or how far apart they should be.
The CP can be found in a wind tunnel or through CFD (Computational Fluid Dynamics) but they are both kind of expensive. The alternative is a risky series of flight tests where you gently expand the envelope as you move the CG aft and test control force and pitch response. That's the way they did it in the first years. Move the CG aft, reset the stab for stable flight, measure the control response. Then repeat it again till the plane won't recover from a departure. When the plane gets wrecked, use the CG from the previous flight for all production planes.
I wouldn't recommend that process any more.
Hank
|