Keith,
The whole idea of pitching moments, why they should be a constant about the AC, but that they can be either negative or positive for a cambered airfoil about the C of P makes me realize I’m out of my league in fully understanding this subject.
I can’t seem to find any of these diagrams you mention that illustrate the pressure envelopes above and below the aerofoil at various angles of attack. I have those that show the magnitude of the upper and lower C of P versus distance along the chord from the LE. And I’ve come across many graphs the past week showing the pitch moment about the AC as a constant.
Any available on the internet you know of?
Such a diagram would make it easy to understand the contribution of the tail to stability, once one adds in the moment from the aircraft C of G. And consider then, the C of G range of the whole aircraft and the limitation/capabilities of the tail can be further understood.
And provide some clear reading to the M crit, M buffet, thread still ongoing
Thanks for your informative post
Milt,
I’m not trying to split hairs here, but based on what I’ve interpreted from Keith, I’d add to your fine post that perhaps longitudinal stability in some aircraft could still be achieved by having the C of G just slightly aft of the C of P (yes, I do mean C of G aft of C of P), for cases where there is a nose down pitching moment from the C of P. In such case, the tail could still provide a slight tail down force. And of course, the full aoa would need to be considered.
Hawk