Originally Posted by
WillowRun 6-3
Is there a source you can identify here for the information in your post, fdr??
Hi WR.
PM me and I can send you that research paper, it is recent, but it shows what I previously commented on 2 years ago. It isn't from TBC, but it should have been obvious to anyone who had more than a passing knowledge in aerodynamics. Heck, had anyone bothered to sit down with a cup of coffee and have a cogitation on the subject that should have been obvious. I alluded to this when MCAS became publicly disclosed, you may recall; it would have been a few quick test flights to optimize, and corrections to the performance to remove the surprise benefit that the nacelles would have certainly given to Vs1g, at the apparent surprise cost of non-linear longitudinal stability. That's what I would have recommended, but that opportunity was lost through the way things work in external certification in August 2016. Anyway, long stab in this case was a simple fix had anyone bothered to ask outside of the cloistered workshop. Institutions become parodies of themselves, with diminishing returns over time; it is the nature of systems without external input and reviews. Sucks to be us, I guess.
P.S.: While the image and graphs show CL and CD, it should be clear to anyone involved in the art that lowering the CLmax at high alpha for an inboard section of a swept wing will increase the nose down pitching moment of the full wing directly, and will result in a reduced down wash in the affected area proximate to the nacelle/wing flow field that will result in a reduction in the CL of the tail plane for part span in the wake of the wing, which would directly have improved the stick force/g of the aircraft. Quick guess, the effect on stall speed would be less than 1.5% change, and that would have been able to be optimised. Thats about a ~2kt Vs1g change, which is... about... maybe 100' of TODR, or 200lbs of payload loss, rough order.
FWIW, the guys that did the CFD did a nice job, seems to be void of artifacts, and shows some flow structures that are pleasing to see properly modeled.