Hello again! I'd like to address a few questions to somebody here or from anywhere who has enough good knowledge in aerodynamics and/or flight dynamics, because I really don't want to waste time. I know that there's no simulations on a PC that could have reached a 100% accuracy level so far and I'm not asking for that!
But I believe that I have the right to ask some questions regarding the F-15C's PFM as long as the DCS's site claims it to be an authentic recreation of the real F-15C's flight behavior, as the statement tells: "Professional Flight Model (PFM), developed in cooperation with F-15 pilots"
If there is any F-15C test pilot, active or ex pilot who can help to answer the 2 following questions, I would greatly appreciate. The subject of this post is mostly concentrated on the 2nd question, which is more important:
1. What is the highest negative AoA that the F-15C's flight control system allow for the real aircraft? I know that at negative AoA the wings won't benefit of the higher energy vortexes created between the engine inlets and the canopy which help increase both the fuselage's and a good portion of the wing's lift, lateral-directional stability and critical AoA (that apply when flying at positive AoA), because they won't generate at negative angles, so there is a huge constraint in negative alpha due to these factors, but how far this restriction reaches?
You do know what a roll due to yaw is, as well as an adverse yaw due to roll (the yaw due to roll is not the subject) when we are at positive alpha (AoA)! For instance, and especially on high sweep wings (like the F-15) with 0 dihedral between the wings, when you have 1G at a constant given AoA and you yaw the aircraft only by rudder input, the leading wing will have a greater lift gradient (what we usually call the lift vs alpha slope) than the lagging wing, which creates a lift asymmetry between both wings, thus the leading wing "rolls around" the lagging one in the same direction of the yaw, but what should normally happen (how would the airplane react) when you have negative alpha (AoA) giving the same conditions, of course at -1G the least? That's right..., you should get an opposite roll due to yaw and vice-versa for yaw due to roll (the plane will yaw in the same direction as the roll).
So, for stick forward conditions (where the alpha is enough negative to have the wings produce negative lift) every reaction in yaw and roll is reversed when the corresponding input is solely applied.
2. The second question is: Why does the F-15C in the sim tend to react correctly in the first moment when we have the stick held full forward (with 0 side stick or 0 aileron input) having the aircraft settled at a new equilibrium negative AoA, then apply a full boot of rudder (doesn't matter if the yaw CAS is switched off or on) to any side and have it rolling in the opposite side of the yaw (which is correct for negative AoA), just to see it starting to roll in the same side as the yaw as if the AoA became suddenly positive, but the lift continues to be negative? What logic does this have I don't know and if there's any reason why would a real F-15C react this way i'd greatly appreciate the correct answer...!
Now in order to be more precise in what i'm saying, i've made up a short video where these inputs are illustrated and every reaction by the aircraft can be observed:
I've only made this video for the F-15's updated flight model investigation purposes, not for criticizing or any other reason than to promote what has already been gratefully achieved and done well...!
Thank you!:thumbup: