85th_Maverick Posted December 21, 2019 Posted December 21, 2019 (edited) Hello, There are 2 issues that I've recorded in a track file: 1. Somewhere 500km/h and 700km/h, when using full pitch up input combined with a couple of half-a-second left-right roll inputs followed by releasing the roll but keeping the full up pitch input, a constant pitch oscillation has developed to an amount of about 10+ AoA variation. The effect of the plane's pitching moment of inertia (which is alright as it is) coupled with the FBW's programmed logic which tries to maintain a commanded AoA by anticipating the required elevator deflections and elevator deflection rates can sometimes overlap just enough to produce a pitch resonance/oscillation. This looks like a programmed FBW constants issue which should be relatively quickly solved by slightly reducing the elevator's pitch rate dampening deflections. The same pitch but also yaw oscillations can be found on the DCS F-18C lot 20 at different speeds and altitudes, but there should be another thread opened to deal with it. 2. Much later in the track you can see that at higher altitudes, when the KCAS gets above 600-650, the airspeed and Mach will start to rise when climbing and decrease when descending. From the outside view though, the laws of physics are normal, the speeds seem to vary normally when climbing/descending, but only from the cockpit the things are a upside down. This can be related only to a HUD indication issue. Here's the track: F-16 FBW pitch dampening + high altitude airspeed and Mach cockpit indication versus attitude bu.trk Edited December 21, 2019 by 85th_Maverick Omitted that the pitch oscillation is within a range of speeds Good knowledge and common sense make the absurd run for defense. Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!
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