zero Posted June 12, 2017 Posted June 12, 2017 (edited) Study the vortex lift on delta wing. Disclaimer: I have very little experience in tight turns with M2k. Only a few fights with Mig 15 AI. My rig is below spec. 4mb ram. That said. World 1.5 runs flawlessy at high settings since old days with spec 32bit and 2mb ram. Learned about the vortex generated lift, I wanted to see the effect. Ref my latest post in performance thread. Ref diagram (typical Mirage wing), the vortex generated lift starts at AoA 10`. Burst at AoA 18`. And stall occurs at AoA 24`. These data should be relevant around Mach .85 regime. Test flight with clean aircraft. Data acquired from Tacview. Tight turn. Roll 90`then stick quick and hard back as possible. Keep nose at horizon. According to reference data there should be quick instantaneous turn, then sustained turn with quick increase in drag. My first attempt failed due to black out. Recovered with nose down attitude. Tacview data during instantaneous turn: Mach: .89 AoA 13.1 G: 5.9 Approx same data 2 seconds later. Lost it 10 seconds later: Mach: .92 AoA 17.9 G. 8.9 (Black out) Next try (No black out) Full 360`turn in approx 30 seconds. Mach .95 AoA: 11.5 G: 4.7 Sustained after 180`turn: Mach 1.00 AoA 12.1 G: 5.7 After approx 400` turn The drag increased too much. Mach .46 AoA 25.6 G: 3.8 Approx 460` Aircraft slide slipped quickly down (nose still perpendicular to horizon) – end of sustained turn. Mach .32 AoA 33.4 G 2.2 Vertical speed increased to over – 11000 m/min Recovery no problem 20 seconds later. Wings level. Pitch up 8`. Mach .31 AoA 17.5 G 1.2 ……… Next – figure out vortex lift in wings level attitude: Mach .42 AoA 9.0 G 1.0 Vertical speed v/s + 2100 m/min Increase AoA. The vortex lift should kick in: Mach drops down to .36 AoA 10.4 G .9 v/s + 1900 (slight drop) Increase more AoA: Mach .30 AoA 14.2 Still climbing + 1250 m/min Running out of oomph: Mach .27 AoA 15.7 G .7 v/s +21 m/min Pitched down and recovered. Next try: Vortex lift should burst around AoA 18 and stall at 24. IMO there should be a lack flight control authority as vortex burst probably goes over whole wingspan hitting wing trailing edge and top of elevator surface. To be short: aircraft mushers (pitch up/down) in this area. Typical: Mach .29 AoA 18.2 G 1.0 v/s – 1500 m/min Mach .22 G .7 AoA: 22.8 v/s -1600 m/min Recovery – full AB to Mach . 41 in 11 seconds. Conclusion: Not expert – your opinion? Now to the really bad part! :no_sad: Is it a bug – or was the aircraft damaged during high G turn? I do not know. Read on. Dive start with full AB – wings level. Pitch down – 35 HUD freezes 99 knots – no drop in altitude. (analog instrument moves) Tacview data: During 16 seconds dive (pitch down -50) AoA 2.4 G .2 The Mach increases only from .38 to .87 (in 18 seconds). The graph in Tacview looks very strange… Leveling out Mach .91 AoA 5.8 G 3.4 In a split second the aircraft pitch violently to AoA 81.6 and disintegrates. Again: Is it a bug – or was the aircraft damaged during high G turn? Next flight. :thumbup: Of course I wanted to confirm this. Tried several dives. Zero G dive. Half roll to inverted dive. All in full AB. Everything. Guess what? Not able to duplicate the previous strange dive. Pitch -40` From Mach .37 to Mach 1.00 in 15 seconds. Curves on Tacview graph make sense. :pilotfly: Edit: Remember I turned App on once to read AoA on HUD (and off again) Could this be the culprit? Program assumes that gear down structurally and aerodynamically. Troubleshooting test with dive both with gear down and once with App mode activated once. Neither replicated the bugged dive. Edited June 13, 2017 by zero
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