bkthunder Posted May 16, 2016 Share Posted May 16, 2016 I was doing aerobatics with the mirage and this dawned on me: I noticed that whenever I pull the stick, the elevons are going up, and they stay up to some extent as long as I keep pulling. Now this would seem to make sense, but actually I think it doesn't. The M2000 has relaxed stability, which means that the aircraft is inherently quasi-unstable, and small movements of the control surfaces have a big effect. One of the big advantages of this, is that in a high-g pull, the elevons are staying pretty much in a central position, thus causing less drag. In the F-16 for example, a pitch up moment is initiated by a rapid upward movement of the elevons (to "unsettle" the aircraft), and immediately after, the elevons go back to neutral or even pitch down, because the aircraft tendency is to pitch up uncontrollably, so all the FBW is doing after the pitch up impulse is given, is trying to keep the situation under control and avoiding departure. In the DCS M2000, I noticed that the aircaft acts as if it did't have relaxed stability, but rather neutral stability. If it had relaxed stability, the elevons wouldn't need to keep pitching to maintain a certain rate of turn. Have a look at these pictures, you can see that the aircraft is in a pitch-up / high AoA status, but the elevons are actually slightly negative. http://www.airliners.net/photo/United-Arab-Emirates/Dassault-Mirage-2000-9EAD/2359952/L/ http://www.airliners.net/photo/France---Air/Dassault-Mirage-2000C/0949590/L/ http://www.airliners.net/photo/Taiwan---Air/Dassault-Mirage-2000-5Ei/1836040/L/ 5 Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
robban75 Posted May 16, 2016 Share Posted May 16, 2016 I've noticed this as well. At subsonic speeds the elevons should only point upwards(very briefly) when the pitch is initiated. After that they will aid in trimming/stabilizing the turn rate by adding lift behind the CoG. This allows for a maximum usage of the wing area. Link to comment Share on other sites More sharing options...
Rlaxoxo Posted May 16, 2016 Share Posted May 16, 2016 Interesting catch [sIGPIC][/sIGPIC] Youtube Reddit Link to comment Share on other sites More sharing options...
bkthunder Posted May 17, 2016 Author Share Posted May 17, 2016 I understand this is not particularly interesting for most people (what the hell is relaxed stability anyway???), but I think its pointing to some flaws in the flight model. Does the DCS Mirage have a correct CG and CL location? Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
Gliptal Posted May 17, 2016 Share Posted May 17, 2016 The aircraft as it's modelled in DCS most probably does not have a relaxed stability. Link to comment Share on other sites More sharing options...
bkthunder Posted May 17, 2016 Author Share Posted May 17, 2016 This is probably opening a can of worms (hopefully won't require a re-write of the FM and FBW logic!), but painful as it may be, I hope you will simulate a true relaxed stability + FBW model. After all, this is one of the most distinguishing features of the Mirage. Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
Rlaxoxo Posted May 17, 2016 Share Posted May 17, 2016 (edited) Can you show me videos not pictues doe? For example this: https://youtu.be/ehOpxhAFGkQ?t=72 It's using elevons to pitch up and hold pitch but it goes negative to reduce pitching and stuff like that can't be seen in the picture Edited May 17, 2016 by Rlaxoxo 1 [sIGPIC][/sIGPIC] Youtube Reddit Link to comment Share on other sites More sharing options...
bkthunder Posted May 17, 2016 Author Share Posted May 17, 2016 I looked for videos first, but cannot find anything clear enough, so pictures do a better job IMO. Besides, if you are familiar with the concept of relaxed stability and how it affects the aircraft, you don't really need to see any pictures or videos. The center of gravity is behind the center of lift, so the aircraft will always want to pitch up, and that's why they have FBW: it's totally counter intuitive to push on the stick if you're trying to go up, but that's what the FBW is doing for you. You pull, the FBW pushes to control the AoA that would otherwise lead you to a stall and departure. Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
Shahdoh Posted May 17, 2016 Share Posted May 17, 2016 Yes, it will do that to maintain straight flight, but to continue to "pull" into a turn/climb, the elevators will continue to pitch up, making minor counter controls in opposite direction to keep it from pitching up MORE then what is commanded. The amount all depends on the amount of pitch commanded and current speeds of course. Most of these inputs are to slight/fast to be seen. Link to comment Share on other sites More sharing options...
Gungnir Posted May 17, 2016 Share Posted May 17, 2016 Wow, that's crazy. Talk about a sharp eye, OP. Link to comment Share on other sites More sharing options...
Rlaxoxo Posted May 17, 2016 Share Posted May 17, 2016 Can't wait to test the changes : ) [sIGPIC][/sIGPIC] Youtube Reddit Link to comment Share on other sites More sharing options...
Kayos Posted May 17, 2016 Share Posted May 17, 2016 You Rock CptSmiley!! Always on top of it. Love your module btw. Keep up the good work. [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
wolle Posted May 17, 2016 Share Posted May 17, 2016 super:thumbup: [sIGPIC][/sIGPIC] Intel Core I7 4820K @4.3 GHz, Asus P9X79 motherboard, 16 GB RAM @ 933 MHz, NVidia GTX 1070 with 8 GB VRAM, Windows 10 Pro Link to comment Share on other sites More sharing options...
Jugdriver Posted May 18, 2016 Share Posted May 18, 2016 And Nice Job Thunder! JD AKA_MattE Link to comment Share on other sites More sharing options...
bkthunder Posted May 18, 2016 Author Share Posted May 18, 2016 AWESOME!!!! So glad I reported this, and can't wait to test the updated FM :thumbup::thumbup::thumbup::thumbup::thumbup: Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
ZHeN Posted May 18, 2016 Share Posted May 18, 2016 that was a nice one, bkthunder ! [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
Manuel_108 Posted May 18, 2016 Share Posted May 18, 2016 Thunder and CptSmiley, you guys rock!! Thanks a ton! Link to comment Share on other sites More sharing options...
rrohde Posted May 18, 2016 Share Posted May 18, 2016 Nice collaboration here! Good stuff! PC: AMD Ryzen 9 5950X | MSI Suprim GeForce 3090 TI | ASUS Prime X570-P | 128GB DDR4 3600 RAM | 2TB Samsung 870 EVO SSD | Win10 Pro 64bit Gear: HP Reverb G2 | JetPad FSE | VKB Gunfighter Pro Mk.III w/ MCG Ultimate VKBcontrollers.com Link to comment Share on other sites More sharing options...
LJQCN101 Posted December 18, 2016 Share Posted December 18, 2016 Hi. Sorry to bring back the thread but, after an update somewhere before, we got this problem back? Looks like the flaperon still deflects considerably when turning at low speeds & high AOA. EFM / FCS developer, Deka Ironwork Simulations. Link to comment Share on other sites More sharing options...
LJQCN101 Posted December 19, 2016 Share Posted December 19, 2016 I was noticing this about a week ago and have some improvements for it, but also found a problem with the fuselage aero calculations this weekend that compound the issue further. Hopefully will have a fix in the next update apologies for the regression on this issue. Great, sounds promising. Thanks for the update. EFM / FCS developer, Deka Ironwork Simulations. Link to comment Share on other sites More sharing options...
bkthunder Posted December 20, 2016 Author Share Posted December 20, 2016 Actually I noticed the same since the last 2 patches. Glad it's being looked at! Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
Joni Posted July 30, 2017 Share Posted July 30, 2017 Hi guys! Was this ever fixed? I got the Mirage and started wondering about a lot of stuff. Intel Core i5-8600k + Cooler Master Hyper 212 EVO | Gigabyte GTX 1070 Aorus 8G | 32GB DDR4 Corsair Vengance LPX Black 3200MHz | Gigabyte Z370 Aorus Gaming 3 | WD Black SN750 NVMe 500GB | Samsung 850 EVO 250GB | WD Green 240GB | WD Caviar Black 1TB SATA 3 | WD Caviar Blue 500GB SATA 3 | EVGA 650 GQ 80+ Gold | Samsung CF391 Curved 32" | Corsair 400C | Steelseries Arctis 5 --- Razer Kraken X Lite | Logitech G305 | Redragon Dyaus 2 K509 | Xbox 360 | Saitek X-52 Pro | Thrustmaster TWCS | TrackIR 5 Link to comment Share on other sites More sharing options...
myHelljumper Posted July 30, 2017 Share Posted July 30, 2017 Hi guys! Was this ever fixed? I got the Mirage and started wondering about a lot of stuff. What is fixed ? If you are talking about control surface movement or relaxed stability the current implementation is good IMO. Helljumper - M2000C Guru Helljumper's Youtube https://www.youtube.com/channel/UCK3rTjezLUxPbWHvJJ3W2fA Link to comment Share on other sites More sharing options...
bkthunder Posted July 21, 2022 Author Share Posted July 21, 2022 (edited) I have to bring this up again. With the latest udate from today 2.7.16.27869, the relaxed-stability seems gone. The elevons are in the up position for as logn as you pull the stick. Sorry to see this bug come bug after so long. Please fix it again Edited July 22, 2022 by bkthunder Windows 10 - Intel i7 7700K 4.2 Ghz (no OC) - Asus Strix GTX 1080 8Gb - 16GB DDR4 (3000 MHz) - SSD 500GB + WD Black FZEX 1TB 6Gb/s Link to comment Share on other sites More sharing options...
myHelljumper Posted July 21, 2022 Share Posted July 21, 2022 4 hours ago, bkthunder said: I have to bring this up again. With the latest udate from today 2.7.16.27869, the relaxed/stability seems gone. The elevons are in the up position for as logn as you pull the stick. Sorry to see this bug come bug after so long. Please fix it again Hi, This is a known issue. The current iteration of the FM and CDVE is not final and we already have a internal build where the aircraft is neutrally stable and the elevons are behaving as they should. We even have implemented the USEL (Ultime secours, Last resort) control mode, where the stick directly control the elevons. This internal version is still work in progress and might take some time to be released as we want it to be perfect. The Mirage 2000 has a tricky airframe and it proved difficult achieve a correct result. We feel the current OB version is good enough for now until we have the final FM and CDVE. As soon as we have more info to share we will, thanks. 1 1 Helljumper - M2000C Guru Helljumper's Youtube https://www.youtube.com/channel/UCK3rTjezLUxPbWHvJJ3W2fA Link to comment Share on other sites More sharing options...
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