BMS Other Fighters Mafia (BMSOFM) Journal
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<p>Ok, prelim numbers are looking good for the Hornet’s airfoils. Just need to fine tune known conditions and prepare for the unknowns. Also, we are moving forward with the BE sim (and MatLab) that will be the prelim testing environment for our new Hornet & airfoils, before converting the coefficient data over to the F4BMS format . . . stay tuned!<br /><br /><img class=“ql-image” src=“https://i.imgur.com/gugvNck.jpg” /><br /></p>
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<blockquote>Ok, prelim numbers are looking good for the Hornet’s airfoils. Just need to fine tune known conditions and prepare for the unknowns. Also, we are moving forward with the BE sim that will be the prelim testing environment for our new Hornet & airfoils, before converting the coefficient data over to the F4-BMS format . . . stay tuned! <br /><br /><img class=“ql-image” src=“https://i.imgur.com/gugvNck.jpg” /></blockquote><p><br /><span style=“background-color:#dcdcdc”>Just a question: how will you go from your computed airfoil Coef to the aircraft one ?</span><br />Even for the clean airfoil I’m a bit surprised by the Cl/Cd reaching 30… (not to say how it is far away from the RL Hornet max Cl/Cd)</p>
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<p>The ratio you see there is only relative to the airfoil itself, not the complete aircraft. With ‘clean’ wings, I regularly see ratios of 20->60:1 (with Reynolds ranging from 3.1M to 17M+ on laminar foils with NCrit values ranging from: 5 -> 10). So what you are seeing there is not unreasonable, to say the least . . . Thank you for helping me clarify that.<br /><br />Airfoil data wll be plugged into a “Blade Element” simulator (& MatLab), which will include airframe & foil lift - drag coefficients. Then the whole aircraft compared against ‘known’ documented conditions (NASA & NATOPS docs) to validate the performance data we will be producing . . . .<br /><br /><br /><br /><em>**Sidenote: I am seeing a CFD cl/cd ratio of 54:1 (@ 4 degs AoA, 17.5M Re) on the Hornet’s main wing. From the time I have spent in the DCS:Hornet (700+ hours) this same performance (minimal parasitic and induced aircraft drag) was also seen at +4.0 degs AoA too . . .</em><br /><br /><br /></p>
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<p>A reality coming soon . . .<br /><br /><img class=“ql-image” src=“https://i.imgur.com/4t1OmzW.jpg” /><br /><br /><img class=“ql-image” src=“https://i.imgur.com/hXMRckI.gif” /><br /></p>
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<p>So . . . another aspect we will be able to accomplish will be an aircraft’s perfomance capability against another. Welcome to the world of the E-M diagram, a theory brought forward by both Col. John Boyd (fighter jock) and Thomas Christie (mathematician). These charts will also be a validation test against the models we produce and will be compared against known EM plots from the NAVAIR or USAF sources.<br /><br />Shown here are a T-34C Mentor vs. a Bede BD-5J, quite the fight would ensue! One can quickly tell the BD-5J has the instaneous [loss of altitude and/or airspeed, -Ps values] turning advantage at ~112kts @ 35 degs/sec. It would be a really interesting ‘rate-fight’ at around 114 knots (@ 19.2 degs/sec) where both aircraft exhibit a, Ps=0 value (sustained turn-rate with no loss in airspeed or altitude)<br /><br /><img class=“ql-image” src=“https://i.imgur.com/kig04iO.png” /><br /><br />Bede BD-5J<br /><img class=“ql-image” src=“https://i.imgur.com/br2ztLN.jpg” /><br /><br />T-34C Mentor<br /><img class=“ql-image” src=“https://i.imgur.com/h6S5POG.jpg” /><br /></p>
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<p>Good Day, All. Here’s our update for today…<br /> I have been notified that the Mafia hotspot fixes created for 4.35 have been put the base 4.36 install. We are honored the Dev’s include our stuff! Meanwhile, we continue to work on the F-18C flight model. At his point we are working under the assumption that it will not be ready when 4.36 comes out. So, we have already created an “Install Pack” that will have everything you need, including a User Guide, and don’t be worried that it’s some nightmarishly complex procedure. <img src=“/plugins/nodebb-plugin-emoji/emoji/android/1f628.png?v=1g16vn91q2r” alt=“” class=“not-responsive emoji emoji-android emoji–fearful” /> <br />This will also help the other Hornet variants like the EF-18M and the CF-188. I also have a little side project going where I’m experimenting with how the new Hornet stuff relates, or basically how <em>can </em>it relate, to the F-18 E/F and the Growler<br /> <br /><br /><br /><br /><br /></p>
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<p>@drtbkj excellent news, magnificent I would say, that the development team will take part of the FM work and base it on 4.36, wonderful. We are making progress.<br /><br />regards</p>
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<p>Bug FM Status: I have been working closely with a PhD in Aeronautics. I am in the process of creating all the coefficients and guidance <control> laws for an F/A-18. It will have to be tested in another 6-DOF sim (JSBSim) beforehand though, to make sure all the numbers pan out properly. Then copy all the coefficients over to BMS acdata format. Then a ‘good run through’ with all of our <in house> beta testers, then a ‘release to the wild’ with one of the most accurate representations of our wonderful Bug (within BMS limits), for all to enjoy! Sadly, these FM changes will not make the initial 4.36 release deadline, but will be worth the wait . . .<br /><br /><br /></p>
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<p>@TGW Do’nt you think it is exactly what has been done before ?</p>
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<p>@TOPOLO I’m not sure what you mean</p>
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<p>@TOPOLO <br /><br />Yes, I am sure it has, but whom are you speaking of that has done this, and how does this relate to BMS? Slightly confused about your statement??</p>
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<p>@TOPOLO <br /> Well, once again I’m not sure what you mean, or your purpose in asking. I can add to TGW’s “what this means to BMS?” is simply to improve the BMS Bug, and by extension the other jets in BMS. And, we are committed to do it the best way we can<br /><br /><br /><br /></p>
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<p>@drtbkj <br />how do you think the current BMS F-18 FM has been set up ?<br />don’t you think all CL, CD and others have been computed point by point ?<br />what make you think the bug FM is so wrong that it needs to be redone from scratch…<br />why don’t you try to compute the F-16 FM using the same method you are using for the Hornet and compare with HFFM to benchmark your methodology ?<br /><br />I’m not saying you are wrong, or you will not succeed, I’m just trying to understand what you are trying to do, and why…<br />No one has ever computed a fighter performances the way you explain you want to do it, so I’m just curious <br /><br />sorry for the typo errors, I’m far away from my keyboard…<br /></p>
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<p>Hi, Topolo. I have to preface my reply by telling you I am not the Tech Brains of the Mafia. So, I can’t discuss the specifics at your level, and don’t want to give you bad information. You are welcome to visit our Discord and ask all the tech questions you want. Heck ,maybe you can even help us do it better. I can just say we are doing what we think is the best given our Members’ skill sets.<br /> But, there is one general thing in your post I wish to respond to… You wrote “what makes you think the Bug FM is so wrong that it needs to be done from scratch?” I do have a specific reply to that question. We most emphatically do NOT think the Bug FM " is so wrong" We are offering to help refine it, not replace it. I , and all of the Mafia, have repeatedly said we are building on the foundation laid by the BMS Dev’s. That is not rhetoric on my part., but simple fact.<br /> Let me give you a bit of “Mafia History” .When 4.35 came out and the hotspot issue popped up , the Dev’s made it clear that they just didn’t have the time or focus to work on the Other Jets in BMS. In fact, Mav-JP came on the old Forum and said he wished some “third party” would come in and help with the OJ’s. That’s not a direct quote, but that was the idea. I wonder sometimes if he even remembers writing that, as that statement was what got me thinking about creating the Mafia in the first place. Sidenote to Mav: Is this an example of "be careful what you wish for? .<br /> Anyway, in simple non-technical terms, what we are trying to do is: help.</p>
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<blockquote>why don’t you try to compute the F-16 FM using the same method you are using for the Hornet and compare with HFFM to benchmark your methodology ?</blockquote><p><br />This is on the to-do list (to validate our process) with your vehicle also, thank you for mentioning it!<br /><br /><br /><br /><br />PS: Excellent dissertation, on the paper (F-4 Phantom II Flight Model Identification) you did for the F-4, by the way!!<br /></p>
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<p>@TGW <br />I do beleive F-16 is the best test case to validité your approach, it is one of the most documented flight model, with different sources that make a global consensus.<br /><br />You can also compute EM diagrams from your aerodynamic computation and compare them to official ones. For BMS flight model, the maximum difference in sustained turn rate between BMS and RL manual values are under 3-5% for every Mach values between minimum sustained speed +50kts and M0.95. (For clean a/c or with 2 fox-2)<br /><br />Once you have reach such accurracy, you can assume your aérodynamic computation as correct, and so use it for a less documented aircraft.</p>
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<blockquote>PS: Excellent dissertation, on the paper (F-4 Phantom II Flight Model Identification) you did the F-4 by the way!!</blockquote><p><br />You can find the same for MiG-21, F-5 and Mirage III family. (The case of the MiG-23 is a bit different)<br />I’ve used the result of these analysis to feed BMS FM, even if it was not the initial purpose.</p>
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<p>Hello,<br /><br />besides these technical perspectives, there is -a little something I really would like to recall, from a pilot’s perspective.<br /><br />Aircraft rarely have the same performance, from day to day… Engine output may vary a bit, while airframe may have suffered some slight twisting that changes not only the behavior of the plane inflight, but also the global performance.<br /><br />So, while I think it’s great to spend time on a flight model, please also remind that flight model will necessarily be always wrong.<br /><br />How many times did I said to myself during take-off or inlight : “Geez, what’s happening with this plane ?” Piloting is not only a matter of mathematics, it’s also a matter of events and fortune.<br /><br />Then, there is something which is often missing in flight simulation which is : flight stick sensation. It’s really good to bring a flight model close to the real deal in term of performance charts, but what about the physical flightstick feeling ?<br /><br />This perspective is also really important, because piloting is mainly about flightstick sensation. I can’t really remember avionics of aircraft I flew in real life. But I can perfectly recall how I felt them from my pilot’s seat through my hands.<br /><br />My advise is : when doing a flight model, try to talk to fighter pilots who really flew this aircraft, and ask them : “How was the aircraft inflight”. "“Please tell me about flightstick sensations”. Every pilot will remember how they felt their aircraft, because this is what piloting is about and why it’s so hard to become a fighter pilot or a surgeon : most of the work is in your palm and fingers, not in books and charts !<br /><br />I never flew 5th generation fighter aircraft and will never do, but it was like that on 3rd and 4th generation fighters.<br /><br />Cheers,<br /><br />Radium<br /></p>
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<p>Laudable stuff, but you are going to have to be pragmatic about cfd results probably. simulating the stall point and high AoA lift requires a very very dense mesh (y+=1) for the entire lifting surface and I presume you won’t have access to that kind of computing power.</p>
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<p>@Easy <br /><br />Have you used STAR CCM+, or better yet, Ansys Fluent? Computational power used to be problem in the past, but with coders accessing CUDA SDK’s for GPU core assisted computation, even end-users can get alot of work done, in short periods of time now without needing a server farm for assistance . . .<br /><br /></p>