stefasaki

Hi there! just tried this mod out, it's a great addition I have to say! I have a few concerns about its new missiles though, each and everyone of them has some kind of issues. I used this mod mainly as an adversary and these are the problems I found about its missiles : The MICA IR is hardly a threat since a single maneuver will make it stop. Its drag while maneuvering is considerably overestimated. The MICA NG and the METEOR have similar problems: their speed is too high (both reach Mach 16... haven't you noticed that?!?) and this also means that they won't hit anything if they loft because the missile goes pitbull just a couple of seconds before intercept and it does not have the time to maneuver towards the enemy (the missile will fly over the target at mach ~12 while pulling max G's). If the missile does not loft it becomes unavoidable due to its ludicrous speed. I hope you can sort these things out. Best regards

There’s also another minor nuance that should be easy to correct: at 710 JPT we currently get the 15 seconds warning, which should happen at 780 JPT. According to your manual the time limit at 710 JPT should be 15 minutes

After reading part of the su-27sk manual the deep inverted stall looks realistic, it supposedly is very hard to get out of it. It seems however too easy to enter it. Per the manual you need a negative AOA and an airspeed lower than 310 km/h, which is also what happens in DCS, the problem is that often in the game you can enter the inverted stall while recovering from a cobra-like maneuver, as the game thinks for some reason that your AOA becomes negative, while it should always remain positive. Basically any pitch down with the direct control mode (even from 90+ degrees of AOA) will result in an immediate negative AOA, this is why it’s very easy to enter it in the game if you’re not being careful

The last 1-1.5 seconds you are referring to are needed to align with the runway, the turn is already completed. If anything it looks closer to 13 than 14 seconds. You cannot replicate that time in DCS without over g-ing or disabling the FBW. Yeah, I know about the problems in the transonic region, I hope that will get fixed, as it certainly is a bigger problem than the probably slightly underestimated Cl max. edit: actually the Cl max may be correct, it's just that the FBW in the sim fails to keep max AOA as the speed drops below cornering speed and therefore the Cl decreases. if the aircraft were capable of keeping max AOA for the entire circle then we might see a 13 sec full turn even in DCS

Hi! I just wanted to point out that the all time best 360 turn done by a fighter jet at an airshow goes to the su-27 (-PD variant flown by Kvochur) which routinely did it in 13 seconds. That was the last maneuver of Kvochur's demos in the Nineties, the aircraft was very light at the time of that manuever (17500 kg or so) and it wasn't by any means a sustained turn. Still, no other aircraft comes even close to that. In terms of DCS performance the Su-27 can't do better than 14 seconds without disabling the FBW, so there is some room for improvements there, while the MiG-29 is quite accurate, as a 16 seconds full circle (the best done by a Fulcrum at airshows) can be easily replicated. I find the mig-29's flight model to be quite realistic and well done actually. Here's a video of the 13 seconds turn (4:25 -> 4:38) :

@nighthawk2174 I think the point they were trying to make about the f-15 was the fact that accurate drag indexes aren't taken into account, nothing to do with the acceleration of a clean F-15C, for which all kinds of charts are available and we are mostly sure that, at least for a standard day, the in-game performance is correct. There are minor errors anyway, but nothing big enough to be game changing like for the flanker. An example is that the F-15C in DCS reaches a maximum Mach number of 2.606 regardless of temperature, and that's not correct, only at very low temperatures it should be possible to reach that speed. On the other side I have a feeling that the Eagle doesn't perform as it should at very low temperatures in DCS, as its acceleration and climbing ability aren't influenced much. But this again is very marginal and the game is accurate enough for the eagle really. The correct drag indexes for the various pylons would be a nice addition though (if they are really wrong in the game). The problem we are discussing here concerns the acceleration of the su-27, for which no official charts are available. The effect of temperature on acceleration is significant, but it usually is in the order of 15-30 % for every 20 °C of difference (when not close to the maximum speed in that particular condition). The discrepancy we have here at mach 1.1-1.3 is in the order of 150%. An error is clearly present. The video is just there to prove that something is wrong indeed, it's not meant to provide data to be used in modeling.

That's understandable. Is there any high altitude acceleration number that we might crosscheck with DCS?

I did that test with a clean aircraft, meaning that a slighly better result was expected. What we really would need is an official acceleration chart...

@BBCRF I just checked the 1100-1300 (true airspeed, km/h) acceleration at 2000 m of altitude and the su-27 in DCS needs about 12 seconds with a total weight of 20000 kg. However, the su-30mk2 in the video needs about 9~10 seconds to do the same (940 to 1110 indicated airspeed, assuming standard day) at over 3000 m of altitude. Are you sure that your value was for true airspeed and not for indicated airspeed? Anyway, a 20% improvement in acceleration is typical for low temperatures, that could explain the discrepancy between the video and your data, what isn't explained is the enormous difference in the 1100-1300 range (indicated airspeed), suggesting that the biggest modeling error is in the drag coefficient at Mach 1.1-1.3

The aircraft in the video is pointing down slightly in the first part, but it points upwards in the 1100-1300 range, and that's where we have the biggest difference. It never actually goes to 2900m, what you see there is a typical dip in the altimeter reading across Mach 1, it's a known thing. You should just check the vertical speed indicator. Of course that video cannot be taken as reference for further modeling, it is merely there to show that the current su-27 in DCS is, in fact, wrong. Also I don't get your statement about the 430 km/h thing.... I just chose to measure the 600-1100 and 1100-1300 segments.... it's just a choice, we are also sure that the engines are fully spooled up at 600 km/h in this case

I ran a first acceleration test with the su-27 in DCS just to give some numbers on the current situation. This test was run in standard DCS conditions (surely this is a higher temperature than the one in the video, but the purpose of this test was to show the order of magnitude of the discrepancy we currently have) with a lightly fueled Su-27 (which would obviously be lighter than the su-30mk2 in the video). The altitude was 3200 m and all the speeds are indicated airspeeds in km/h, times are in seconds: 600-1100 1100-1300 Su-30mk2 (IRL) 21~22 18~19 Su-27 (DCS) 32 70 The results show clearly that this difference in acceleration cannot be attributed to differences in ambient conditions/airframe but that a modeling error is evidently present. The current difference in acceleration that we have between real life and DCS in the 1100-1300 km/h range is comparable to difference that lies between a Formula 1 car and a sedan car (in the 0-100). That's why I think that a rework would be nice, this is not some minor modeling error.

Subsonic acceleration is mostly correct, I did that test and the result was close to 15 seconds, which should be the correct value. The problem is in the transonic regime.

ok I have found something that may be called as proof for the current poorly depicted transonic acceleration. This is the video of an accident due to engine fire of an su-30 MK2 (same engines as the su-27) during a maximum acceleration test. The HUD shows an acceleration from 600 to 1100 km/h (indicated airspeed) in around 21 seconds and a 1100 to 1300 km/h run in 18 seconds. Mach 1 at 3000m should be around 1015 km/h (again ,indicated airspeed), so the transonic regime is fully captured here. What happens in DCS is a huge disparity in both ranges but the 1100 to 1300 suffers particularly. Take the su-27 in DCS, bring it to 3200 m of altitude as in the video and perform this same test. The disparity is just unbelievable. I'll post here my DCS times when I'll have time to run a few tests with different fuel loads and temperatures. I thought that some of you might like to try this themselves first.

That's pretty much what I mean. You found exactly a 50% difference, which is not realistic at all (my disparity was slightly larger because my time with the eagle was slightly lower). Should we post this as a different thread? This risks to go unnoticed otherwise (as it did for 3 or so years)

The climb schedule is similar for most fighter jets. The SEP is highest at around Mach 0.9 and a climb should be performed at around that speed. Both the f-15 and the su-27SK manuals that are available online confirm this: for the f-15 we have the full max SEP graph on its performance appendix that shows you that the eagle follows that, while for the incomplete su-27sk manual there's just written that a maximum climb to 11000 m should be performed at around Mach 0.9. Also, changes in climb schedule have a lower order of magnitude effect on the overall time to mach 1.6 (you can test this yourself in DCS) compared to the 60% difference that we currently have between the two aircrafts. The eagle should have the advantage but, in particular for a clean aircraft, this should be very slim. The gap increases between the two aircrafts if they carry missiles, but that's understandable. The problem is the base value. My personal estimate, coming from experience with various aircrafts manuals and a degree in aeronautical engineering, is that the difference between a flanker and an eagle at low fuel and in a clean configuration should not be more than 5~10% (and closer to 5)

I should have worded that differently. A common test is a mixed time to climb and time to speed. It’s relevant for scramble scenarios. Time to 11000 m and mach 1.6 is a common test for interceptors, as it gives you an idea of both climbing and acceleration. The su-27 suffers particularly on this aspect in DCS

Do you mean a graph of the transonic acceleration in DCS or in real life? We should be able to produce a graph from DCS quite easily, while for the real acceleration charts that's a different thing, I don't have them and I really don't think they're available anywhere. All we have is some talking from flanker pilots in the russian section of this forum and common sense that tells you that there's clearly something wrong about it, given the huge disparity between its behaviour and that of all the other fighters with movable intake ramps of the game. Also at higher speeds, around mach 1.6, the flanker starts accelerating as much as the eagle. It's really an odd behaviour, I don't know why it isn't addressed more often

The SU-27 has always lacked some thrust in DCS after it got its PFM. I personally did not notice any difference lately and i find the actual acceleration to be quite realistic in the low subsonic range. Its problem is in the transonic regime. If you've ever tried to do some time to climb tests I am sure you've noticed that too. At the moment a low fuel, clean Flanker needs about 60% more time to reach Mach 1.6 than the Eagle from a standing start, and that's ridiculous... (it seemingly needs an infinite amount of time to get over mach 1.2) but you don't notice this problem in a dogfight because its performance in the subsonic range is totally believable and most likely correct as i already stated. An official figure we have is the 15 seconds needed to go from 600 to 1100 km/h at sea level with 2000 kg of fuel, and in the game we can match that result. In conclusion, if there's anything to fix, it's not the slow speed range.

unfortunatley that's just a reskinned F-15C from FC3....meaning that it has the same performances as the Eagle. Being able to land at 140 KIAS in the 104 is kind of an immersion killer, and that's why VSN mods are great but just for aircrafts with performances already similar to the eagle (i believe they can only change acceleration and a few other parameters). And this is also why we need a good F104 mod by FTV!! Btw I just cannot wait for the G-91 to come out! Great job so far!

I don't think it is available anymore... i am sorry. I also don't think that I would be allowed to redistribute it. How about a VSN su-35 in the future?

Thank you rifter! The mods still work on open beta indeed, and every original mod works too (mb339/A4). For some reason ISVA's SU-35 is still working also on stable even though it certainly uses fc3 files. And thank you razo+r for your quick update too! @jjl9999 i own FC3 of course

Hi! Just after installing a bunch of the free modules on trial for this month all of my VSN mods stopped working. I can see them but i can no longer fly them. Am I the only one with this issue ? Any ideas on which files are responsible for corrupting these mods? This happened on stable 2.5.5

I am sure that a lot work is being done, but the newsletter from ED states that the previous study was primarily about finding a realistic zero lift drag value, not maximum lift, so ED itself doesn't claim to have the perfect model. I did my work, i used my expertise to report a bug. CFD is a complex tool, you could make a washing machine fly with the wrong assumptions, i am sure they will get to a good model with time. Up to a few months ago the aim-120 was a damn dart, and I am pretty sure that some work produced that model too. I provided some sort of solution: focus on the dynamics of the early stages of flight. And I am sure they are doing that as I read on the newsletter that they are looking for pitching moments and pitch stability (not previously done before), which for sure will greatly increase the accuracy of the simulation. Tell me what "work" should I do .... I do not work for ED, I have my own problems

First thing, if a bridge constructor told you that a particular bridge doesn't look safe wouldn't you at least listen to him? and yes, 50 g are not required, my point is exactly that, you can steer using thrust if you have it, and absurd turns are possible if employed correctly. You don't need an incredible amount of lift to do that, hence you can achieve a hit like in the first reported real life aim-120 kill. Second thing, the insane thing about that situation was the insignificant energy loss, what is more insane if you want is their subsonic behaviour (I would design airliners like an aim-120 if that were to be true) and their capability to pull 30 g only using lift at 15000 ft at Mach 1.6. As a last statement, i find your attitude to be wrong in a constructive environment, please consider being more flexible. Thank you

It's common to lose more allied aircrafts due to mountains than to enemy fire... usually i solve this by making allied flights immortal... otherwise I would lose half of them across the caucasus. Fuel management is the next major problem.... if allied aircrafts won't crash into a mountain, they will still eject while attempting to land (in the usual 3/4 allignment attempts) as they will have finished their fuel. This is just a humorous statement of course, the game itself is the best in its class and i am glad it exists, I just hope it will continue to get better, thanks ED