Fox One

It's been 1.5 years since this module went "early access". And after 1.5 years what is discussed in this thread I would describe as a VERY MAJOR flight model error. This is not nitpicking. It's an error you don't need any real world diagram to detect; you need just a little common sense. How can you realease a FM version with such aberrant behaviour? Then say "ok guys, I'm on it". You embarrass yourself if you keep doing that every week. Modules made by ED and Belsimtek never went early access with such visible from the Moon flight model inaccuracies. Have you seen any perceptible change in F-5E flight model? Even now this Mirage flight model is still not ready for early access. By now after 1.5 years this FM should be in the "final touches" phase, not with elementary stuff grossly wrong. After 1.5 years I think that's enough time to form an opinion, so I don't think I am being too harsh. For 1.5 years this FM was continuously tweaked one way or the other based on what people write on the forum. Right now this FM has ZERO credibility. I intended to write on the forum about several things that are obviously inaccurate, however I gave up. I would be only wasting my time. If the guy making the FM is not competent enough for the job and constantly needs arrows to point him in the right direction because he doesn't figures on his own obvious errors, there's really no hope. I regret very much buying this module. Lesson learned. If the FM of future modules will be made by the same guy, this is definitely my first and last Razbam module. The good side - more money will remain in my pocket.

I performed the following test. With 50% fuel at low altitude, I performed slow horizontal flight with a speed corresponding to an AOA of 20 deg. For both F-15 and Su-27 with the speed close to constant the necessary RPM was about 83-84%. With Mirage 2000 afterburner is needed. How on earth could the difference possibly be that huge? Let's pretend for a moment the Mirage FM is accurate. This would mean the aircraft could only be classified as a disaster and a complete failure. Have you ever seen a relatively recent fighter aircraft of any type needing afterburner to perform slow speed/high AOA flight? The 20 deg AOA figure is actually quite conservative, with the likes of F-16 or Mirage 2000 slow flight is routinely performed at airshows with an AOA in the 25 deg region. I really don't want to hear the "it's a delta/high drag" lecture. Yes it's a delta but not like a Mirage III delta. With the Mirage III performing slow speed/high AOA flight the elevons would be deflected upwards at a pretty considerable angle, effectively dumping lift of the platform and greatly increasing trim drag. Mirage 2000 is a relaxed static stability delta. Performing slow speed/high AOA flight the elevons are close to neutral or even deflected slightly downwards, further increasing lift, as you can clearly see here If the Mirage 2000 was really so draggy and aerodynamically inefficient at an AOA of 20 deg compared with the like of F-15, the designers would have chosen a different aerodynamic scheme. They would have figured that much, that the plane won't be competitive. But the designers knew that a delta with relaxed static stability and a wing with adaptive polar due to use of leading/trailing edge devices/control surfaces can be competitive because trim drag would be reduced very much compared with a Mirage III. Flight models is an incredibly complex and difficult task. Very very few people have the required brainpower to make a decent FM. Sadly the creator of this FM is not one of them.

60 rounds according to MiG-21F-13 flight manual.

I don't think it is. If it was, you would have to only tap W key and the limiter would be switched off. Probably would also be an animation of the switch on the left panel. But instead you have to hold W key. Since overpowering the limiter is the only other way to exceed limits, this must be what holding W does. Whether it does or does not, the fact remains that the stabilizer in simulator moves too slowly. I posted 3 videos in this thread with Su-27 aircraft just before takeoff where a stabilizer deflection rate more than 1.5 time faster than the one available in the sim is observed. In simulator the available rate is 18 deg/s (see first post). Visually I can tell you right away this is a ridiculously slow rate for any fighter aircraft from any era. MiG-29 stabilizer has an available deflection rate of 38deg/s (source, MiG-29 practical aerodynamics manual). That is more than 2 times the rate available for Su-27 in simulator. Besides being a larger and heavier aircraft than MiG-29, Su-27 also has relaxed longitudinal static stability. Fast stabilizer deflection rate is very important, if not vital. I would expect a deflection rate for Su-27 at least equal to that of MiG-29. It's engineering common sense. I timed the Su-27 deflection rate from videos and came to 30deg/s (post #1). But that is not necessarily the max rate available for the real aircraft. A pilot making a final check of the controls right before takeoff on the runway, probably does not very often check pitch control by pulling the stick fully as fast as he can. As I have already explained in this thread, the rate available in the test I performed on runway before takeoff has nothing to do with the AOA/G limiter (post #11). I repeat that even if the limiter was working in the test discussed here, the limiter is a stick stop and not some sort of a "stick damper" that slows the stick along its entire motion range. The fact that on the runway deflection test holding W key suddenly you have a rate of more than 40deg/s available does not make any sense IMO. What would make sense is if such a rate would be available without holding W key.

D model used Shrike missiles in Vietnam, there is plenty of photo and video evidence.

Test was done selecting "Takeoff from runway" from ME. Please read post #11.

From real flight manual, the limiter works only in FCS mode "flight". With gear down the FCS is in "takeoff-landing" mode. The limiter is a stick motion restrictor using inputs of AOA, G, AOA rate, G rate, pitch rate and whatever. It's not like the limiter has 2 parts for G and AOA and one or the other works. It is a single stick motion restrictor that works to limit the AOA or G, whichever happens to be above a certain value. And even if the limiter worked with gear down too, it needs AOA or G input to be above a certain value. With aircraft on the runway I am giving it an input of 1G and zero deg AOA. In such a situation the limiter does not restrict or slow the stick motion in any way. Yes!

^^^ Yes, with W key pressed the stabilizer moves fast. By pressing W we tell the simulator that we are applying an additional 15Kgf to the stick to overpower the AOA/G limiter. The problem is in the RL videos the stabilizer can be moved in pitch at a rate that is not available in simulator with W unpressed, but it should. The pilot in video links on this page moves the stabilizer at a faster rate than what is possible in DCS without overpowering the limiter because the limiter is OFF anyway due to gear down. He also doesn't press the W key because in Cyrillic alphabet there is no W letter :)

Other videos where stabilizer deflection rate in pitch is visible:

In this video at 51s time the pilot performs a final flight controls check on the runway just before takeoff (as RL manual recommends). He does a full nose up deflection of the stabilizer, and such a deflection rate is certainly impossible in current DCS version. Obviously the flight control system was in "takeoff-landing" mode. The AOA/G limiter works only in "flight" FCS mode (IRL and in simulator). Switching between "takeoff-landing" and "flight" mode is done with the landing gear handle. So the AOA/G limiter doesn't work with gear down and does not limit the stabilator rate in any way in the test I done with aircraft on the runway.

I made the timing with time acceleration set to 1/16, then divided the result by 16. Measurement was made with aircraft on runway just before takeoff, not in direct control mode.

Since the last few versions of DCS the Su-27 stabilizer moves too slowly in pitch. I timed it with the aircraft on ground and a full nose up deflection (that is a 20deg angle) takes 1.1s. This means the available rate is about 18deg/s. I don't believe for a second this is realistic :D I searched youtube and found several adequate videos and timed how long it takes IRL. Concluded that a full nose up deflection of the stabilizer takes about 0.65-0.7s. This means the available rate is about 30deg/s. So in simulator we have an available rate that is more than 1.5 times slower than IRL. This slowness you can really feel in flight. When the rate was reasonably accurate (a few months ago, I can't say precisely) the pitch "nimbleness" was already pretty mediocre due to size and weight of the aircraft. Now it is rather poor and I think stabilizer slowness in pitch is the cause.

@foxbat155 The device in your pictures is for calibrating the DUAS-69 probe (the alpha/beta probe on the Pitot boom), as you can see from its name DUAS69 and the alpha/beta rows in the table. DUAS comes from datchik ugla ataki i skoljenia - that is alpha/beta probe. The probe on the side of the air intake feeding cockpit AOA indicator is called DUA-3.

And what exactly are you LOLing about? I only corrected an affirmation made by Frederf about the real aircraft. I didn't say if 1° is a big deal or not. That's nice but I do want to contradict you right now. The attached image is a page from "MiG-21bis flight-technical chracteristics" manual.

Wrong. The 1° angle you are talking about is actually zero for MiG-21.

https://youtu.be/IXUDx7bsDYE?t=62

Any news about this? It's been reported five months ago...

Yes, almost ;) Allow me to help by pointing out only the most obvious, visible-from-the-moon errors, look at image in post #81 The windshield and canopy are like 20% too tall, air intakes are like 10% too tall and are not tilted down. The air intakes on the real aircraft are tilted down 3 deg. Ejection seat headrest is a complete joke. Ventral fin is inaccurate. I'm not sure if you know that Skylark's drawing is made by measuring the real aircraft, so everything you see there is accurate to the last mm. Also, nice try with your attempt with overimposing Skylark's drawing on your model showing "perfect match". I appreciate the honesty :thumbup:

It's a 360 deg video. Use the mouse to rotate the view until you see the instrument panel. What is interesting to this thread starts at 63s as my original link shows.

Currently in simulator the elevation cursor in search mode is obviously showing the angle between the antenna and the local horizon. Antenna pitch stabilization in search works fine, it's just the elevation cursor that is incorrect. Real manual states clearly enough that cursor shows angle between the antenna and the ARL, which implies that due to antenna pitch stabilization in search, if you change pitch the elevation cursor should move. In video link in first post it is clearly visible that elevation cursor moves in opposite way to the nose movement in pitch - nose moves up, elevation cursor moves down. Just as expected from flight manual description. So there is no misunderstanding of the system on my part.

bump :)

It seems to me what you are describing here would happen to an aircraft with unboosted elevator control, lowering the flaps would change downwash and that would change airflow direction over elevator, producing an elevator hinge moment that would translate into a force that would be transmitted via elevator control linkage back to the pilot. As you know, this does not apply to the F-86 which has an irreversible hydraulically actuated elevator. It doesn't matter if due to flaps lowering the elevator hinge moment changes; at 140kts the actuator will easily keep the elevator in the same place and no force will be transmitted back to the pilot. The F-86 having an irreversible hydraulically actuated pitch control with no pitch ratio changer or anything (just a classic force simulator spring and a trim actuator), this means applying 7 pounds of pulling force on the stick will ALWAYS produce an elevator leading edge down deflection, no matter what the elevator hinge moment is, what the airspeed is, etc. Only exception might be at very high speeds where elevator actuator might have insufficient force to deflect the elevator the commanded amount, but that's definitely not the case here, we're talking about 140kts experiment here. The actuator at that kind of speed would have no problem coping with any kind of elevator hinge moment. The pitch control being what I described above, with an F-86 aircraft trimmed for horizontal flight (as the table in discussion shows) applying 7 pounds of pulling force on the stick will ALWAYS cause a stick back movement, and that will ALWAYS produce an elevator leading edge down deflection.

Actually, on F-14A the airspeed is not displayed on HUD in any of the modes. You have to use the cockpit instrument...

I think I found what is the problem here. Or at least a part of the problem. Silly me for not figuring this sooner. I did a ground effect test. With the MiG-15 with gear down and full flaps I performed perfectly horizontal flight at 250Km/h very low above the runway, main wheels about a diameter above runway. Then performed the same test at 50m altitude. In both cases, the necessary AoA was exactly the same. This means there is no ground effect simulated. I performed similar tests with all Belsimtek aircraft. F-15, F-86 - same thing, no ground effect simulated. The only aircraft with ground effect simulated is the F-5. This is quite surprising, considering the F-5 is recent, but the initial release of F-15 and F-86 was more than two years ago! In MiG-15's case ground effect would easily decrease touchdown speed with like 15Km/h, probably more. Obvious request to Belsimtek: please implement ground effect for all aircraft. Pretty please :)

jojo, you are overcomplicating things when there's really no need to. What inputs the real flight control system uses to do its "magic" or how exactly does it is not what I'm asking here. In the attached track I'm flying the F-15. At low altitude and supersonic speed I pull the stick until I hit 3G, then for the rest of the loop I don't move the stick at all. Despite the great variation in speed and altitude during the loop, G remains between 2.8 and 3.2. That could be described as deplacements par G sensiblement constants. Le manche permet donc de piloter un facteur de charge. - that is exactly what I am doing here! With the stick in a certain position in pitch I am asking the aircraft to give me a certain G, and the flight control system will do its best to try to give me that, as long as it is still possible. I believe the real Mirage 2000 at speeds above 300 behaves in exactly the same way as I described above for the F-15. Actually I would be very surprised if it does not. 15test6.trk