Maverick Su-35S

Roger jcomm, that's simply the prop's effect induced yaw as I told and as I repeat it only affects the P-factor if there's no rate of change in AoA or sideslip and I didn't say anything contrary to this! Again, this is yaw induced roll, which mainly generates a P-factor that depends on angle of sideslip and dynamic pressure and as the ball stands deflected (meaning that there are sideforces, lateral accelerations or the existence of a yaw rate that would create them) there's also a small gyro effect (precession) that takes place. I also know this and there was no need to mention it again. I feel like we're not going anywhere with this! If you feel that I don't understand something else, I'm pleased to listen, otherwise I know how these effects occur and repeat myself, the only thing that bothered me was some particular effect's magnitude when the prop is not spinning anymore (is stopped) and for instance that can only be the P-factor (cause there's no talk about gyro effects or gyro precession if there's no angular momentum) Again, this is the case when a prop is still spinning with some given rpm and I've also confirmed/told that the gyro effect (precession) is somewhat countered with the P-factor, so we're again saying the same thing and neither of us understands what does the other one try to say different;)! Thx. jcomm, cheers!

Look, you don't have to teach me about flight dynamics or stable/unstable systems cause I know them better than you think! You are wrong and contradict yourself when you talk about an unstable system which behaves like a stable one..., that means you didn't understand what instability is. By saying that you or a machine can keep a pen "upright" with constant forces, without oscillations (and I've already mentioned this), then it means you don't know what you're saying. I say again: When it passes over a certain limit, not even the robot/computer or whatever can turn it relatively stable again. You try to prove that you know things better, when actually and honestly, you don't...! This is one example that I know about which has 2 degrees of freedom (I hope you know what a degree of freedom is), and a programmed arm will keep it in a RELATIVE upright position, but not absolutely upright as you told/think!. Watch from 0:55: Now about fighter aircraft...! Do you know when a fighter aircraft actually becomes unstable (when the static stability margin becomes negative)? How would you describe the control surfaces deflections that control the stability of such an aircraft? Indeed the static stability margin may become negative, but only in some conditions that you definitely didn't mention which leaves me with the thinking that you actually don't know about. You are talking to me about fly-by-wire and active control systems and about control theory and such..., that are being used to make an unstable system behave relatively like a stable one, but it more seems that you can't handle such things, or at least this is what you make me think! Speaking of witch..., to give you a hint that your examples are contradictory to what you say, I was able to fly the Su-27 with ASC direct control ON, do well controlled manoeuvres including shooting other aircraft with the gun in a dogfight, and land as smoothly as normal. Now you should also try and fly and control the Su-27 in pitch with the ASC direct pitch control on and tell if that's unstable while flying..., if so, where..., if not, why? If you can't answer this question correctly, then we have nothing more left to talk about on this subject! Don't get me too wrong, but I actually started to loose my patience with those trying to look smarter before they know what they're actually saying, sorry...!

When the aircraft goes above a certain airspeed for which the airflow is supersonic from the nose (except in front of it where it will always be locally subsonic) to tail, then that can be called supersonic flight..., anywhere below this speed where subsonic flow regions appear anywhere on the airframe, even at the tail of the plane, then that Mach number or airspeed is called transonic, so it can no longer be attributed to a supercruise flight. The transonic regions may vary from anywhere between 1.15 to as much as 1.3+ depending for airfoil section, 3D wing's shape (aspect ratio, wing sweep, etc.) and overall airframe's shape. So in this case, some aircraft are physically supercruising only after a given Mach number while some others don't. For this reason, supercruise flights are called to be that way, by convention, only after a certain Mach number had been reached, for instance nowadays it's considered so only after Mach 1.5, which is far from 1.08 or 1.1 that some talk about! Indeed the soundwaves are falling behind the aircraft as it goes faster than exactly 1.0 and can't be heard outside the Mach Cone, yet it's still transonic...! The F-15 is only able to reach higher transonic flights with full MIL power (without AB), not supersonic.

Hi jcomm, That's adverse yaw due to roll, and although you didn't mention the blades spin direction, by what you say, they should be spinning to the right and if you were telling about P-factor, it develops from the beta (sideslip) and AoA only (the roll alone does not affect P-factor) and thus judging by this it results that the P-factor would tend to pitch the aircraft down (as the 12 o clock blade would have more lift than the 6 o clock one) and it would later counter with the gyro effect which would tend to yaw the aircraft to the right and I've already mentioned before that the P-factor and gyro effects are countering each-other (each having it's particular magnitude). The P-factor's magnitude is affected by a law described as the derivative of the P-factor to the AoA + a derivative of it to the beta angle, while the gyro effect's magnitude is affected by the derivative to AoA rate + the derivative to beta angle rate, at least the theory tells it, so one depends on the static angles, while the other depends on their rate of variation. No need for further explanations cause I know these things well too, it's the magnitude of the overall effect that bothered me from the very beginning if you understand...! They are being simulated, and they had been so from the first prop plane that appeared, the P-51D, but the overall values just seem out of the ordinary, but I take Yo-Yo's word for it and try to believe that this is realistic. Cheers jcomm!

Right Yo-yo, indeed I haven't flown nor seen a RL footage of a blades stopped aircraft gliding where the pilot would pitch or yaw the plane in that condition to encounter the kind of swirl effect that we have, and after all that I've said and told that there can't be such high variation of lift/drag ratio or of either of them separately when the blades are stalled (especially in low blade pitch), when the AoA and/or Beta of them varies, I'll take your word as it is even if I'm not fully convinced (based on what I've mentioned) that even for a prop aircraft with quite high sum of blades area to wings area ratio it would be plausible to get such swirling effects when you vary the AoA and/or sideslip. All I'm saying (being skeptical) is that the swirl effect developed in such conditions should be smaller than it is, but this is only how I see it. Thanks!

Hi Exorcet, I know you're a car aerodynamicist if I remember correctly and I'm glad to talk with you. You're right, I did not have them together and I've also mentioned myself it would normally be needed to do so, this time I only took the fuselage separately for those who believe so much in having the fuselage generate so much lift and opposed to that of the wings. I wanted to show the aberrancy of their theory by making this compromise. The initial CL.max of 0.9 was for the whole aircraft together with the elevator at 0 deflection and normally I didn't do quite a right thing adding the fuselage as a standalone body to something that already had an overall lift distribution, but I say again, I had to find a way to dismiss some ideas that the fuselage (even if the wings would have 1 deg. of positive incidence) which should create an even higher tendency for downward/negative lift, can do such things as we see. Indeed, you're right, but the MAC on which the whole wing's performances (in some areas) can be reduced to make calculations simpler and not affect reasoning, is overall cambered and has a slight washout (negative incidence gradient across the spanwise for a smoother lift distribution) as well. Either way, the F-15 (50% fuel, no weapons) has a lower wing loading AND higher CL slope than the MIG-21 (50% fuel, no weapons) and even with a cambered MAC it still flies with both the longitudinal axis and MAC's chord with a slight positive attitude angle and positive angle of attack respectively but higher than 0 (in level flight). The same thing does apply for the Su-27. Only a combination of a highly cambered airfoil and very low wing loading could possibly allow for an aircraft traveling in transonic-supersonic to fly at a negative real AoA at +1G, especially in the presence of shock stalls (which greatly degrade the lift slope and stall AoA values). I've attached a track where you can select either the F-15 or the Su-27 where you can test them or watch how they perform. I'm not saying that negative angles of attack aren't possible (talking about wing only, no need to discuss about fuselage which has very little effect anyway). In the right circumstances of camber, indicated airspeed (dependent on dynamic pressure) and wing loading, it is possible to obtain negative angles of attack flights, at positive G-loads. One good example for such situations would be the gliders which are having just the kind of high cambered MAC and very low wing loading which allows them to fly with negative AoA at or even above 1G at low subsonic Mach numbers, but I say again..., there is nowhere near that case for the MIG-21...! There is no explanation for why the MIG-21 does such a thing in our simulator, even if there were no shockwaves to separate flows (stall), there is no explanation than the fact that there is a mistake or error somewhere in the aerodynamic analysis. I'm feel sorry, but this is how it is. It might not be a huge error at all to most of us and we're all pleased with how it flies in general, but in this particular situation something shows up as not being physically right whatever we might think!

Hello everyone, I know that some don't like to see me very often while others share my thoughts and knowledge and know what I'm talking about. The MIG-21 is known to be an aircraft with quite a good longitudinal static stability margin (great arm between CG and general center of lift or pressure (CP)). Now this is perfectly reproduced by our sim up to a given AoA, after which the things start to go wrong. The longitudinal static stability (or otherwise referred to as pitch stability), as long as it's still positive, not neutral or negative (no known fighter aircraft has it negative even if you hear some ignorant saying: "Unstable aircraft, Unstable aircraft!", don't bother with him, cause he doesn't know what he's saying...), should allow an aircraft to keep reducing it's angle of attack as close to 0 lift as possible, when the elevator is at 0 (neutral). All modern fighter aircraft are being designed to have a reduced longitudinal static stability margin or very close to 0 (relaxed static stability aircraft) in order to obtain much better flight characteristics by having the elevator take part in lifting the aircraft, so a more reduced longitudinal static stability aircraft would have a more downwards deflected elevator which produces lift in the same direction as the wing, thus increasing the total lift. So far, there isn't any aircraft that would be unstable, because after all, unstable IS unstable and no computer can bring it back once it passed over a certain limit and might mostly be able to hold it only through oscillations (it's like trying to keep a pen in equilibrium on your finger) and no such thing exists for flyable aircraft, but anyway this is not our issue here and the MIG-21 doesn't do this either, I just wanted to point out the 3 different situations so no one could confuse them. The problem is that after some patches ago (don't know how many), the MIG-21's FM had been tweaked and some things have gotten better, but other things are not doing the same, and here's how it is: 1. The pitching moment has some strange behavior between certain AoA values. The first one would be exactly where the wings start stalling, which is 32-33 deg. AoA on the AoA indicator or 20 deg. of real AoA as measured more correctly. Starting from the stalling AoA and continuing to slightly increase it, an abrupt and strong pitch stability reduction occurs and according to the elevator deflection that the aircraft has at that point, the AoA accelerates rapidly to about 30-40 deg. or so where it abruptly stops! This could only be imagined as the CP would sharply move quite forward and very close to the CG (not beyond which would mean "unstable") in the range of one or 2 degrees of AoA and then coming back almost close to it's original position when the AoA reaches about 30-40 as I said. Now, although there might be some heavy flow detachments starting from the trailing edge towards the leading edge (on the upper surface for positive AoA), while part of the leading edge might still retain flow attachment due to the vortexes generated between the leading edge and root which would translate into the high loss of longitudinal static stability margin because the CP moves forward towards the vortexes, the fact that when reaching about 30-35 deg. AoA the stability margin becomes abruptly very high, which isn't right, even if we'd talk about the vortex breakdown that might occur and which would increase the pitch down moment, still the transition shouldn't be so rough. So, all I'm saying is that the transition or traveling of the center of lift or pressure "CP" shouldn't be so abrupt and should be as smooth as it can be found for the F-15 which should have quite similar static stability characteristics in reality. Another and much greater issue is that when reaching 90 deg. of AoA, which can only be reached through stall spins (which is absolutely normal for such a highly stable aircraft), after reducing the yaw rate to 0 the aircraft trims itself to 90 deg. of AoA like if it's statically relaxed there and won't budge in pitch whatever you'd try. This is also abnormal..., normally the higher the AoA (after the stall occurs) the higher the stability margin and therefore the higher the stabilizing moment should be towards reducing the angle of attack, but it seems that at 90 deg. there is no more stability margin left at all. 2. Indeed the stalled lift is no longer 0 cause that wasn't correct, but it's still very small compared to what it should've been, at least from my personal point of view. As you increase AoA and go passing through critical and start stalling, from the maximum achieved G-load, it drops to about 20-25% of what it had been shortly before stall, which still looks not OK. There should be some more...! There are a lot of CL vs AoA diagrams to be found for whole 3D wings, not just for airfoils, that could give a general feeling of how much should the lift drop after the stall and with what slope it should continue to rise as the AoA continues to rise throughout and beyond the stall up to 40-45 deg. from where it naturally starts dropping towards 0 as the AoA reaches 90. Furthermore, for a delta wing and mostly for highly swept deltas, the stall should be more docile/gradual due to the strong vortexes that are being generated between the leading edge's root and the fusealge and also, before the vortex breaks up (some 5-10 more deg. of AoA (depends from a wing to another) since the stall occurred) the lift drop beyond stall should be smaller than for a straight, high aspect ratio wing...! I tell these facts because this is my domain and there is proof for this. I'm not complaining about this, but..., there should be a lot more lift remaining after the stall occurs. Please test it: MIG-21 80..90 deg. AoA gives 0 pitching moment.trk Thank you!

You know 100% inside and out of subsonic + compressible aerodynamics? Now don't get me wrong, but I'm an aerodynamicist and I don't make such claims although I know and have learned a lot having a decade of experience in this domain including supersonic airflow and even so..., I know that I'll never know it all even after I die, but hearing you saying that no wing should ever produce lift if it doesn't have positive AoA..., just leaves me speechless! What about cambered airfoils, I guess you heard about them, right? Even car aerodynamics take the lateral shape of the car as an airfoil and it NEVER had been symmetrical...! I honestly bet you meant something else by what you told!

Are you sure?... If the real MIG-21 would fly straight and level at the so high negative angle of attack in our sim, please show me a real life footage of that or some relevant real life data which to make me believe that, otherwise this is only what ED's CFD or their third party members CFD or a form of aerodynamic analysis that would suggest such a thing and it's not the first and will not be the last time when those kind of analysis, not supported by real data, could be wrong. Now, this happens to be my domain and I'm curious about the results that can come up...! Let's presume that the MIG-21's lift produces a maximum lift coefficient of 0.9 (from some real aerodynamic tests with no flaps it almost reached 0.9 at very low subsonic Mach numbers for 1:1 scale model) at a critical or stall AoA of about 20 and a 0.016 lift coefficient at 0 AoA. Later I should turn the AoA from degrees to radians in order to use it in calculations to determine the lift slope of the MIG-21's wing for low subsonic speed. I've talked early in this year to a RL and active MIG-21 pilot in order to have the maximum (critical) AoA and 0G AoA which I desperately wanted to know because I debated the real AoA vs indicated AoA of the MIG-21 on a thread that I've started on the subject much earlier before. Now let's calculate the lift to AoA derivative or slope (which is otherwise important to predict the lift coef. at any given AoA) by dividing the lift difference to AoA difference on the linear lift/AoA margin only (at least 2 degrees AoA before stall): 0.9 - 0.06 / (18*pi/180) = 0.9 / 0.3142 => lift slope of MIG-21's wings alone = 2.6738 We must know that the CL of an aerodynamic component like wing, fuselage, fin, etc., for some AoA (already knowing the slope and the CL at 0 AoA) is: CL = CL at 0 AoA + lift slope * AoA in radians By knowing from experimental results that the mig-21's wings produce about 0.06 lift coef. at 0 AoA, then for -2.5 deg. AoA which is now equivalent to the -2.5 pitch down attitude that the fuselage's axis has in straight horizontal flight, we should get a positive wings lift coefficient at which the plane should be flying with, but sadly this is what we get: 0.06 + 2.6738 * (-2.5*pi/180) = -0.0567 So, there you go, -0.0567 lift coef. at -2.5 deg. The plane should in NO WAY keep flying straight and leveled as it seems to do in the sim, but rather plunge at some negative G-load instead. The wings should produce such negative lift coefficient alone at that negative AoA. In order to produce no lift, the wings should be flying at this AoA: -0.06 * 180 / (pi * 2.6738) = -1.2857 That's the 0 lift angle of attack -1.2857 Now let's calculate the lift slope for fuselage also (for the sake of discussion) where the fuselage would have a CL (lift coefficient) of 0.024 at 10 deg. AoA (obtained this one using a CFD). As you can see, the fuselage would produce mostly 0.048 lift coefficient at 20 deg. AoA, so it's very small in comparison to the wings..., and if you want a relation between them: 0.048/0.9 = 0.0533 (so 5.3% of the total lift is produced by the fuselage itself), but let's see the fuselage's lift slope now...: 0.024 / (10 * pi/180) = 0.138. THAT'S your lift slope for fuselage only! As a contradiction to some who believe that the fuselage produces upward lift by being pointed downwards like that, guess what..., the fuselage's lift coef. at 0 AoA is about 0.0005 and at -2.5 deg. AoA where the game tells that the plane still has 1G, the lift coef. for fuselage only is: 0.0005 + 0.138 * (-2.5 * pi/180) = -0.0055 Now as a final conclusion, let's calculate the total LIFT (careful, not lift coefficient or CL) for the MIG-21 at near sea level altitude using the following well known formula: Lift = q * A * CL MIG-21's wing planform area (A) = 23 m^2 MIG-21's fuselage planform area (Af) = 7.25 m^2 q, which stands for dynamic pressure, where "rho" is the local air density and near sea level it can be taken as 1.2: q = 0.5 * 1.2 * (1300/3.6)^2 * 23 * -0.0567 = -102033.75 Newtons of lift force produced by the wings alone. Now let's calculate the lift force from the fuselage (which is ALSO NEGATIVE and not positive as everyone started thinking) q = 0.5 * 1.2 * (1300/3.6)^2 * 7.25 * -0.0055 = -3119.85 The TOTAL lift would now be: -102033.75 + (-3119.85) = -105153.6 Newtons..., which is as negative as nothing can stop it. The weight of a MIG-21bis (took from mission editor) with 50% fuel, having it's mass multiplied by the gravity acceleration: (7480kg + pilot) * 9.81 = (7480 + 90) * 9.81 = 74236.34 Newtons of weight force. Now if we divide the lift force to weight force we'll get the G-load: -105153.6 / 74236.34 = -1.4165. There you go now..., the G-load should be -1.4165. Even with some error from my part let's say..., the G load still can't be even 0, with no room for saying it's above 0 or equal to +1. Let's stop calculating for the alt of 10000 meters and presume that for the same "q" (dynamic pressure) that occurs at much higher true airspeed and Mach number but the density drops much also (the dynamic pressure is what matters), the negative lift would provide almost the same negative G-load as for near sea level, which is about the same -1.2 Gs! Keep in mind that these calculations took the presumption of having the CL constant with Mach number. This CL only varied with AoA here and was taken for a very low Mach number, but in reality, shock stall phenomena would make things even worse and would require the aircraft to stand at an even higher AoA in order to maintain a straight and level flight..., and there's nothing like that seen yet in DCS, but I can only wish for better days when ED will actually take into account that variation too. It would definitely make a much greater difference and realistic challenging experience. Some can also check this for MIG-21's lift variation with Mach at constant AoA: http://forum.keypublishing.com/attachment.php?attachmentid=180128&stc=1&d=1262166833 Indeed this is the variation of lift coefficient (NOT DIRECT LIFT, learn what a lift coef. is) with Mach number when a critical angle of attack is held constant, but the general shape of the curve will remain almost the same (slightly flattened so the variation would be a bit lower) even at lower AoA where the wing still produces a non-zero lift coefficient. That drop of lift coefficient and then rises again (somewhere at the middle) is the so called "shock stall" which no aircraft escapes from, sooner or later as Mach increases. And as a matter of fact, I didn't even need to tell any of this..., it could've been obvious and simple enough for anyone to just try and compare how the MIG-21 with it's very poor lift slope wings and almost symmetrical airfoil which produces very little lift near 0 AoA flies at such negative AoA in relation to the F-15 and Su-27 under same conditions, cause they all have PFM. Someone should try and fly the F-15 and Su-27 in level flight at supersonic and find out that they always have positive AoA at any height and even with empty weight (almost no fuel left) when flying supersonic. If there was an aircraft to have a nose down attitude at supersonic (even regardless of shock stall that I discussed about and doesn't exist yet...) that should've been the F-15 which has a drastically cambered airfoil which produces a lot of lift at null AoA, and even so it keeps a positive alpha or near 0 in such circumstances...! Try it: F-15 & Su-27 supersonic AoA in level flight.trk

Ok, that's right! My brain hurts...! What would the icing, or not, of the pitot tubes ever have to do with what you clearly see? The icing affects pressure sensors such as altimeter, variometer (vertical airspeed) and forward indicated airspeed and AoA vanes which you clearly know, but NOT EVER IN THIS WORLD it can affect gyroscopes (artificial horizon indicator) and what you can see! Why are you lying to yourself that way? There is no descent even in the video! Can't you see that even in the next video at high altitude where the density is almost a quarter than it is at sea level and so would the dynamic pressure and IAS, the nose is still pointing downwards? Well, if you mentioned this..., tell us about this magic zone where the lift goes against the laws of physics! When any aircraft reaches a critical Mach number know as "Mach Drag Rise", where the drag starts rising rapidly (as Mach continues to increase towards 1) on par due to shock resistance (which besides the modification of important thermodynamic parameters, is nothing more than an abrupt deceleration of the upcoming air making that air almost move with the aircraft) and to "shock stall" (here's a link:http://scilib.narod.ru/Avia/DAC/dac.htm#1_1_3) where the LIFT suffers a massive degrade as Mach continues to increase up to a given number, from where the lift starts rising again with Mach number until the wing alone becomes supersonic (Mach 1-1,1...) and then will starts degrading again as the Mach number continues to increase towards hypersonic. The "shock stall" which is inevitably going to happen to any man made aircraft once the wing of that aircraft has 3 zones of airflow on it (2 subsonic and one supersonic) has never been seen in DCS neither in SFM, nor in AFM/PFM up till this day, at least not by me. This wasn't such a great concern for me cause I haven't seen it here..., but seeing such aberrant values and seeing people trying to give all sorts of explanations to themselves of what is happening, explanations which ultimately tend to mislead from the initial facts and which will NEVER help us evolve and find the truth..., is a bit disappointing!;(

1. Tsagi S-12 is not symmetrical, it still produced minor CL (lift coeffiecient) at exactly 0 AoA. 2. The MIG-21's fuselage shape, especially due to it's very low planform projected area in relation to that of the wings, shouldn't produce even 20% of the wing's lift. The MIG-21's wings have zero degrees of incidence (angle between wing's root chord and fuselage's axis), so if the fuselage is at exactly 0 degrees on the artificial horizon so should the wing be at 0 deg AoA in also. That's the answer, not that the fuselage creates opposite lift to the wing, cause that won't happen, except when the wing's incidence would be drastically high positive or high negative...!

YES! It is safe to assume it is not more correct than it was before and even if generally seems more correct than it was before in some places, it is less correct at other important places. I'm not looking to say this, but maybe I should mention that I'm an aerodynamicist, flight dynamics specialist and pilot and I know exactly what I'm saying! The MIG-21, had very realistic pitch-yaw-roll couplings and oscillations at high AoA spins and lovely wing rocking at high AoA when almost no yaw rates were developed, among it's first patches (early when it came in DCS). These might've been modified a bit and have different values but are still present in some form and they might still be realistic. The ONLY problems with it's FM at that time were the "stalled lift" which came to zero, the rolling moments that were too high due to aileron deflection at some AoA and the high reduction in pitch stability (tended to pitch up) immediately after the wings stalled. When the wings stalled they produced 0 lift (you could tell that by the G load indicator returning to 0 when stalling) which is wrong. In real life, when a wing or even airfoil (infinite wing span wing) stalls beyond a certain AoA, it still provides lift, but only between 50..66% (depends on 2D/3D shape) of what it should've had if there was no stall and as the AoA continues to increase after stall, so should the G-load or lift should also increase with further AoA even through stall..., cause that's reality...! Here's a picture for closer understanding of how lift develops with AoA between null lift AoA and 90 deg. AoA: http://www.aerospaceweb.org/question/aerodynamics/q0194.shtml It never hurts to learn aerodynamics now and then and you'll always learn that you could've known more...! Another problem that I told above was the fact that with the wings stalled, the center of lift moved too much forward (relative to the CG position), making the plane almost become unstable and tended to pitch up a lot, but this was partially fixed, because when passing through about 10 more deg. of AoA beyond that of stall with the remnant pitch up momentum that was accumulated, the aircraft suddenly develops a high pitch down moment although your stick is still full aft...! No matter if you try to pitch rock up and down and then back up to pass beyond that "magic" AoA which tends to snap your nose down, you still can't pass it. It's like a wall that the AoA slams into. Indeed as the AoA continues to increase, so should the pitch down moment continue to increase as well, but that should be a smooth and nice transition to higher pitch down moment up to about 90 deg.AoA, yet it seems that somewhere around 30-35 deg. of AoA (real AoA better seen from outside the aircraft using smoke and not the AoA indicator which indicates much higher values than real) the pitch down moment is even higher than it should be at 90 deg. of AoA with full forward stick, for this kind of aircraft in particular. These were 3 things that seems like were tried to be fixed, but it seems that one of them (the pitch moment due to AoA) turned even worse than it was and the lift due to AoA beyond stall isn't high enough because for example even if the airspeed is almost constant (doesn't drop much) and you pull the stick until you reach your maximum G-load/lift and continue to pull and increase AoA beyond stall, the G-load drops to about a quarter (25%) of the lift it had at critical AoA (keeping in mind that the airspeed didn't drop more than 8-10%), so it's still not enough. The lift or G-load should still be somewhere between 50-66% left after the stall developed. P.S.: Stall has nothing to do with airspeed as most people tend to think it has or learned so and makes them not understand aerodynamics anymore..., in reality ONLY the AoA governs stalling up to supersonic speeds and only from there the stall occurs according to both AoA and airspeed.

You need stall and spin? First off, make sure your pitch trim and indicated airspeed (IAS) combination allows your AoA to go beyond the red mark on the AoA indicator when you pull full aft stick, cause no matter how slow you fly, if the trim is pretty much pitched down, you can barely reach the yellow mark on the AoA with full aft stick, so you must trim to pitch up as much as needed in order to go beyond stall AoA with full aft stick. It was the trim that didn't allow most of you guys to have full pitch up elevator travel in order to overshoot the critical/stall AoA. To induce a spin, you must simply use cross-controls (aileron and rudder inputs opposite to each-other) and a yaw rate will develop opposite to your aileron and towards your rudder. In order to get out of spin, use cross-controls in the opposite direction now, having the stick (aileron) towards the spin and the rudder opposite to spin and you'll stop the spin.

Hi man! Sorry to intervene, but "Otto" most probably have referred to the engine seizure phenomena before the patch which seems to have disappeared after the patch, so he probably didn't change his flying techniques and engine management at all. I don't know, it's up to him to answer this, not me..., I'm only curious if he really referred to the manual pitch engine seizure before and after that patch without treating the engine differently in between. That's when tracks are of 100% value of truth, but maybe now he can't revert to the earlier version in order to make the comparison by tracks.

Hi Flieger, I've also started applying sharp full inputs of rudder, by instinct, rather than constant (cause I saw I couldn't hold) inputs due to the yaw instability and I have an answer for why the RL pilots of WW2 were able to takeoff more easily from 2 points (but landing remained a 3 point touchdown or else they could easily roll over) is because they mainly did it from grass terrains, not from tarmac/asphalt, where the grass had lower friction coefficient and so the main gear tires could slip sideways more and more as the speed build up providing lift and thus reduce the effect of instability, but if we try doing so in DCS at this point it would be perfect suicide due to actual grass grip. About the tail heavy characteristics as compared to the E model in that vid (I firstly didn't know about this difference) I also thought but I didn't know for sure, so this applies to be authentic for the K model at least. About the aerodynamics of the aircraft I can say that the slats pop out about 1..2 degrees of AoA before the buffet onset (which triggers airframe shake) which is fairly good, otherwise if they deflect when the buffet already occurs it would be too late to develop a smoother airflow once the transition to turbulent already started, so from an aerodynamicist point of view this is correct as it is!

Thank you all..., happy skies!

Hi Sporg, I also lifted the tail 1 to 2 seconds prior to takeoff many times with flaps settings varying from null to full in the BF-109 K4, but couldn't maintain a perfect straight line whatever I tried on two points due to the very limited yaw stability (using only the rudder without diff brakes, of course...), at least at lower IAS where the dynamic pressure is quite low for control. With P-51 and FW-190 Dora I otherwise can hold a straight line for long distances because the yaw response and it's stability are much greater for those 2 aircraft in comparison to the 109. I'll check out that forum link you gave me about this subject. Thanks!:smilewink:

Thanks Yo-yo..., I believe you took the effort to mark the important info in red, so I thank you once again for that. This is probably for the G2 (as the bottom suggests) and if you know that it has the same stability characteristics compared to our aircraft (K4), then I'm happy to know the truth now and no longer believe that something could've been wrong with the CG's position. Now I've got a better picture of how the longitudinal static stability margin and maximum aft CG positions evolve with indicated airspeed at a given engine torque, RPM and trim setting. The stability margin increase with airspeed can also be confirmed by the fact that when the airspeed is higher (mostly above 350-400km/h), the virtual stick travel (NOT the personal joystick as some might confuse with) is actually greater when pulling until the stall starts to buildup, as the stability curves/slopes within the diagram prove. Even if the stick travel between the aerodynamic limits seems small, I can't be more happier to know this is true with our airplane!:thumbup:

Honestly I don't have any access to such data, that's why I was wondering if the CG might not be a little too far aft. I now understood from Jcomm and might definitely correlate with what you're telling about balance curves (probably stability derivatives) which vary with engine power setting, so I'm all hats down if that's the case for the pitch stability behavior..., but I'm still curious if this plane couldn't have been ridden only on the 2 main gear with the tail lifted to have the plane almost horizontal without loosing directional control that easy, so now I'm pointing my view towards the yaw stability problems when rolling at high speed on 2 wheels on the ground. Thank you!

Did you even watch the track to understand what I meant? It's all about the REAL stick travel of the BF-109 between having it at almost null lift and then at maximum lift (critical AoA), which of course it's the virtual one in the cockpit for this subject, not mine at home! Doesn't matter how much I move mine, I can move it even 1 millimeter if that makes you happy, it's all about the virtual stick's travel between null lift and stall! I'm using a Hotas Warthog and it doesn't make any sense!

Hi, Did anyone else notice the little quantity of stick pull needed in order to have the BF-109 pitch up until it stalls? Now I don't need to be an aviation expert or engineer to find out that with this airplane you are able to vary the angle of attack from null lift towards maximum lift (near stall) with just 5 cm (about 2 inches) of stick travel. The way the BF-109 K-4 feels when handled in pitch gives you an immediate feeling of a plane with very little longitudinal static stability margin left (that's when the CG (center of mass or gravity) is almost near the CP (center of lift/pressure)). Now I don't know why..., but the BF-109 handles almost as difficult in pitch control as the Su-27 (which I had a lot of fun with in the meantime) with ASC direct control ON. It's not that hard but tends to be like it. I know that the P-51D has a reduced pitch stability margin, but that's only when the central fuel tank is full and it's particularly available for it because of the laminar flow wings (it was among the first and few WW2 aircraft to use laminar airfoils) which had this habit of "throwing" the CP rapidly forward as the pilot starts pulling on the stick (gaining AoA), thus making the aircraft reach a stall AoA very easily and quick, but the BF-109's flight behavior should most probably be nowhere near such characteristics. I'm not a noob flyer nor trying to say anything against the BF-109's FM, but I doubt that in the 1940's when they built this plane, they did so wanting the pilot to control the AoA range from very little or no lift angle of attack to almost stall angle of attack by just moving the stick that little (which is about 10% of the maximum stick travel). What would they do such a thing for, cause it doesn't make any difference at high speed, and less to say at low speed, because normally you'll reach about the same angle of attack for the same stick travel at any airspeed, so this wouldn't make any sense to have so much stick travel if it wouldn't be useful, right? Had any RL BF-109 pilot (or someone who knows and can tell) tried this particular aircraft in DCS and felt like the stick travel according to AoA gain is correct? If so, I'm very happy to understand that, cause otherwise I think something's not right! Here's a closer look using a track and at some point you'll see the stick's position at stall and how much more stick travel wasn't even used: BF-109 FM's pitch static stability.trk From my perspective, either the general center of lift (neutral point) is a bit too forward or the CG is a bit too aft close to the lift center, giving a very little gap between them, thus leaving the aircraft with the feeling of very little pitch or longitudinal static stability when flown. One more aspect makes it possible for the CG to be too far aft, because when on the ground and rolling at considerable speed (about 150km/h and higher/lower), the plane brakes with quite a remarkable force (similar to the P-51) but doesn't have any tendency towards flipping over it's nose and as far as I know in fact, the BF-109 had a very likely desire to flip forward when the brakes were applied over a certain amount, so it's very likely that the CG is quite aft compared to the real plane. Another proof that the CG might be too far back is this video: Try this with our BF-109 K4 and you'll loose directional control (yaw) very quickly because it's very unstable in yaw while rolling on the ground. You can only takeoff and land from and on 3 points (main gear and tail wheel), otherwise it's very easy (and almost impossible to stop) to get a side slip and ultimately flip on a wing and this has nothing to do with the infinite grip of the grass, cause even on tarmac/runway you can't hold a straight line before you actually lift off completely or when you touch down with the main gear unless you also put the tail wheel down and hold it, you won't hold a straight line no matter how good you are...!

It's weird how nobody talked about this before, cause it's well into one year since it came in and it's obvious this is abnormal...! Let's hope for the best!

Thanks Kane, Let's see what Yo-Yo has to say! Also, don't forget that sometimes the flywheel is spinning at highest rpm after the crew cranked it up and when you press the starter nothing happens but you can still hear the flywheel spinning..., so this also happens from time to time! Let's hope for the best!

Hi Yo-Yo, I know what you're saying, and that's the P-factor effect and if I remember correctly, a similar discussion had place for the P-51's behavior regarding the same aspect. I'm not telling that I don't believe you, but all I'm saying is that the P-factor, especially when the blades are in low pitch (or lowest anyway), the difference in AoA felt by each blade (as the plane's AoA and beta angles (side slip) vary) has VERY little affect (almost insignificant) on the CL and CD (or lift and drag) of each blade as they are all stalled anyway, and I believe you know it too...! For me it's impossible to accept that the variation of lift and drag on each blade, which indeed vary with AoA and beta, can have such a huge amount of effect when the blades are stalled. Even if the blades would be in high pitch (or highest possible) and not stalled yet, the yawing and pitching moments created on the tons of metal (aircraft) can't be as high as when the prop is spinning and in fact they are even greater than if it was spinning and you can also check that out. Check the gyro and P-factor when the prop is spinning at high RPM and when it's stuck and you'll see the same thing that I'm talking about! Just please..., show us a real life footage or some wind tunnel test data or any kind of real life proof that an aircraft with stopped props would behave like this and swirl so much in pitch and yaw and I'll believe you! Please don't get me wrong, I have at least 10 years of experience in aviation and I'm a pilot, I have seen many and learned many things, yet if there's something that might seem impossible from my perspective and in fact it's true, please be the one to show it and I'll happily respect it. Thank you Yo-Yo!