Cmptohocah
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Posts posted by Cmptohocah
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8 hours ago, KlarSnow said:
Yes, they have done this for well over a year at this point in the AIM-120 IIRC when they fully modeled the flight controls of it. As it and the sparrow are the only missiles on the new API that models all of that, they are the only ones that exhibit that behavior. Everything else just goes completely neutral controls after battery death.
What is preventing the control surfaces from going back to neutral if there is no energy source to counter the relative wind force imposed on to them? Mechanism friction?
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4 minutes ago, KlarSnow said:
I'm sorry but you cannot ignore the direction and pitch angle of anything in flight. That is ludicrous. If things are changing you are not in equilibrium. Its pitch angle is changing, its heading is changing. The tiny .1G here doesn't matter, we are talking about miniscule increases or decreases in drag here that are more than made up by gravity as it falls. Again the object is not in equilibrium so it will not and cannot remain static, once it has stopped changing its flight path, then it can sit in perfect equilibrium as you describe.
How can a pitch change occur with AoA staying the same? Maybe TacView mesures AoA of the control surfaces?
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37 minutes ago, Exorcet said:
It is not. Level flight must have lift = weight. You don't change lift by changing speed.
Not much I can reply to this, except you might want to re-check on how lift is generated by a lift surface.
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15 minutes ago, KlarSnow said:
Here
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Tacview HUD view of the missile in question during the time period in question. It is falling, its pitch angle is decreasing, so it MUST accelerate.
Pitch of the missile does not matter here. First of all it's impossible for AoA to stay the same with a lower pitch, so there is something wrong in how TacView interprets pitch I guess.
Anyway at a constant AoA, from what it seems maximum attainable for AMRAAM in this case, there is no way its physically possible for it to accelerate. It just physics. Also notice in the last slide #5 it's pulling 0.1G than slides 2 and 3. And yet it's accelerating.
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31 minutes ago, KlarSnow said:
The extreme example of this is what is the drag force of a stationary object. Zero. What is the AOA of a stationary object? Is the drag of a 5 Knot object the maximum it could possibly be? No its very low. Slower or higher AOA does not necessarily equal maximum drag. It depends very much on the situation, the aerodynamic properties of the object as Exorcet describes, and what is happening.
Drag force on an object no moving in a fluid is zero - that is correct.
QuoteWhat is the AOA of a stationary object?
This question is not valid. There is no Angle of Attack for an object that is not moving through a fluid (air). The lift surfaces are not "attacking" anything since there is no flow, so I guess the correct answer would be "infinity"?
Maximum AoA (just before stalling) of a lift surface, in fact equals maximum attainable lift force for a given speed. So when ever you have max AoA you will have maximum possible induced drag happening for a given speed. The amount of that drag will vary with speed, at higher speeds more lift is produced and thus more drag is produced. What I am talking about here are not absolute values, like: is there more drag at 5km/h or at 500km/h? At both speeds and any other speed in between and around these, induced drag will always be at its maximum at max AoA.
To put it more simply: induced drag (and there for total drag) will be higher at max AoA than at AoA=0 at "X" speed. Now you can substitute the "X" with what ever speed you like, but the statements holds true. -
34 minutes ago, Exorcet said:
It is only one factor in the amount drag produced, and the drag is only one factor in acceleration
Yes that's technically correct, but I don't see your point. It is one of the contributors to drag, how does this change what I have stated?
34 minutes ago, Exorcet said:The engine and gravity's contributions depend on where they are pointing relative to the direction of motion, they can cause acceleration or deceleration. This is very relevant in this case since the missile isn't flying in a straight line, so gravity's contribution to acceleration is constantly changing. I think the graphs are actually making things harder to understand because they are masking the 3D nature of the problem.
Again correct, but I was trying to explain how AoA influences the drag force. Of course if you fly 90deg straight up and have your thrust reversers on, then both gravity and thrust oppose movement.
34 minutes ago, Exorcet said:Your lift didn't change. The weight of the plane has stayed constant, so in order for the forces to balance out, lift must also stay constant. What you did by slowing down was shift your position on the L/D curve, and the effect of that depends on where L/D max is located. If L/D max is at 400, you actually lowered drag by slowing down, no matter what happened to AoA.
This is incorrect, but when you slow down to 400km/h and keep your original angle of attack, the effective lift is less than what you had at 500km/h because the airflow over the wing is not sufficient anymore to produce the same amount of lift. The only way you can keep the same lift force at 400km/h is by increasing the AoA so that your lift surfaces produce the same amount of lift as if flying at 500km/h.
The effective lift force stayed the same, 'cause the weight did not change, but what happened with the increase AoA is that the drag component of lift (remember total lift has 2 components: one acting up to keep the airplane in the air, second one opposing the thrust) is now facing further back contributing to total drag. That's why you need to push the throttles forward in order to keep 400km/h.
You have lowered the parasitic parasitic drag, that is correct, but you have increased the induced drag.
Finally I think this quote sums it up really nice:
QuoteTypically at low AOA, the coefficient of drag is low and
small changes in AOA create only slight changes in the
coefficient of drag. At high AOA, small changes in the AOA
cause significant changes in drag. -
56 minutes ago, Exorcet said:
Why is this important? AoA =/= acceleration or speed.
There is a large ramp up of AoA before the erratic behavior. There is no increase in drag during the nose swinging, if you average out the erractic period, the AoA is roughly in line with what it was before the missile went crazy, so there isn't really a reason to expect it to slow down more.
Angle of attack is important because it dictates the ammount of drag force produced. Drag force oposes movement, think of it as a brake. Engine and gravity promote movement.
For example, if you are flying straight and level, at 500km/h at 50% engine power if you slow down to 400km/h and still want to keep level, you need to increase your AoA to increase generated lift. You got more lift out of your wing so you can stay level, but since there is no free beer you also incresed drag and that 50% engine power ain't gonna cut it. So now you need more power to overcome that drag, otherwise you will continue deccelerating.
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21 hours ago, Ironhand said:
Everything else aside, that
R-77'smissile’s behavior was bizarre beginning roughly 1 minute into it's flight. It was tracking the aircraft, then suddenly began switching back and forth between something off to its left and the original target. Finally it shifted back to the original target and continued to track it for the next minute, even though the target was about 50° or more above the seeker head.Very good point, and if you actually look at the graph you can see that when this erratic angle-of-attack "dance" started, the loss of speed actually started to slow down, instead of speeding up. One would expect that with hard maneuvering the drag force increases, not the other way around.
I actually waited for a very long time, before I have decided to make this post. It seemed that AMRAAM's loss of energy was way below what it should be, but I never actually had any concrete evidence that this is happening - until this track that is.
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On 8/18/2022 at 2:23 AM, KlarSnow said:
The point you indicate here
is when the flight path and nose of the missile goes from above the horizon to below the horizon. Why would it not accelerate as gravity is no longer slowing it down but increasing its speed.
the AOA dip immediately after (red line) when it changes direction is also commensurate with a 10 knot speed increase.
like to be clear you are talking about a small 10-20 knot increase in airspeed as the missile goes from pitched up to pitched down. That is very much not unreasonable, nor does it defy physics.
Ok the arrow is a bit skewed, that's my bad, but take that yellow line as a reference then. You see a dip in airspeed left of it? This means that there was some acceleration occurring while the AoA stayed pretty much the same.
P.S. Technically AoA was not constant, but what happened to the airspeed is not consistent with what the AoA was indicating in a sense of conservation of energy.
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8 hours ago, GGTharos said:
.... and we start to pick them up as they're in their beam maneuver (he alludes to but does not describe the counter). So great, you found one of the few times this happened
I don't know if there was something said about this in the rest of the video, but it has nothing to do with the notch.
I agree it has nothing to do with the notch, it's just that he mentions it before the notch part and it reminded me that we have perfect binary radar acquisition in DCS. It would be great if we had some sort of radius inside which you can't really tell how many targets are there.
Another pair of Eagles, had the same issue in '99 against the Fulcrums as they initially taught there is only one there until they got separated enough and/or Eagles got close enough to be able to discriminate between the two.
10 hours ago, henshao said:Without getting into too much detail about these systems, the F-15s were almost certainly in High PRF track (lock) when they got notched on that steep lookdown beam maneuver, because their selected weapon was the Sparrow which requires HPRF for guidance. Whether it would have worked against Medium PRF, who's to say (I doubt it) but it does highlight another rarely mentioned advantage of the AMRAAM, beyond launch-and-leave capability: the ability to stay in Medium PRF track for target prosecution
As I am reading the timeline of events in Debrief a Complete History of U.S. Aerial Engagements - 1981 to the Present (Brown, Craig), the Eagles locked up the Fulcrums at about 25 miles, at which point the Fulcrums "initiated a beam maneuver" and then took a course towards their base. It sounds to me more like they detected they were spiked by the Eagles and just decided to turn around and go home (the strike aircraft they were launched against were already headed home). At this time, another group of Fulcrums popped up at less than 15 miles, nose on the Eagles which were in pursuit of the first group of Fulcrums moving away. It seems like a typical Soviet/Iraqi "drag and bag" tactic where one group is basically baiting the enemy for another group to exploit.
While the second Fulcrum group lead prosecutes the Eagle lead, he is killed by Eagle wingman. They form up at very low altitude heading away from the area when second Fulcrum group wingman is announced by AWACS to be in pursuit. The Eagles turn around, apparently to the Fulcrum's ignorance, and split up to simultaneously visually ID their pursuer and take position to attack him. When "Rico" passes underneath and is certain the other jet is Iraqi, he maneuvers hard to get on its six. The unaware Fulcrum finally gets wise just before "Rico" is in "the elbow position" and starts to turn hard. Our beloved, underrated F-15 however is not so easily outturned; after a time, Rico is finally in position to shoot, nose-on at the bandit's six o'clock. At only 1000 feet above the ground, the Fulcrum attempts a Split-S, but even a Mig-29 cannot complete such a maneuver with such little airspace and flies into the ground.
Is medium pulse repetition frequency more resistant to notching? If so, I would be very happy to learn why.
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I am having major issues spotting targets visually. In the screenshot below you can see that I have a target locked at less than 4km and I can't see it - possibly even less as the screenshot does not capture it. I've heard and seen people spot targets in DCS in excess of 20km. Someone on SRS mentioned that they can see at more than 20NM. Any idea what might be happening here?
My graphics settings:
My hardware:
Monitor - LG Flatron IPS225
GPU - GTX 1660 SUPER
P.S. My eyes are fine - had them checked already
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6 hours ago, GGTharos said:
Yes look up the event, I know what you're talking about. It's not the simple fact you stated
Here you go:
Shame we don't have cell resolution implemented in DCS
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3 hours ago, nukeproof said:
Dessert =
Ahahahahahaahah, I could not stop laughing.
2 hours ago, GGTharos said:Often failed to notch, not often notched. Yes, there were situations where the initial geometry was bad but that wasn't a deliberate act.
Not according to the pilot that encountered it. He specifically said that the MiGs went into notch preciselly at a distance at which the Eagle's radar was most prone to it. I will see if I can digg up this interview...
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2 hours ago, Gahab141 said:
Which radar had been often notched in combat? Real life isn't a game, real rwrs aren't as precise as in DCS
F-15C's during "Dessert storm" by Iraqi pilots.
You don't need RWR to notch a radar, in fact SPO is next to useless for this.
It's enought to know the emitting radar's heading, which you can use your own radar for.
RWR is DCS is a bit arcady.
P.S. you can use a data-link also if available
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40 minutes ago, KlarSnow said:
The acceleration occurs when the missiles flight path goes from above the horizon to below the horizon,and when it briefly unloads AOA during the nose swap, what exactly is wrong there. And as to the turn the only thing I have concluded is tacview is assessing turn rate based on change in nose position.
The AOA does not change. Have a look at the graph please.
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Ok there seems to be some confusion here. Let me put in more simple terms what I mean:
Turning motion is by nature accelerated motion. In order for anything in this universe to turn, i.e. not
flymove in a straight line, there must be acceleration, that is "a force", present. On the ground for vehicles, this force comes from friction between wheels and the ground and in the air it, usually, it comes from lift (neglecting propulsion here). To make a circle (turn) in any plane (vertical, horizontal or oblique) there has to be a force present. Without force there is no circular movement and consequently no turning. That's why @KlarSnow mentioned turn-radius, it's a radius of a circle
42 minutes ago, KlarSnow said:The force is coming from gravity, again a rock thrown through the air is stalled, does it accelerate?
It accelerates until its drag force equals the gravity acceleration force at which point it stops accelerating and drops at a constant speed, also known as "terminal velocity". At that point both the drag force and the weight are in equilibrium (tough word to spell :D). See when you let go of a rock from a balloon, for example, it's initial speed is zero and so is its drag force, but as the rock accelerates (and picks up speed), the drag force increases until the two match.
53 minutes ago, Dragon1-1 said:...Nose position is very important, for two reasons...
Sorry I meant it's irrelevant to the topic I am trying to discuss - that is: it does not matter where the nose is pointing or how fast IT changes direction. What matters is how entire aircraft/missile changes direction, i.e. turns, i.e. "draws" a circle.
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3 minutes ago, KlarSnow said:
Ok on reviewing that I really don't see anything untoward, the missile basically swaps its nose from max AOA to the right to max AOA to the left, the actual flight path does not change. It is still stalled and the turn rate you are seeing is just the nose moving. As to the acceleration, its falling downhill. Stabilized in a stall at max AOA, it will pick up speed as it falls so again I dont really see any issue here.
Like you still can point the nose of an aircraft post stall with control surface movements, that's all that's happening here, it has a very high nose movement rate for a second as it swaps from one side to the other, but it is stalled so the actual flight path barely moves.
It can't be stalled as stalled aircraft can't change its flight path - the missile did a 110turn before it hit the ground.
It also can't pick up any speed as a constant AOA produces constant drag so where is the acceleration force coming from? No force, no acceleration.
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1 hour ago, Dragon1-1 said:
Depends on how you (or in this case, TacView) defines turn rate. If you define turn rate as a rate of flight path heading change rate, a falling rock can't have any. If you define turn rate as nose heading change rate, then it can (if you define a "nose" on it). I strongly suspect TacView uses the second definition. Normally, flight path rate and nose rate are closely coupled, but if AoA is increasing during the turn, then it means the nose is rating faster than the flight path (this is the cause of the phenomenon known as "accelerated stall" or "high-speed stall"). Moreover, in a tumble, nose position uncouples from the flight path and can take wild values totally unrelated to flight path rate.
Also, it's quite possible to turn with less than 1G, it's called an unloaded turn. In fact, if you turn 90 degrees and unload the rudder to 0G, you can load the stick to any value you wish and your heading will change. Just remember that you're in freefall on the horizontal axis and thus accelerating towards the ground.
For me when I talk about turn rate, I mean the flight path heading change rate. Nose position is completely irrelevant in this case, as it means nothing in a sense of turn performance. I am not sure what TacView considers as turn rate - I certainly hope not the nose position.
Could you please elaborate a bit more about the "less than 1G" turn? Where is the turning force coming from? How are you loading the stick and not producing any G forces? Thanks in advance.
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5 hours ago, Бойовий Сокіл said:
IRL and DCS. He is refering to Datalink - how the missiles receives guidence commands before its seeker can see the target reflection.
I think the question was: where the link to support the claim that is has/does not have INS?
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4 hours ago, AeriaGloria said:
A spinning and falling rock might have a turn rate of 100 degrees per second, but is still experiencing 0 G.
I wouldn’t confuse turn rate either with actual change in flight vector. When tacview tells you turn rate it isn’t telling you “this is how fast it’s changing course” it’s only telling you how fast the rotation is. You have to compare AOA with turn rate to really get how that turn rate compares to the flight vector, or just watch it in tacview.
Also, you point on your screenshot of it holding 25 degrees AOA and not de accelerating. But the missile is basically at 400 knots, as your tacview graph shows that is basically the stall speed of the missile. So when it falls from stalling, it’s defiantly going to accelerate a bit or de accelerate less. A plane that stalls and holds max AOA might still accelerate as gravity brings it down and causes spin/autorotation. At such stall speeds, the only way to lose even less speed would be to go straight up into 0 G so you can’t stall, and then that could only be maintained until the missile would be turned downwards and can’t maintain 0 G anymore.
I think you might be confusing some terms here. A falling rock can't have any turn rate as it can't pull any Gs.
In order for a flying object to turn it has to provide some sort of force that will allow it do so. This force is called G and it is responsible for making the object turn, that is change its direction. The more G, the higher the turn rate, or if you will more degrees per second. That's why if an airplane or a missile is flying under 1G it can only go one way - straight. At 1G it's heading change per unit of time (second) is zero.
Stalled airplane or missile reached its maximum AOA and is producing maximum drag force. It cannot accelerate if the AOA stays the same as the drag force is constant. From the graph above you can see that the angle-of-attack stayed pretty much constant. I didn't understand the rest of the "zero G" portion of what you wrote at the end.9 hours ago, KlarSnow said:I would really compare the turn rate to the assessed turn radius, because those are tied to the speed. 13 degrees per second turn rate vs a 2km turn radius at 360 km/hr don’t match up for an actually turning object. The turn radius if it was actually turning 13 degrees per second at that speed should be something in the vicinity of 4-500 meters, not 2000. A 2km turn radius at that speed matches a 2.8 degree turn rate. I feel like you are looking at a transient rotation of the missile here. The same btw applies to all three of the snippets you presented. The Turn radius matches a 2-3 degree turn rate for that airspeed. The turn rate seems to match nothing.
the turn radius is a much better representation of The actual flight path of the object than the turn rate.
As to the airspeed increase. A pitch angle would help here. The missile could be pointed straight down at max AOA in which case gravity will make it accelerate.
Well if the TacViews telemetry is correct, anything more than 2-3 degree TR, as you have suggested, is wrong and opens up possibility for investigation into why is it happening.
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Hi @KlarSnow,
the TacView track is attached below (it has been trimmed to save space). You are looking for AIM-120C launched by "VOODOO 1-1". -
3 hours ago, BIGNEWY said:
If you think there is a bug here we would need to see track replay examples.
thanks
Hi @BIGNEWY,
This happened on a MP server. Shall I still go ahead and upload the track?
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45 minutes ago, KlarSnow said:
It is stalling at this point, so its AOA is going to be pegged, as to the turn rate, is the missile rotating, or is its flight path actually moving, these are two different things, in a stalled state of flight the missile isn't actually changing its flight path its just rotating as it falls. This is also why it accelerates, it's falling. Essentially you are saying that an aircraft spinning with a 50 degree per second or faster spin rate is unrealistic because of how much G they are pulling. They are still pulling 1 G, but tacview doesn't show lateral G (yaw) at all, and that can be very disconnected from flight performance.
Like just to be clear, based on the airspeeds you have presented this is a missile that has missed its target and is falling at terminal velocity (360Km/hr), completely stalled (max AOA 25 degrees pegged) and apparently autorotating at some rate. This doesn't appear to be remotely affecting guided performance or its ability to hit the target. like look at the turn radius vs the turn rate. This looks much more like an autorotating stalled ballistically falling missile than anything else. IE it's not a factor to anything.
Do you have the entire tacview of this missiles flight, because based on the parameters shown this is my conclusion, not anything untoward in the missile dynamics or flight model. If you had the entire tacview of the missile and its flyout instead of just the snippets that would help illuminate what is actually going on.
Hi @KlarSnow,
thanks for your reply. It's a bit difficult to format quote of your post, so I will leave the replies here:
1. I am talking about the missiles ability to turn - please note I am not talking about its rotation around the axis of symmetry, i.e. its roll. What I am referring to is its ability to change heading, that is to turn. Turn rate is a function of G and velocity. What the TacView screenshots are showing is that the AMRAAM is creating turning performance beyond its physical potential to do so. Unless TacView is wrong, it's not possible for a flying object to create any sort of turn rate while its G load is at or below 0. To put it simple: no G, no turn and there fore no heading change (turn rate).
2. You mentioned the missile being ballistic. Just to clarify, objects falling ballistically are not capable of making any sort of maneuvering, i.e. heading change. Ballistic objects get their initial conditions at the time of the launch and then it's up to physics to "guide" them rest of they way. Think of throwing a rock - that's a good example. Problem with this particular track is that the missile is not ballistic as it's performing a 110degree turn while stalled at a very high AOA and pulling impossible Gs. To be honest, it's not clear from my post that the missile was turning, but it will clearly be visible once I upload the track.
3. You are right, the missile is not posing any immediate threat, but the point is that the underlying physics is something to be looked into. Also this AMRAAM in particular had the added benefit of harassing my RWR since it could actually "track" the entire time.
4. I do have the entire TacView file and I will upload it here after trimming some time latter today.
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Looks like there is a slight issue with the AMRAAM's drag: it is capable of sustaining high angle of attack (~25 deg) without really loosing any airspeed and all this with it's rocket motor off.
Another issue it that is capable of producing very high turn rates at almost 1G (+/- 0.2G) at extremely low air-speeds (below 600km/h). Also it seems to be able to turn by pulling less then 1G which is physically impossible as the G force is the one responsible for creating turns.
Here are some screenshots from TacView:
1. Title: High turn rates at less than 1G!!!
2. Title: AMRAAM losses almost no speed and even accelerates at high AOA
In the following chart one can see that during very high AOA (>25deg) the missile not only does not loose speed, at one point it actually starts accelerating:
This missile flight was recorded in multi-player. I don't have a track per se as it is quite large, but I can upload it upon request.
DCS lost another faithfull simulation enthusiast
in Flaming Cliffs 3 Bugs & Problems
Posted · Edited by Cmptohocah
Had to fix grammar erros
After more than 10 years flying this amazing simulator I have decided to make one final post as a sign of fare well.
I hope this post won't get deleted as the contents might not be in line with the company policy.
I've seen this sim bring me much joy over the years, but as the platform gained popularity I've witnessed many dark moments about it also, which ultimately led me to a decision to drop it.
For who ever has time or cares to read this post, I would like to briefly state the reasons why:
1. Eventually the sim moved from a "let's have as close as possible to real life" to "we need to sell as much as we can" and "we need to keep paying customers happy".
2. My impression is that every time core issues are addressed on the support forums, there is an "army" of users that try to discredit such claims by spamming the threads with nonsense and "watering out" the original issue.
3. Every post that is in line with the company's "let's sell more products" get swiftly replied to and marked as "investigating" (yes I mean you "holy" AIM-120 posts
), but anything critical gets neglected, buried under a bunch of useless information (please see point above) and ultimately conditioned by the famous "provide valid track" clause - not every nonsense that happens in DCS MP can replicated easily on a private track 
4. Simulator clearly moved from Soviet - US era, to "hey we have all the documents we need to produce high-fidelity NATO aircraft/weapons which are not classified" to "sorry we can't use any Soviet hardware 'cause information on these needs to be provided to use by unclassified public sources" - double standards if you ask me, but this is just my impression.
5. Neglecting one thing that keept this thing (DCS) alive since its inception: "Flaming Cliffs" or as it was called in the good ol' days (personal opinion) "Lock On" \m/
6. Last, and the most important thing for me personally, caving in to market pressure instead of pursuing realism in one way or the other.
I know my post might seem opinionated and I am ready to accept that.
If I am being truly honest to my self, DCS died for me the moment it became "pay to win platform", but I have ignored this fact for some years in hope that I was wrong.
Since my adventure with the sim started in the days of "Lock On 1.2" I felt the need to post this in the "Flaming Cliffs" part of the forum.
I would also like to thank @dundun92@GGTharos@Falcon_S @mousepilot@okopanja@Ironhand and many, many others that were there over the years trying to make this "sim" better.
P.S. If any of the admins has time, please check my "stale" post about the 120's contrails issue, I've provided real live proof.
"So long and thanks for all the fish!"
All the best,
Nix