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Floppy_Sock

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  1. @[TLC]MasterPooner Another - arguably more dangerous consequence of compression is colloquially referred to as a mach tuck. Even at aircraft speeds well below the mach 1, the air above the airfoil can approach and exceed the mach 1 and a standing normal shock forms. This is what causes the terrible buffeting and control surface flutter. This pushes the center of pressure rearward. It also effects the downwash over the elevator - both of which contribute to a nose down moment. In combination with the less effective control surface, this can turn into an unrecoverable dive. This was why the p38 had dive brakes - it had a critical mach number of 0.65 which was easy to achieve. My point above is that the only aircraft that does this correctly is the me262. Edit: I was wrong - the p38 does have increasing nose down behavior at high speed modeled.
  2. While we're talking about compression, why is the nose heavy pitching moment near and above the critical mach number not present?(mach tuck) You can take the 51 in a full power dive from 30k feet, at 20k you're well above critical mach number and there's no noticeable change in pitch behavior. Edit: This is at odds with the me262 for example which seems to have the tuck behavior included, though it seems to be quite scripted. Edit 2: the p38 exhibits this behavior as well but it's not as intense as in the 262.
  3. Do we know what the configuration of the 80s 51 was. I remember reading that as well and being surprised the stick forces were so heavy. Maybe CG related? A fully loaded 51 with guns, radio, etc probably has a lower stability margin and therefore lighter stick forces?
  4. @ACG_Orb Yeah your CPU seems to be breezing through all this which is is a good thing. I'm somewhat surprised that RTSS is helping that much but I think your conclusion is correct - that your GPU is struggling here, at least in the 90FPS case - your GPU cannot keep up with that 11ms frametime. But at 60hz you're GPU is well capable of handling that load. The issue now is those little intermittent jitters that you see toward the tail of the curve above the 16ms frame time limit. Those are the "spurious" frametimes which I was talking to @SCG_Wulfe about. I'm not sure how one gets rid of those, at least in your case maybe RTSS does seem to be helping there?
  5. @ACG_Orb When you get change to test, post a screenshot of your results from fpsvr / advance frame times as well as your in game settings. I have a sneaking suspicion that the new update is probably hitting your gpu much harder and it's struggling to keep up? When you say patch, you're talking about the render change patch or the most recent?
  6. @ACG_Orb I must admit that when I wrote my initial response I forgot I was on the VR forums for some reason so it was a little silly / stupid of me to mention RTSS since it's really a tool for 2D users. I don't know what VR hardware you're using but if you use steamvr / steam in general I highly recommend FPSvr. https://store.steampowered.com/app/908520/fpsVR/ It will give you substantially more information about your frame times than RTSS. More specifically, it will tell you if you're CPU or GPU bottlenecked when it comes to frametimes. It can be overlayed in your headset nicely. (it's $4) If you're not interest in paying, the advance frametime graph in steamvr can give you the same information with even more detail but I find that the HMD overlay is intrusive and actually can an impact on your performance since it's rendering the entire figure in your HMD. https://developer.valvesoftware.com/wiki/SteamVR/Frame_Timing But, it can be a nice way to at least get an idea, if it will record up to 2000 frames if you drag the bar at the bottom out and when you see stutters in game, just briefly take a peek at it on your monitor to get an idea where you're rig is struggling and adjust your settings accordingly.
  7. Yes you're correct about that. I know very little about biology (I study compressible flow and control theory). That being said, see the following excerpt from the following paper, Tripp, L. D., Warm, J. S., Matthews, G., Chiu, P. Y., & Bracken, R. B. (2009). On Tracking the Course of Cerebral Oxygen Saturation and Pilot Performance During Gravity-Induced Loss of Consciousness. Human Factors, 51(6), 775–784. https://doi.org/10.1177/0018720809359631 For a first stab at this, I think? (please correct me if I'm way off here) it's reasonable to assume the glucose/oxygen consumption rate of neurons is constant. One would need to derive a transfer function from cerebral blood pressure to rate of removal of metabolic residue to properly characterize the transient behavior of the FBP.
  8. @ACG_Orb using fpsvr? Yes there is an in game overlay you can enable and lock to a fixed position. i think the steamvr frametime graph cannot be fixed in virtual space - it’s locked to your hmd so it follows you around while you move your head. It’s super intrusive while playing in multi.
  9. @QB.Gregor- Wow it’s really obvious there. Maybe it’s imgur being weird for me but maybe it’s compressing? I don’t see any of the contacts other than the 2 on the horizon when I look at them there. But I appreciate your post. It’s clear that this wasn’t fixed in the last spotting update. This is motivation to think of a more comprehensive test! Thanks for bringing this up!
  10. @QB.Gregor- Ah thanks for the captions! Wait there’s 5 contacts? I only see 2 right below the horizon! Could you maybe highlight the other 3 - I’m clearly blind.
  11. @QB.Gregor- It’s important to know the ranges that the contacts are at. As I noted in my original post, I observe a bubble where the scaling is correct. It’s at very far ranges - somewhere at/above 5km that I observe this scaling behavior. At least in my testing replay. By AV do you mean alternate spotting? In which case no, it is off. Before I proceed I should reiterate that there is clearly more to this that I / we don’t understand. Testing needs to be done systematically, across different maps, aircraft, ranges, altitudes, aspects etc before a conclusion can be made. I take it it’s ordered from lowest to highest resolution? I clearly see the contacts better in the first picture - which I think is what you’re alluding to. Note that I’m just looking at them on Imgur where they’re compressed. I need to look at them in full Rez and compare the contact size pixel for pixel. I take it you’re already clipped the relevant part out which is what you’ve posted? It would be nice to have the full image including the cockpit. This is a sure way to compare scales up close vs far away.
  12. @[DBS]Browning This is the curve that the paper has come up with. I would recommend that pilots without a g-suit would follow the lowest or second lowest horizontal tails. A g suit will improve the performance in the tail. @JG27_PapaFly Yes, you’re correct that different data sets were included in the test. However, that is precisely what makes this test so valuable. It shows that regardless of agsm/g suit/ onset rate - the FBP remains constant. The way I understand it at this point is as follows: 1. GLOC is clearly a function of the lack of oxygenation of the brain. 2. The body adapts (slowly) to changes in blood pressure in the brain. This vascular response is what the devs talked about in their original article. The body will naturally raise the blood pressure when exposed to +Gz and conversely, lower it when exposed to -Gz. 3. All external methods to prevent/delay GLOC, namely, any form of AGSM, g-suits, and seat angle, work to increase cerebral BP or reduce the reduction in cerebral BP due to acceleration. AGSM can range from straining to the modern “hick” (which is actually a modified version of the “H1” which substitutes holding your breath with screaming against a partially closed glottis). The effect these factors have on the curveis depicted by the different tails in figure 3.a above. 4. For any choice of prevention method or combination thereof, there always exists a +Gz which will be sufficiently large such that the entire combination of prevention methods + natural cardiovascular response will not be sufficient deliver blood to the brain. From the results published by Whinnery, we can conclude that this functional buffer period (FBP) is constant. If this were not the case, then there clearly should not be such a well defined vertical asymptote in the data. 5. Fatigue during maneuvering comes predominantly from the isometric contractions involved in AGSM, and from stick forces in warbirds. I only have a single data point for the rate of fatigue during AGSM but a us military study claims that fatigue is on the order of 1g/20sec. I think one can come up with much better models for this. There is good published data for fatigue, or the diminishing of force output during isometric contraction that can extrapolated here. Indulge me for a minute and tell me what you think of the following. A proper physiological model for g tolerance should best be expressed as a function of cerebral blood pressure. The two primary systems which are affected by +Gz acceleration are the eye and brain (obviously). One can characterize the vision loss as a function of cranial blood pressure - a quick glance at Wikipedia says vision symptoms show up at around 10-20mmHg BP. Similar characterizations for consciousness can be derived from the curve above. There’s a source for this in Whinnery’s paper. But right off the bat we can say that if BP in the brain is zero - or effectively zero, GLOC will occur after 9 seconds. The model for both visual and consciousness can be expressed in terms of the stored oxygen supply in the brain and ocular tissue. (Read this as an equation, just written vertically) Oxygen stored in the brain tissue at next simulation step = Oxygen stored in the brain tissue at current simulation step + Oxygen added as a function of BP - A constant consumption rate by the cell (this is chosen so that if no oxygen is added, the pilot should be out in 9 seconds) We can write a function for cranial blood pressure as follows: Cranial PB = BP from the heart (this term contains the transient cardiovascular response to acceleration - raising BP when exposed to +Gz and lowering it when exposed to -Gz) + BP from AGSM (This term depends on pilot fatigue and wounds) + BP from g-suit (this can just be a fixed value for simplicity) - BP due to acceleration (lets assume no hemodynamics for simplicity, I.e. acceleration affects the cranial BP instantaneously) The only two terms which have dynamics are the fatigue model and the cardiovascular response - it’s probably more than reasonable to fit them with some first order transients to keep the model simple. The fatigue model can take into account things like stick forces too which the sim already has. It could enter without any additional work to add to model fidelity. Something like this is brutally easy to code - first order discrete systems are just summations at every simulation step. This does a couple things. It introduces two time scales. Fatigue operating on the order of minutes and tissue oxygenation which operates on the order of seconds. Currently, I think there only exists one time scale. As such, when your pilot gets “exhausted” he can hardly sustain any g. However, the recovery timescale is on the order of minutes even for a very short exertion. By separating the dynamics into two time scales, you get more aggressive short term dynamics. Since tissue oxygenation now operates on the order of 10’s of seconds in both exhaustion and recovery, it prevents players from pulling excessively long and aggressive maneuvers since the threshold for gloc decreases rapidly after the FBP. However it doesn’t require you to get a new pilot or take an extended break after a few aggressive maneuvers. Tissue oxygen level will recover with sufficiently low +Gz or a full unload quite quickly. However, since the recovery of ocular / cerebral tissue from oxygen deficit is now not a direct function of G, this crazy bunting to reset your g-tolerance won’t work anymore. Furthermore, this model still rewards pilots for loading gently in a similar way without hamstringing abrupt maneuvers which are necessary when defending. Tissue oxygen level has to be managed to prevent GLOC from one maneuver to the other, but when tying multiple maneuvers together, you now eat into physical fatigue. This recovery is much longer. While your pilot is physically exhausted, long drawn out maneuvers such as scissors, defensive spirals against a fresh pilot will leave you outclassed. Yet, you still are able to perform short aggressive maneuvers such as break turns which do not exceed the FBP.
  13. @[DBS]Browning Yes, you reach the same peak accelerations, but the pilot cannot tolerate these same jerk (Rate of change of acceleration - in case you’re unfamiliar) that an air racer does - which is the more important point. When they that loop which peaks at around 10G, they’re sustaining onset rates in greater than 7G/s. That is largely an irrelevant comparison since I don’t think those heavy warbirds loaded with guns, ammo, and fuel can load that fast anyway. The break turn chart I showed above is a lowly 2G/s. And it’s not that they’re super humans, it’s that the model is simply wrong. The physiological argument is as follows: the brain cells enter a state of self preservation (which induces LOC) after about 9 seconds of ischemia (lack of blood flow). Within that period, the cells are consuming their stored oxygen and still functioning. There is data to show in other papers that hypoxia related symptoms appear earlier than the 9 seconds leading to a short bout of confusion before LOC but that’s another discussion. (It’s quite an interesting read - they put people in a centrifuge and told them to do math problems until they blacked out - the performance declined substantially a few seconds before LOC). The tail section of the tolerance curve - aka what happens after 9 seconds is actually what needs to be discussed. In some tests, it’s found that for subject without a g suit and no agsm experience, the tail of that curve is quite low (about 4g). But again this is after the 9 second transient stage where pretty much any g load is tolerated.
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