cw4ogden

That’s also an excellent point. The hip certainly isn’t the latest hot module, but it’s fan base is large. But the hind is going to be the biggest helo release, to date I would assume. And therefore an excellent time to throw one stone at two birds. I appreciate the feedback. And I’m not dying on the hill of it being incorrect, so much as warranting a relook. The community is divided hotly divided, that should be enough to investigate. And as you mention, because the Hind may be similarly modeled.

Good eye. I looked for wind cue on the approach but didn't see any. That's probably why they want a track file instead of video so they can see the exact parameters.

Thanks for the vote of support. I mainly just wanted it relooked. My case is almost entirely circumstantial. It may very well be realistic that the Mi-8 rides a lot closer to the VRS flight envelope than my frame of reference, but there's not much evidence that's the case, and a fair amount it indicating it behaves much the same as any similar helo. So, hopefully this means mission achieved. I took it on knowing it was already a severely beaten horse, so just hearing they will revisit it as a pretty big win, in my opinion.

Thank you. I think the video linked offers better evidence than my track files. I've learned to fly the module as it is, and I really had to try to force it in the track files. I don't know if that's me just adapting, or evidence the modelling is pretty darn close, but is still off enough to feel quite wrong to someone familiar with the phenomenon. I've really tried to kick around is this broken, or am I not an objective observer, and I can't quite say anymore. As I mentioned anecdotally somewhere in the post, my first encounter with VRS in the HIP I had to google what was trying to be modeled, because it felt so absolutely foreign. I think the moddelling of the phenomenon is quite good, Induced from an OGE hover it is spot on. But the parameters where you are susceptible to it need the relook. I have experienced and seen far too many DCS Mi-8 crashes that the flight profile just isn't enough for the ensuing disaster that follows.

I'm not sure your meaning? The DCS Mi-8 is easy to get into VRS or the actual aircraft is easy to enter VRS. If you scroll up to the start of the topic, you will see: I started the thread by asking that very question to an active MI-8 instructor friend of mine. "Is the Hip more prone to VRS than other helicopters?" His answer was pretty definitively "No." I'd ask you to read through the whole thread, where I wage a fairly lengthy war on why VRS isn't realistically modeled in DCS, the Hip specifically, and upon what experience base I draw those conclusions upon. I'm a retired U.S. army heavy lift standardization helicopter pilot who used to demonstrate VRS. And I know it sounds self serving to come here and tout credentials, but I am an expert on rotary wing aerodynamics and VRS in particular and because I want to make the point: it's not even required to be demonstrated to new pilots. Virtually no one gets a demonstration of VRS going through flight school, or did at least, unless it was because their instructor went out of his or her way to teach it. It is for most pilots purely book knowledge. I certainly didn't receive a demonstration. Then I got into it once in real life, survived the test, to learn the lesson if you will, and it became a pet peeve of mine, that we didn't teach it. I went out of my way to demonstrate it because, although exceedingly rare, VRS can absolutely kill you, and very quickly. So, in addition to being an expert, It falls into the category of one of my pet peeves, I went out of my way to demonstrate to pilots that it is deadly, even though it wasn't required. But how it works in DCS is sketchy at best. VRS kills people the way sticking a fork into the toaster kills people. And that is only if they don't know about the hazard or are operating in extreme high G.W. high D.A. situations and get careless. I'm glad they tried to model it, but I also think it's worth the time to get it right. It's also why mine is the umpteenth thread about VRS, from other real pilot's who say the same exact thing.

12:40 seconds: There is no way that flight profile should result in a VRS accident. The Vortices would be shed because he is not descending into them. Here you can see the difference. At about 1 minute in. Notice how the bird flies fine, even backwards in a descent. It isn't until he tries to descend vertically into his own rotorwash does VRS happen.

@NineLine Here are a couple of track files. My beef is it seems you can get into VRS, in the MI-8 without one critical element. But it is the most important element, vertical or near vertical descent. If I had to guess, I'd say the VRS algorithm is looking for parameters of flight associated with a Pilot's rule of thumb for avoiding VRS. In other words, if the manual says use caution below 40 KIAS, that doesn't mean the phenomenon can happen at 40 knots. They throw in fudge factors for tailwinds etc. A big grey area to stay out of. VRS can happen, and can only happen, when the helo is descending vertically into it's own downwash, and with sufficient rate of decent. You have to be going straight down into your rotorwash. That appears to be the piece that is improperly coded. It should be absolutely impossible to encounter VRS with an approach angle less than about 32 degrees as indicated on the VRS diagram. I believe on track 2, the first signs of VRS start occurring in the 30 knots range, and it is fully developed with 20 knots of forward speed. 1.trk 2.trk

Sorry for the delay. I got burned out on this thread. Indeed, the fact we are arguing about it speaks volumes of the simulator, as does the fact about half of the responders or more won’t take at face value, the multiple real life pilots telling the community it’s wrong. It’s a great sim. I’d go the trackfile route, if it seemed there was any enthusiasm for fixing it, but it feels like the only enthusiasm is to find a way to impugn what several of us are saying, and that is, it isn’t correct. There is a tiny window in landing profile where you can be descending directly in your own downwash. You have to be in that downwash descending vertically or near vertically for this phenomenon to occur. I did try a few tests with smoke on the ground and I was hoping the airflow was modeled in the smoke, so I could see the vortex, unfortunately it doesn’t seem to be. You have to find a very precise attitude and descent angle to encounter VRS because by definition if you are not going directly down into your downwash, the vortices are washed away. I’ve also rewatched the VRS accident videos and will offer two more pieces of anecdotal evidence from viewing them: There appears to be no attempt at corrective action, indicating VRS is rare in the hip, and not some boogeyman waiting for the slightest inattention to rate of descent. if it was as bad as depicted in DCS, it would be known in the community and they’d have reacted with some form of corrective action. I can see none. The fact there are recoded accidents points, ironically, to it not being crazy deadly. I.E. we haven’t seen an R22 mast bumping crash in years because it is a known and well fleshed out hazard. In my estimation, they crashed not knowing what was wrong with their aircraft. Secondly, both accidents happened in essentially vertical profiles and one actually was drifting backwards. thats what it takes to get into VRS, you have to be going straight down into your downwash, who’s angle is dictated by the surface winds and your relation to them. With a 15 knot tailwind I can get into VRS at 15 knots, but otherwise, no, you just can’t. Because I can’t simultaneously be going both fifteen knots forward and in a vertical descent. Its not unless you find that one perfect pitch, power and airspeed setting and deliberately hold it there, and even then you have to descend too fast. And I’d just reiterate, I would like to test this, but I’m burned out fighting with people, developer has yet to chime in, and I largely feel stupid for thinking I could break through the nonsense, when so many have already failed. None of that is directed at you, it’s just explaining why I’m accepting defeat over learning how to do trackfiles and conducting more extensive flight testing. No one cares, and to many it’s a badge of honor they can fly the “deadly” hip.

Roger, same as 47 before we got fadec controls. We had Incr / dincr to set but rrpm but it was governed by some fairly simple flywheel governors and manipulating fuel control.

I gotta look at what to see what it’s called but I’m assuming it’s being controlled by my slider which is how I go from idle to flight rrpm. Thanks for the replies. That’s a fairly significant difference in rrpm at takeoff settings. That could certainly be a cause I’d thus far not considered. It may be the 47 is just really better than average similar bird regarding VRS because in any given profile that extra RRPM and lack of rail rotor would and could be the difference. And it’s the lack of upflow that feels off, as I stated somewhere up there in the post. But that much difference in RRPM on its face, might be the difference I’m feeling. There would be noticeably less upflow. And at the end of the day that’s a decent answer for why at least. it would also explain why tweaking the throttle levers works in the sim to make it feel more “right” to me, even if it is incorrect procedure.

And looks like it’s not readily available if either know what the mi-8 main rotor spins at in terms of revolutions per minute. how is RRPM set in the hip? I’d assumed it was fixed by the maintenance pilots with fuel flow and track, as it seems not adjustiable by the pilot, or am I missing a switch etc?

And @AlphaOneSix It also possible my hip flying friend isn’t on the mark and the hip just really is a bit more susceptible to it than I’m used to. For many of the reasons you both and others have cited. I can google it, but I want to, probably already should have taken a look at what the revs per minute of the hip main rotor is because if it is significantly less than the 47, which Iirc is 225 then it’s likely my source led me astray. it still perplexes me there isn’t more in the way of literature on it, but I can’t in good conscience say it’s wrong, and I’ve fleshed it out fairly well now, but I just can’t tell if it’s right or I’ve learned to live with it.

Good to know. @Viktor_UHPK I'm curious which manual is that you're referencing? I know, at this point how to work around the VRS. My question is how accurate is it? It's much harder to get into now that I've learned the module, but I still think there is something off with how it's working. I get that following a shallow approach to land will keep you out of it, but in reality, you need to be fairly steep for it to be a problem. It's unfortunate VRS diagrams are notoriously non-aircraft specifc, but the way I read the diagrams, and the way we always flew IRL, unless you were coming in in excess of 30 degree approach angle, VRS was not part of the equation. As I mentioned earlier, we even had a rule of thumb for flying: if your intended landing area is at or above your feet / pedals area, you were safe from the portion of the aerodynamic envelope prone to VRS. You didn't have to consider rate of descent at all. You just can't get into it on approach, in anything but a very steep approach (barring a large tailwind or high altitude operations near max G.W.).

Excuse the formatting (copy paste) From MI-8 flight operations manual - seems the throttles are meant to be set all the way up for anything above about 3000' https://www.scribd.com/document/322000057/Flight-Operation-Manual-for-the-Mi-8-Helicopter 2.8.3. Take-off-landing operations and maneuvers at low speeds near the ground at airfields and sites, located at altitudes higher than 1000 m, are made with at least 93% revolutions of the main rotor for the purpose of ensuring reserves of pedal control in these modes. Also from Mi-17 manual: Reduction of the gas generator rotor speed below 85 to 88 % at an airspeed close to zero even at the main rotor speed within the acceptable limits, causes transition of vertical descent at a speed up to 20 m/s (vortex ring condition).

I know it's a long shot getting any re-look. I'm trying get to the bottom of whether or not it's even a problem, which by community standards, is an un-setttled question.

I did some testing and am leaning towards a theory: The VRS issue I have may be the autorotative brake state not being implemented, or implemented correctly. Also called windmill brake state. Test number one I repeated a few times, but want to try more iterations was as follows: 1000' AGL near zero forward airspeed, rate of descent around 400 m's on the VSI. Results: modeled well. Feels right for an out of ground effect, high OGE, "I got distracted" type of VRS. Pitch / roll controllability remains good, if not a little too good in a developed Ring state. What I was unable to do, and leading back to the first point, was break a developed ring state by dumping collective and entering the windmill brake state. methodology: High OGE hover, induce VRS, confirm by adding collective, verify increased vertical descent rate - corrective action, bottom collective pitch and break the vortex via upflow through the rotors - does not seem to work as it should. Test number two: Tactical approach to LZ style landing / traditional dust landing style approach. (Fast approach, with an aggressive decel - understanding we are talking cargo helicopter standards) This style approach should also be riding the autorotative brake state, and yet, what it feels like is I still have to avoid VRS criteria during transition through ETL, even though my rotor is mostly unloaded, due to the upflow resulting from the decelerative attitude. You can't simultaneously have a vortex ring building while the rotor is being driven, or is unloaded by autorotative upflow. You can get into a VRS type state by botching the approach and arriving too high, but flown to the ground in the manner of what would be a dust landing, but flown properly, the airflow never comes up through the rotor disk. Additionally and possibly related, dumping the collective to the floor in cruise flight, again in the autorotative brake state regime, the aircraft falls out of the sky. It shouldn't. It feels like upflow and autorotative brake state is not working, or not strong enough. If I dump the collective with, say 100 knots forward airspeed, I should be able to remain in level flight for quite a while, in a decelerative attitude, exchanging speed for level flight. The hip just seems to drop like a rock regardless of how much rotor disk you tilt into the wind.

@AlphaOneSixI’d welcome a better qualified expert if you know one. I don’t write off the possibility it’s correct, but you really could Certify the DCS hip model for flight in real life without serious control measures that would be reflected in real world literature and real world history / real world training procedure etc. I can’t find. I’m having a hard time putting my finger on what’s off or feels off, other than to say it feels far too susceptible to it. Maybe it’s a simism, but I’ve flown dozens of helo sims and had aircraft in crazy flight profiles that ride the edge of the flight envelope for good reason and I’ve never had a problem with VRS the way here, it can render you a smoking hole in seconds. Nor do I know of anyone who has. I welcome evidence to the contrary. My intent isn’t to die holding a hill, but also to not have people see helicopter flying as an inherently unsafe. I don’t think the mi-8, if it flew like it did here could be certified. Yes it’s Russian, and they are different than us but we’d see a string of these fatalities if it was accurate.

@Fri13 I want to run a couple tests once DCS finishes updating. I'm going to try to find the actual source of what feels wrong and see if I can provide an example of it. I take your points, and I'd reiterate I'm not saying it's off by a lot. It needs a tweak. Not an entire rework. The coding is good for VRS, I like how they modeled it. I just question it's accuracy based the fact everyone has to learn how to fly the DCS mi-8. Everyone qualifies their statement with, I had trouble with VRS at first, but I learned to live deal with it. The actual reality is the vast majority of people never experience VRS. Not intentionally, nor inadvertently. VRS accidents are rare. They happen, but they are rare. And DCS doesn't feel wrong, necessarily. Just wrong for the conditions, lightly loaded aircraft operating near sea level, it's far too aggressive. The current flight model is what I would expect to feel operating at high altitude near max gross weight. Conditions where you are on the edge of the phenomenon. Not sea level, not lightly loaded and not doing a simple approach to landing.

Sure, but that only takes a swing at me the observer. It doesn't account for the multitude of other anecdotal evidence. You can not minimize the importance the pilot plays in simulation development, or you do it at least at your peril. And here we are. With a glaring flaw in the flight model, and you want me to chock it up to my memory is fuzzy. Maybe so. But all other evidence brought forth indicates my observation is correct. No specific MI-8 charts for VRS No long list of lessons written in the blood by dead mi-8 crews No credible people arguing "hey, actually it is that bad." No hint of it being vested in reality from a guy who flew a similiar aircraft and took it on himself to say, that's not enough, ask a real real expert. Who confirmed VRS doesn't plague the Mi-8 community the way it plagues the DCS community. It should be manifestly impossbile to get into VRS with any approach angle less than about 30 degrees, which is a very steep approach. Yet we have a forum with post after post of "why do I die when I try to do a simple landing"? Say you like it, say it's part of the DCS experience, just don't say it's representative of reality because it isn't for the many many reasons I've cited.

Hey thanks for the post. I'm in need or moral support. Additionally, there would absolutely be VRS pilot charts specific to weigh configurations and density altitudes that anyone arguing against should be able to find quite easily. All this back and forth aside. The VRS modelling is close. It's not too far off. But where it is off, it is off in a big way if I can encounter it under normal flight maneuvers. Dynamic rollover, settling with insufficient power, Loss of tail rotor effectiveness (not implemented I believe), ground resonance, retreating blade stall, blade compressibility, and vortex ring state: None of these are unknown quantities. We pour over charts before every takeoff, mostly nowadays by computer which is sad a bit in and of itself, because you really lose the context of the numbers you generate. There is no conceivable way, in my self proclaimed expert opinion, they can have VRS right as it currently is modeled. Now invariably someone will counter with the charts exist. And they do. At the test-pilot and engineering level. And the fact they are not generated for the pilot in any Mi-8 specific form yet discovered by the forum army, we can assume, and have confirmation from my source, it doesn't fly significantly different than any other helicopter with regards to VRS. And I'm saying as a a guy with extensive time in a similar bird, extensive time in simulation community both professional and as a hobbiest, training the exact flight condition to instructor pilot candidates, because you don't get the demonstration as part of any curriculum I just wouldn't sign you off to be an Instructor without having felt it personally. Because this is my bailiwick and a pet peeve of mine personally within that bailiwick I can say without hesitation, something is very off with VRS. I want to check approach angles and run some more tests, but it is wrong, close, but wrong enough to be considered a serious bug in my opinion. There's no way in hell I'd certify this flight model as is, and it's only because of the valiant, yet unfinished attempt at modeling a complex aerodynamic phenomenon that is VRS. VRS is by and large not part of any pilot's thought process, except for when operating under very specific flight parameters. It is deadly, it is not common.

I'll also claim expertise on flying without haptic feedback and evaluating accuracy of flight modeling because I have done that, professionally. There are plenty of good arguments like why tempt fate potentially breaking a great module, but haptic feedback is a lousy one, as is saying pilot's are unreliable reporters of accuracy. There's truth to that argument, but not to the degree expressed in this discussion. And not for something so flagrantly obvious to any pilot with an ounce of time; it's why this topic is the dead horse we are beating. Dead horse arguments only happen when one side is intractable in their belief the horse is even a horse.

I’d counter your first argument with training. When a line pilot arrives at the instructor pilot course (us army) they can fly like champs. But you ask them to demonstrate a VMC takeoff pattern and approach, like they are the instructor telling me the “student” what to do, they fall apart. Until you are trained to do it, you can’t fly and give instruction on a task at the same time. As a matter of personal insight learned as an instructor training new instructor pilots, what you’d call situational awareness, is nothing more than division of attention and prioritization of tasks. No one can do two things at a time with the one fabulous caveat - if you can do one, or the other, or better yet both without thinking about it. The way you drive without thinking about it. A new instructor pilot cannot talk and fly at the same time usually. both go to varying degrees of shit depending on personal aptitude and preparation, ie how long did you rehearse you’re “MOI” or method of instruction. Prescripted sentences like “to begin the VMC takeoff, apply smooth collective input while simultaneously achieving a positive rate of climb and and accelerative attitude” while they are demonstrating the maneuver. With time, they can speak, but their flying looks like crap until they can either fly or talk without thinking about it. that’s all situation awareness is, diverting your attention amongst many things and keeping track of which will kill you first. Any task you can do without thinking is gravy on the potatoes. Nor everyone can do this job. A significant portion bordering on half are born straight out of training to be lifelong co-pilots. Not everyone makes pilot in command, fewer still become instructors, and fewer still the instructor for the instructor pilots. The sentiment I’m getting is it’s like flying is some sort of cowboy shit, and pilots are stupid stick wigglers, and that’s just not the case. I don’t claim to be an expert lightly and for much beyond the scope of what’s being discussed here. But for VRS in a medium lift cargo helicopter, I am an expert.

A more naive version of me might have thought I’d be welcomed as someone with authority finally throwing the bullshit flag on a known issue, and prepared to make a case on your behalf, with evidence both tangible and circumstantial to make your sim more accurate. silly me.

@HiobIn no world does it make sense to pit your extensive YouTube viewing history against my credentials and call it a draw because you just won’t come around to reason. And asserting pilots are a poor resource for determining a simulation’s authenticity is one of the stupidest things on its face I’ve ever seen asserted. Who then do you put the task to? if you’d devoted 1/3 of your energies wasting my time to looking into my assertions and observations you’d have likely learned something. but here we are, you steadfast in your life experience endowed sense of authority and my absolute inability to crack your severe case of Dunning Kruger syndrome. I’m out. I don’t need the aggravation arguing with you brings me.

I didn’t throw out a thesis, I made an observation based on many many factors all of which you, as you say reject summarily, without offer anything substantive to the conversation. You can not get into VRS in the conditions you can in DCS, that is my observation. It’s manifestly impossible in probably any helicopter because the aerodynamics don’t work the way the DCS hip teaches you that you have to fly. Congratulations, and welcome the world of bad habit transfer if you ever get the chance to be an Mi-8 pilot. You have lots of hypothesis and theories on why my observation is wrong. I merely have an observation. I have hypothesis for why the observation might be happening, but you're not acknowledging my observation as even valid much less getting to my hypotheses.