Баги, проблемы Великолепной Восьмерки

[cw4ogden]

4 hours ago, Wadim said:

Considering all of the above, I assure you, the behavior of our model, in this flight mode, has about 99% correspondence to a real helicopter.

I don't doubt the sincerity of the effort put into the coding.  I do question the model itself.  Not because you or the team didn't do a good job doing research or gathering data, but because introducing a bug, unintentionally, just isn't as impossible as you want it to seem.  

#1. I understand you believe it is modelled correctly, and it may very well be.  I'm not here to badmouth the development team, but, you've yet to address or acknowledge the discrepancy we found.  It's a discrepancy, something to look into.  I'm not claiming it is hard and fast proof of a bug.  Just asking others to check a quirk that may or may not be responsible for what feels off in the flight model.    

#2. You'd be better served proving to me the Mi-8 flies like the model does in DCS.  In other words, I believe it is within realm of possibilities that the Mi-8 is somehow more susceptible the VRS than other helicopters, but I've seen no evidence of it.  

 

My hypothesis is if the Mi-8 were as deadly in regards to VRS as it is modeled in DCS, there would be much more information in the way of charts and performance planning information.  You'd need it just to survive.  If the real life Mi-8 rides a lot closer to the VRS envelope than my point of reference, in reality, that's acceptable.  I want "correct" behavior.  I don't want a dumbed down version.  I just want it to be accurate.  You believe it is; I am not totally convinced.  Mainly because I can get into VRS in DCS in situations I don't feel I would in real life.  

That may be differences in the aerodynamics of the different aircraft, or it is a bug.  To me it feels like a bug, because I can get VRS in DCS in conditions I assert you couldn't in real life.

I'll add that the modelling of VRS when induced from an OGE hover feels exactly right.  What feels off is being able to get into VRS in situations where the downwash would be well behind the aircraft. 

I can test the data all day long, but I am not an unbiased observer anymore.  I believe, maybe not with 99% certainty, but believe there is a decent possibility an error crept into the flight model.  So I'm asking others who are not vested in the outcome to test what we found.  That's all.  

I am fine with being proven wrong, I'm not an Mi-8 expert.  But if it was my code, my work, I'd want to look into any suggestions I got it wrong.  If it was my community to manage, I'd never let that community flop around like a dying fish for years without putting this to bed.  It's either based in reality, and I'll take the egg on my face, OR, something is slightly off, in which case a fix would be warranted.  I hope you get where I am coming from.  Maybe I am beating on a dead horse, but lets make sure the horse is really dead.

I don't think the modelling is off by much, I think it needs a tweak, not a complete rework.  

[cw4ogden]

@Wadim

Forgive my drawing technique, but this is what I feel is going on.  A VRS susceptibility range that is exaggerated.  

Track file shows aircraft entering VRS from above ETL (which is impossible) at 30 KIAS or about 55 kmph.  Aircraft should not be susceptible to VRS, regardless of rate of descent, or approach angle at that speed, as stated earlier.  Even the Mi8 flight manual says only below 40 kmph.  

 

ETL being defined as operating in clean air.  Above ETL, induced flow is behind the aircraft before it can be re-ingested into the rotor system.  Being above ETL and getting into VRS should be mutually exclusive.  You can't experience both simultaneously; being below ETL is a prerequisite, a requirement for VRS.  

Or, possibly the problem isn't with VRS at all, but the transition airspeed range for ETL, but something seems off if I can get into VRS at 55 kmph, above ETL in conditions the phenomenon can not exist, due to it's very nature.  VRS is re-ingested downwash, and by definition, ETL is when you are free of operating in your downwash.

2.trk

Edited June 1, 2021 by cw4ogden

[cw4ogden]

I've heard a lot of people say essentially, "You're case is purely circumstantial!"  

And I will concede this point, with the caveat: it's a special kind of circumstantial.  
It's a Prima Facie case - Prima Facie -  "sufficient to establish a fact or raise a presumption unless disproved or rebutted."

In my track file, the aircraft enters VRS at 30 KIAS or about 55 kmph.  This is above ETL and above ETL by the very definition of what ETL means, you physically cannot induce VRS, period.  It's an aerodynamic impossibility.

That is not circumstantial, that is prima facie.  

I don't need to prove the MI-8 VRS modelling is wrong, you need to prove to me that the MI-8 can in fact, encounter VRS at 55 kmph.  
On it's face, prima facie - everything we know about VRS says you must be below the effective transitional lift airspeed to encounter VRS.  VRS is a phenomenon of re-ingesting the air you have induced a downward momentum. 

 

"Effective translational lift (commonly referred to as ETL) is a term used to describe the airspeed at which the entire rotor system realizes the benefit of the horizontal air flow. This happens when the helicopter's rotor disc moves completely out of its own downwash and into undisturbed air."

"A vortex ring state is when the helicopter’s downwash recirculates into the induced flow and the helicopter descends while under power."

 

The two are mutually exclusive. I don't have to prove that.  It is correct on the face of it.  My case is prima facie, a very special kind of circumstantial.  I don't have to prove this point, it must be disproven, or the findings to be shown in error.

Edited June 1, 2021 by cw4ogden

[Wadim]

1 час назад, cw4ogden сказал:

@Wadim

Forgive my drawing technique, but this is what I feel is going on.  A VRS susceptibility range that is exaggerated.  

Track file shows aircraft entering VRS from above ETL (which is impossible) at 30 KIAS or about 55 kmph.  Aircraft should not be susceptible to VRS, regardless of rate of descent, or approach angle at that speed, as stated earlier.  Even the Mi8 flight manual says only below 40 kmph.  

 

ETL being defined as operating in clean air.  Above ETL, induced flow is behind the aircraft before it can be re-ingested into the rotor system.  Being above ETL and getting into VRS should be mutually exclusive.  You can't experience both simultaneously; being below ETL is a prerequisite, a requirement for VRS.  

Or, possibly the problem isn't with VRS at all, but the transition airspeed range for ETL, but something seems off if I can get into VRS at 55 kmph, above ETL in conditions the phenomenon can not exist, due to it's very nature.  VRS is re-ingested downwash, and by definition, ETL is when you are free of operating in your downwash.

2.trk 224 \u041a\u0431 · 0 скачиваний

 

 

21 минуту назад, cw4ogden сказал:

I've heard a lot of people say essentially, "You're case is purely circumstantial!"  

And I will concede this point, with the caveat: it's a special kind of circumstantial.  
It's a Prima Facie case - Prima Facie -  "sufficient to establish a fact or raise a presumption unless disproved or rebutted."

In my track file, the aircraft enters VRS at 30 KIAS or about 55 kmph.  This is above ETL and above ETL by the very definition of what ETL means, you physically cannot induce VRS above ETL.  Period.  

That is not circumstantial, that is prima facie.  

I don't need to prove the MI-8 VRS modelling is wrong, you need to prove to me that the MI-8 can in fact, encounter VRS at 55 kmph.  Not the other way around.  

On it's face, prima facie - everything we know about VRS says you must be below the effective transitional lift airspeed to encounter VRS.  VRS is a phenomenon of re-ingesting the air you have induced a downward momentum. 

 

"Effective translational lift (commonly referred to as ETL) is a term used to describe the airspeed at which the entire rotor system realizes the benefit of the horizontal air flow. This happens when the helicopter's rotor disc moves completely out of its own downwash and into undisturbed air."

"A vortex ring state is when the helicopter’s downwash recirculates into the induced flow and the helicopter descends while under power."

 

The two are mutually exclusive. I don't have to prove that.  It is correct on the face of it.  My case is prima facie, a very special kind of circumstantial.  I don't have to prove this point, it must be disproven, or the findings to be shown in error.

I don’t understand why you are saying all this?
Do you think the model will be changed?

What's the point of your messages?

[cw4ogden]

8 minutes ago, Wadim said:

 

I don’t understand why you are saying all this?
Do you think the model will be changed?

What's the point of your messages?

To identify if there is a bug.  
Yes!, Of course, I think the model should be changed, if it is found to be incorrect.  Who wouldn't?

I don't understand why you can't look at the data?  
Or explain how a helicopter encounters VRS above ETL?

You make an assertion everything is correct, but offer only reassurances and credentials without addressing the points made.

My point is to find out if the flight model is accurate.  You say yes.  And you should know, but also can't answer my very simple questions, like how does a helicopter get into VRS above ETL.  This should not be possible, do we agree on that?

Edited June 1, 2021 by cw4ogden

[Wadim]

26 минут назад, cw4ogden сказал:

To identify if there is a bug.  
Yes!, Of course, I think the model should be changed, if it is found to be incorrect.  Who wouldn't?

I don't understand why you can't look at the data?  
Or explain how a helicopter encounters VRS above ETL?

You make an assertion everything is correct, but offer only reassurances and credentials without addressing the points made.

My point is to find out if the flight model is accurate.  You say yes.  And you should know, but also can't answer my very simple questions, like how does a helicopter get into VRS above ETL.  This should not be possible, do we agree on that?

 

 

[cw4ogden]

10 minutes ago, Wadim said:

 

I've watched that video and the other VRS Mi-8 accident several times and I have two takeaways / observations:

 

Number one:  He has no forward momentum at all.  None.  That is to be expected when you descend straight down like he tried to.

Number two:  That pilot applied no corrective action.  He pulled more collective.  

That tells me he didn't know what was wrong with his aircraft.  He crashed from lack of training.  He failed to identify the emergency proceedure and was therefore unable to apply corrective action. 

Which also tells me VRS accidents in the MI-8 are rare.  Or there would be a strict training proceedures, proliferous amounts of literature, and way more accidents, none of which seems to exist.  The Mi-8 is one of the most fielded helicopters in history, and you can find exactly two videos of VRS accidents and they are both pilot's going straight the hell down.  Not moving, not above ETL.

Those pilots crashed in vertical descent profiles, and they by all appearance, where caught completely off guard by VRS.  That is not the same as the bird being overly dangerous.  They were overly careless.  Or they did not fully understand the flight profile they were operating in.

And you still can't answer a simple question of mine.  How does a helicopter encounter VRS above ETL.  Have you watched the track files.  Have you tested any of this yourself, or are you just trolling me at this point?

Let's just start there and see if we can agree on one simple thing as fact.  Can you get into VRS above ETL.  It is a simple place to start.  Yes or no?

Edited June 1, 2021 by cw4ogden

[cw4ogden]

What you are arguing is that because we have one video of a VRS accident, the aircraft is "dangerous" and therefore the flight model is correct.  That's some pretty specious reasoning.
That video, that accident is not representative of anything I've asserted.  I've have stated, induced from an OGE hover, the modeling is great.  It reacts just like the video and is everything I would expect from a VRS simulation.

But find me a video with an Mi-8 doing 55 kmph and crashing from VRS.  That would be useful evidence.  This is not.  The aircraft should do exactly what it did in that video and it does in DCS.  It just also does a whole lot more, like kill you from VRS above ETL which is a fugazi.  It's a phony.  

 

[cw4ogden]

There's really only one sticking point here.  Can you get into VRS above ETL?

That is a simple yes or no answer.

If you answer yes, that's a different debate.  It would beg the question: "How?"

If you answer no, it is incumbent upon you, or ED to see if the flight model is wrong, or if our testing methods are to blame.  We did the due diligence.  We obtained the data incumbent upon us as required by ED in the form of the track files to submit a bug report.  Yet, I can not tell, at this point, if you've even viewed or considered the evidence.  You seem to be dismissing it as out of the realm of being possible.

To build a cathedral, you need to lay the first stone.  And that stone is can you get into VRS at or above ETL?  Nothing else contributes to the conversation until you weigh in on that question, and it's ramifications.  The ramifications being to explain what's going on in the track files, if it isn't VRS above ETL.  Because we have to start with the foundation of being in agreement on the basic facts.  

Edited June 1, 2021 by cw4ogden

[Wadim]

1 час назад, cw4ogden сказал:

There's really only one sticking point here.  Can you get into VRS above ETL?

That is a simple yes or no answer.

If you answer yes, that's a different debate.  

If you answer no, it is incumbent upon you, or ED to see if the flight model is wrong, or if our testing methods are to blame.  We did the due diligence.  We obtained the data incumbent upon us as required by ED in the form of the track files to submit a bug report.  Yet, I can not tell, at this point, if you've even viewed or considered the evidence.  You seem to be dismissing it as out of the realm of being possible.

To build a cathedral, you need to lay the first stone.  And that stone is can you get into VRS at or above ETL?  Nothing else contributes to the conversation until you weigh in on that question, and it's ramifications.  The ramifications being to explain what's going on in the track files, if it isn't VRS above ETL.  Because we have to start with the foundation of being in agreement on the basic facts.  

 

Answered in a personal.

[milit]

52 минуты назад, Wadim сказал:

Answered in a personal.

А почему в личке?

Мне, например, тоже интересно, есть какие-либо аргументы, кроме уже озвученных по данному вопросу.

[cw4ogden]

From the FAA handbook on helicopter flight.  Note the passages in BOLD text.  

 

Vortex Ring State Vortex ring state (formerly referenced as settling-withpower) describes an aerodynamic condition in which a helicopter may be in a vertical descent with 20 percent up to maximum power applied, and little or no climb performance. The previously used term settling-with-power came from the fact that the helicopter keeps settling even though full engine power is applied. In a normal out-of-ground-effect (OGE) hover, the helicopter is able to remain stationary by propelling a large mass of air down through the main rotor. Some of the air is recirculated near the tips of the blades, curling up from the bottom of the rotor disk and rejoining the air entering the rotor from the top. This phenomenon is common to all airfoils and is known as tip vortices. Tip vortices generate drag and degrade airfoil efficiency. As long as the tip vortices are small, their only effect is a small loss in rotor efficiency. However, when the helicopter begins to descend vertically, it settles into its own downwash, which greatly enlarges the tip vortices. In this vortex ring state, most of the power developed by the engine is wasted in circulating the air in a doughnut pattern around the rotor. In addition, the helicopter may descend at a rate that exceeds the normal downward induced-flow rate of the inner blade sections. As a result, the airflow of the inner blade sections is upward relative to the disk. This produces a secondary vortex ring in addition to the normal tip vortices. The secondary vortex ring is generated about the point on the blade where the airflow changes from up to down. The result is an unsteady turbulent flow over a large area of the disk. Rotor efficiency is lost even though power is still being supplied from the engine. [Figure 11-3] A fully developed vortex ring state is characterized by an unstable condition in which the helicopter experiences uncommanded pitch and roll oscillations, has little or no collective authority, and achieves a descent rate that may approach 6,000 feet per minute (fpm) if allowed to develop.

 

A vortex ring state may be entered during any maneuver that places the main rotor in a condition of descending in a column of disturbed air and low forward airspeed. Airspeeds that are below effective translational lift (ETL) airspeeds are within this region of susceptibility to vortex ring state aerodynamics. This condition is sometimes seen during quick-stop type maneuvers or during recovery from autorotation. The following combination of conditions is likely to cause settling in a vortex ring state in any helicopter: 1. A vertical or nearly vertical descent of at least 300 fpm. (Actual critical rate depends on the gross weight, rpm, density altitude, and other pertinent factors.) 2. The rotor disk must be using some of the available engine power (20–100 percent). 3. The horizontal velocity must be slower than effective translational lift. Situations that are conducive to a vortex ring state condition are attempting to hover OGE without maintaining precise altitude control, and approaches, especially steep approaches, with a tailwind component.

 

When recovering from a vortex ring state condition, the pilot tends first to try to stop the descent by increasing collective pitch. However, this only results in increasing the stalled area of the rotor, thereby increasing the rate of descent. Since inboard portions of the blades are stalled, cyclic control may be limited. The traditional recovery is accomplished by increasing airspeed, and/or partially lowering collective to exit the vortex. In most helicopters, lateral cyclic thrust combined with an increase in power and lateral antitorque thrust will produce the quickest exit from the hazard.  This technique, known as the Vuichard Recovery (named after the Swiss examiner from the Federal Office of Civil Aviation who developed it) recovers by eliminating the descent rate as opposed to exiting the vortex. If the vortex ring state and the corresponding descent rate is allowed to progress to what is called the windmill brake state, the point where the airflow is completely up through the rotor, the only recovery may be an autorotation. Tandem rotor helicopters should maneuver laterally to achieve clean air in both rotors at the same time. For vortex ring state demonstrations and training in recognition and recovery should be performed from a safe altitude to allow recovery no less than 1000 feet AGL or the manufacturer’s recommended altitude, whichever is higher.

 

To enter the maneuver, come to an OGE hover, maintaining little or no airspeed (any direction), decrease collective to begin a vertical descent, and as the turbulence begins, increase collective. Then allow the sink rate to increase to 300 fpm or more as the attitude is adjusted to obtain airspeed of less than 10 knots. When the aircraft begins to shudder, the application of additional up collective increases the vibration and sink rate. As the power is increased, the rate of sink of the aircraft in the column of air will increase. If altitude is sufficient, some time can be spent in the vortices, to enable the pilot to develop a healthy knowledge of the maneuver. However, helicopter pilots would normally initiate recovery at the first indication of vortex ring state. Recovery should be initiated at the first sign of vortex ring state by applying forward cyclic to increase airspeed and/ or simultaneously reducing collective. The recovery is complete when the aircraft passes through effective translational lift and a normal climb is established.

 

 

 

Hence, my point.  VRS and flight above ETL are mutually exclusive.

 

Source: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch11.pdf

Edited June 1, 2021 by cw4ogden

[thunderstorm09]

Everyone deep into the manuals I guess, proper answer about this question you will get soon.
With respect

[Wadim]

21 минуту назад, thunderstorm09 сказал:

Everyone deep into the manuals I guess, proper answer about this question you will get soon.
With respect

Already received.
Man has no brake.
Speaks, speaks ... but does not understand the meaning.

Don't understand the essence.

Edited June 2, 2021 by Wadim

[YuKoN]

16 минут назад, Wadim сказал:

Уже получен.
У человека нет тормоза.
Говорит, говорит ... но смысла не понимает.

Вадим, объясните же нам смысл. По существу вопроса вы так ничего и не сказали

[Wadim]

6 минут назад, YuKoN сказал:

Вадим, объясните же нам смысл. По существу вопроса вы так ничего и не сказали

Как это не сказал?
И видео привёл, и методику отработки тестирования, и скорости!
Что вам ещё нужно???

[YuKoN]

Видео видел, методику нет. И о чем это говорит?

Основной вопрос был о том, что в режиме висения режим вихревого кольца наступает при 5м/с, а при горизонтальной скорости 30км/ч при вертикальной 3,5м/с у  нас в ДКС. В реале это так же, или нет?

Edited June 2, 2021 by YuKoN

[Frogen]

Парни, не горячитесь, и не требуйте немедленного ответа. Кому интересно, действительно интересно, начните с изучения аэродинимики,

Идут конструктивные переговоры. На всех, возможных языках. Это не быстро.

И по теме, есть среди Вас специалист по аэродинамике, который бы смог ПРАВИЛЬНО и понятно для всех перевести явления с русского на английский. Разговорный тут не "катит". Люди работают, но это не бысто, повторюсь, однако..

Нужен очень узко специальный английский, тот, который используют американские пилоты, или на край, англичане.. 

Что бы было понятно. как пример Терминология ИКАО

Снижение , предпосадочный маневр - Approach.... 

Аварийное снижение  emergency descent heading

Edited June 2, 2021 by Frogen

[Wadim]

18 минут назад, YuKoN сказал:

...

Основной вопрос был о том, что в режиме висения режим вихревого кольца наступает при 5м/с, а при горизонтальной скорости 30км/ч при вертикальной 3,5м/с у  нас в ДКС. В реале это так же, или нет?

 

Скрытый текст

Методика была в другом сообщении...

Нет. Не так.
При уменьшении скорости без взятия шага вертолёт и так увеличивает вертикальную скорость.

Параметры зависимости перехода в режим вихревого кольца по поступательной скорости не достаточно изучен. 

Однозначно ясно одно - чем больше поступательная скорость, тем легче выйти из этого режима.
Посему, мы исследовали только вывод из полного вихревого кольца. Это когда вертикальная скорость более 10 м/с, и вертолёт не реагирует на шаг.

Как научного работника, эта тема меня заинтересовала.

Как реального лётчика - нет.
 

[Frogen]

13 минут назад, Wadim сказал:

  Показать содержимое

Методика была в другом сообщении...

При уменьшении скорости без взятия шага вертолёт и так увеличивает вертикальную скорость.

Это особенности аэродинамики вертолёта, при пилотировании на II режиме.  ТО, что вдалбливают курсантам с 1 курса. И в теории , и на практике.. Как ни странно, но это прекрасно смоделировано в мат.модели Ми8.

Там еще много есть особенностей, но это не тема этой темы.. 

Но, этот фактор играет важную роль в формировании пограничных состояний в режимах от ГП до моторного планирования (в том числе и с гашением скорости) до попадания в ВК. 

Читаем и изучаем аэродинамику )). 

Edited June 2, 2021 by Frogen

[jager_jager]

Как NS430 починить нет информации?

 

Edited June 2, 2021 by jager_jager

[Frogen]

6 минут назад, jager_jager сказал:

Как NS430 починить нет информации?

 

Не знаю, как скрывать картинки, но сделать их маленькими, очень просто. Выделить и потянуть за край. (кому надо, посмотрит в полном формате, и форум не загромождён)

 

По теме.. ) Если это 2d версия, то по умолчанию она выводится в правый нижний угол. Что то придумывали?

Перезапуск.

Ремонт

Удаление модуля и переустановка. 

Edited June 2, 2021 by Frogen

[SL PAK]

Может это глюк от настройки графики "масштабирование интерфейса"?

[Vital061270]

У меня модель 2D. Да, Frogen прав. По умолчанию, навигатор падает в правый нижний угол. Но мышкой его можно таскать куда угодно по экрану. И увеличивать и уменьшать его размер, тоже можно мышкой, (навести курсор на угол навигатора, зажать лев кнопку мышки и тащить)

на "полтиннике " не работает (там своего барахла итак хватает)

Edited June 3, 2021 by Vital061270

[sLYFa]

17 hours ago, Wadim said:

  Reveal hidden contents

Методика была в другом сообщении...

Параметры зависимости перехода в режим вихревого кольца по поступательной скорости не достаточно изучен. 

То, что это очень сложный процесс с точки зрения аэродинамики, никто не спорить. Но как пытался объяснить англоязычный товарищ, с нарастающей скоростью, когда площадь НВ, не подвергнутая влиянию струи того же НВ (что как раз является причиной ВК, где НВ засасывает свою же струю), увеличиваетя, переход в режим ВК должен происходит на меньших вертикальный скоростях, чем в режиме висения. В ДКС, как раз наоборот. 

Я понимаю, что ФМ десятилетней давности наверное никто уже ковырять не будет. Надеюсь у Ми-24 будет правильно.