cw4ogden

Это явление, по общему мнению, происходит только при очень низкой скорости полета, в диапазоне 20 км / ч. Как видно из видео и всей документации.

Эффекты VRS исчез за пределами скорости поступательного движения приблизительно Vx / vh = 1 Падфилд (ссылка 39) описывает состояние вихревого кольца следующим образом. На очень малых скоростях полета (менее 10 узлов) и умеренные скорости снижения (от 500 до 1500 фут / мин, в зависимости от загрузки диска) расход ротора становится увлечены вихревым кольцом тороидальной формы, что приводит к обширная рециркуляция во внешних областях диска ротора. Аналогично сваливанию в самолете самолет, по крайней мере, с точки зрения последствий для траектории полета траектория, но совершенно непохожая по аэродинамическому происхождению,

"Ряд предложенных границ для состояния вихревого кольца представлены на рисунке 33. граница из модели ONERA VRS основана на Падение Vz встречалось при летных испытаниях вертолета. В граница для модели VRS настоящего исследования основан на устойчивости динамики полета вертолетов и конвертопланы. Остальные границы основаны прежде всего на вибрация и неровности, с которыми сталкивается вертолет в VRS. Особо следует отметить границы, которые Васидзу построены для ΔT / T = 0,15 и 0,30 (ссылка 30), которые являются можно найти в многочисленных документах по VRS (в том числе в США. Армейский полевой устав FM 1-203, Основы полета). На рисунке 34 представлены границы VRS вертолета на основе летные испытания D6075 Taghizad et al. (ссылки 44, 46, 47). Падение вертикальной скорости в первую очередь определяет границу, но также показаны точки, в которых колебания увеличиваются. В граница из модели ONERA VRS включена. Taghizad, et al. пришел к выводу, что при более низкой скорости движения более 20 км / ч, верхняя граница оказывается на низкой и примерно постоянная скорость снижения (Vz около –4 м / сек)."

https://rotorcraft.arc.nasa.gov/Publications/files/Johnson_TP-2005-213477.pdf "Грубое поведение вертолета в вихревом кольце состояние было объяснено нестабильным характером течения. Во время тестов визуализации потока (поз. 20) периодический наблюдалось опрокидывающее движение диска ротора, вызванное тот факт, что полное вихревое кольцо вокруг кончика круга никогда не было получено. Если вихрь на одной стороне диска нарастал, вихрь на другой стороне искал освободиться, чтобы увлечься окружающим воздухом. А мгновение спустя образовался новый вихрь, чтобы заменить последний один. Грубое поведение было более выраженным для снижение в прямом полете, чем в вертикальном полете, но очень наблюдалась регулярная периодичность. Диск ротора упал регулярно с тем же периодом, что и выпадение хвостовые вихри. Период ротора модели был около 2 секунды. При более высокой скорости движения грубое поведение ротора в состоянии вихревого кольца исчезли, поскольку вихри были снесены, прежде чем они смогли создать вихревое кольцо вокруг ротора."

Это вертикальное воздушное явление, любое значительное движение в сторону или вперед не позволяет вихрям достичь устойчивого состояния. В каждом примере с пилотом все в порядке, вплоть до почти нулевой скорости. Обратите внимание, что вихрь остается позади него, пока скорость полета не станет почти нулевой.

Это то, что мне кажется DCS MI-8: преувеличенная кривая. Близко, но слишком далеко по горизонтали вправо.

Так выглядела бы диаграмма VRS, если бы ее можно было встретить во всех режимах полета. Это грубый пример, но он должен выглядеть примерно так:

My apologies, you said it was not needed, so I stopped providing translations. Прошу прощения, вы сказали, что в этом нет необходимости, поэтому я перестал предоставлять переводы. Вертикальная скорость - это вертикальная ось графика. Он обозначен как V / V для вертикальной скорости и имеет корреляцию один к одному, что обозначено двумя цифрами «1.0». Все, что вам нужно сделать, это вычислить свою воздушную скорость ETL и установить горизонтальную 1,0 для этой скорости. График показывает, что это корреляция один к одному. Для любого профиля полета существует только одна воздушная скорость, угол захода на посадку и скорость отклонения, и их можно найти на диаграмме. Теперь преобразуйте единицы в вертикальную скорость. Пример: 1 км / ч = 0,28 м / с если у вас воздушная скорость ETL, примерно 50 км / ч, исходя из самой высокой оценки, которую я видел. 50 x 0,28 = 1,0 на графике. Вот как это работает. Теперь посмотрите на линии, которые я нарисовал, потому что, если вы понимаете, вы понимаете, о чем я говорю. 50 x 0,28 устанавливает 1,0 на 14 м / с. Это полностью развитое состояние вихревого кольца. Середина круга, обозначенного 1.0 вы можете интерполировать, чтобы приблизительно определить, где находится верхний край конверта, путем измерения расстояния между нулем и верхом конверта VRS и линией 1.0. Вот почему диаграмма универсальна, она продиктована вашим конкретным самолетом. Скорость ETL незначительно меняется в зависимости от планера. если вы не понимаете таблицу, вы не понимаете VRS. Я понимаю, о чем вы говорите, теоретически в прямом полете. Это может произойти, потому что ротор всегда вызывает поток. И я понимаю, что вы можете перевести роторную систему в состояние вихревого кольца с помощью необычных маневров. Но эти маневры все равно должны заставить вас погрузиться в собственный поток. Что вы физически не можете сделать, кроме скорости полета выше ETL. Чтобы перейти от высокой скорости к спуску в собственный поток, ваш вектор скорости должен двигаться прямо под водой ротора. Это может произойти при любом количестве углов полета и профилей захода на посадку. Но они должны соответствовать диаграмме. Вы должны спускаться в собственном воздухе. это может быть вызвано быстрым замедлением пилота и постановкой самолета на хвост. Но вы вложили свой вектор скорости в пух. В этом случае из-за замедления ваши роторы были наклонены вверх, навстречу набегающему потоку. в прямом полете ваш индуцированный поток должен оставаться в области роторной системы достаточно долго, чтобы вы погрузились в него. При скорости воздуха от 30 до 40 км / ч ваш индуцированный поток проходит далеко позади самолета, прежде чем он снова попадет в роторную систему. Все, что вам нужно знать, есть в таблице Это не хвостовой винт VRS на скорости 80-100 км / ч. Похоже, что то, что вы описываете, исчерпывает авторитет педали. Означает срыв лопастей рулевого винта, вызванный слишком большим спросом на повторный набор номера. И, что приводит к потере эффективности рулевого винта из-за условий сваливания, разделения ламинарного потока, а не образования вихрей. Хвостовой винт VRS так же наклонен на 90 градусов. Обычно вызвано поглощением вихрей от несущего винта или зависанием хвостового винта прямо против ветра. И то, и другое было бы эквивалентом вертикального или почти вертикального спуска. для этого требуется источник индуцированного потока. Ветер не дует вверх и вниз, поэтому ветер при парении отлично подходит для несущего винта, но может обернуться катастрофой для хвостового винта на очень узком участке круга в 360 °. Главный ротор VRS очень похож, это очень маленькая полоса области вектора шага / скорости, где вы удерживаете ротор в его собственном индуцированном потоке. И даже тогда вы должны в нее спуститься. Я могу парить в ОГЭ и безопасно спускаться, но я не могу сделать крутой подход, не опасаясь внезапной смерти? Бред какой то. Потому что, если это то же самое для рулевого винта в прямом полете - невозможно получить VRS. То, что вы описываете, - это совсем другое. Остановка рулевого винта из-за избыточного спроса. Это лопасть рулевого винта, превышающая критическую AOA. Не обязательно явление вихря, и определенно не явление вихря, если вы говорите о скорости 100 км / ч. Если только вы не получаете вершины от несущего винта, но даже они будут уходить со скоростью 100 км / ч.

This is what I think you are all stuck on. They are aerodynamically two different things. Separation of laminar flow and vortex ring state. You will absolutely have separation of laminar flow in a developing Vortex Ring state. But you are attributing other causes of separation of laminar flow to Vortex ring state, that are not that phenomenon. VRS is confined to those flight profiles more or less bounded by the regions of that chart. If the mi-8 module flew anything like that chart, we would be sipping tea right now, instead of this. People seem to want to throw a lot of spaghetti at the wall and hope something sticks. But do so without refuting the points I’m making. Or dismissing out of hand the evidence I’m citing. You can tell me I just don’t get it, but is that what’s really going on here? I make a point, it gets dismissed outright, with no refutation, or I’m told I’m a stupid American pilot, or I need a VR, or a seat shaker, or more spaghetti gets tossed about. i’m done. I’ve been arguing this for three flipping months. Fix your bug, don’t try and throw more spaghetti at me. Or live in denial of reality.

This is not tail rotor VRS at 80- 100 kmph. It sounds what you are describing is running out of pedal authority. Meaning blade stall of tail rotor, caused by too much demand for right redial. And Resulting in loss of tail rotor effectiveness due to stall conditions, separation of laminar flow, not vortex formation. Tail rotor VRS is same phenomenon tilted 90 degrees. Usually caused by ingesting vortices from the main rotor, or hovering with your tail rotor directly into the wind. Both of which would be the equivalent of a vertical or near vertical descent. it requires a source of induced flow. Wind doesn’t blow up and down, so that’s why wind at a hover is great for the main rotor, but it can spell disaster for a tail rotor, in a very narrow sliver of a 360° circle. Main rotor VRS is much the same, it’s a very small sliver of the pitch / velocity vector area, where you keep the rotor into its own induced flow. And even then you have to descend in it. I can hover OGE and descend safely but I can’t do a steep approach without fear of sudden death? Nonsense. Because if this, Same thing for the tail rotor in forward flight - not possible to get VRS. What you describe is a different thing. Stalling the tail rotor due to excess demand. This is a tail rotor blade exceeding a critical AOA. Not necessarily a Vortex phenomenon, And definitely not a vortex phenomenon if you’re talking 100 km/h. Unless you’re getting vertices from the main rotor, but even these will be gone by 100 km/h.

If there is something bites MI-8 pilots in the butt above 50 km/h, if such thing actually even exists, it is not vortex ring state. Or you are doing airshow maneuvers and it serves you right for not understanding the demon you’re playing with. VRS you must be in your own downwash at least long enough for the next blade to pass. Undisturbed air has no induced flow. If every blade is getting it clean bite of air you have no induced flow to act on the rotor system. it is the very reason for the existence of transitional lift benefits. It is why your helicopter goes up faster in forward flight than at a hover. It’s why there is a one to one correlation in the chart, and why the chart doesn’t continue horizontally to these airsspeed you refer to. It has a limit bounded by a horizontal rate of motion. If it did not that circle would extend horizontally the length of the chart. What you are trying to say is there is no upper airspeed limit to which VRS is a threat and that is false. anyone who reads the graph can see that. I think you are letting something theoretical get in the way of how it actually works, or mixing and matching up multiple different phenomenon. it boggles my mind, there is no equivalent term to ETL in your flying culture. But it certainly explains why this phenomenon would be confusing. This is obviously not something well understood by the MI-8 community. It is not something well understood by the US Army either. Most of my career vortex ring state was called settling with power, Which has lead to much confusion over the years. Only in recent years it’s been clarified. So I do know this is not well understood. But having nearly killed me, in my case trying to come to a stop too fast at a landing zone, it is some thing I spent years learning about. The average pilot does not understand VRS, this is true. But this is my personal enemy. I took time to learn the demon.

This is true, but it ignores the fact that certain parameters are required and those parameters are documented in the chart. I can get into the VRS anytime I have a vortex ring state. But a vortex ring state can only develop under certain conditions. You are telling me these conditions exist outside the standard VR as envelope and I see no evidence that is true. Show me a chart with these flight regimes you speak of Where I can be moving horizontally and get into vortex ring state. I will submit you cannot because they do not exist. vortex ring state is a vertical or near vertical descent phenomenon. Or Placing the aircraft in such an unusual attitude, as to affect the same thing.

Vertical speed is the vertical axis of the graph. It is labeled V/V for vertical velocity and has a one to one correlation, as indicated by the two “1.0‘“s . All you need to do is figure out your ETL airspeed and set the horizontal 1.0 at thus speed. The chart is telling you it’s a one to one correlation. There is only one airspeed, approach angle and rate of dissent for any given flight profile, and it can be found on the chart Now convert units to vertical speed. Example: 1 kph = 0.28 m/s if you ETL airspeed is roughly 50kph based on highest estimate I’ve seen. 50 x .28 = 1.0 on the chart. That’s how that works. Now look at the lines I drew because if you understand that you understand what I’m saying. 50 x .28 sets the 1.0 at 14 m/s . That’s fully developed vortex ring state. Middle of the circle labeled 1.0 you can interpolate to approximate where the top edge of the envelope is, by measuring the distance between zero and the top of the VRS envelope, and the 1.0 line. This is why the chart is universal, it is dictated by your particular aircraft’s ETL speed varies only slightly by airframe. if you do not understand the chart you do not understand VRS. I get what you’re saying that theoretically in forward flight This can happen because the rotor is inducing a flow always. And I get that you can put a rotor system into a vortex ring state with unusual maneuvers. But those maneuvers still have to make you descend into your own downwash. Which you physically cannot do it but airspeed above ETL. To go from high speed to descending into one’s own downwash, your velocity vector must move straight below the rotor wash. That can happen in any number of flight angles and approach profiles. But they must conform to the chart. You have to be going down in your own air. this can be caused by the pilot rapid decelerations and standing the aircraft on its tail. But you have put your velocity vector into your down wash. In this case, the deceleration has tilted your rotors upwards into the oncoming flow. in forward flight , Your induced flow has to remain in the area of the rotor system long enough for you to sink into it. And air speeds above about 30 km/h to 40 km/h, your induced flow is well behind the aircraft before it can be ingested into the rotor system again. Everything you need to know is in the chart you refuse to look at.

Look at the two blue lines. If I keep my rate of descent above the horizontal blue line - No VRS is possible. If I keep my approach angle shallower than the blue line - No VRS is possible. If I want to know the airspeed range it occurs, the 1.0 on the bottom of the graph is correlated to ETL. Above 1.0 horizontally also No VRS is possible. This is what I am saying. Everything you need to know is in the graph, if you know what you are looking for and understand the concept of VRS.

No, you just physically can't get VRS in horizontal flight above ETL airspeeds. And no, just no to that last sentence. Show me a cruise flight VRS accident or any VRS accident that caused a structural failure in flight. Ridiculous. If VRS was easy to understand, we wouldn't be having this conversation.

You seem to be mixing rotor tip vortexes with vortex ring state. Not the same thing. One is a normal phenomenon always present, the tip vortices. VRS is an abnormal flow state with vortexes developing inboard due to combination of induced flow and rate of descent. if you look at a VRS diagram you see that both vertical speed and approach angle are critical. Stay below 30 degrees or keep your rate low enough, it should be manifestly impossible to encounter VRS. I think you misunderstand the phenomenon if you are saying it can be encountered in all modes of flight. You can't get into to VRS above ETL because you are not recirculating the same air. That air is behind you before it's induced flow can be a factor. By this logic, if I can get into VRS at any airspeed, why no VRS in cruise flight with collective reduction? You need specific criteria to encounter VRS. In any discussion of VRS, Russian or American, the very first criteria listed is always vertical or near vertical descent. This is a low airspeed phenomenon by its very nature. http://www.svvaul.ru/nashi-resursy/knigi-onlajn/aerodinamika/604-pilotirovanie-vertoljota-na-rezhime-malykh-skorostej#:~:text=Самопроизвольное How do you decrease rotor pitch to a critical angle and achieve a blade stall? This seems to makes no sense.

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 translational lift 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

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

Yes, that is my beef. It is modeled well when entered from a hover OGE or very steep approach. It's off, if the most dangerous region is near ETL where, by definition, once beyond, you are not subject to vortex buildup. Around ETL I should be very slightly susceptible, and if I do get into it, it's going to produce a rolling moment, initially at least, as the aft portion of the head encounters it first, from induced from of the forward half, which is still in clean air, all offset by 90 degrees. It's conceivable the Mi-8 goes through ETL much higher speed than normal helos, but I find it unlikely, and unsupported in any documentation. But if that is the case, the modeling may be fine. Regardless, that is the crux of my argument, something is wrong regarding VRS kicking in while you have enough forward airspeed and / or shallow enough approach angle that you should be well clear of your downwash. At this point, the flight model is either off, or the hip exhibits behaviors unlike any other rotary wing aircraft flying. And it's totally undocumented and has led to surprisingly few accidents.

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.

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.

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?

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?

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.

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.