Talk:Vortex ring state

Page contents not supported in other languages.
From Wikipedia, the free encyclopedia

Vortex Ring State[edit]

At the top is says that settling with power is also knowen as vortex ring state, yet, at the end, it says that they are similar, implying that there are differences between the two. --Soupisgoodfood 17:30, 31 July 2006 (UTC)[reply]

OK. I've done a bit of research and it seems that settling with power and VRS are the same thing, but people often confuse settling with power as not having enough power to stop a decent. Because of the confusion and because VRS sounds more technically desciptive, I think settling with power should redirect to VRS, rather than the other way around. Any supporters? --Soupisgoodfood 18:19, 31 July 2006 (UTC)[reply]

What's effective translational lift? Could someone explain that on the main page where it is mentioned? Thanks. --Joe056 14:54, 22 October 2006 (UTC)[reply]

Done. Soupisgoodfood 13:16, 29 October 2006 (UTC)[reply]

Born2flie: No, I don't think this article should redirect to VRS, since Vortex ring is being used to explain a generic aerodynamic effect, even though it more thoroughly explains the effect in helicopters than this article. I would work on expanding this article and explaining it much more thoroughly. I will add it to my list to work on. --16:16, 12 January 2007 (UTC)[reply]

Choice of words[edit]

I really like the article saying failure to notice and take correct actions could result in "settling all the way down to the ground." Common parlance would probably use phrases like, "Crash" or "Put your butt through your helmet." —Preceding unsigned comment added by 70.158.35.226 (talk • contribs)

I agree. This article doesn't seem to be written for people who don't understand the terminology already. Jabberwockgee (talk) 00:56, 4 August 2009 (UTC)[reply]

Wording & Crash[edit]

Removed reference to the crash of David C. Allison. NTSB report http://www.ntsb.gov/ntsb/GenPDF.asp?id=ATL93FA127&rpt=fa does not support that the crash was caused by Vortex ring state in spite of it being a likely contributing factor. —Preceding unsigned comment added by Jeffgoin (talk • contribs) 00:20, 28 March 2008 (UTC)[reply]

Not listed as a cause or a contributing factor in the NTSB accident brief. --Born2flie (talk) 14:43, 22 May 2009 (UTC)[reply]

"removing any one of them escapes the condition"[edit]

"Since all of these conditions must be present, removing any one of them escapes the condition." This MIGHT be true in practice, but the argument is presented as it MUST be true by mere logic, which is not the case. It is possible that 3 conditions are required to enter a given state (i.e. VRS), but once caught in this state it is very difficult to escape it, requiring different conditions than for entering the state. --boarders paradise (talk) 05:06, 17 May 2009 (UTC)[reply]

It isn't difficult to escape, the issue is whether or not the conditions under which the state is encountered allow for the escape. Realized early enough and with enough power margin, power application can remedy the situation. If the aircraft is well established in the state, only enough altitude to allow time to transition to some form of horizontal translating flight limits the pilot from recovery.
Your argument says that it MIGHT be true in practice, suggesting that your problem is that it is presented as if it MUST be true, but then you proceed to argue that it ISN'T true. The statement is worded poorly, because you don't simply remove the operating condition, rather you remove the aircraft from the state by changing the conditions in which it is operating, but that isn't a difficult task. If any of the conditions are not present, you are not in the state, and it is possible in some instances to have all of those conditions present and still not be in VRS. --Born2flie (talk) 14:35, 22 May 2009 (UTC)[reply]

Rename to Vortex ring state[edit]

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the move request was: page moved. Vegaswikian (talk) 17:39, 10 October 2011 (UTC)[reply]


Settling with power → Vortex ring state

  • This article should be renamed to Vortex ring state (which currently redirects to this article). VRS is more descriptive than settling with power. Glrx (talk) 22:49, 3 October 2011 (UTC)[reply]
    • The first thing that "settling with power" made me think of was settling a political dispute by sending the army in, and similar. Anthony Appleyard (talk) 05:53, 4 October 2011 (UTC)[reply]
  • This article has a stub-and-link at Vortex ring#Vortex ring effect in helicopters. Anthony Appleyard (talk) 05:51, 4 October 2011 (UTC)[reply]
  • Support. Settling with power is a US Army Aviation-centric term to describe vortex ring state (VRS). FAA uses VRS in the rotorcraft manual cited in the article. No US Army publications are cited. -- Born2flie (talk) 18:24, 7 October 2011 (UTC)[reply]
The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

When not to add cite tags and then not say anything about them on the talk page...[edit]

Well, never. But especially when one can follow a link to another Wikipedia article containing a reference for the statement which contains that link. Citation for vortex being responsible for the crash of the Black Hawk during the bin Laden raid added. Hopefully that's what was being requested, and not a citation for the claim that bin Laden was killed. 72.200.151.13 (talk) 15:03, 8 February 2014 (UTC)[reply]

Quadcopter and UAV operators (including full size UAV Helicopters) Vulnerability to VRS[edit]

There is a tendency to ignore the physics of scale involved in quadcopter and other UAV helicopter's vulnerability to VRS. Under what physical grounds do any editors deny that VRS does not affect other rotorcraft at any scale. The weight of the craft only determines the proportional size of the vortex ring state. The vehicle has to be kept up in the air by some means and that is going to create a VRS - even in jet powered vertical flight like the Harrier and F-35B.

By presenting VRS information to pilots and operators (of UAVs) the skies are more safe and flight is less costly due to less crashes. But, quadcopter operators must be noticed that their craft are vulnerable to VRS in order for them to reap the rewards of that knowledge. Why is there such resistance to presenting basic scientific knowledge on this page. There has been an attempt to say that YouTube videos are not an acceptable demonstration of scientific principles. This is clearly opinionated and unacceptable since it depends on the quality of the video and its content. A YouTube video that clearly demonstrates VRS in quadcopters and replicates the phenomenon numerous times and teaches how to avoid the problem clearly has the qualifications to demonstrate the VRS effect on small quadcopters.

When the article moves on to include "Tandem rotor" helicopters in the "Pilot reaction" section, the physics changes slightly and presents a door for the introduction of scale issues into the discussion. It is in this section where it is appropriate to note the vulnerabilities of quadcopters - but it must be noted or the scientific benefit of the article is significantly reduced. Since those who pilot aircraft do not make the same sacrifices as those who simply operate UAVs, there is a question of investment in their actions. This is understood, but the danger to the public and others is real if the quadcopter or UAV helicopter should not operate as intended.

Science should not be withheld when safety is an issue.

By way of compromise, title the revised section "Pilot or Operator reaction"; but reinstate the comment on the vulnerability of quadcopters to VRS. — Preceding unsigned comment added by Cetaman (talk • contribs) 05:43, 26 September 2014 (UTC)[reply]

Radio control helicopters - vertical recovery from apparent VRS[edit]

It seems that most high powered aerobatic radio control helicopters can change "vertical" speed quickly, despite operating at relatively high rates of "vertical" speed, being able to quickly transition from a high relative descent rate to a high relative ascent rate (or vice versa if doing the same maneuver while inverted, or either way if oriented sideways with the main rotor nearly vertical). During the transition, it would seem that the helicopter would be "descending" at a high rate of speed while accelerating "upwards", with some "upwash" flowing through the inner radius of the rotor, until it transitions into an "asscending" state, but VRS, if it occurs, doesn't seem to be an issue. I'm wondering if relatively large rotor diameter and a high power to weight ratio is helping here. Rcgldr (talk) 04:00, 7 May 2016 (UTC)[reply]

We need a reference to add this to the article, otherwise it is all speculation. - Ahunt (talk) 12:09, 7 May 2016 (UTC)[reply]
Other than numerous videos demonstrating these type of maneuvers, the only article I found for a relatively small rotor diameter of 11.125 inches is this one Abrego1_AHS02.pdf . This NASA article basically states that VRS reduces thrust, but thrust remains positive and increases with collective pitch. In the case of high powered radio control helicopters, thrust to weight ratios are 4 to 1 or greater, which requires a relatively large diameter rotor, and the graphs in the article show a decrease in thrust less than a factor of 2 for a relatively small rotor diameter of 11.125 inches. Radio control helicopter forums mention VRS as an issue only for models with relatively low power to weight ratios. The high powered models can recover by using "positive" collective. Video of a 6 kg model producing 36 kg thrust at 2:26 700_lift. Example stunt video with link to second video trex800. Rcgldr (talk) 23:42, 7 May 2016 (UTC)[reply]
This is actually taught in helicopter school that in helicopters with high power-to-weight ratios that you can power-out of VRS and exit the top of it. - Ahunt (talk) 23:54, 7 May 2016 (UTC)[reply]
So I'm wondering if it's the power to weight ratio alone, or if rotor diameter plays a roll. In the case of high powered radio control helicopters, the transition from negative to positive pitch can occur at fairly high speeds, reversing the flow through the rotor quite rapidly. This is probably a better example video, a rapid "pop" recovery out of a high speed auto rotate descent at 0:30 auto_rotate_pop . I've read that an unloaded Skycrane can power out of VRS. This would seem to conflict with the concept that the rotor is stalled to the point that adding collective would just make it worse, but adding collective and power is how the models and the Skycrane can recover from VRS. With the reversed flow at the center, it would seem that the inner portion of the rotor is stalled (depending on collective pitch), and that the only initial downwash would occur at the tips, related to tip vortices, which would eliminate the stall at the tips, which in turn would drive the downwash inwards over the plane of the rotor. The transition seems to happen quite rapidly in the case of stunt models. Rcgldr (talk) 00:44, 8 May 2016 (UTC)[reply]
Interesting video, but those all appear to be autorotations and VRS does not occur in autorotations, just when power is on. - Ahunt (talk) 00:45, 8 May 2016 (UTC)[reply]
The descent may be due to autorotation or powered descent with negative collective; in both cases, there is upwash through out the plane of the rotor. Then the collective is changed to positive with power (or momentum in the case of autorotate), while there is still upwash through the plane of the rotor, so wouldn't this result in a momentary VRS? Rcgldr (talk) 02:36, 8 May 2016 (UTC)[reply]
VRS only occurs when power is applied in a powered hover descent, it doesn't occur in autorotation, even when collective pitch is applied at the bottom as in the video (I've done hundreds of autos like that in full sized helicopters) and never in forward flight, as it requires the air to be recirculated though the rotor and this only happens in a hovering descent. - Ahunt (talk) 11:48, 8 May 2016 (UTC)[reply]
OK, getting back to helicopters with high power-to-weight ratios that you can power-out of VRS - Rotor speed can't change quickly, so increasing power normally coincides with increasing collective, but this seems to conflict with the articles comment about lowering collective (perhaps going into autorotate) to recover from VRS, which makes sense if the helicopter is already at max power. Maybe this is the difference between vortex ring state, which is a condition of the air flow around the rotor, versus settling with power, which apparently means settling while at max or near max power, where increasing collective which would require more power, is not an option (since already at max power). Rcgldr (talk) 22:54, 8 May 2016 (UTC)[reply]
Outside of model helicopters, the rotor speed on helicopters is usually governed and therefore pretty much constant. For most helicopters the only way out of VRS is to lower collective to reduce the recirculation of air and to apply forward cyclic to fly out of the recirculating air, but of course this can only be done if there is height to do that. Very high powered helicopters can muscle their way out of VRS by exiting the recirculation via the top, but this only works with a lot of surplus power. - Ahunt (talk) 12:29, 9 May 2016 (UTC)[reply]

Assessment comment[edit]

The comment(s) below were originally left at Talk:Vortex ring state/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Born2flie: Should explain the condition more thoroughly as well as some diagrams describing what is happening. --17:03, 12 January 2007 (UTC)[reply]

Last edited at 17:38, 10 October 2011 (UTC). Substituted at 10:05, 30 April 2016 (UTC)

Diagram for vortex ring state needs to be updated[edit]

settling.html includes a more accurate but somewhat exaggerated example of a vortex ring state in figure 2-81. Also in the cover page of FAA helicopter hazards pdf What's missing in the wiki diagram is the central upwash that also contributes to inner vortices. The main issue with the central column of upwash through the rotor is a stalled state of the inner rotor blades. Rcgldr (talk) 00:37, 28 June 2016 (UTC)[reply]

Powering out of vortex ring state[edit]

In the case of high power to weight models, such as an unloaded Sky Crane (about 45% of peak torque needed for hover), or a 3d aerobatic model, there's enough excess power to recover from a vortex ring state even with just a thin ring of downwash. In the case of 3d aerobatic helicopters, rapid transitions in collective are possible where upwash through the entire rotor can quickly transition into downwash (or vice versa if inverted), even with rapid power / collective changes.

Possible explanations: This is a case where tip vortices may be helping, as the transition from upwash to downwash starts at the tips where the vortices form (eliminating stall), then due to the induced flow related to viscosity, the ring of downwash at the rotor tips quickly expands inwards towards the hub. It's also possible that even though the rotor is stalled, with enough power to overcome the drag, there's enough lift inspite of the stalled condition to recover. Rcgldr (talk) 19:42, 27 June 2016 (UTC)[reply]

Your ideas here are quite interesting, but to add this to the article we would need to cite a reference. - Ahunt (talk) 20:34, 27 June 2016 (UTC)[reply]
"Also notable of the Skycrane, it is one of the few aircraft capable of powering out of a vortex ring state.", from skycrane.html. Note that the rotor spins at about the same rate at all times, so all that excess power is used by increasing pitch (and drag), which some articles claim makes a vortex ring state even worse. The Vuichard recovery method also increases power and pitch to take off settings, and then moves laterally left or right to minimize altitude loss during recovery. Getting back to the point, it's somewhat known in the helicopter community that the Sky Crane is one of the few full sized helicopters that can power out of a vortex ring state. It's a bit more common knowledge in the model helicopter / multi-rotor community that high power to weight ratio aerobatic models can easily power out of vortex ring state, but lower power to weight ratio models, typically multi-rotors (like a quad copter) can't power out of vortex ring state (often resulting in hard landings to "pilots" unfamiliar with vortex ring state issues), and require lateral movement to recover. Example post from a radio control group forum "Most 3D-capable RC models running mid-high HS (head speed) and 11°+ collective should have no trouble powering out of VRS. " models and vrs Rcgldr (talk) 00:34, 28 June 2016 (UTC)[reply]
Again that is interesting and most likely quite accurate, but neither of those refs are useable on Wikipedia, see WP:SPS. Need better refs to add this. - Ahunt (talk) 13:55, 29 June 2016 (UTC)[reply]
and yet the radio control quadcopters section cites a youtube video (there is a self published web page that refers to that video, but it's not cited). One of the comments in that youtube video provides a link to another youtube video of an aerobatic quad copter and asks why that model doesn't have vortex ring state issues. Again it's a power to weight ratio (I recently responded to that comment). Rcgldr (talk) 20:07, 29 June 2016 (UTC)[reply]
The only video embedded in that forum I see as, "this video does not exist". - Ahunt (talk) 20:15, 29 June 2016 (UTC)[reply]
I was referring to the section Vortex_ring_state#Radio_control_quadcopters, which cites this youtube video: quad copter vrs. One of comments for that youtube video links to another youtube video aerobatic quad copter. You previously mentioned that helicopter pilot schools state that high powered helicopters can power out of vortex ring state, is this included in any of the textbooks used by those schools? Rcgldr (talk) 20:31, 29 June 2016 (UTC)[reply]
Fun video, but not WP:RS. I don't have any refs from my pilot training that say this. - Ahunt (talk) 21:32, 29 June 2016 (UTC)[reply]
The video about quad copters in vortex ring state is the only cited reference for the section on radio control quad copters. Rcgldr (talk) 22:52, 29 June 2016 (UTC)[reply]
Some You Tube videos are more reliable sources than others. That one is from a drone school and is only used to support one simple statement that small drones are subject to VRS. The one you noted is from some You Tube user who only uses his first name (Grant) and would be to support a lot more complex claims. It really would be best to have a more indisputable ref. - Ahunt (talk) 23:41, 29 June 2016 (UTC)[reply]
I assume that all rotorcraft are subject to VRS, but some of them can power out of VRS, including aerobatic versions of small drones. The fact that some rotorcraft can power out of VRS should be noted somewhere in the article, but I don't know what qualifies as a reliable source, for example, a drone school run by a single person, versus an aviation article written by a single person. Rcgldr (talk) 00:36, 30 June 2016 (UTC)[reply]
I think your conclusions there are accurate, we just need a source for it. - Ahunt (talk) 01:23, 30 June 2016 (UTC)[reply]
  • I found a reliable source regarding the Sky Crane and the power required to climb out of VRS: "... try to climb up from VRS by increasing power. It is known, that required power for such maneuver is about twice the power needed to hover flight, and there is only one helicopter that can do this: Sikorsky S-64 Skycrane without container mounted." from institute of aviation - fluid dynamics. Rcgldr (talk) 10:55, 30 June 2016 (UTC)[reply]
Many radio control helicopters and some quad copters (multi-rotor) have much more than twice the power it takes to hover, so for these models, climbing out of VRS should not be an issue.Rcgldr (talk) 10:55, 30 June 2016 (UTC)[reply]
You can certainly add that about the S-64 with the ref, but adding the drone part would be WP:SYNTHESIS. - Ahunt (talk) 11:50, 30 June 2016 (UTC)[reply]
That's why I separated the part about radio control helicopters from the part about the Sky Crane and the required power (I added one more blank line to make this clear). The Sky Crane was the key example of powering out of VRS that I was focusing on since it's full scale and not a model. The article only notes that quad copters are subject to effects like VRS. It doesn't make any claims for or against the existence of models that could power out of VRS. Rcgldr (talk) 15:12, 30 June 2016 (UTC)[reply]
  • I'll see if I can find a reference, but it would seem some versions of the [MBB_Bo_105]] (military, Red Bull, ...) would also be able to power out of vortex ring state, since they have enough power to do aerobatics such as loops. video of Red Bull heli . Rcgldr (talk) 21:42, 1 July 2019 (UTC)[reply]

Explanation for correction[edit]

When using translational movement to recover from vortex ring state, the focus is related to moving out of the induced flow (upwards at the hub and outside the tips, downwards just inside and near the tips), without explaining that the size of the vortices is greatly reduced due to flying into clean air where there isn't enough time for an induced flow and related votices to build up. Rcgldr (talk) 02:34, 28 July 2016 (UTC)[reply]

Vortex Ring State - introduction[edit]

The first section of this article includes this statement: Essentially, the helicopter descends into its own downwash. When the condition arises, increasing the rotor power merely feeds the vortex motion without generating additional lift. However, one of the factors describing vortex ring state is a relative upwash that gets drawn back into the rotor induced flow, which may include upwash through the plane of the rotor near the hub of the rotor.[1] Vortex ring state is one of 3 working conditions, propeller working state, vortex ring state, and windmill brake state. [2] A helicopter descending into it's own downwash may present a momentum issue, but that's not considered vortex ring state.

As for the second part of the statement, it is possible to power out of vortex ring state (generate additional lift), but this requires having about twice the power it takes to hover (for example, a Skycrane can power out of VRS). [3] Rcgldr (talk) 21:22, 20 September 2016 (UTC)[reply]

References

  1. ^ http://www.copters.com/aero/settling.html
  2. ^ http://www.aviationtoday.com/rw/personal-corporate/personal-ac/Flying-Through-the-Vortex_85872.html
  3. ^ http://scs-europe.net/conf/ecms2007/ecms2007-cd/ecms2007/ecms2007%20pdf/ese_0121.pdf

Pilot or operator reaction[edit]

The article's method of recovery mentions reducing collective and using forward cyclic, but Vuichard recovery instead increases collective to hover or greater setting and uses rudder (tail rotor) and sideways cyclic to recover with lateral motion, reducing the altitude loss compared to the classic recovery method. Vuichard Recovery .pdf. Rcgldr (talk) 18:39, 24 April 2017 (UTC)[reply]

For model multi-rotors (or model single rotors), the issue with being able to recover from VRS by simply adding power is an issue of power to weight ratio, not size, although smaller models may require a higher power to weight ratio to power out of VRS due to the inefficiency of smaller props. Rcgldr (talk) 18:39, 24 April 2017 (UTC)[reply]

Conflicts in article[edit]

Under description, "As forward airspeed decreases and vertical descent rates increase, an upflow begins because there are no airfoil surfaces in the mast and blade grip area.", ... "In this state, the helicopter is operating in its own downwash". A helicopter descending into it's own downwash may present momentum issues, but part of vortex ring state is due to the upwash near the hub. Rcgldr (talk) 16:50, 30 June 2019 (UTC)[reply]

In the introduction, "When the condition arises, increasing the rotor power merely feeds the vortex motion without generating additional lift" with cited reference, however the section "Powering out of vortex ring state" notes that the Sikorsky S-64 Skycrane, (when unladen), is able to power out of vortex ring state, noting that this requires having about twice the power it takes to hover also with a cited reference. Although I haven't been able to find a citable reference specific to vortex ring state, aerobatic radio control helicopters have thrust to weight ratios around 5 to 1, well beyond what would be needed to power out of vortex ring state, and the helicopters routinely do high speed descents and are able to transition into a high speed climb in a fraction of a second. Rcgldr (talk) 16:50, 30 June 2019 (UTC)[reply]

So where is the conflict? - Ahunt (talk) 20:07, 30 June 2019 (UTC)[reply]
@Ahunt:If a helicopter is "operating in it's own downwash", there is no upflow at the hub, and the inner part of the rotors would not be stalled. The statement: "Increasing the rotor power vortex motion without generating additional lift", isn't true, since increasing rotor power alone is one way the Skycrane can recover from vortex ring state, and is also part of the Vuichard Recovery Technique (in addition to using tail rotor thrust to move laterally). Rcgldr (talk) 15:13, 1 July 2019 (UTC)[reply]
So what wording are you suggesting? - Ahunt (talk) 00:37, 2 July 2019 (UTC)[reply]
@Ahunt:I'm not sure of the exact wording, but rather than "operating in it's own downwash", something like "operating in induced vortices large enough to significantly reduce lift, to the point that many helicopters can't compensate for the reduced lift by increasing power". This would explain why the typical recovery is to move laterally, since that moves the rotor out of the vortices and into relatively undisturbed air, and the part about "significantly reduce lift", rather than "increased power ... without generating additional lift" explains why some helicopters with sufficient power (such as the Skycrane), can simply increase rotor power enough to compensate for the reduced lift. Rcgldr (talk) 03:24, 2 July 2019 (UTC)[reply]
I would support that. It is consistent with he training I had on the subject and makes logical sense. - Ahunt (talk) 13:26, 2 July 2019 (UTC)[reply]
I removed the paragraph " ... descending into ... downwash ... without generating additional lift", since the introduction and later description already explain that vortex ring state is related to upwash through the hub, resulting in "severe loss of lift". The intro already covers the momentum issue of a helicopter descending into it's own downwash in a reference about Transport Canada's meaning for "settling with power". Rcgldr (talk) 13:44, 7 July 2019 (UTC)[reply]

Detection and correction[edit]

From the second paragraph: "so as to get out of the column of air created by the rotor downwash", however the point of moving laterally is to move out of the vortex ring, not out of the downwash. I'll wait for feedback before making any changes. Rcgldr (talk) 14:28, 9 August 2019 (UTC)[reply]

about the image used to illustrate vortex ring state[edit]

Hi. What the image in the article shows is not the dominant mode of vortex rings, but the second one. The first order one actually flows through the rotor downwards, and then returns through the outsides of the rotor to the top, under atmospheric pressure forcing.

There are higher modes such as this one, and they are relevant to e.g. autorotation. They might be mentioned e.g. in how to recover from the state, by modulating the engine power stochastically (some military helicopters do that automatically if they detect a ring state or some other comparable conditions).

But let's still keep the picture straight: the first mode here isn't like the one in the picture. Settling with power/vortex ring state actually has a wider, much more dire donut shaped flow field around the blades, and out from them, upwards. That's why you lose the first order, nonresonant, most salient thrust field upwards: the air suddenly loses traction, because of the loss of effective viscosity. "When the field wants to move as fast as your airfoil's effective downward momentum shift, you just can't hold onto it." Decoy (talk) 02:26, 13 February 2022 (UTC)[reply]

Retrieved from "https://en.wikipedia.org/w/index.php?title=Talk:Vortex_ring_state&oldid=1210882104"