Talk:Stall (fluid dynamics)/Archive 1

Archive 1

"G-stalls"

I thinks this section is poorly written, unclear, and factually incorrect in some spots. Just for starters, it should be called "accelerated stalls," the much-more-widely used term, at least in the U.S. (Is G-stall a military or British term? Anyone care to chime in?). I will rewrite it. Anyone mind? Also, it might be a bit difficult to include just the right amount of detail. Would it be appropriate to go into a full-blown discussion of the V-G diagram in this article? I am leaning towards "yes." Vessbot 07:17, 25 Jan 2005 (UTC)

As its original author I feel a bit annoyed by your description of my writing - but go ahead, if you think it needs changing. Some additional contributions have been added since I put it in there, and to my mind the mention of centrifugal force is wrong and in error - we are talking only about WEIGHT, which increases in a turn. (If this sounds odd, then check your definition of weight - it's not MASS). Since lift must counteract weight then lift must increase in a turn; if the wing can't produce the needed lift then it will stall. I don't really see why this is hard to understand. G-stall is the term I've always used and heard from others, I'm from the UK. I don't think it's military term. Graham 05:18, 26 Jan 2005 (UTC)

You wrote: This is a condition where the wing cannot produce enough lift to support the aircraft's weight and centrifugal force, in spite of otherwise flying at a reasonable airspeed and angle of attack.

What does "reasonable angle of attack" mean? Stall will occur at the same angle of attack regardless of the G or speed. There is a simple mathematical relationship that equates the speed at which that will occur with the G/load factor.

"Significant amount of gee?" What is significant? A stall at any G above 1 is an accelerated stall by definition.

" In most types of GA aircraft, high-speed G-stalls are unknown because structural failure will usually occur before the G-stall condition could be met," ... ridiculous. See above. In the U.S., for example, the limit load factor for Normal category airplanes is 3.47 G's. Thus, if you stall a plane at any load factor between 1 and 3.47, that's an accelerated stall. That is sometimes practiced at the private pilot level here.

Vessbot 07:20, 26 Jan 2005 (UTC)

So fix it. Carping about it won't help, and just pisses people (me) off. Graham 05:16, 21 March 2006 (UTC)

A G-stall (or high speed stall) is when the inertia of the moving aircraft increases the weight as it is attempting to change direction, overcoming the lift of the wing. This usually happens in high speed turns or pull-outs from dives. The aircraft wants to continue in its straight path but the increase in wing incidence as the aircraft attempts to change direction increases the angle of attack over that which it as able to support the increased weight due to the G. The aircraft continues moving in the same direction but the nose pitches up, causing a stall, because the aerodynamic lift from the wing is not sufficient to change the flight path with the increased weight due to the G. If the aerodynamic force on the wings is too high, or the pull out too sudden, this can cause structural failure in the wing, leading to the wings 'folding up'.

Put simply it's like this; The aircraft's ATTITUDE changes with pulling back on the control column, but the aircraft's DIRECTION OF MOTION does not change (due to inertia) hence the airflow over the wings changes its direction relative to the wing, it now moves towards the wing from a direction that is more below than before, increasing the actual angle of attack, causing a stall.

This phenomenon is unlikely to be experienced in General Aviation aircraft as it requires somewhat extreme maneuvres such as is only required in high speed aerial combat, where the lift forces and inertia are high, and if attempted in light aircraft these are quite likely to result in structural failure.—Preceding unsigned comment added by 213.40.248.50 (talk) 11:55, 23 September 2009

Complexity of introduction

The introduction of this article would make sense to someone who already has a good understanding of the subject field, but I think it's perhaps too technical for a general introduction. Terms like "chord line", "angle of attack", "lift-coefficient", "angle-of-attack curve", "linear and nonlinear regimes", and "flow separation" are not in general use, but the article expects readers to understand them. While technical descriptions are certainly appropriate, there will be a lot of people coming to this article wanting to know what "stall" means and going away without an answer. Could someone knowledgeable about this topic possibly write a brief paragraph giving a basic overview to the uninitiated? -- Vardion 8 July 2005 22:41 (UTC)

Disambiguation

I'm going to turn this into a disambiguation page, then create a new 'Stall (flight)' page to cover this subject. There are too many legit other stall definitions, and the (flight) modifier will be consistent with other flight pages, such as Spin (flight). I'll move the discussion over to the new page so it stays with flying stalls, any objections? - Chairboy 20:36, 19 July 2005 (UTC)

Sounds like a good idea to me - go for it. Graham 01:20, 20 July 2005 (UTC)

I went for it. Created Stall (disambiguation) and put a link at heading of Stall (flight) to go to it. There are a bunch of pages that link to Stall that should have autolinked to Stall (flight), this method should reduce the workload that converting all of them would require. - Chairboy 16:35, 22 July 2005 (UTC)

This seemed needlessly tangled, since all the links to stall were meant to go to stall (flight). I created stall (enclosure) for all the other meanings and left a link at the top here, then moved this back to Stall. Thanks to those who started cleaning up links immediately; I got called away from the computer right after the move and came back to get started with cleanup only to find most of it done! Thanks, — Catherine\^talk 19:18, 3 March 2006 (UTC)

Just because some aircraft enthusiasts (me included) have created the most links to stall doesn't mean that Catherine is right. 90% (very approx) of the time "stall" is used it's engine stopping the general pop'n has in mind; 10% it's enclosures; 1% it's aerodynamic. When someone comes to the Wikipedia article then disambiguation is required. I think Chairboy's treatment is correct. I will wait a while and re-do his changes. And then I will hunt out double redirects in aviation articles and replace stall with stall. OK? You can help if you like. Paul Beardsell 09:26, 2 September 2006 (UTC)

OK, I did that and I am currently working through the double redirects. Paul Beardsell 16:39, 30 September 2006 (UTC)

Image captioning problem

Historical versions of the image as it was being discussed

Latest SVG version

The recently added image includes a caption "tilt with respect to horizontal plane". Thus MUST be changed to "tilt with respect to airflow", otherwise it is simply incorrect. In addition, the images themselves are a bit misleading to my mind. An unstalled wing shouldn't be shown with a trail of turbulence left behind, since this isn't there. The flow is smooth. Graham 05:37, 13 February 2006 (UTC)

On further thought I decided to temporarily remove the image from the page. It can be reinstated once the problems are fixed. I decided to do this because anyone coming to this article with this image in its current form will leave with the wrong information. We don't want that to happen, and since the text is OK, this is the best way forward that I can see. Graham 05:40, 13 February 2006 (UTC)

The more I think about it, the more troubled I am by this image. I think it should not be reinstated. I have written a criticism of it at Image talk:StallFormation.gif. Most surprising is that the image was sourced from NASA - they ought to know better than this. Graham 05:50, 13 February 2006 (UTC)

Wow, that is bad. I don't know aerodynamics very well, but maybe we can patch things up with Photoshop. I've uploaded two new versions, one with the "with respect to airflow" change, because that's blindingly obvious. The latest version has an additional airfoil diagram at the top for 0° that says "laminar flow, no turbulence". Does that latest version of Image:StallFormation.gif look correct? --Interiot 09:50, 13 February 2006 (UTC)

Good work on the caption. Unfortunately I'm still unhappy about the rest. There simply is no "separation point" in existence until the onset of the stall - so the images at 4° and 8° are still wrong. I'm not even sure that the approach of describing the stall as an existing separation point moving forward is going to get us anywhere, especially as the article itself doesn't take this approach - in fact "separation point" isn't even mentioned. At the onset of the stall there is an airflow detachment or separation, but it comes into being at that time - yes, it moves from the trailing edge forward as the AoA increases, but this change occurs over a very narrow range of angles close to the stall (say from 15° to 17°). AoA less than that are fully laminar. I think NASA must have commissioned this artwork from a graphic artist who was given a rough description to go on with few details, and basically got it wrong. A simple fix would be to change the captioning of the angles - change 4° to 15°, 8° to 15.5°, etc, but a better fix would be to change it more radically by showing the more conventional "airstream" lines that usually are used (in fact, that's another thing - the portrayal of the turbulence here looks like the wing's on fire or something - it doesn't properly illustrate what is happening all around the wing.) However, let's get some other views on this before entering into a load of edits. It might even be better to start over - I might look into doing it myself if I can make the images look decent. Graham 22:23, 13 February 2006 (UTC)

Yeah, I don't fully understand the topic myself, but have a bit of Photoshop experience, and would love to find/create an image as necessary. Okay, next proposal: we just have two wings, one at 13° that shows 100% laminar flow lines around the wing (eg. like this). And then below that, a wing marked "15°, stall point", something like what's there now or this or this, with the laminar flow lines going around the wing, except for the separation region. Also, if the article doesn't mention "separation point", should that phrase be left off? Or, I've seen other pages [1] [2] refer to it as the "transition point" as well, would that be more appropriate? --Interiot 23:59, 13 February 2006 (UTC)

Sorry to challenge what some of you have written, but as an Aeronautical Engineer I have to say some of the statements above are wrong. To begin with, unstalled wings often DO leave a turbulent wake behind. A wing that is 100% laminar wouldn't leave a wake, but these are practically impossible - almost all wings are turbulent, and so leave a wake behind, even in normal unstalled flight. This turbulent wake accounts for a significant portion of the aircraft's drag. Secondly, the 'separation point' nearly ALWAYS exists on a wing. As shown on the image here, it's the point at which the boundary layer 'trips' from laminar to turbulent, increasing dramatically in thickness. This point exists on all normal wings, and is not related to stalling. --dSpammer 22:00, 13 August2006 (BST)

If you are willing to make the images, that would be great. I started to have a go but I got very frustrated with the free dumbass drawing package I was trying to use (Eazydraw) which makes drawing basic bezier curves unnecessarily complex. Anyway, I think your proposal sounds good - an unstalled wing at some angle (it doesn't need to be 13°, anything reasonable - say 6°, which is a typical AoA in straight and level flight) with laminar flow lines and no turbulence, separation point or any of that malarkey. Then a wing partially stalled (15° say) where the flow is laminar over the first half or so, then breaks away, and one fully stalled where the flow is not attached at all, and spills over the leading edge. Those photographs you linked are very informative and could well be used as a basis - the depiction of turbulence is difficult and just using hatching is a bit lame - some sort of eddying would be great. I think we should avoid using any captions that mention 'separation point' - it should be obvious from the drawings that the airflow has detached and that ties in with the description in the text. Graham 04:24, 14 February 2006 (UTC)

Okay, the image isn't perfect, but I uploaded a new version. Since I don't even know what a proper airfoil is really shaped like, it's a more conservative modification of [3]. If there's a good sharp image of what turbulence looks like, I might be able to trace that. But is the latest version of the image semi-acceptable? --Interiot 18:38, 25 February 2006 (UTC)

Much, much better. The only comment I'd make is that in the 25° case, the separation point could be right "on top" of the foil's curve, rather than further back as it is now, but if it's a lot of work to change it then it's acceptable anyway. Graham 03:21, 26 February 2006 (UTC)

Done. Although note that the 25° one was previously unmodified from the original image, so it may have been okay as it was before too. --Interiot 20:18, 26 February 2006 (UTC)

Re the suggestion that Washout be merged with Stall

I think there needs to be a subject on Washout but my comments in Washout about the terrors of wing tip stall should be located under the general heading of Stall. When I changed Washout I was trying to correct the previous version which suggested the sole reason for washout was to optimise wing efficiency ie reduce induced drag, whereas avoidance of tip stall, which is more important, wasn't addressed. So I changed the text leaving the structure unchanged. Now, what about the Stall section? It seems to me that a few changes are needed. Take the first sentence "In aerodynamics, a stall is a condition in which an excessive angle of attack causes loss of lift due to disruption of airflow". Read this through the eyes of someone who really wants to know what 'stall' is ie doesn't know already. Do we really mean that excessive AofA causes LOSS of lift? LOSS of lift? Is it leaking away? Or do we mean that the lift is less than would have been achieved were the wing not stalled? If the latter, why don't we say that? Also the discussion above re the diagram seems to suggest that there are only two airflow regimes, laminar and separated. Laminar is very, very difficult to achieve and not possible with an aerofoil section like that shown in the diagram. What will arise at angles less than the critical angle is turbulent (but not separated) flow. --FHBridges 19:03, 1 March 2006 (UTC)

So do you want the article written for the layman or the expert? My view is that it's the layman we are writing for every time, though having said that it doesn't mean being patronising and omitting important detail where warranted. I agree with your comments about the explanatory paragraph being not very enlightening to the uninitiated, but then introducing complexities such as truly laminar flow being rare is going too far the other way. In simple terms the laminar = unstalled, separated/turbulent = stalled equation is valid, and that's good enough to get you a very good appreciation of what a stall is, if you don't know anything about it. Anything more than this is detail, and while some detail is good, getting into discussions about nuances of aerofoil shape and what truly laminar means and so forth isn't to my mind going to be very helpful. You can get 99% of the way in a few sentences - the remaining 1% we can leave to the expert texts aimed at graduates studying aerodynamics, who we most definitely are not writing for. Graham 03:36, 2 March 2006 (UTC)

The articles need to be written for the layman. I didn't suggest adding complexity by discussing the problems of achieving laminar flow - it has no relevance to this topic. But I disagree with your equation of laminar = unstalled, separated/turbulent = stalled. The flow around an aeroplane isn't laminar it is turbulent. Turbulent flow is understood to mean turbulence which is small in scale compared to the body in question. My objection is the use of the terms 'laminar flow' and 'turbulent flow' in the figure . Laminar flow is the holy grail of aerodynamicists - if it could be achieved the effect on aviation would be enormous. It would be wrong to imply that it is commonplace. Turbulent doesn't equate to stalled. Better descriptions would be 'steady flow' in place of 'laminar flow' and 'separated flow' in place of 'turbulent flow'.--195.93.21.5 19:13, 2 March 2006 (UTC)

Oops. I composed the above without signing in. Didn't realise you could do that! Didn't intend to be anonymous. --FHBridges 19:21, 2 March 2006 (UTC)

I concur with that - perhaps our friendly illustrator could do one more iteration of the drawing? Graham 22:59, 2 March 2006 (UTC)

How's that? I'll try to keep the latest versoin of the .psd posted too, in case others eventually want to make changes. --Interiot 02:24, 3 March 2006 (UTC)

Umm..not an expert, but am an ex-fighter pilot. Just wondering why 'washout' needs to be folded into 'stall' section, when linking to it seems to work OK. Linking gives you the wonderful benefits of consulting any encyclopedia, namely the joy of discovering things such as 'washout' also describing an enema.

By coincidence, also describes what I felt like doing when I experienced a 'high-speed stall', (yes - yet another name for G-stall or accelerated stall) in a Jaguar, (not a car) at low altitude over Scotland.

If you're looking for a simple description of what a 'stall' is, how about the one advanced by my old flight instructor - "it's when your wing stops holding you up"

John—Preceding unsigned comment added by 84.205.101.169 (talk) 21:17, 20 March 2006

Back to the original subject - washout. I recommend moving it to the entry for "Wing". Because it does not just apply just to aerodynamic stall issues but also to aerodynamic efficiency, I believe it fits better there than under "Stall". Then it can be linked to "Stall" and vice versa. And it really shouldn't be sharing a page with railway info and an entry about Jamaican purgative practices, eh? Hatcat 17:11, 22 March 2006 (UTC)

Washout is introduced into the design of a wing in order to ensure that the tip stalls at a later point than the rest of the wing - if it does not, then when the tip stalls it is likely to drop the wing and induce a spin. Washout has a counterpart (wash-in) where the local incidence is increased above that of the rest of the wing on order to ensure that that part of the wing stalls first. The same effect as wash-in may be achieved by the use of strakes, usually at the inboard leading edge of the wing, such as on the DHC Chipmunk, which are there to ensure that the wing root stalls before the tips. The Chipmunk and the earlier military Tiger Moth also have horizontal anti-spinning strakes positioned at the tail designed to ensure that any spins are not flat ones, and they work by ensuring that the tail has more drag/lift than it would without the strakes, hence helping the aeroplane remain nose-down during a spin. — Preceding unsigned comment added by 80.4.57.101 (talk) 21:53, 2 February 2012 (UTC)

Birds

I have a bird book at home, which details how aq bird can stall in flight.

Is this notable?

Because I notice this article only discusses powered flight.

Simple Description

Stall

Is when the wings of an aircraft are no longer capable of deriving enough support from the air in order for the aircraft to maintain altitude. Although a stall usually occurs at slow speeds with excessive nose up attitudes it can actually happen over a wide range of speeds and attitudes.

There simple and to the point. Everyone agree with my definition? (contributed by User:43R35)

I like this simple definition. The subject can be as complex as you like. But, considering the number of words used, that would be the best paragraph of the whole article (many of which are seriously in need of improvement). I suggest you insert it as the introduction. EDIT BOLDLY! Paul Beardsell 09:39, 2 September 2006 (UTC)

Sorry, no. Every aircraft descending from cruise altitude to landing is "no longer capable of deriving enough support from the air in order for the aircraft to maintain altitude", but it is not stalling. It is simply that the lift being generated by the aircraft is less than it's weight. --dSpammer 22:05, 13 August2006 (BST)

Not correct. If lift is less than weight then there is an imbalance of forces and acceleration in the direction of the imbalance occurs. Not movement but acceleration. It's Newton 2. E.g. That an aircraft moves forward at a steady speed does not mean thrust exceeds drag. (Should one not understand that then one is not qualified to comment.) Similarly: If an aircraft is descending at a steady rate (say 500 ft / minute) this does not mean the (vertical component of) lift is less than weight. Should dSpammer pull back on the controls he will find that his previously descending aircraft was indeed creating enough lift to maintain altitude. Of course, the aircraft will, after levelling off, start to slow down and will eventually stall if thrust is not applied. Descending is simply another way of maintaining airspeed - it's a substitute for missing thrust. So dSpammers criticism of the suggested para is not valid. Paul Beardsell 09:56, 2 September 2006 (UTC)

I have just noticed Paul Beardsell's comment above. It is 4 years and 4 months late, but better late than never. Besides, I wasn't a registered User in 2006. Paul wrote If lift is less than weight then there is an imbalance of forces ... This is not correct. It is correct to say If aerodynamic force is less than weight then there is an imbalance of forces.

Lift and drag are man-made and arbitrary components of aerodynamic force. It is convenient to isolate the component of aerodynamic force that is perpendicular to the flight path and call it lift, and the component that is parallel to the flight path and call it drag. In unaccelerated flight, the aerodynamic force is always equal to the weight; and the only situation in which the lift on the aircraft is equal to its weight is in straight and level flight. When the aircraft is climbing or descending the lift is less than the weight, and it is the drag and thrust which complete the vector triangle. In Flight Dynamics 10 students draw the triangle of forces on a glider in steady descending flight to show how the three forces - weight, lift and drag complete a right triangle in which weight is the hypotenuse and both lift and drag are less than the weight.

I also disagree with dSpammer's comment that an aircraft descending to land is no longer capable of deriving enough support. By virtue of the aircraft's speed it is capable of deriving enough support, but the pilot chooses not to derive lift equal to the weight so that the aircraft descends. He can't land otherwise. Dolphin (t) 10:03, 19 January 2011 (UTC)

However, there are many paras in the article which are in need of severe editing. Paul Beardsell 09:39, 2 September 2006 (UTC)

Proposed merger: Stall speed

A proposed merger of Stall speed into this article has been sitting around for over a year. It makes sense to me, and shouldn't be too hard to accomplish. Any problems? PubliusFL 19:58, 10 January 2007 (UTC)

Stall fence

is stall strake the same thing as a stall fence? --Kvuo 02:10, 17 June 2007 (UTC)

Deleted short paragraph Jan08

Have just deleted a short paragraph. Jan 28 2008. Don't think it will upset anyone, but will provide a brief justification here in case: Paragraph seemed to be written by someone thinking of a particular class of aeroplane. Not reasonable to say that non-pilots will be worried (with the implication that pilots will not be worried) for all aircraft. For some aircraft pilots will be worried too. Anyway even pilots will be worried if it's accidental. And the point about height is made elsewhere in the article. Assuming nobody objects for a few weeks (say by the end of Feb 08) then please feel free (anyone) to delete what I've written here as it will cease to be of any interest. Rowmn (talk) 23:22, 28 January 2008 (UTC)

WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 10:03, 10 November 2007 (UTC)

Engine stall section seems misleading

The "misconception" of engine stalls being related to areodynamic stalls is not actually a misconception at all (for jet engines). An engine stall happens when the engine compressor blades stall out, the same sort of aerodynamic stall as described for the wing. That tends to cause reverse flow (known as surge), resulting (often) in an impressive fireball shooting out the front of the engine.

It's also possible for a compressor stage to have a "partial" stall. In that case one stalled blade makes the next one stall. The that one makes the next one stall. Etc. But the first stalled blade recovers. That recovery makes the next one recover. Etc. So a "stall cell" rotates around the stage.

Thus, claiming that engine stall is an unrelated misnomer is wrong (for jet engines, anyway). It's actually a very closely related phenomenon. (What people call an engine stall in a piston engine is a different matter.)

Furthermore, the entire section was unattributed, and there was no evidence given that this is a "popular" misconception. In my personal experience, almost everyone understands that planes can glide and that losing lift on the wings is not related to a car engine dying if you forget to declutch at a stoplight.

—Preceding unsigned comment added by 130.76.32.181 (talk) 22:44, 19 January 2009 (UTC)

Rather than deleting the section mabye we can rewrite it. I agree with the section that the public does not understand the difference between an aerodynamyc stall and an engine stall and that is really what the section is trying to express. 20:41, 20 January 2009 (UTC) —Preceding unsigned comment added by RP459 (talk • contribs)

I really don't think it is popular. And it's even arguable that it's a misconception. The entire section rests on the fact that "stall" has more than one definition. This is an entire section which could be resolved down to one disambiguation reference.

Perhaps later I'll write a section on gas turbine engine stall. I can reference it; I'm an aero engineer and I have the appropriate textbooks right in front of me. That will solve some of the problem with this section.

But I still don't see any reasonable purpose for it at all. However, I'll hold off on re-deleting it, since I don't want to start a reversion battle. —Preceding unsigned comment added by 130.76.32.145 (talk) 20:51, 20 January 2009 (UTC)

There is a whole article on compressor stall. On the other hand, it is only mentioned here in the See also. Should it be mentioned earlier in the article, especially if, as above, the physics is the same? Gah4 (talk) 00:12, 2 August 2019 (UTC)

Angle of attack indicator

In the Graph section, it is stated 'very few aircraft have an angle of attack indicator.' But further down the page, in the Stall warning and safety devices it says 'Many aircraft have an angle of attack indicator '. Which one is right? Abercrombiefiz (talk) 07:02, 12 February 2009 (UTC)

I have changed the latter comment to say Most military combat aircraft have an angle of attack indicator ... ... Dolphin51 (talk) 11:39, 12 February 2009 (UTC)

Cl graph not correct

The graph showing Cl vs AOA is incorrect. At the critical angle Cl drops only a small way and then flat plate lift takes over so that Cl actually rises again. The Cl does not drop to zero except at 90 degrees. This is a *really* common error splattered all over the internet and books on lift. This subject was researched at Sandia but I can't find a publishable graph showing the correct result. I could graph one up from their data but maybe one of you eds. know of an open source?? Here is a good discussion on the real behaviour:

http://www.aerospaceweb.org/question/airfoils/q0150b.shtml

What to do? Cheers MarkC (talk) 03:39, 23 April 2009 (UTC)

The offending graph was created by User:Interiot. This user has been inactive since December 2007 so it is unlikely he (or she) will amend the graph in the short term. I have removed the offending graph and replaced it with one that is similar but does not incorrectly show lift coefficient falling sharply towards zero. Dolphin51 (talk) 01:32, 24 April 2009 (UTC)

Thanks, that's an improvement to be sure. But (you are going to hate me for this) it is not correct to say that an aircraft cannot operate beyond the stall angle. High performance planes can and they replace the missing lift with thrust. Would you like to revise the caption and text?

Thanks MarkC 06:34, 24 April 2009 (UTC) —Preceding unsigned comment added by Mbcannell (talk • contribs)

Actaully how about a new section talking about post stall flight, the X-31 was an impressive display with flight at 70 degrees AOA. We could probably grab a NASA picture of it? With high thrust and vectoring post stall manouvers provide a tactical advantage. Cheers MarkCMarkC 06:48, 24 April 2009 (UTC) —Preceding unsigned comment added by Mbcannell (talk • contribs)

I agree it was potentially misleading for the caption to state "An aircraft cannot ...". I agree that rocket-powered airplanes and high thrust-to-weight ratio airplanes can operate at angles of attack greater than their stall angles but this represents the rare exception. In general, fixed-wing airplanes cannot operate steadily at angles of attack greater than the stall angle. That is why aircraft stall with sufficient sharpness that it is possible to identify the moment at which they stall, and to measure the airspeed at which the stall occurs.

I have changed the caption so it says "Aircraft cannot operate steadily ...".

If the X-31 has been demonstrated to operate steadily at an angle of attack greater than the stall angle feel free to insert this information, with a suitable citation, into the article on the X-31. It would be inappropriate to insert it into Stall (flight) because it represents the exception rather than the rule. Dolphin51 (talk) 11:13, 24 April 2009 (UTC)

Aeroplanes can fly well beyound the stall. I fly models; they fly the same way as full-size aeroplanes but you can do things too risky for manned aeroplanes. The flight pattern for this kind of post-stall flight is nicknamed 3-D, and includes frequent transitions between unstalled and prop-hanging fflight. For a demo watch:

http://www.youtube.com/watch?v=TEnC68qb5I0

Full-size aerobatic aeroplanes are also frequently flying beyond the stall in part of their manoevres. —Preceding unsigned comment added by 78.147.130.92 (talk) 11:56, 15 January 2010 (UTC)

Tail stall

Hi all, how about adding a section on tail stalls? They have been implicated in some recent crahes... Cheers MC MarkC (talk) 14:53, 5 June 2009 (UTC)

Turning flight stall

$W=L\times cos(bank\ angle)$ —Preceding unsigned comment added by 200.255.9.38 (talk) 11:42, 18 January 2011 (UTC)

History

Needs a "history" subsection. I remember reading someplace that Orville accidentally "discovered" this on a flight at Fort Myers where a passenger was killed, and Orville badly injured for life. It seems odd now, but they were bent on "flying" and hadn't quite got around to analyzing the practical aspects of "not-quite-flying." Student7 (talk) 14:50, 1 October 2011 (UTC)

Another editor researched this. See Talk:Fort Myer. Student7 (talk) 13:26, 22 October 2011 (UTC)

Tip Stall

I apologize in advance if this is the wrong place to submit suggestions - but I am absolutely LOST in this Wiki hierarchy! :)

I would like to submit a suggestion that the subject of "Tip Stall" (aka 'Wing Tip Stall') be incorporated into the section/page titled 'Stall (flight)'.

A quick Wiki Search will advise such page doesn't exist, however it will also show the term is mentioned prolifically in many other places. I can assure you it is a topic of great interest (and concern) in model aviation circles, for one, and from both eyes-on experience and much reading there is obviously a LOT of confusion as to what a tip stall actually is, ie confused with other aeronautical actions eg accelerated stalls & turning stalls. It would be very nice to have a Wiki reference to cite to those lost souls who don't really know what they did wrong or what actually happened. I would readily volunteer to submit such info but lack the technical expertise for Wiki submissions & especially for the proper way to integrate it into the existing Stalls (flight) page.

Respectfully submitted, and thank you for listening. ~Jay F — Preceding unsigned comment added by 184.3.66.204 (talk) 11:37, 24 August 2012‎

This is the perfect place to submit suggestions aimed at improving the coverage of this subject. Thanks for drawing it to our attention.

I agree that Wikipedia should have coverage of the phenomenon known as tip stall. It doesn't warrant its own article but it can be covered in one or more of the existing articles. The only existing articles that touch on the subject are this one, Spin (aircraft) and Autorotation (fixed-wing aircraft).

Everything written in Wikipedia articles should be attributed to a reliable, published source. The most common reason that Users haven't yet written material on a particular subject is that they don't have suitable reliable, published sources to which to attribute what they know to be correct. Do you have a good source for material on tip stall?

Don't forget to sign with the four tildes (ie four wriggly lines. On my keyboard, the tilde is the key in the top left corner.) Dolphin (t) 12:18, 24 August 2012 (UTC)

Stall with a paraglider

A picture of a stall with a paraglider, maybe something for this article.--Luxo (talk) 22:11, 24 January 2013 (UTC)

High-altitude stall

This article appears to need a section related to high-altitude stalls. See comments about this term at Talk:Air France Flight 447#RfC - What "Summary" should the Accident have?. The term occurs as early as 1988; see page 440 in Human factors in aviation, p. PA440, at Google Books.

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Thanks, SBaker43 (talk) 11:23, 24 May 2013 (UTC)

The relevant paragraph on page 440 of Human factors in aviation states:

3. While climbing to altitude, the crew of a DC-10 flying from Paris to Miami programmed the flight guidance system to climb at a constant vertical speed. As altitude increased, the autopilot dutifully attempted to comply by constantly increasing the pitch angle, resulting in a high-altitude stall, loss of over 10,000 feet of altitude before recovery, and damage to the empennage that was not discovered until after the plane crossed the Atlantic and landed in Miami (NTSB, 1980).

In this paragraph, the words "high-altitude" are redundant. The paragraph would be just as meaningful if it said "... increasing the pitch angle, resulting in a stall". I believe the author has used the words "high-altitude" simply to alert the reader that the stall didn't occur near the ground. As the aircraft lost over 10,000 feet of altitude before recovery, clearly the stall occurred somewhere above 10,000 feet.

The stall of an airfoil is determined by the lift coefficient, Mach number and Reynolds number. Whenever the lift coefficient reaches its limiting value for the prevailing Mach number and Reynolds number, the lift coefficient will no longer increase even though the angle of attack may continue to increase. The occurrence of a stall is not influenced by the altitude at which the airfoil is operating. Unfortunately, the expression "high-altitude stall" implies that a stall at high altitude is somehow different to a stall at low-altitude. It isn't.

Clearly, Human factors in aviation is not a reliable source on matters related to aerodynamics. It is likely that specialists in human factors consider a high-altitude stall to be significantly different to a low-altitude stall on the grounds that pilots don't expect to stall at high-altitude and may become complacent about the risk of stalling during the cruise phase of flight. Page 440 and adjacent pages are addressing problems related to pilots placing blind trust in instruments, autopilots, navigation equipment and other systems. These pages are not focusing on the aerodynamics of airplanes.

I suggest "high-altitude stall" is not a recognized phenomenon and should not be given its own section in Stall (flight). The article should clarify that occurrence of the stall is determined by lift coefficient, Mach number and Reynolds number; and therefore other related parameters such as aircraft weight, load factor, angle of attack, angle of bank, equivalent airspeed etc. It should not imply that occurrence of the stall is influenced by altitude. Dolphin (t) 00:19, 26 May 2013 (UTC)

I agree, a stall at high altitude is no different from one down low, except you have more time for recovery. It is not a different aerodynamic phenomena. - Ahunt (talk) 11:22, 26 May 2013 (UTC)

" ... The occurrence of a stall is not influenced by the altitude at which the airfoil is operating... " - unfortunately it is. The air thins as altitude is gained which effectively means there are fewer air molecules going over the wing. Hence the stalling TAS increases as the aircraft climbs until at the aircraft's absolute ceiling any attempt to increase height even further without adding additional power (so increasing airspeed) will result in a stall. Thus any aircraft trimmed in to a climb, or on autopilot set to climb, on a constant power setting will eventually stall upon reaching the limiting altitude for that power setting. — Preceding unsigned comment added by 95.149.55.99 (talk) 20:32, 20 May 2019 (UTC)

Stalling speed (at a nominated weight) is an important characteristic of any fixed-wing aircraft. It is regularly mentioned in conversation and in writing about an aircraft’s performance and handling. It is always the indicated airspeed at which the stall occurs. It is never the true airspeed.

The stall occurs at a particular angle of attack, and therefore at a particular lift coefficient, and indicated airspeed (at a nominated weight). The fact that this fixed indicated airspeed translates to a true airspeed that varies with air density is insignificant and is rarely, if ever, mentioned in reliable sources on the subject of the aerodynamic stall. (It is, of course, mentioned in writings about the influence of air density on an airspeed indicator, and the difference between true airspeed and indicated airspeed.)

95.149.55.99 has written "any aircraft trimmed to .. climb .. constant power setting will eventually stall .." That is not true. If the pilot trims the aircraft to climb at, say 100 knots IAS, then when the aircraft reaches its ceiling it will continue to fly level at 100 knots IAS. Similarly, "or .. autopilot set to climb .. on a constant power setting will eventually stall .." That is misleading. Yes, some aircraft have stalled when the autopilot was set to CLIMB; but that was because, as the aircraft climbed and the excess thrust from the engines decreased, the autopilot progressively reduced the indicated airspeed in an attempt to maintain the target rate of climb. Dolphin (t) 02:11, 21 May 2019 (UTC)

See: West Caribbean Airways Flight 708. — Preceding unsigned comment added by 95.144.50.133 (talk)

Thanks for that link. I have looked at it quickly, and I will look at it more thoroughly in the near future. The article omits some obvious information so it leaves me puzzled. In an accident report of this kind I expect to see comment about the functioning or otherwise of the stall warning system. Also the article describes the pre-crash scenario as a deep stall. Modern aircraft including the MD-80 series cannot be type-certificated if there is any hint they might be vulnerable to deep stall. That is why many aircraft are equipped with a stick pusher system. I think the article could do with some polishing to eliminate the obvious shortcomings. Dolphin (t) 22:50, 1 August 2019 (UTC)

Today I made three edits to West Caribbean Airways Flight 708. I hope these edits improve the article from the aeronautical and accident investigation perspectives. Dolphin (t) 09:24, 21 August 2019 (UTC)

Duplication of images

In the lead to Stall (flight) there is presently a diagram depicting deep stall. It is the same diagram as the one that is used later in the article to support the sub-heading Stall (flight)#Deep stall. Duplication of an image is discouraged in any article unless there is a really good reason. Deep stall is a rare form of the stall phenomenon so a diagram that targets deep stall is not a good one in the lead to this article. If there is to be an image accompanying the lead I think it should be an image appropriate to the general form of aerodynamic stall that occurs at high angle of attack in most aircraft. I am in favor of deleting the deep stall diagram from the lead to this article. Dolphin (t) 10:19, 15 July 2013 (UTC)

I agree! Do we have a better lead image? - Ahunt (talk) 11:10, 15 July 2013 (UTC)

How about the image in the lead to Flow separation? Dolphin (t) 11:55, 15 July 2013 (UTC)

That one is okay. - Ahunt (talk) 13:01, 15 July 2013 (UTC)

Done. See the diff. Dolphin (t) 08:20, 16 July 2013 (UTC)

Analytical prediction of stall onset

Wondered if we wanted to add this to the page: http://dx.doi.org/10.1017/jfm.2013.440

From the abstract: Computed results show agreement with marginal separation theory at low and with available experimental data at higher. This simplified approach provides a universal criterion to determine the stall angle of stationary thin aerofoils with a parabolic nose.

Research has been published in Journal of Fluids Engineering and Journal of Fluid Mechanics. — Preceding unsigned comment added by 75.81.139.106 (talk) 03:36, 15 October 2013 (UTC)

Nose down control, or lower the nose?

I modified the article to clarify the difference between the aircraft 'nosing down' by itself, and the pilot 'nosing down'. I was careful to avoid implying that once the nose has dropped, the pilot must lower the nose further in order to recover from the stall. [this] further edit was intended to simplify, but the article now appears to imply just that.

Some texts are not very clear about this but I have just checked Langeweische, Stick and Rudder, p.33. It says that when the nose drops in the stall, the aircraft is already attempting to recover by itself. If the pilot removes his back pressure which created the stall, it will recover. Also, [FAA Advisory 120-109] p. 14, requires a, "nose down pitch control".

In my stalling training, I had to learn not to lower the nose too much and lose more altitude than necessary in the recovery. I understand that a nose-down control movement is what's required at this point, not necessarily forcing the nose to drop further.

I suggest a different wording is needed. Burninthruthesky (talk) 16:02, 24 July 2014 (UTC)

You make a good point - in most light aircraft the nose only needs to be lowered once, either by the pitch-down effect of the stall itself or by pilot input, but not really both. I have further simplified the wording, but see if that is an improvement or not! - Ahunt (talk) 16:53, 24 July 2014 (UTC)

I like your thinking. I think it's best for the article not to get bogged down in unnecessary detail. Thanks. Burninthruthesky (talk) 18:33, 24 July 2014 (UTC)

That was my approach, keep it simple! - Ahunt (talk) 18:42, 24 July 2014 (UTC)

Requested move 2 November 2018

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this section.

The result of the move request was: moved as unopposed. (closed by non-admin page mover) feminist (talk) 10:37, 17 November 2018 (UTC)

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Stall (fluid mechanics) → Stall (fluid dynamics) – Fluid mechanics comprises both fluid statics and fluid dynamics, but stalls have got nothing to do with the former, and indeed the article currently (and correctly) opens with "In fluid dynamics, a stall...". The current title therefore is unnecessarily generic and not consistent with the lead. Deeday-UK (talk) 20:52, 2 November 2018 (UTC) --Relisting. KCVelaga (talk) 03:20, 10 November 2018 (UTC)

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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 or in a move review. No further edits should be made to this section.

MCAS

Should MCAS be mentioned or discussed in this article? Gah4 (talk) 18:07, 19 March 2019 (UTC)

No, why would it? Tens of thousands of aircraft accidents have involved stalls. One or two new accidents are not notable to this topic. See WP:RECENTISM - Ahunt (talk) 18:19, 19 March 2019 (UTC)

No, not the accidents, but the system for preventing stalls. Yes, specifically, the accidents are not notable here. It does mention stick shaker, but not (I might have missed) how it detects them. Gah4 (talk) 20:31, 19 March 2019 (UTC)

OK, it does mention stick pusher, and I suppose MCAS should be a subset of stick pusher. It is is exactly stick pusher, then it wouldn't be new, and likely not a fancy new name. Should MCAS (again, without mention of accidents) go into stick pusher? Gah4 (talk) 20:36, 19 March 2019 (UTC)

The MCAS is more than a mechanical stick shaker or stick pusher. It is adequately covered here right now. That links here, which is appropriate. I can add a "see also" to stick pusher. - Ahunt (talk) 22:06, 19 March 2019 (UTC)

Proposed merger: Post stall

@John Vandenberg, Ahunt, Ariadacapo, Pieter1963, and Agateller:

I propose that the article Post stall be merged with this article (and Post stall be converted to a redirect.)

Post stall has been in existence for a dozen years but it contains little information. The information it contains is technically incorrect because it states that post stall behaviour is a function of airspeed whereas, in fact, post stall behaviour is a function of angle of attack. If anything can be salvaged from Post stall it can be inserted into this article. Dolphin (t) 13:11, 23 September 2019 (UTC)

I agree, it should be merged in here, redirected and the merged text fixed so the text is about angle of attack and not airspeed. Plus I would question why it is included in the navbox on aerial warfare! Nothing in that stub relates to its possible uses in air combat. - Ahunt (talk) 13:38, 23 September 2019 (UTC)

I agree too! -- Ariadacapo (talk) 07:13, 24 September 2019 (UTC)

I have begun merging "Post stall" with this article - see my diff. I have also removed "Post stall" from the Aerial warfare navbox. Dolphin (t) 13:11, 2 October 2019 (UTC)

Greek translation: απώλεια άντωσης f

• απάντωση, from απο- and άντωση

• https://el.wiktionary.org/wiki/απο- (here it means removal) — Preceding unsigned comment added by 2a02:2149:8844:a300:40d2:8f7f:20bf:767 (talk • contribs)

Can you explain your point with regard to this article? - Ahunt (talk) 15:09, 6 September 2021 (UTC)

Deep stalls and canard-configured aircraft

I'm no expert, just someone who wants to learn. There is no explanation of how a canard-winged aircraft can get into a deep stall, which is defined by the article as turbulent airflow from a stalled wing at such a high angle of attack that it interferes with the tail control surface effectiveness and possibly rear-mounted turbine engines. The article notes that two Velocity (canard-configured) aircraft crashed due to deep stalls, but there is nothing in the area that would be affected by the turbulent air from a stalled wing in such aircraft, no control surfaces, stabilizers, or engine inlets. The [Aviation Safety Network] article on the Piper Advanced Technologies crash says it was likely a flat spin, not a deep stall. Yes, I would like to know how this works, but more importantly, I think the article needs to explain how this works. Thanks! Dcs002 (talk) 01:15, 8 August 2023 (UTC)

Note: The next subsection on tip stalls describes the tendency of swept wings to stall at the tips first, giving a nose-up attitude at stall onset, leading to a super-stall, which is given in the previous subsection as a synonym for a deep stall, though this doesn't fit the definition given in that subsection at all. As the canard-configured aircraft were swept-wing, were they actually unrecoverable tip stalls? Does the definition of deep stalls need to be expanded to include these nose-up tip stalls? If so, shouldn't tip stalls be included under deep stalls? Or does a tip stall become a deep stall only after its nose-up attitude is unrecoverable (which again would require redefining a deep stall)? Dcs002 (talk) 02:05, 8 August 2023 (UTC)