Talk:Spin (flight)

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[edit] Misc Discussion

I am about half way through my PPL (Exercise 18) and was aware of spinning, but no where near as much as I was going to be after my first lesson on Saturday 10 January 2004.

I am learning at Chester Flying School, but they do not have planes you can spin in. For this I went to Barton Aerodrome and the Lancashire Flying School - for a lesson with Bob Knight. He chose the plane carefully, a Grob G115.

I had tried to prepare myself for what was to come (remember your build up to the first stall and the subsequent "what was all that about"?), but was blown away by the sensations when we entered the first spin. I knew he had used full left rudder, but would not have wanted to bet more than a fiver as to what direction we were actually spinning - irrespective of the odds. I am sure he was worried I was going to throw up in his nice plane, but it was my head that struggled to cope, not my stomach. My first reaction was what on earth am I doing here on a Saturday afternoon spending good money on something the CAA don't consider necessary. My follow up, more considered thought, was that I would have no chance of coping with this without hands on experience and instruction. I honestly believe they should either rip out exercise 11 from the books or include it properly, with training.

We did three more spins, with me in full control of the third. For the fourth, I used too little rudder and put it into a spiral dive from which Bob (who was not impressed) recovered.

I came away with a combination of a renewed respect for this pass time I have taken up and a determination that I want to "master" spinning, so have booked myself in for another lesson this Friday, 16 January.

David Savage david@pacificchartered.com

Re: Edits by bannaramabingbong. As discussed on his talk page, I'm not sure that some of the changes made are an improvement. For example calling a spin an 'aggravated uncoordinated' stall rather than a 'special case' of stall, to my mind adds no worthwhile information to the article, in fact, it makes it more impenetrable by the layman. This is not a flight manual. We need to be factually correct but without bringing in technical jargon that obscures the readability. There are other similar changes I have a slight problem with. In addition, some of the corrections for "grammer" [sic] introduce numerous spelling and grammar errors of their own. We need to discuss the specific issues that people may have with the article and reach a consensus, not enter into an edit war, which is counterproductive. Graham 23:48, 11 Oct 2004 (UTC)

I've overhauled the spelling (possibly just typos) and a little grammar/style. I've added a link to sailplane. My only query is the type of English – U.K. or U.S. – intended by the original author. The Wikipedia rule is to stick to the original intent, but there's a bit of a mixture here. I started changing it (for example &slquo;practise&srquo; rather than &slquo;practise&@srquo; as a verb), but then noticed lots of &slquo;center&srquo;s, etc., so thought that I'd better stop. Any advice? Mel Etitis (Μελ Ετητης) 15:27, 4 Feb 2005 (UTC)

Be bold, make a decission and stick to it. Aberglas 01:25, 6 Feb 2005 (UTC) aberglas

As I created the article initially, I can tell you I use British English. But there have been many, many edits since. Graham 05:02, 29 January 2006 (UTC)

I see that User:Aberglas has removed one of my additions; I suspected that I might have misunderstood the point being made — the problem is that, as it stands, that passage reads rather obscurely. Could we discuss it so that it can be made clear? Mel Etitis (Μελ Ετητης) 10:24, 5 Feb 2005 (UTC)

If you are talking about spin-resistent airplanes then there are some aircraft that simply will not spin (with normal CoG). Eg. ASK 21 glider. So it is more than holding control positions. But in any case this is covered a few paragraphs down, so there is no need to repeat it where it was. Aberglas 01:21, 6 Feb 2005 (UTC)aberglas

Sorry, my fault — I didn't say which edit I was talking about. It's in the fifth paragraph of the first section: “This is largely achieved by ...”. As it stands it's unclear what the ‘this’ starting the second sentence refers to, and I wanted to make it clearer. The term ‘manoeuver’ was apparently wrong, but can you think of some other way to do what I was trying to do? Mel Etitis (Μελ Ετητης) 10:29, 6 Feb 2005 (UTC)

[[User:Aberglas|Aberglas], that's perfect — exactly what I had in mind but couldn't work out how to do. Mel Etitis (Μελ Ετητης) 10:14, 7 Feb 2005 (UTC)

I'm curious about the reference to spinning through cloud - personal experience?  :-) Brendano 22:33, 31 Mar 2005 (UTC)

Just reading the first few sentences, I find a conflict in the definition of a spin already. The way I've learned about spins, is that they are NOT stable to an airplane, and with controls neutral, an airplane should recover from it eventually on its own. The only dangerous situation where an airplane will NOT recover on its own, is a spiral, where there is no stall, but the plane is essentially in a steep decending turn, with speed increasing rapidly. To keep an airplane in a spin, the pilot needs to hold the rudder all the way left/right, and the elevator up all the way. Am I wrong?

Ted Vailas --Tvailas 20:25, 15 July 2006 (UTC)

  • I believe what you're describing is the Beggs-Mueller spin recovery technique, which I don't see anywhere on Wikipedia...I may have to incorporate it into the article sometime soon. Essentially, you let go of the controls, and the plane does in fact recover itself from the spin. However, as I understand it, all airplanes have different spin characteristics, so some can easily recover from spins, while others simply don't have the control authority. Or, a given plane technically can recover, but the altitude that it takes to effect the recovery is more than you'd ever have flying the plane, etc. It just depends on the plane and the situation. Yvh11a 06:47, 17 July 2006 (UTC)


[edit] Aerodynamics of a Spin

Is it always true that both wings will be stalled? I was always taught that both wings are stalled, one wing stalled more than the other. I had a designated examiner insist that an airplane can spin with one wing stalled and one wing flying. Wouldn't this result in a roll/spiral. (Imagine one wing being completely torn off.) Comments?

I don't think it's very useful to talk about degrees of stalling - once stalled, the wing is stalled. You can't really say one wing is "more stalled than the other", neither are producing any usable lift. This reflects the lift curve for an aerofoil which basically drops off almost vertically beyond the stall angle. I suppose you could say that one is more beyond the stall AoA than the other, but it makes no difference to the lift produced - there is none. I'm not sure about the case of one wing stalled and the other not. I guess there is a very small range of AoA and yawing that might produce this condition, but as soon as the stalled wing drops, the aircraft will enter a very different flight envelope from what it was in just prior, which could be a spin or a spiral dive... depends on the exact conditions and the aircraft's characteristics I suppose. Graham 04:59, 29 January 2006 (UTC)

It seems that people are confused on the topic of a spin. It is true that in a spin one wing is more stalled than the other hence increased drag and autorotation. For reference, refer to AC 61-67C. You can find it at: http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/A2FDF912342E575786256CA20061E343?OpenDocument

That's a very useful reference, the article should probably link it. However, you appear to be wrong that it discusses "one wing stalled more than the other" - I couldn't find any passage that could be interpreted as meaning this, though admittedly I did speed-read it rather than go through it meticulously. When I get more time I'll read it thoroughly. However, just from physical principles the description "one stalled more than the other" doesn't really mean anything in my view. At the onset of the spin there is an asymmetric stall condition for sure, but by the time it is fully developed both wings are thoroughly stalled. The spin autorotation is sustained by the airflow over the machine in this stalled state as a whole - much as a sycamore seed will spin down to earth when it falls. If you think of the lift curve of an aircraft as a right-angled triangle shape with the hypotenuse the linear lift and the steep drop as beyond the stall, and the drag curve as a square law with an almost vertical slope coinciding with the stall, beyond the stall point the L/D ratio is going to be very close to zero for a wide range of AoA. It doesn't matter whether the L/D ratio is 0.01 or 0.001 (which might conceivably be the case for one wing and the other in a spin), it's not going to a) hold up the plane and b) create enough difference to sustain the spin. This is not a 10:1 difference, it's about a 0.0009% difference, since such a tiny difference in lift is overwhelmed by other forces, like gravity and drag. The falling aircraft is not a naked pair of (stalled) wings, it is the whole thing, and the rotation is caused by airflow around all of it, not just the wings. Graham 05:02, 21 February 2006 (UTC)

I take a bit of issue with the use of "one wing more stalled than the other" This, in my humble opinion, is a bit of bad descriptive language. It seems to be a bad choice of words for the following reason:

A stall is achieved once the critical angle of attack is exceeded. Sounds good. That makes it a finite point in "time". You are not stalled, not stalled, not stalled...stalled. Once the wings are stalled, they are either stalled or not stalled. A clear distinction as they are either less than or exceeding the critical angle of attack. Just like something is either wet or dry. It is either wet or dry. "Moist" is just a degree of "wet". I think a much better way to describe this overall concept is that yes, both wings must be stalled in order to enter a spin; however, in a spin the wings are stalled (and not producing enough lift) but they are producing substandard lift in different amounts. One stalled wing is producing more lift than the other stalled wing causing autorotation.Mkreilein (talk) 03:11, 12 April 2008 (UTC)

[edit] Spins Mandatory

Removed "Spins are huge fun, and should be mandatory for all pilots taking their ppl." for npov.

[edit] 'Inappropriate tone' template added

Today I've added this template to the Recovery section of the Spin (flight) article. The writing style used in this section -- and in a few other places in the article -- seems to this non-aviator to be a mixture of aviation lesson terms, and/or minor vandalism; or perhaps overly-exuberant flight jargon ("chipmunk erect normal"??)

Also, I've moved the third paragraph of the section Aircraft design to here. It also needs editing for style and meaning, see below.

A spin is the aircraft trying to (or very nearly) reach a normal state of equillibrium, if she reaches such a state, then it will take "effort" to get her out again, nothing to be scared of, but you need time, and time = altitude = another try again on another day., spins are fun, try them, they're a wonderfully normal aspect of aewrodynamics that have been wholly misprepresented and misunderstood.

Cheers, Madmagic 01:26, 9 March 2006 (UTC)

[edit] tomahawks are stil certified for spins!

in the article I noticed that it said the certification was removed from the piper tomahawk, preventing it from intentional spins. this is simply untrue, I own one and spin it regularly. I have never heard of the faa or piper removing the spin certification.

[edit] Cleanup

I've redone most of this article. It still needs some work; in particular, it needs to be wikified, and the last two sections (the salesman story and "Aircraft Design") are of dubious value. The sections may also need to be reordered. Above all, please take care to avoid colloquial style, and remember your audience. Wikipedia is not a flight training manual, and this is no place for hangar talk. -- Captaindan 04:19, 10 October 2006 (UTC)

[edit] Sample Video

I don't know anything about this phenomenon (I can't even drive!) but I stumbled across this video [1] whilst browsing the web for something entirely different. Maybe you guys can work it into the article somehow? -- Jasabella 11:39, 10 October 2006 (UTC)

[edit] diagram

I don't understand what this diagram is trying to show. The axes are not labelled, although presumably they are meant to be angle of attack (horizontal) and coefficient of lift or drag (vertical). Also, the "High Wing" and "Low Wing" labels are ambiguous. Do they refer to the pitch of the aircraft or to each wing separately? Coefficient is consistently misspelled.

I don't think that a spin is something that can be easily summarised in one diagram. The whole process from incipient to recovery is described by an angle of attack which is varying in time and along the length of the wings. If someone feels brave, this could perhaps be visualised with a similar animated diagram with an aircraft model superimposed showing how the angle of attack varies in time. The two wings could be depicted with separate colours.

Regardless, I'm going to re-jig this diagram in SVG... --BWDuncan 12:16, 9 November 2006 (UTC)

[edit] Howto

I added the Howto tag, in particular due to the detailed spin recovery procedure. Wikipedia is not a flight training manual. If someone wants to move this somewhere else, please do. Otherwise I will delete that section, unless someone makes a reasoned argument here. I put a generic technical explanation in the next section to cover this. Dhaluza 02:43, 5 January 2007 (UTC)

  • I agree that the list is too detailed for Wikipedia, but I belive some of the info is still relevant. I've condensed the list into readable paragraphs which I hope are just technical enough. I left the howto tag because I still have doubts about the last paragraph--you can't in my opinion have a page on spins without talking about how to get out of them, but no matter how you word it it still reads like a list. I leave the ultimate keep/remove decision up to Dhaluza and the community. Yvh11a (Talk • Contribs) 05:26, 9 January 2007 (UTC)

[edit] Certificated airplane or not

I prefer Shreditor's 3 August alteration where he removed Rstowell's emphasis on certificated airplanes in the opening paragraph. Unfortunately Rstowell reinstated his original comment.

Spinning is a phenomenon that is applicable to all fixed wing aircraft - not just certificated, civilian airplanes. The phenomenon of spinning is equally relevant to military airplanes. It is also relevant to non-certificated civilian airplanes such as experimental aircraft and airplanes that are being test flown with the objective of one day achieving type certification. Wikipedia is an encyclopedia, not a flight manual for civilian flying instructors.

Rstowell's comment about certificated airplanes that are placarded against intentional spinning is in the second sentence in an encyclopedic article about the phenomenon of spinning! There is validity in the comment, but it is not appropriately placed in the second sentence.

The opening paragraph must be about spinning in its most general form and should not be specific about any particular type or status of airplane. Shreditor has the right idea.

The article Spin (flight) contains information about the PARE acronym but I see that this is a registered trademark of Rstowell. I also see that Rstowell has inserted a claim that "90 percent of stall/spin accidents occur at or below traffic pattern altitude". The citation for that claim is a book written by Rstowell himself. A book you have written yourself cannot be nominated as independent evidence for one of your claims. (What evidence, if any, is nominated in the book?) Dolphin51 02:52, 3 August 2007 (UTC)

Yeah, and I don't know why there's a sudden interest in this article. It was beat up and neglected for months. Now I make a few improvements and everyone jumps in. In any case, the introduction needs to be a generic description, and we don't need any self-acclaimed experts chiming by citing their own books. Shreditor 03:08, 3 August 2007 (UTC)

Erroneous information being propagated by fanciers of knowledge about stall/spins was brought to my attention in recent months, so I chimed in to try to improve the quality of the information. I suppose what we really need are contributions by people who think they know something about a subject vs. people who actually know something about it. And I suppose by "self-acclaimed" you mean that when the FAA designates someone as National CFI of the Year in 2006 (in large part because of work done in the stall/spin area for the past 20 years), or when the International Aerobatic Club designates that person an "Official Spin Doctor" for the organization, or when aviation publications routinely solicit advice and recommendations from that individual on stall/spin matters, that that is somehow evidence of "self-acclaim" of expertise in a particular area and thus, we can and should simply discount what that person has to offer here?

As for the citation of one's own book as a source -- ok fine, have it your way. The source for the claim in question comes from a study undertaken by the FAA's Small Airplane Directorate in Kansas City, MO, which looked at 1,771 stall/spin accidents in certificated, single-engine airplanes during the period 1972-1997. I f my book is not a good enough source for the keepers of the gate, then see "Stall/Spin Accident," Proceedings from the NTSB General Aviation Accident Prevention Symposium, Washington, DC, September 21-22, 2000. BTW, this "self-acclaimed" expert was invited by NTSB to participate in a stall/spin panel discussion at this same symposium in DC. And your hands-on experience in this area is??? Rstowell

—Preceding unsigned comment added by Rstowell (talk • contribs) 02:11, 21 September 2007 (UTC)

[edit] Absence of references

Spin (flight) is conspicuously lacking in references. It appears to be written by editors who know what they are writing about (or think they know what they are writing about) but who haven't been sufficiently rigorous to post suitable references to support their additions. This is an encyclopedia. The threshold for inclusion in Wikipedia is verifiability, not truth. See Wikipedia:Verifiability.

This article needs to be cleaned up. New material should not be added unless it is supported by a reference.

I have flagged two of the worst sections - firstly Flat spins. I think this expression is colloquial. The section is not supported by any reference to support its verifiability. Also, the airplane salesman story. This is not encyclopedic so unless it can be made encyclopedic very quickly it must be deleted. Dolphin51 (talk) 01:13, 20 March 2008 (UTC)

  • I agree that the Airplane Salesman story needs to be deleted; the sooner the better. I'd like to save parts of the flat spin section if possible though. At the very least it's existence should be mentioned. Yvh11a (Talk • Contribs) 04:09, 20 March 2008 (UTC)
  • Isn't it a bit arrogant to say that you think the term "flat spin" is colloquial. The statement alone makes it obvious that you have never had any type of flight training or even spent a significant amount of time connected with the aviation industry. It's like someone who has never driven anything with more than four wheels barging in on a group of truck drivers and telling them that you think the term "jack knife" is colloquial. Flat spins are real and they're deadly. Just go to the NTSB Database Query and search "flat spin" and see how many people have died in them. Then come back and tell us that a flat spin is just a colloquial expression. Better yet, instead of saying "This isn't encyclopedic, delete it.", do a little research and add the references. I apologize for my tone but I get pretty ticked when people demand that useful information be deleted from Wikipedia because it's unreferenced, instead of being helpful, doing a few minutes of research and adding references. Rsduhamel (talk) 04:18, 4 June 2008 (UTC)

Hi Rsduhamel. Thanks for contributing to this discussion, and thanks for alerting me to the av8n web site. I was initially surprized when you wrote that NASA research had divided spins into two basic types, so I read the av8n web site very carefully. What I found was that NASA had divided spins into MODES (not types), and not two of them but four: steep, moderately steep, moderately flat and flat. Steep spins are those with angles of attack from 20 to 30 degrees; moderately steep spins are those from 30 to 45; moderately flat from 45 to 65; and steep from 65 to 90. These are not four (or two) different TYPES of spin; they are four (or two) different groupings of angle of attack varying continuously from 20 to 90 degrees angle of attack. NASA found that the characteristics of these four different modes vary widely across the spectrum of angle of attack, but those characteristics occupy a continuous spectrum. For example, the nose attitude in steep and moderately steep spins is described as “extreme nose-down” whereas for moderately flat and flat spins the nose attitude is described as “less nose-down”. There is nothing against nose attitude to indicate that there are two (or four) different TYPES of spin, but there is an indication that nose attitude can lie anywhere on a continuous spectrum, like most other parameters in aviation.

Much of what you have written about flat spins is equally true of steep spins, because the difference between the two is entirely arbitrary (based on alpha). For example, you have written “A flat spin can be deliberately initiated by the pilot and, if conducted in an aircraft approved for the maneuver, is quite recoverable.” I would say this statement is equally true of steep spins and therefore the statement should not be confined to “flat spins” – that is spins with alpha from 65 to 90 degrees. (Would you say a steep spin can not be deliberately initiated by the pilot? Would you say that if a steep spin is conducted in an aircraft approved for the maneuver it is not recoverable? Why is this statement made for flat spins, but not steep spins? What is your point?)

Similarly you have written “A flat spin can also occur if an aircraft's center of gravity is too far aft.” That statement is true of spins in general. It is misleading to qualify the statement by restricting it to “flat spins” – that is spins with alpha from 65 to 90 degrees. Even in an aircraft with a most benign spin (alpha in the twenties), if the center of gravity is too far aft an unrecoverable spin can occur. That is what “too far aft” means.

You have written “Recovery from a flat spin caused by the C.G being too far aft is usually not possible using the flight controls.” This seems to highlight the problem very well. In my experience when people talk about flat spins they usually mean unrecoverable spins. That is why I believe the notion that flat spins are a TYPE of spin is colloquial.

An unrecoverable spin should be called exactly that. Among airplanes that exhibit the steep and moderately steep modes (alpha from 20 to 45 degrees) spins can be deadly, especially when the center of gravity is aft of the aft limit for spinning. There should be no suggestion that it is only flat spins (alpha greater than 45 degrees) that will kill people.

I did as you suggested and interrogated the NTSB web site. When I searched for flat spin I found 6 fatalities. When I simply searched for spin I found 23 fatalities, including the 6 I found using flat spin! (This suggests to me that most of the accident investigators correctly reported using the word spin but a few of them mistakenly reported using the term flat spin – a term NASA only uses for spins with alpha greater than 65 degrees.)

On the matter of TYPES of spin, I think there are only two – erect and inverted. In any given aircraft type the recovery procedure from erect spins is a little different to that from the inverted variety and that is why they qualify as different TYPES. When I find a suitable book I will cite it as a source and make some edits.

Once again, thanks for contributing to this debate. Dolphin51 (talk) 09:27, 4 June 2008 (UTC)

  • Okay, you subscribe to a school of thought that says "a spin is a spin". Your arguments have merit and my first impression is to agree. If you can cite independent research that agrees with your point of view then, by all means, put it in the article. However, even if the overwhelming scientific consensus is that all spins are varying degrees of the same event, the term "flat spin" should not be removed from the article. "Flat spin" means something to many people. Many pilots use the term, NTSB investigators use the term, NASA has defined the term. The article should then explain why many people differentiate between steep spins and flat spins and why the differentiation is not scientifically useful. That will educate people rather that leaving them high and dry if they want to learn what a flat spin is. In fact, if you had said something to the effect of "There is debate as to whether the term 'flat spin' is scientifically useful. The term 'unrecoverable spin' is often preferred (or whatever you would say).", I would have had no problem. But, then, I wouldn't have been prompted to do some research and add to the article.
  • As far as NASAs definition being arbitrary is concerned, it certainly is. Nothing new about that in science. If a tropical cyclone has sustained winds speeds of at least 74 MPH (and it's in the Atlantic or eastern Pacific Oceans), it's officially a hurricane. If the winds are less, it's a tropical storm or tropical depression. There is no significant change in the storm's characteristics at 74 MPH. But it is universally accepted as the dividing line between a tropical storm and a hurricane. The NASA definition of a flat spin seems unlikely to coincide with the point where a spin becomes unrecoverable. That would need to be covered in the article. Rsduhamel (talk) 05:29, 6 June 2008 (UTC)

[edit] In soviet russia, spin makes yankees feel bad

The artile makes spin look like something inherently bad. However, stall (flat spin) can be used for advantage in air combat, for example the latest thrust-vectoring Sukhoi did some marvels at MAKS 2007. Staying in a flat spin fully under vectored control, the Sukhoi-35 can point its nose on the imperialist enemy plane continously and shoot it down. 91.83.24.235 (talk) 21:10, 10 June 2008 (UTC)