Talk:Spin (aerodynamics)

message: Here's how it was for me (a layman) reading this article: "What's a spin? Better look it up on Wikipedia." *Page loads* "Oh hey, there's a picture, that must be some type of spin. OK. Caption says it's called a Spiral Dive." *Starts reading article* "Aha! Here's the part about Spiral Dives! That's the type of spin I just saw in the picture! It says here 'A spiral dive is not a type of spin because neither wing is stalled.'. Oh. Whoops."
The point of this journey through my mind is to say "hey, I think the top image of the article on spins should probably not be the example of a thing that is not a spin."
-Brian Schroth
bschroth@gmail.com
----
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)
replies: text: 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)
thread_title:  Misc Discussion 

message: 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)
replies: text: 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)

text: 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)

text: Thanks Pete. You are most welcome to add your information to the article, providing you are able to cite your sources. Sources must be reliable and published - see WP:RELIABLESOURCES. On Wikipedia, any information that is likely to be challenged must be attributed to a reliable published source to allow independent verification - see WP:Verifiability. To read a little about how we cite references and sources see WP:REFBEGIN. Dolphin (t) 00:16, 12 July 2012 (UTC)
replies: text: A 1972 Flight article "Anatomy of Spinning" here:   — Preceding unsigned comment added by 80.7.147.13 (talk) 16:45, 6 February 2013 (UTC)
thread_title:  Aerodynamics of a Spin 

message: 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)
thread_title: 'Inappropriate tone' template added

message: 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)
replies: text: I agree your cleanup was a major one.  Unfortunately some of the material you removed was quality material supported by in-line citations, and I think some of the new material you added was not supported by in-line citations to allow independent verification.  I have reverted your cleanup, but that doesn't mean you can't suggest changes or additions to the article.  If you see some major areas that should be removed or altered please raise them here on the Discussion page so that other Users with an interest in this article can comment on your views. Dolphin (t) 06:02, 26 April 2011 (UTC)
replies: text: My first try at editing a wikipedia page; I had intended to check in my changes as a proposal rather than mess with the production copy; I see now that I can't do that and will make proposals here on the talk page rather than on the actual text.ChrisOwensBoston (talk) 17:44, 26 April 2011 (UTC)
thread_title: Cleanup

message: I don't know anything about this phenomenon (I can't even drive!) but I stumbled across this video  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)
thread_title: Sample Video

message: 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)
replies: text: I agree that the axes of graphs must always be labeled.  This diagram is commonly found in aerodynamics text books.  The horizontal (x) axis represents angle of attack, and the vertical (y) axis represents the value of the dimensionless coefficients - in this diagram both the coefficient of lift and the coefficient of drag. Dolphin51 (talk) 10:52, 27 September 2009 (UTC)
replies: text:  Since during five years nobody included this essential information in the article, I did it now. And always remember http://xkcd.com/833/! --Feldkurat Katz (talk) 17:57, 25 November 2014 (UTC)
thread_title:  diagram 

message: 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)
thread_title:  Howto 

message: 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)
replies: text: 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)
thread_title:  Certificated airplane or not 

message: 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)
thread_title:  Absence of references 

message: 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)
thread_title:  In soviet russia, spin makes yankees feel bad 

message: The comment about the thrust vectoring Sukhoi made me recall that in the last 20 years or so, thrust vectoring has brought gobs of controllability to post-stall (High AOA) flight.  I'd like to see a section discussing this important new marvel.  Some noteworthy vectoring airplanes come to mind for me:  F-18 HARV, X-31, F-22.  I see there is a very good thrust vectoring article.  The new section wouldn't need to describe all that detail, just show how it makes for High AOA / post-stall controllability.  
Gobs of thrust help too - as AOA increases beyond stall, lift lost by the wing can be replaced (though inefficiently) by thrust as the main thrust line noses upward.  Lots of thrust combined with vectoring could (I imagine) overshadow and obviate the fact that the lift curve is negative above stall AOA (and all the dynamic and spin implications caused by that).
-- Gummer85 (talk) 06:33, 20 March 2009 (UTC)
thread_title:  Control in post-stall regime - Improvements in last 20 years 

message: Is there a better picture of an aircraft in a spin? This picture looks more like a spiral dive (I don't have experience here, so please anyone jump in).  — Preceding unsigned comment added by 128.250.86.130 (talk) 07:13, 27 June 2011 (UTC)
thread_title: Regarding the main picture

message: The final paragraph starting "Today, spin training ..." is poorly composed, lacks citations, reflects irrelevant personal viewpoints, and alludes to the licensing and training practices of only one of many licensing authorities. A complete history of spin training ought to address the reasons for the removal of mandatory spin training from training programmes under some major licensing authorities.
* Sounds like you are in a position to improve it then. Ex nihil (talk) : Ex nihil (talk) 11:15, 6 August 2018 (UTC)
thread_title:  History 

message: The statement in Entry and Recovery "In an upright spin, both roll and yaw are in the same direction, but an inverted spin is composed of opposing roll and yaw." does not appear to be true. What is this statement actually trying to say? Roll and yaw are in the same direction whichever way up the plane is. Of course, the upside down elevator reverses the stick pitch sense but yaw and roll are identical inverted or upright and the rudder and aileron controls are also unchanged. I get the impression that this paragraph  was initially written by somebody who knew what they were talking about but it has since been embellished by folk who don't.  I am, (was) a pilot who has done spins although not inverted spins and cannot conceive that yaw and roll suddenly part company just because I'm upside down. Perhaps somebody could take a look at the whole section. Ex nihil (talk) : Ex nihil (talk) 08:07, 13 August 2018 (UTC)
replies: text: See: US Navy Flight manual - inverted spins. In an upright spin to the right, as the plane yaws to the right, the left wing starts moving faster than the right wing, generating more lift on that wing than the right wing. Thus, the left wing rises while the right wing drops. In an inverted spin, lift is inverted as well. As the plane yaws right, the faster-moving left wing drops and the right wing rises. It's extremely disorienting, as mentioned in the flight manual, because our sense of balance is more attuned to the roll than the yaw, it feels like you're spinning in the opposite direction than you actually are, thus recovery relies solely on instruments to determine the proper control inputs. Zaereth (talk) 17:35, 13 August 2018 (UTC)
thread_title:  Entry and Recovery 

message: Other than the history, this article seems to rely on NASA and the FAA. I haven't analysed it but that is my impression. Yes, there are some non-US citations, but can it be globalized more by using other sources? Humpster (talk) 12:11, 24 March 2024 (UTC)
thread_title:  Americentric ?