User talk:Dolphin51/Archive 1

Static margin
Dear Dolphin51: I like the improvements on center of pressure and static margin. I have one question; why are you distinguishing between neutral point and center of pressure. on the center of pressure page you introduce neutral point but it is not obvious to the non-technical reader what it has to do with the previous discussion on center of pressure. It seems to be an orphaned section. I am an educated reader on the subject and I seem to be missing some subtlety that you are tyring to make.02:22, 3 December 2007 (UTC) —Preceding unsigned comment added by Mangogirl2 (talk • contribs)

Dolphin51: Missile people use center of pressure as the stick fixed location (no elevator deflection) of the aero forces on the airframe for epsilon angle of attack. Thus, the center of pressure at zero angle of atttack is defined as a the location of the center of pressure for the resulting pressure field at finite but small angle of attack. The center of pressure cannot be located at an infinite distance since you take the limit. We speak of the center of pressure at very small angle of attack. You calucalte the center of pressue use tail volumes, etc. Saying the neutral point is the definition of static margin is a circular argument for the non-technical reader. It provides no physical explanation. It really has to do with the lift curve slopes and locations of the wing and tail. The aerodynamic prediction code aeroprediction produces a zero angle of attack center of pressure location. Since my explanation is not strictly correct why don't we delete the discussion of static margin and aerodynamic center related to stability. The aerodynamic center is orphaned also. Also we should get rid of the neutral point discussion. Mangogirl2 (talk) 23:05, 4 December 2007 (UTC)

Dolphin51:I have trouble following your changes to static margin. I feel that if the cg is ahead of the neutral point this should be call positive static margin. Maybe this is a country difference. Please look at the following link for some slides that I think agree with me.http://ocw.mit.edu/NR/rdonlyres/Aeronautics-and-Astronautics/16-885JFall-2004/6B524E1F-39F5-4E57-9B0E-812B40A21CED/0/aircraft_murman.pdfMangogirl2 (talk) 20:30, 12 December 2007 (UTC)

static pressure
Thanks for your kind invite to have a look at this article as it evolves - I should warn you that I'm not a formally trained aeronautics engineer or fluid dynamicist - just a half-trained planetary radio-astronomer :-). So when faced with questions that need clear thinking on fluids fundamentals, I usually reach for my copy of Batchelor! (I've had an article sketched out in my sandbox entitled 'classical theory of lift', which was also meant to be based on Batchelor's discussion, but which has made little progress in the last year).

I'll try and drop by the article over the next few days. Bob aka Linuxlad 15:51, 4 December 2007 (UTC)

Thank you for leaving notes on my user page, about your posts on Static pressure, but you don't need to, because that page is already in my watchlist, so that I get notified automatically. Regards. Giuliopp (talk) 23:55, 11 December 2007 (UTC)

Dolphin51: looks like you are on top of the issue. I will stay out of it. It does seem to be a cultural practice difference. I have worked with UK folks on the guidance issue to some degree and never notices the difference. In fact we cowrote documents together and I never noticed a problem. I know you know what you are talking about. I will have to rewrite my definition of center of pressure to make more sense to the layman. I just reading an internal document about air vehicle stability and they used center of pressure and static margin consistent with my original use but I believe it is a case of all of us knowing what we mean and the explanation is not strictly corrrect for the unintiated. I will have rewrite missile center of pressure to be more transparent.Mangogirl2 (talk) 15:31, 20 December 2007 (UTC) Here is a link that I believe matcher Mangogirl2's view of center of pressure of an entire vehicle. http://exploration.grc.nasa.gov/education/rocket/rktcp.htmlMangogirl2 (talk) 19:48, 21 December 2007 (UTC)

Your concerns regarding the Bernoulli's Principle article
Hello!

I understand your concerns regarding the section the tries to do away with BP as the main source behind lift. Explaining away one faulty explanation with one a little less faulty but still lacking explanation can certainly put a strain on one's sense of accuracy.

I have however argued - on talk:Bernoulli's principle - that we should keep the section mostly intact. For my reasons for feeling this way, please see that page and continue the discussion there. And thank you for the heads up. :) --J-Star (talk) 12:33, 31 December 2007 (UTC)

Static Margin
dolphin51 -- Just read Static Margin. It is really good now. Good job. This has been an enjoyable experience in that it sharpened my understanding of somtehing I had gotten somewhat blase about. Thanks for challenging me. I have been roving the aerospace topics over the last year. So maybe we meet. I hope you have a good year in 2008. Mangogirl2 (talk) 04:47, 8 January 2008 (UTC)

Static Pressure
Looks really good now. Gman is really belaboring a point that needs no belaboring. Words mean what we choose them to mean. Ever instance I have ever seen in fluid dynamics agrees with you. Gman repeated point about dynamic pressure not being a real pressure is unwarranted. For an isentropic reduction in speed the stagnation pressure is the "static" pressure plus the dynamic pressure (as we all know). Dynamic pressure is as real as any thing else. Way to go. —Preceding unsigned comment added by Mangogirl2 (talk • contribs) 01:53, 16 January 2008 (UTC)


 * Ask Dolphin51 about my "unwarranted" claim on dynamic pressure: the current revision of static pressure says that "[total and dynamic pressure] are not pressures in the usual sense - they cannot be measured using [a] mercury column", i.e. dynamic pressure is not defined in terms of force onto an area, which is what I said. [Note: Dolphin51 is right about dynamic pressure but wrong about total or - better - stagnation pressure, which is indeed defined as the force per unit area in the fluid, at a stagnation point and can be measured with any Pitot tube]. Let's close the circle, anyway: dynamic pressure is clearly correlated to "static" and stagnation pressure, sometimes very simply by Bernoulli's equation (when applicable), sometimes not so simply (compressible flows) but it is always a quantity well distinct from the other two and with a different physical meaning (not force, but density square velocity). Is that warranted enough?


 * As for the static pressure article, I'll come back to it at a later date. Yours Gman (talk) 01:06, 17 January 2008 (UTC)

Gman has written (17 Jan 08) Dolphin51 is … wrong about total or - better - stagnation pressure, which is indeed defined as the force per unit area in the fluid, at a stagnation point and can be measured with any Pitot tube. I agree that total pressure and stagnation pressure are identical numerically in incompressible flow, and also in isentropic compressible flow. For that reason we regularly interchange them. However, the two are not synonymous. The concept of total pressure has meaning at every point in a fluid flow field. Stagnation pressure is simply the pressure (aka static pressure) at a stagnation point (and there may be no stagnation point in the flow field.)

I maintain that it is not possible to measure total pressure. When people want to know the total pressure along a streamline, or in the efflux from a reservoir, they can be ingenious and artificially create a stagnation point, usually by inserting a Pitot tube in the flow. They can then rely on the fact that stagnation pressure is numerically equal to total pressure and state confidently that the total pressure along the streamline is equal to the pressure measured using the Pitot tube.

In supersonic flow the stagnation pressure downstream of a shock is not equal to the total pressure upstream of the shock. As a consequence, a good deal more ingenuity is needed to compute the total pressure. In summary, total pressure is a mathematical concept and is not amenable to measurement, but stagnation pressure, being a pressure (aka static pressure) is readily amenable to measurement.

It is meaningful to contemplate the total pressure in the flow in a nozzle or diffuser, but it is not meaningful to contemplate the stagnation pressure in a nozzle of diffuser because clearly there is no stagnation point in such a device. Dolphin51 (talk) 11:30, 20 January 2008 (UTC)


 * Ah, ok now it makes sense. I had forgotten about the subtle difference between total and stagnation pressure, which becomes evident in non-isoentropic flows. In light of that, I believe there's quite some work to do to Total pressure (aside from the static pressure controversy), if anyone wants to have a go at it. Giuliopp (talk) 22:33, 20 January 2008 (UTC)

Haven't heard much from you in a while.Mangogirl2 (talk) 01:48, 5 March 2008 (UTC)

Hi MG2. I thought you must be on vacation! I have left a message for you on your Talk page under Neutral Point. Dolphin51 (talk) 03:37, 5 March 2008 (UTC)

Dolphin51: I missed the Feb 7 note. Also, I ran out of things that I know enough to write about. Been busy with Science Fairs. Do they have them in your country? Mangogirl2 (talk) 03:25, 7 March 2008 (UTC)


 * Hi MG2. I don't know what a Science Fair is, so I guess we don't have them in Australia.  In recent years "hands-on" science centres have become very popular, and with good reason.  In my city we have Questacon, a dedicated hands-on science centre.  See Questacon.  It is mostly manned by volunteers.  Is this anything like your Science Fair? Dolphin51 (talk) 10:48, 12 March 2008 (UTC)

Dolph51: There is a good description on Wikipedia under science fair I have changed my name to skimaniac. —Preceding unsigned comment added by Skimaniac (talk • contribs) 18:23, 13 March 2008 (UTC)

Load factor (aerodynamics)
I had to cut a major part out of Load factor (aerodynamics) because of copyright violations. Now the article has no introduction. If you have time, can you give it an introduction? Cheers, Kingturtle (talk) 13:22, 12 March 2008 (UTC)

Thanks Kingturtle. I have posted a reply on your User talk page. I have also initiated a discussion on the Talk:Load factor page. Dolphin51 (talk) 00:34, 13 March 2008 (UTC)

Vortex generator
Thanks for your recent edits to Vortex generator. Your info there looks pretty accurate and reasonable, but other than citing two FAR/air regs, you haven't provided any refs for the information. My own experience suggests that your info is right, but I don't have a ref to back it it. All factual edits in Wikipedia must be supported by references see WP:citing sources.

Lately Wikipedia has been under the gun in the general press for doing damage with unreferenced articles. For anyone who doesn't think it is important for Wikipedia to be scrupulously referenced, I suggest that you read this CBC article. A lack of references can cause real damage in some cases. Obviously your edit on vortex generators isn't going to get anyone labeled a terrorist, but refs are still needed! - Ahunt (talk) 11:13, 14 March 2008 (UTC)


 * Thanks for your note. It isn't a personal crusade of mine. In the past I have had text I had put into articles tagged for lacking sources. At first I found it annoying, because it was stuff that I "just knew", but then I had the official policies pointed out to me. The CBC article really just cemented the issue in my mind and I came around to the official policy way of editing Wikipedia - when adding substantive text (not just spell checking or fixing grammar and wikilinks). The main articles on this are: Citing sources and Original Research. Essentially things that we all "just know" from our own personal experience do not belong in an encyclopedia, because they are unverifiable.


 * As it says in the policy Verifiability:


 * "The threshold for inclusion in Wikipedia is verifiability, not truth. "Verifiable" in this context means that readers should be able to check that material added to Wikipedia has already been published by a reliable source. Editors should provide a reliable source for quotations and for any material that is challenged or is likely to be challenged, or it may be removed." This is policy, not optional and not a personal crusade.


 * Adding fact tags where they are needed is also policy:


 * "The burden of evidence lies with the editor who adds or restores material. All quotations and any material challenged or likely to be challenged should be attributed to a reliable, published source using an inline citation.[1] The source should be cited clearly and precisely to enable readers to find the text that supports the article content in question.


 * "If no reliable, third-party sources can be found for an article topic, Wikipedia should not have an article on it.


 * "Any edit lacking a reliable source may be removed, but editors may object if you remove material without giving them a chance to provide references. If you want to request a source for an unsourced statement, consider moving it to the talk page. Alternatively, you may tag a sentence by adding the template, a section with , or the article with  or  . Use the edit summary to give an explanation of your edit. You may also leave a note on the talk page or an invisible HTML comment on the article page."


 * So policy actually says that each sentence should be fact tagged, but this is clearly overkill when several paras are added.


 * The use of the "ref improve" tag has not proven enough to motivate editors to add citations. There have been many articles "ref improve" tagged for over a year and not only are no refs added, but lots of new material has been put in without citations. Generally the use of "fact" tags seems to improve the chances of editors adding the references.


 * I spend a lot of my time on Wikipedia actually finding refs for other people's edits and "fact" tags actually help me know exactly what needs a source. They aid the collaborative process.


 * The fact tags also serve an important role for non-editing members of the public (including the media) who are reading an article. They show that the information is not referenced and therefore should at best be considered unreliable.


 * Despite the policy that says to just remove the information, I believe that "Fact" tagging is usually a better approach, especially in cases like the text you added where my own experience indicates that your info is probably correct, but I can't source it from the internet or my own fairly large collection of aeronautical books.


 * As you can see some people think that it shouldn't be fact tagged at all, but quickly removed:


 * "I can NOT emphasize this enough. There seems to be a terrible bias among some editors that some sort of random speculative 'I heard it somewhere' pseudo information is to be tagged with a 'needs a cite' tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information, but it is particularly true of negative information about living persons.


 * –Jimmy Wales"


 * I didn't tag the first para, because in general the introductory para of most articles does not have a citation, although some do. In most cases it is a summary of the text to follow and rests on those refs. If the intro para has information that seems to make a claim of some fact, rather than a general overview, then it should have a citation as well. In the case of this article I judged it to a very general statement, although perhaps another editor might disagree and prefer it be properly footnoted.


 * I hope this explanation has been helpful. - Ahunt (talk) 13:47, 14 March 2008 (UTC)


 * Thanks for your comment on my talk page. I am guessing that all means that you don't have a reference for the text that you entered in the article and that it is all from personal experience? - Ahunt (talk) 15:02, 15 March 2008 (UTC)


 * To help out on this issue I found sufficient refs to back up the text and expand it somewhat. - Ahunt (talk) 16:17, 15 March 2008 (UTC)


 * Glad that was all helpful. The article is looking much better! I agree that using Busch's article which requires a free membership is not ideal. EL says these should be avoided for external links. Citing_sources has nothing to say on the subject. I usually do avoid these sorts of refs, but Busch's article was too good a ref to pass up. Let's see if anyone objects! - Ahunt (talk) 12:17, 17 March 2008 (UTC)

Edit of 203.218.190.157 on Bernoulli's principle
Hi Dolphin51. It is very well possible that 203.218.190.157, who seems to be new to WP, did his removal of this example in good faith. The example is quite dubious, given all discussions about "misunderstandings" on lift. Crowsnest (talk) 11:38, 25 March 2008 (UTC)

Hi Crowsnest. I see that you and the special contributor have deleted the description of lift and Bernoulli's principle. You will notice that the text you deleted contained a reference:

''When a stream of air flows past an airfoil, there are local changes in velocity round the airfoil, and consequently changes in static pressure, in accordance with Bernoulli’s Theorem. The distribution of pressure determines the lift, pitching moment and form drag of the airfoil, and the position of its centre of pressure.” Clancy, L.J., Aerodynamics, Section 5.5''

This is a very, very powerful reference. Very powerful indeed. This book is very comprehensive in the field on aerodynamics, and its author L.J. Clancy is one of the doyens of aerodynamics, at least in Europe. In contrast, the Bernoulli Sceptics (you are one of these) never, never quote a reference of any kind when you do your work.

The threshold for inclusion in Wikipedia is verifiability, not truth. See WP:Verifiability. Whether your deletion is true or not is of secondary importance. Verifiability is paramount and I have provided the reference to Clancy's words on the matter. What do you have to say about verifiability of your point of view? If you have a reference, please reveal what it is. If you don't, please immediately re-instate the text you have deleted.

It is not sufficient to say "see the discussions on lift". There is a lot of material on the Talk:Lift page. I don't intent to wade through it to find what you have in mind, or to find a reference for you. Dolphin51 (talk) 11:51, 25 March 2008 (UTC)


 * Hi Dolphin51. You are right. My apologies for reverting your restore. Best regards, Crowsnest (talk) 11:58, 25 March 2008 (UTC)


 * Hi again Crowsnest. Thanks for your latest message.  I started a new topic in Talk:Bernoulli's principle to highlight the problem.  Thank you also for restoring the deleted text.  When I saw that it had been restored I went back into my new Talk article and deleted references to "Crowsnest".  Happy editing!  Dolphin51 (talk) 12:20, 25 March 2008 (UTC)


 * Sorry for calling this example dubious. I am just overly triggered by anything related to lift force and Bernoulli's principle, due to the section "A common misconception about wings", which is all about different ways how to determine or how not to determine lift force, and has nothing to do with Bernoulli's principle. Crowsnest (talk) 12:51, 25 March 2008 (UTC)

Troll?

Is it possible that Rcgldr/203.218.190.157 is a troll? Based on this entry: I'm beginning to have my suspicions... ComputerGeezer (talk) 22:50, 1 April 2008 (UTC)
 * No, I've visited that web site, but had no plans to quote anything from that website, although that site does include text about static ports, a real world example that differences in air stream velocity don't produce lift. Rcgldr (talk) 21:18, 1 April 2008 (UTC)

Hi ComputerGeezer. I don't think he is a troll. I think his enthusiasm for participating on matters of aviation greatly exceeds his expertise. So far his efforts have been harmless because he has not edited the main article, only the Talk page. He only started contributing to Wikipedia on 31 March, and everything he has contributed has been on the Bernoulli Talk page. He displays a high degree of self-confidence but his writings don't warrant that self-confidence. He mostly writes nonsense. I am about to comment on his latest contribution. Best regards. Dolphin51 (talk) 11:03, 2 April 2008 (UTC)
 * Ok, I'll sit on my editing fingers for a while. (I think you're right, it's just that the last one moved from misunderstanding into silliness and made me start considering alternative explanations.) ComputerGeezer (talk) 14:08, 2 April 2008 (UTC)

1999 South Dakota Learjet crash
Hi. Thanks for your message and its "heads up". Maybe one day Wikipedia will include an Automated Edit Warning System that features a "LINK UP!" alert... Sardanaphalus (talk) 12:12, 30 March 2008 (UTC)

PS The way in which creatures such as dolphins move so rapidly through water with such seemingly work-defying ease is one of those natural wonders I'm particularly impressed by. Thanks for the reminder on your userpage.

thanks: wing Warping
I added references explicitly. Since I had linked to the Wright Brothers Page and to the wing warping page that had references to authoritative sources, i thought I didn't have to insert them in the section I added. The Wright Bros page talks extensively about the lack of realization of the need for aircraft control before the Wrights. The other big contribution of the Wrights was the wind tunnel for scale model testing. Saltysailor (talk) 02:35, 9 May 2008 (UTC)

AfD nomination of Laurence Clancy
I have nominated Laurence Clancy, an article you created, for deletion. I do not feel that this article satisfies Wikipedia's criteria for inclusion, and have explained why at Articles for deletion/Laurence Clancy. Your opinions on the matter are welcome at that same discussion page; also, you are welcome to edit the article to address these concerns. Thank you for your time. Do you want to opt out of receiving this notice? RolandR (talk) 12:44, 11 May 2008 (UTC)
 * Sorry to hear that the article on L.J. Clancy has been deleted. Crowsnest (talk) 08:40, 19 May 2008 (UTC)

Talk:Spin (flight)
I have never flown an aircraft as Pilot In Command but I grew up on a airport and had AvGas in my blood for most of my younger years. I just never went as far as to get flight training. Therefore, I'm surprised that you, as a trained pilot, disputed the validity of the term "flat spin". Before taking this as another personal attack, please read on.

Over the last couple of years, I have seen a great deal of accurate and useful information disputed or even excised from Wikipedia by know-nothing buttinskis who have nothing better to do with their time than peruse Wikipedia for unreferenced statements to dispute. Those who believe that Wikipedia should err on the side of exclusion have won-out over those of us who believe that it should err on the side of inclusion. Your suggestion that the term "flat spin" should be removed--a term that is used in countles books, manuals, official accident reports and published scientific research--made you look like one of the above. The last thing I expected was to find out that you have experience in aviation.

So, my question to you now is, as a trained pilot, why do you think "flat spin" is a colloquialism? Is there a school of thought, that I'm unaware of, that says "a spin is a spin, there is no 'flat spin'"? —Preceding unsigned comment added by Rsduhamel on June 5, 2008.

Hi again Rsduhamel! Thanks for explaining your viewpoint. It gives me the opportunity to explain mine. As a pilot, flying instructor and aeronautical engineer I have carried out a lot of spins and read quite a few books on the subject. I am very respectful of all spins, including those regarded as steep spins (alpha less than 45 degrees). It is not only flat spins (alpha more than 45 degrees) that are potentially hazardous. Flying instructors regularly demonstrate to their students the way their airplane spins, and also the recovery procedure. They don’t demonstrate steep and flat spins. In my (general aviation) experience, single-engine airplanes have one spin mode only. It is not possible to choose whether to put these airplanes into a steep spin or a flat spin. It is only possible to put them into a spin and then accept whatever angle of attack is the result. I have in front of me the excellent book Aerodynamics for Naval Aviators by H.H. Hurt Jr. It contains comprehensive information about spins. The terms flat spin and steep spin are not used anywhere in the book. Every reference is about spins in general without regard to whether the angle of attack is less than, or greater than, 45 degrees. In my experience, professional aviation books talk inclusively about spins without attempting to differentiate them into steep and flat spins. The av8n web site is generally very good, but it does misuse the notion of the “flat spin”. NASA distinguishes between steep and flat by arbitrarily using an angle of attack of 45 degrees. NASA does not claim there is a significant change in the character of spins at the 45 degree point. I intend to use the comment facility on the av8n web site and draw the misuse of "flat spin" to the attention of the authors.

As Spin (flight) exists at present it contains a number of anomalies. Here are a few of them.

Under Steep spin it says:

 * A steep spin can be initiated by applying rudder while beginning a stall. (No citation provided.)  This is the initiation procedure for spins in general, not just steep spins.  This sentence would be fine if the word steep is deleted.
 * Recovery from a steep spin is usually accomplished by neutralizing the ailerons and applying rudder opposite to the direction of yaw. (No citation provided.)  This is a general recovery procedure applicable to spins in general, not just steep spins.  This sentence would be fine if the word steep is deleted.

Under Flat spin it says:

 * if an aircraft is not rated for flat spins, it is unlikely that the pilot will be able to recover from a flat spin. Some airplanes are rated for spins, and some are not rated for spins.  Airplanes are not rated for different types of spin.  The sentence implies that the pilot will be able to recover from a steep spin, even if it is not approved for spinning – very dangerous implication - a young pilot might try a steep spin in an aircraft not rated for spins!  This sentence would be fine if the word flat is deleted.
 * A flat spin can be deliberately initiated by the pilot and, if conducted in an aircraft approved for the maneuver, is quite recoverable. This is true of all spins, including steep spins.  This sentence would be fine if the word flat is deleted.
 * Recovery from a flat spin caused by the C.G being too far aft is usually not possible using the flight controls. If the CG is too far aft any spin is usually not recoverable.  This is true of spins in general, including steep spins.  This sentence would be fine if the word flat is deleted.

I understand your frustration at seeing Wiki editors deleting information they disagree with. However, be aware of this guidance: WP:BeBold

Best regards. Dolphin51 (talk) 03:39, 6 June 2008 (UTC)

More on flat spins
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.

As far as the guideline WP:BeBold. Great idea but often abused. In my observation this abuse has often led to the people with the strongest opinions controlling the content. I have cut my editing back, perhaps, 80 percent. This is mainly because I spent too much time fighting to keep material from being deleted (mine as well as other's). So, the next time someone wants to delete the article about Dmitri Maksutov, because inventing an important type of telescope isn't notable enough to to warrant an article in Wikipedia, more power to them (That was someone else's article, not mine, I just saved it). Rsduhamel (talk) 05:30, 6 June 2008 (UTC)


 * Hi again Rsduhamel! I believe we have found common ground and are in complete agreement.  Your analogy tropical cyclones and 74 MPH is brilliant.  It hits the nail on the head perfectly.


 * I agree that "flat spin" is used widely, but in a subjective manner. The av8n web site exposes the NASA research very well.  If I do some editing on Spin (flight) in the near future I will cite the NASA research - it shows what flat spins are, and what they are not.


 * If you look at sites such as Stall (flight), Static pressure, Position error, Longitudinal static stability and Bernoulli's principle you will see that I have cited the excellent book Aerodynamics by L.J. Clancy. I wrote a biographical article about Laurence Clancy and posted it on Wikipedia.  Unfortunately others thought he was not notable enough, even though he was the author of an excellent book cited often in Wikipedia (probably only be me, unfortunately).  The end result was my article was deleted and there is no longer any trace of it on Wikipedia.  (See above in my User talk page and you will see a bit of the deletion activity.)  I was disappointed that I was unable to save my article, but I guess them's the rules on Wikipedia.  I think I have got over it.


 * Best regards, and happy editing! Dolphin51 (talk) 01:48, 7 June 2008 (UTC)

Thanks
Thanks for your input at Talk:Siphon! Third-party reviews help in these debates.--Yannick (talk) 13:53, 8 June 2008 (UTC)

Re: Adidiabatic process
I agree that adiabatic is also widely used for irreversible process in which no heat is transferred. However, in theoretical physics, we tend avoid using the word adiabatic for such irreversible processes. I can't really point to a source that says this, because it is just a custom that theoretical physics professors stick to when they teach to students. The reason why we do this is because we base thermal and statistical physics on fundamental physics, in particular quantum mechanics.

So, when we explain what "work" is we consider some isolated system which is in some energy level. We slowly change an external variable (e.g. volume) and the value of that energy level changes. The "adiabatic theorem" of quantum mechanics guarantees that the system stays in that energy level. So, it would be confusing to use the same word "adiabatic" later on in the course to describe e.g. the free expansion process, which is precisely not adiabatic in the sense used earlier in the course.

I agree that everything has to be sourced in wikipedia, so I don't mind if my comment in the article is removed. But it would be a good idea to point out the apparent contradiction between "adiabatic" as used in quantum mechanics as that contradiction is very relevant for theoretical physics students. Count Iblis (talk) 14:44, 16 June 2008 (UTC)


 * Thanks Count Iblis. If the expression adiabatic process has a slightly different meaning in quantum mechanics than in thermodynamics this should be dealt with by creating a sub-heading called something like Adiabatic process in quantum mechanics.  It is not desirable to deal with the two different meanings in the one paragraph.  Alternatively, if this concept in quantum mechanics is sufficiently significant it could become the subject of a separate article, possibly titled Adiabatic process (quantum mechanics).  Dolphin51 (talk) 04:20, 17 June 2008 (UTC)

Re: Isenthalpic process
The previous version suggested that enthalpy stays constant in an isolated system. But in a completely isolated system (kept at cnstant volume) the internal energy will stay the same. So, if we want to mention a generic class of insenthalpic processes, then we should point to adiabatic processes that happen under constant pressure (change in E + P V = absorbed heat = zero).

Of course, this does not mean that the reverse is true, i.e. an isenthalpic process is not necessarily a process that takes place under constant pressure. Just like energy can be conserved in an open system too (if as much energy flows into the system as flows out). Count Iblis (talk) 15:00, 16 June 2008 (UTC)

Re: Vandalism
Sorry, but you don't understand your own sources. I'm going to revert you every time you make nonsensical statements in wikipedia articles.

What you are doing is writing something like:

1 + 1 = 0 See source X

when source X talks about artithmetic modulo 2.

You are insisting on keeping that sentence in the article when it is clear that for an isolated system with fixed volume H = E + P V is not conserved, only E is conserved. Your source says H is conserved, but then the meaning of that is in a completely different setting. And the article doesn't talk about that at all.

You are talking about a system in which you define some system boundaries, you have a generator that can extract work and only that work counts as work done by the gas. But where in the aticle are these details mentioned? Nowhere! Count Iblis (talk) 23:30, 17 June 2008 (UTC)

Anyway, I've taken up this matter with wikiproject physics. There is a longstanding issue with below standard material in the thermal physics articles. The only way to sort it out, i.m.o. is to prove what you want to say from first principles and not to point to sources. Count Iblis (talk) 23:37, 17 June 2008 (UTC)

Article Joule–Thomson effect vandalized by me!
Check it out. I'm sure that your sources say that the gas does no work here (because it should be obvious that there is a generator somewhere that is supposed to extract work and the gas moving through the valve is not letting a turbine spin) :) Count Iblis (talk) 23:41, 17 June 2008 (UTC)

Bernoulli Principle and lift
Looking at the discussion thread and at several web sites, I have questions rather than suggestions for changes, I'm posting these here, since I assume it's inapropriate to post questions in the discussion threads on articles (would be nice if wiki articles had a seperate page for questions). It might help if I start with Newton stuff first.

My simplified version of newton explanation of lift: air is accelerated downwards and slightly forwards, resulting in reactive lift and drag forces. Work is done on the air in the process of producing lift and/or drag, resulting in a change of the total energy of the air.

One question about terminology. Induced drag is defined as the drag associated with producing lift. Does induced drag times distance equal the component of work required to produce lift? Does parasitic drag times distance equal the component of work required to produce the remaining drag (not sure if friction is included as part of parastitic drag)?

I'm am having problem understanding Bernoulli Principle and lift as described in the discussion thread on Bernoulli principle. I don't understand why near horizontal air flow relative to a wing, results in a vertical force reaction. I understand the concept that pressure and airspeed have an inverse relationship in a closed system (such as Venturi effect used in caurberators). Getting back to wings, it's an open system, and air is accelerated towards lower pressure areas, and away from higher pressure areas from all directions (almost, air can't flow through the solid wing). I read that streamlines can be considered "closed" systems, but wouldn't low pressure areas draw air from outside the streamline as well as from the streamline itself?

Take the case of a wing where almost all the lift effect occurs from above the wing, which was mentioned in the discussion. If Bernoulli principle is about the near horizontal air flow over such a wing, so that the air is accelerated horizontally backwards relative to the wing, then it seems the result would be thrust and not drag. Where is the source of drag in this case? I've seen wind tunnel videos, and it's clear that the pulsed smoke stream above a wing ends up well ahead of the pulsed smoke stream below the wing. The only thing that would make sense here is that almost all the drag would occur from below the wing, but it would seem that the primary method of creating drag below a wing would be to increase the pressure below the wing, and this would conflict with the concept that all of the lift effect occurred from above a wing. What am I getting wrong here?

It was mentioned that airfoil simulation programs calculate pressures, lift, and drag, from air speeds, but aren't those air speeds also just calculated values? What was the point of that statement?

From my point of view, if it was simply stated that wings produce lower pressure areas above and/or higher pressures below, causing a net downwards acceleration of air, where the accelerations correspond to the transitions in pressure areas, and that for all of the air affected by a wing, speed^2 corresponded inversely with pressure I wouldn't have a problem (I'm guessing that there is some slight mistmatch in speed versus pressure due to work being done and a change in total energy of the air). It's the apparent emphasis on the horizontal flow across a wing that has me confused, since if using the air itself as the frame of reference, then the flow (and acceleration) of air corresponding to lift is downwards.

Lastly, how would Bernoulli Principle be modified to calculate (predict) the net work done on the air? Jeffareid (talk) 21:58, 20 June 2008 (UTC)


 * update- maybe I'm making a bad assumption about work performed on the air, changing it's total energy. From an air based frame of reference it's clear that the net result of a wing producing lift (and drag) as it passes through the air is a net downwards and forwards velocity of air. Is the total energy of this air (pressure + kinetic) changed by the wing, or is all the increase in speed offset by a decrease in pressure? It seems that some work is being done, using a closed system example like birds or a model flying inside a truck, where the result is that the flying birds or model increase the pressure diffrential (versus height) so the net downforce exactly equals the combined weight of birds or model (assuming no vertical component of acceleration of center of mass here). Jeffareid (talk) 07:25, 22 June 2008 (UTC)


 * assuming that a wing does peform work on the air, which seems to be implied by the term induced drag, is all of the work done related to drag only, or is work also peformed related to lift? Assuming that work related to lift is peformed, then how is this accomplished? This violates the Bernoulli principle in that the air ends up with a higher velocity, but not a corresponding decrease in pressure. For the flow over a wing, perhaps Conada or similar effect is deflecting (accelerating) air downwards more than what simply decreasing pressure would accomplish, which would account for an increase in speed without a corresponding decrease in speed. Jeffareid (talk) 07:25, 22 June 2008 (UTC)


 * lastly, the newton approach is so much simpler as it just leaves out the nasty details. Encarta used to explain lift via Bernoulli principle, but later corrected this to simply state lift occurs because air is deflected downwards and leaving out all the details. Sorry for all the questions, but just once I'd like to get a good understanding of this, even though I'm not an aerodynamics engineer (which doesn't seem to help since they can't agree either). Jeffareid (talk) 07:25, 22 June 2008 (UTC)

Reply to Jeffareid
Jeff

Here are my thoughts on the first of your questions. Your words are in bold. I will provide more information in the next day or two.

Work is done on the air in the process of producing lift.

Actually, very little work is done on the air to produce lift. Work is force multiplied by distance, but only if the force vector is parallel to the distance vector. If the force vector is perpendicular to the distance vector no work is done and so there is no increase in the kinetic energy. For example, when a vehicle such as a bicycle or automobile travels around a circular path there is a significant centripetal force acting on it, but this centripetal force is perpendicular to the vehicle’s velocity vector so no work is done and the kinetic energy of the vehicle remains unchanged.

Lift is defined to be perpendicular to the airfoil’s velocity through the atmosphere so you might expect lift to do no work on the air. However, the downwash associated with the airfoil’s trailing vortices causes the air close to the airfoil to be moving in a slightly different direction to the airfoil’s velocity through the atmosphere. (This small difference in direction is called the induced angle of attack.) Consequently, lift does a small amount of work and this causes some of the air to have kinetic energy associated with its downward motion. The airfoil constantly has to provide this kinetic energy and this is one explanation of induced drag. The greater the induced drag the greater the kinetic energy of the air moving in the downward direction.

Work is done on the air in the process of producing drag.

Part of the total drag is induced drag. The other part is parasite drag. Parasite drag causes some of the air (the wake) to try to tag along behind the airfoil, long after it has passed. The work done on the air by parasite drag causes some of the air to have kinetic energy associated with its forward motion.

Does induced drag times distance equal the component of work required to produce lift?

Yes. This component of work causes an increase in kinetic energy associated with the downward motion of the wake.

Does parasitic drag times distance equal the component of work required to produce the remaining drag (not sure if friction is included as part of parastitic drag)?

Yes. (Friction, or skin friction, or viscous forces, are included in parasite drag.) This component of work causes an increase in kinetic energy associated with the forward motion of the wake.

… wouldn't low pressure areas draw air from outside the streamline as well as from the streamline itself?

No. Air accelerates towards low pressure areas, and decelerates away from high pressure areas. The resulting motion is described by the streamlines. The streamlines show exactly where the particles of air are moving. Particles of air don’t move across streamlines because the streamlines show the actual movement of the particles.

Imagine some particles of air being given a pencil so each one can draw a line as they move. The result of all those pencil lines is a number of streamlines.

When you ask whether air is drawn from outside the streamlines you are thinking of isobars (lines of constant pressure). Streamlines are not isobars. Think of the weather map – the wind is shown by small arrows. At ground level the wind blows across the isobars but it doesn’t blow across the arrows – the arrows show the wind’s actual direction. Each arrow is parallel to the local streamline.

Take the case of a wing where almost all the lift effect occurs from above the wing …

It is accurate to talk about the pressure above the wing being lower than elsewhere. It is also accurate to talk about the pressure below the wing being greater than above the wing. Lift is related to the difference in pressure on either side of the wing, so it is not accurate to say more lift is generated by one side of the wing than the other. (Put it another way - when you clap hands you can't say one hand makes more noise than the other.)

It is a bit like talking about a child’s toy balloon. The size of the inflated balloon depends on the difference in pressure between the interior of the balloon and the atmosphere. It would not be reasonable to say the interior of the balloon contributes more to the size of the balloon than the exterior. It is reasonable to say the pressure in the interior is greater than the pressure in the atmosphere.

Dolphin51 (talk) 03:42, 24 June 2008 (UTC)

'''If Bernoulli’s principle is about the near horizontal air flow over such a wing, so that the air is accelerated horizontally backwards relative to the wing, then it seems the result would be thrust and not drag. Where is the source of drag in this case?'''

On the upper surface of the wing, from the leading edge to about the point of maximum airfoil thickness, the air undergoes a spectacular acceleration. Then from the point of maximum airfoil thickness to the trailing edge the air undergoes a deceleration so it leaves the trailing edge of the wing at the same speed as the air coming from the lower surface of the wing.

A typical airfoil section has its maximum thickness at about 25% of the chord (distance from leading to trailing edge.) So from the leading edge to the 25% point the air accelerates spectacularly. Then from the 25% point to the trailing edge (ie 100%) it decelerates to roughly the same speed at which it approached the airfoil, and the same speed as the air coming from the lower surface. In contrast, air passing via the lower surface of the wing does not undergo any acceleration. It simply passes from the leading to the trailing edge at roughly constant speed.

Because of the spectacular acceleration and then deceleration the air travelling via the upper surface arrives at the trailing edge long before its partner arriving via the lower surface. The two partners never meet again, not even long after the wing has passed. This is known as cleavage.


 * I've read from more than one site that once the deceleration occurs, the flow transitions from laminar to turbulent, and got the impression that this is how fluids and gases behave in general, and not just within the boundary layer near a wing (I'm not referring to the seperation bubble, just the transition into turbulent flow during deceleration of air) . Maybe this is wrong? Jeffareid (talk) 05:49, 3 July 2008 (UTC)

The parasitic drag on the wing is partly due to the viscous nature of the air flowing past the upper and lower surfaces of the wing. (This is called surface-friction drag or skin-friction drag. It is just like trying to pull a knife quickly through a viscous liquid like honey or oil.)  The air passing over the upper surface is travelling faster than the air passing over the lower surface so the drag on the upper surface is higher than the drag on the lower surface. (Any attempt to measure the drag simply measures the total drag. It is not possible to measure the drag on upper and lower surfaces separately.)

The other part of the parasitic drag on the wing is due to the lower pressure in the wake. (This is called form drag.) Near the leading edge of the wing the pressure is high – it is called stagnation pressure because the air is stopped against the solid surface. In contrast, in the wake at the trailing edge of the wing the air is not stopped and so the air in the wake has a pressure less than stagnation pressure. With higher pressure pushing backwards on the leading edge of the wing; and lower pressure pushing forwards on the trailing edge of the wing, the net result is a backwards force opposing the forward motion of the wing. This is usually called form drag and it is a component of parasitic drag.

What am I getting wrong here?

This is a situation that has puzzled many people over the centuries. One of the earliest scientists to grapple with the puzzle of why drag occurs was d’Alembert. The puzzle became known as D'Alembert's paradox. The puzzle was finally solved by the German scientist Ludwig Prandtl who discovered the existence of the boundary layer, and how a viscous fluid exerts a resisting force opposing the motion of any solid object.

'''It was mentioned that airfoil simulation programs calculate pressures, lift, and drag, from air speeds, but aren't those air speeds also just calculated values? What was the point of that statement?'''

If we specify a particular airfoil, its angle of attack and its speed through the air it is possible to determine the streamline pattern around that airfoil, and also the airspeed at any point around the airfoil. (The first person to do this mathematically was the Russian mathematician Nikolai Joukowsky. His mathematical technique is known as the Joukowski transformation.)  When we know the distribution of airspeed all around the airfoil we can use Bernoulli’s principle to calculate the pressure at any point, and the pressure distribution all around the airfoil. When we know the pressure distribution we can readily calculate lift and form drag.

The point of the statement is that it isn’t possible to take a particular airfoil, angle of attack and airspeed and directly calculate lift and form drag. It is necessary to first calculate the airspeed distribution around the airfoil. When we have the airspeed distribution all that is necessary is to apply Bernoulli’s principle to convert the airspeed distribution into a pressure distribution. (When people say Bernoulli’s principle is not applicable to lift on an airfoil they are completely wrong.)

Lastly, how would Bernoulli’s principle be modified to calculate (predict) the net work done on the air?

Bernoulli’s principle doesn’t talk about work being done on the air. (Also, nothing is achieved by modifying Bernoulli’s principle.) The simplest way to calculate the work done on the air is to use the Work-Energy Theorem which says that the work done on a body is equal to the change in energy of the body. (Positive work causes an increase in energy; and negative work causes a decrease in energy.) In the case of a wing generating lift as it moves through air, the Work-Energy Theorem says the work done on a parcel of air is equal to the change in kinetic energy of that parcel of air. So if a wing approaches a small parcel of stationary air (zero kinetic energy), and after the wing has passed that small parcel of air has kinetic energy of X joules, the wing has done X newton.metres of positive work on that parcel.

The motion of that small parcel of air will be downwards and forwards (in the same direction as the wing). The downwards component is a result of having exerted induced drag on the wing; and the forwards component is a result of having exerted parasitic drag on the wing.

I will deal with your remaining questions in a day or two. Cheers. Dolphin51 (talk) 12:31, 24 June 2008 (UTC)

From my point of view, if it was simply stated that wings produce lower pressure areas above and/or higher pressures below, causing a net downwards acceleration of air, where the accelerations correspond to the transitions in pressure areas, and that for all of the air affected by a wing, speed^2 corresponded inversely with pressure I wouldn't have a problem.

There are numerous ways to explain lift on an airfoil – some simple and others complex. The simple ones are relatively limited in their scope, and the complex ones are very comprehensive. Each person should choose the explanation he or she feels most comfortable with. When that person feels the chosen explanation does not explain some important aspect of lift it is time to move on to more comprehensive explanation and begin to comprehend that one. If you are most comfortable with the Newtonian explanation then there is nothing wrong with that. Stick with it.

However, the Newtonian explanation of lift doesn’t explain why airfoils always have thin, sharp trailing edges. Nor does it explain such things as trailing vortices and wake turbulence. When you want to understand why airfoils have sharp trailing edges it is time to move on to grasp the Kutta condition. When you want to understand trailing vortices it is time to move on to the circulation theory of lift (see Kutta-Joukowski theorem.) But if those things never bother you there is no reason to grapple with them, and no reason to go beyond the Newtonian explanation.

I'm guessing that there is some slight mismatch in speed versus pressure due to work being done and a change in total energy of the air.

No, there is no mismatch in speed versus pressure due to these two things. Where there is a mismatch in the speed of the fluid and the fluid pressure is in the boundary layer close to the surface of the body (in this case an airfoil.) The speed at a point in the boundary layer is slower than you would expect from the pressure at that point. But the boundary layer is very thin – think of a sheet of thick paper. In the boundary layer the fluid slows down due to viscosity, but without the corresponding increase in pressure predicted by Bernoulli’s equation. Bernoulli’s principle applies with absolute accuracy everywhere in a moving fluid (without any mismatch) except in places where viscous forces occur such as in the boundary layer and in the core of vortices.

Is the total energy of this air (pressure + kinetic) changed by the wing, or is all the increase in speed offset by a decrease in pressure?

The wing changes the dynamic pressure (kinetic energy) and the pressure of the air but one offsets the other as predicted by Bernoulli. The total pressure (or total energy) remains unchanged for all the air influenced by the wing except the very small amount that enters the boundary layer and eventually ends up forming the wake.

Some of the air passes the upper surface of the wing. Its speed increases significantly as it passes the first quarter of the upper surface of the wing. As it does so, its pressure falls significantly. (That is why the lift experiences lift.) By the time it has reached about the end of the first quarter it begins to decelerate until it reaches the trailing edge. As its speed reduces its pressure increases. At the trailing edge the stream from the upper and lower surfaces join up. They are both moving at about the same speed and have the same pressure.

Even though the air passing the upper surface increases in speed, and its pressure reduces, the total pressure (dynamic pressure plus pressure) remains constant throughout the whole flow field (except in the boundary layer and the core of vortices.)

'''Assuming that a wing does peform work on the air, which seems to be implied by the term induced drag, is all of the work done related to drag only, or is work also peformed related to lift? Assuming that work related to lift is peformed, then how is this accomplished?'''

All the work done on the air is related to drag. Some of the work is induced drag times distance travelled, and this work equals the kinetic energy added to the wake in the form of its downward velocity. The remainder of the work is parasite drag times distance travelled, and this work equals the kinetic energy added to the wake in the form of its forward velocity.

Most of the lift performs no work because the lift vector is almost perpendicular to the direction of motion. I say almost perpendicular because it is ninety degrees minus a small angle called the induced angle of attack. The component of angle of attack called the induced angle is the small component due to downwash related to the trailing vortices.

This violates the Bernoulli principle in that the air ends up with a higher velocity, but not a corresponding decrease in pressure.

Not true. The speed rises and falls, but always with a fall and rise in pressure, exactly as predicted by Bernoulli’s equation (except in the boundary layer and the cores of vortices.)


 * What about the case of an electric driven turbine or propellor? In this case it seems that there would a significant increase in pressure and speed of the air just aft of the turbine or propellor, and therefore a signifcant increase in total energy of the air. Ultimately, isn't a wing, propellor, or turbine just an air pump? Jeffareid (talk) 05:55, 3 July 2008 (UTC)

The newton approach is so much simpler as it just leaves out the nasty details.

See above. If you like the Newton approach, stick with it. There is nothing wrong with it, and it is clear and simple. Similarly, there is nothing wrong with the Bernoulli explanation, or the circulation theory, but they are more complex and not so easily grasped intuitively.

I'm not an aerodynamics engineer (which doesn't seem to help since they can't agree either).

In fact, aerodynamics engineers and fluid scientists do agree. (These people mostly work with the circulation theory of lift.) What is often disputed is what explanation of lift is the best one to use to help student pilots, aviation enthusiasts and other beginners. Traditionally, Bernoulli’s principle was used to explain lift and there is nothing incorrect about this approach but some teachers consider it too complex for beginners, particularly those without a background in math and physics. Consequently some teachers and authors have used the Newton approach. The great error made by some of the latter is to teach that Newton’s third law explains lift and therefore Bernoulli must be wrong. (There are many areas in science where a phenomenon can be soundly explained by more than one law or principle. It is false to suggest that if one explanation is correct all the others must be incorrect.)

I hope this helps. If it doesn’t, don’t hesitate to ask more questions. I will do what I can to explain. Happy editing! Dolphin51 (talk) 04:15, 27 June 2008 (UTC)


 * Thanks for the detailed response. I had the impression that induced drag was more significant a factor than it apparently is. The other issue I was thinking of is that streamlines will follow over the top of cambered airfoils (Coanda effect), and much of this acceleration would be perpendicular to the path of the stream line, not doing any work, but would accelerate air downwards (which in turn would result in a reduction in pressure of the air further above getting "sucked" downwards). About the experts not agreeing, this was mostly related to the comments about the Anderson and Ebehart web site lift.htm. Jeffareid (talk) 05:57, 3 July 2008 (UTC)


 * Similar to the flying birds inside a close truck, I assume that the total weight of the atmosphere on the earth is equal to the sum of the weight of the atmosphere and all the aircraft that are flying (at any one particular time, assuming no vertical component of acceleration of the aircraft), which is just another example of wings acting as air pumps. Jeffareid (talk) 05:59, 3 July 2008 (UTC)


 * The last question I can think of is why were these cool looking flat top curved bottom airfoils used on these pre-shuttle prototypes? For example, the M2-F2 glider, m2-f2.jpg, and the rocket powered M2-F3 (added a 3rd vertical stabilizer, and it reached a speed of mach 1.6, which would imply that it wasn't that draggy) M2-F3.jpg Jeffareid (talk) 05:57, 3 July 2008 (UTC)


 * As a bit of a thanks, some links to radio control videos. First a highlight video from radiocarbonart, which sells videos of radio control gliders (and electric version). Go to this link RCA_previews and click on endless lift 2, which near the beginning, includes a short clip of a true flat spin (on this model each entire wing moves as and aileron (they move independently or together), which allows such models to go into and out of "helicopter" mode). I have a few radio control videos here radio_control_videos.htm. The rc gliders are mine. Jeffareid (talk) 06:16, 3 July 2008 (UTC)

strange request...
Hey, I am currently a pilot and a 4th year aero student and I will be taking a flight controls/dynamics class in the fall. I'm studying for the class now and I'm struggling with arriving at the closed loop state equations and the transfer functions from the short-period perturbation dynamics diff eqs. I have no idea what to do because all I learned in my diff eq class was how to solve standard laplace transforms and things with the famous tables. I don't know whats going on. (btw.. I'm one of these "learn everything intuitively" people because I will probably forget the mathematics eventually and will only remember what things "feel" like...this is half the reason I became a pilot so that I could feel the equations instead of just writing numbers down.) Sorry to bother you and any help would be GREATLY appreciated! Katanada (talk) 19:47, 24 June 2008 (UTC)

Hi Katanada. You have my sympathy! Like you, I'm a pilot (but not current), and an aeronautical engineer. The subjective elements of flight dynamics we retain readily, and for a long time, but the advanced math takes a lot, lot longer to become intuitive. My advice is that there is no alternative to working carefully through the text-book and doing a few example problems along the way. (If your prescribed text-book doesn't inspire you as much as you would like, don't hesitate to search out a better book.) Nothing helps grasp new ideas in math as much as doing a few example problems, preferably where you can find the correct answer so you can keep at it until you get it right. Also it is my experience that in classes with a lot of intimidating math, they don't really expect students to be able to regurgitate the high-level stuff in the exam - they usually set an exam that assesses whether each student has grasped the important basics and is able to use that to handle some of the basic math. So don't study the high-level math with the objective of committing it to memory - memorise the fundamentals, and get a feel for where the fundamentals lead to, but it would not be an efficient use of your time to try to memorise the high-level stuff. Good luck in the fall! Dolphin51 (talk) 03:13, 27 June 2008 (UTC)

re: center of lift
Rereading my references (see the talk page) I've determined that way back when I should have simply worked on the aerodynamic center article rather than starting one on center of lift. The term is often used, but it's synonymous with AC, rather than CP. Hopefully this is a satisfactory solution to the issue! ericg ✈ 01:07, 28 June 2008 (UTC)

re: Ashes articles
I didn't vandalise English cricket team in Australia in 1994-95. I have been seperating the tour articles and the Ashes articles, as the Ashes have notoriety in their own right, but the tour match information does not belong in the Ashes article. Therefore the material related to the Ashes can be found in 1994-95 Ashes series, and the rest of the tour matches are at English cricket team in Australia in 1994-95, as is the case with all of the other editions I have completed. It is a large project, but i have done most of the 90's and created many of the early series already... Robert Fleming (talk) 13:10, 9 July 2008 (UTC)

Leading edge slot
Hi, thanks for your kind note. You are quite right, in interleaving my edits in between yours I screwed up. Let me reinstate the text and ref that you noted that I deleted and then you can see if that fixes it. - Ahunt (talk) 21:11, 24 July 2008 (UTC)

Flight Mechanics
Your discussion of steady state climb and dive is quite correct but you might want to mention unsteady climb (and dive) achieved by lift greater than weight. A glider can make loops by pulling an angle of attack where lift is greater than weight. As you point out this does not change the total potential energy (except for the drag losses of course) but you can climb without thrust. My poorly trimmed hand launched gliders do it all the time (at least until they reach zero speed and plumment to the ground)Skimaniac (talk) 04:59, 27 July 2008 (UTC)

Thanks for the Welcome back. It means a lot.Skimaniac (talk) 02:29, 29 July 2008 (UTC)

Welcome
I received your welcome notice on my user talk page. Given that you didn't respond to my question as to why I'd been welcomed some years after my first posting, I took it as condescending ... that aside from the redundance of such a late "welcome". I've also seen other users' "welcome" graffiti on other users' talk pages, and every one is different. Surely the best way to accomplish this would be to create a welcome package for "new" users and then post a simple message, such as " "? Just sayin'...--Rfsmit (talk) 23:09, 30 July 2008 (UTC)


 * No condescension intended. I replied to Rfsmit on his Talk page.  Dolphin51 (talk) 02:42, 1 August 2008 (UTC)

I have the same question for the same reason. In particular, is the list of suggested reading simply pro-forma or because you have specific areas of concern and believe that my work is not up to snuff? If the former, then perhaps your welcome notice should say so; if the latter, given the variety of my editing over the last six months or so, it would be far more helpful if you pointed to specifics.

While I have absolutely no illusions that I am a perfect writer or everyone's cup of tea, I write a great deal in a variety of contexts, paid, pro-bono, and avocational and would like to believe that the very limited work (mostly minor edits) that I have done on Wiki is done to a reasonable standard.Jameslwoodward (talk) 14:07, 27 January 2009 (UTC)

Thanks for your quick and thoughtful response. Certainly Wiki can be intimidating -- some of the help pages are not as clear as they might be -- and having an actual human take an interest in my work feels good. I will take you up on your offer of help at some point.

I might suggest that since your initial welcome raised much the same question in me and in Rfsmit, that you might consider modifying it a bit, perhaps something along these lines (using mostly your words),

"Hello XXXX and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay.

In Wikipedia, new Users do not automatically receive a machine-generated welcome. Welcome messages come from individuals so they are personal and genuine. They contain an offer of assistance if such assistance is ever desired.

I suggest to everyone that I welcome that they may find some of the following helpful -- there’s nothing personal in my suggestion and you may not need any of these:

Introduction The five pillars of Wikipedia How to edit a page Help pages Tutorial How to write a great article Manual of Style

I hope you enjoy editing here and being a Wikipedian! Please sign your name on talk pages using four tildes (Jameslwoodward (talk) 13:02, 28 January 2009 (UTC)); this will automatically produce your name and the date.

If you need help, check out Wikipedia:Questions, ask me on my talk page, or place helpme on your talk page and ask your question there. Again, welcome! "

Jameslwoodward (talk) 13:02, 28 January 2009 (UTC)

Looks good -- we make a good edit team. Jameslwoodward (talk) 22:13, 30 January 2009 (UTC)

'Sup
Oh hay look here. Benshi (talk) 06:48, 4 August 2008 (UTC)

And here! Benshi (talk) 08:39, 11 August 2008 (UTC)

Well? Did you look at it! —Preceding unsigned comment added by Benshi (talk • contribs) 06:07, 12 August 2008 (UTC)


 * Hi Benshi. Thanks for the message.  I like the new User page - now yours looks just as professional as the majority.  I visited Youtube.  I like the music!  Pity about one or two people posting comments that will be offensive to some viewers.  The internet is for everyone, of all ages and genders, and in every country so it is a pity that a minority of Youtube visitors try to impress by writing unimpressive things.  Cheers mate.  Dolphin51 (talk) 12:20, 12 August 2008 (UTC)


 * Well it's Youtube, what can I say. By the way, if you didn't notice already I'm only like, 13! Benshi (talk) —Preceding undated comment was added at 05:53, 13 August 2008 (UTC)
 * I'm impressed! Don't be concerned about only being 13.  You have done some good work on trains, railways, and railway towns.  Keep it up!  You're never too young to start serious work on Wikipedia.  Cheers mate.  Dolphin51 (talk) 06:01, 13 August 2008 (UTC)


 * LOLWUT!

Hay I was wondering, what's an aeronautical engineer? What do you do? 58.179.51.127 (talk) 09:43, 14 August 2008 (UTC)

Don't mention it!
I am glad to be of help. :) --PeaceNT (talk) 12:12, 12 August 2008 (UTC)

Need help please
Hello again Dolphin.

I would appreciate constructive help with how to proceed with my first page the http://en.wikipedia.org/wiki/Jen_Delyth

I have registered my complaint at the slamming I have taken from the RHowarth editor, who had no appreciation for the difficulties a new user may experience.

However, I would like to move on with a different editor, as the personal conflict I am experiencing is stressful. I don't know if that would be you, or what the procedure is, but appreciate your help.

I have (after the rough start) done my best to study the Wikipedia regulations and to change and update the page accordingly.

I"ve worked pretty hard on the page, refined the language to be more "enclylopedic", added some outside sources, formated and referenced and added several reputable Wikipedia links with Jen to show connections with other noteable artists/authors.

I understand that this would all have been better submitted through someone who was not connected with the subject. (which I did not initially understand when first posting the page). But I have now done the work, and set up the page, I am sincerely trying to present an unbiased, clear, objective summary of the facts. If I understand the regulations, they are guidelines, and have flexibility. I am being open and transparant, and want to continue in this way.

For the record, this (page creation) is not an attempt for self promotion. Jen Delyth is well known in her field to have made significant contribution to the contemporary Celtic Art genre, and in fact was at the forefront of the revivial of this popular folk art style in this country.

The only way to show that, is through her work. It is difficult to discuss the time frame, and an understanding of the style that she began, that has been emulated (yet not as well as the originator) since.

Within both the Celtic arts community, and fast spreading beyond it, Jen's original "Celtic Tree of Life' design has become an iconographic symbol, that is considered "THE" Celtic Tree of life, misinterpreted as an actual ancient Celtic symbol, and spreading throughout the world as a major archetype.

Its difficult to show the importance of this creation, or the artist who is behind it (except through google searches etc).

Certainly worthy of a Wikipedia reference, and of interest to your community. I would appreciate help in this. How to proceed, with integrity, and get this page worked out.

Is the page as it has been edited now editorially ok? Can you suggest any changes or ways to show this is a good solid contribution?

Also I don't know how to "hide" (blank?) the page whilst its worked on. (It is an embarressment having those messages and tags on there in full public view, when Jen Delyth gets over 600 views a day on her website).

Also, would it help to have just one basic line about the artist and not all the other info, so that others (not myself) can add to the site? (we noticed the Amy Brown site was like that.. She is a contemporary peer artist of Jen Delyth, linked on same Faerieworlds site (which is what brought me to create this page in the first place.. as Jen Delyth is listed as a guest artist there)

I appreciate your help and advice. Thanks, Scott Silverberg 66.117.128.94 (talk) 17:34, 12 August 2008 (UTC)


 * Hi again Scott. Jen Delyth at present looks too much like a general biography of Jen, and not enough like an article highlighting the notability of a notable person.  General biographies are not appropriately placed in encyclopedias, including Wikipedia.  Such biographical articles are regularly deleted from Wikipedia because they fail to demonstrate that the person is notable by meeting the criterion specified in WP:BIO and WP:PROFESSOR.  To reduce the risk of Jen Delyth being nominated for deletion I suggest you amend the article to emphasise the notability and reduce the amount of extraneous biographical information.  I suggest Jen's notability lies in the fact that it is she who designed the well-known Celtic Tree of Life (CTL).  The opening paragraph should say something like Jen Delyth is the artist and author who designed the CTL.  Subsequent paragraphs should explain the CTL, what it is and why it is well known.  Where Jen grew up, where she travelled and how she does her work is interesting background information for her followers, but it promotes the impression that the article is nothing more than a biographical article.  That impression will make the article vulnerable for deletion.  Biographical information that is not related to the CTL should probably be deleted.  (Biographical Wikipedia articles about major figures like prominent Presidents, Prime Ministers and Emperors will be lengthy and contain extraneous detail about their lives, families and places; but for all lesser figures the biographical detail should not be included except where it is directly pertinent to the claim for notability.)  The current heading "Bio" is colloquial.  If it is to be retained it must be expanded to "Biography".  However, you should ask yourself "Is this biography pertinent to Jen's notability as creator of the CTL?"


 * To see what deletion debates look like, go to Current discussions and select one of the dates (in blue). When you see the long list of current debates, select one or two and you will quickly get the feel for how they operate, and what sort of comments people make.  Each debate runs for 4 or 5 days and anyone can add their comments.  At the end of that time if an Administrator's decision is to delete, the article is deleted and gone for all time - never able to be viewed again.


 * Yes, I am an Australian. Whenever you see a User's name in blue, that name is a link to the User's personal page.  If you visit that page you will usually find a little information about the User.  It is the User's discussion page (User talk page) where you can leave a message for the User, as we have been doing.  (Whenever you see a User's name in red, a personal page has not yet been created for that User, so no link exists.  In general in Wikipedia, red means the word(s) have been nominated as a link, but no article of that name exists.)


 * Hang in there. You are learning much faster than I did!  Dolphin51 (talk) 03:42, 14 August 2008 (UTC)

Jen delyth EDIT S. Silverberg
Dolphin... Appreciating your help as I noted on my talk page. From now on will address comments here. The "EDIT" button has dissapeared from the top of JEN DELYTH page... so I can't edit it and add the inline citations you reccomended. Appreciate your help in getting that EDIT access back. Also, can i request an extention in time to get the page updated? Also, someone (not me) has added to the page, and given no sources. should I delete that contribution even though it came from an independant source? thanks a lot, scottSSilverberg (talk) 04:58, 13 August 2008 (UTC)
 * When I go to Jen Delyth I see the edit this page tab at the top. I can't explain why you might not be able to see it.  Try looking for the edit this page tab when you are logged in, and also when you are not logged in.  If you can't ever see the edit this page tab let me know.
 * User:DGG has edited the page and changed one banner for a much less threatening banner. Now, there is no need to up-date by any particular time.  At this stage don't delete the newest unsourced information (unless it is incorrect) - Users tend to react if they see their additions deleted promptly. (Good to keep all participating Users on your side.)  Dolphin51 (talk) 05:34, 13 August 2008 (UTC)

Thanks a lot Dolphin.. Very relieved that the editorial work so far has helped. Still a ways to go.. And still don't see the "edit" button at top of page for main intro section in Firefox (mac) or Safari (mac os x).

However, I now understand the use of the sand box. (apologies for not before). So am doing all main edits on this page, until updating on main page. http://en.wikipedia.org/wiki/User:SSilverberg/Sandbox

Would appreciate a quick look to see if this is much more Wiki compatible.

Adding quotes and references for all statements whenever possible. Not easy to do when "evidence" is not quoted but is found easily on google searches.. which I'm hoping will be valid (to show widespread use of Celtic Tree of Life design and widespread publication of Jen's work..) How does one mention "best selling"?? Her Celtic Mandala Calendar has sold over 100,000 copies.. through her publisher Amber Lotus. How do we express that? And her images are extremely popular out in the world. And it sounds so commercial to say anyway. But if we must show notablity, we need to show popularity as well? Atlhough I think the article you said made it clear that was not altogether the point, but contribution.(I notice other artist pages mention popularity and don't give any sources etc.. Such as the Amy Brown page. and many others.) Jen's contribution is on such a grass roots level, its hard to get the wikipedia standard. But nonetheless, Jen's work has contributed in a big way to a style and spread of Celtic art in this country, starting when she did. But how to show or verify that? I respect and understand this need though.. just a challenge is all.

Well doing my best, and enjoying learning now that things are less emotionally conflicting.

any help and advice, please let me know. thanks again, Scott —Preceding unsigned comment added by SSilverberg (talk • contribs) 06:45, 13 August 2008 (UTC)


 * I think I now understand the problem of no EDIT button. The "main intro section" of any Wikipedia article never has an edit button!  I too find this frustrating, but I am getting used to it.  When you want to edit the "main intro section" it is necessary to select the edit this page tab for the whole article!  (You will see it at the top of the page, between the discussion tab and the new section tab.  It is only the headings listed in the Contents that have their own edit buttons.) Let me know if this helps.  Dolphin51 (talk) 06:56, 13 August 2008 (UTC)

Thanks Dolphin... I could not have worked that out.. even though that button was kind of obvious at the top of the page.. since it was different before. This is better though, because I had to edit each section individually before.. Its 3.34am, and another long night of referencing etc. I have added inline citations as you requested, even though I think it reads a bit strangely to do that rather than footnote references.. However, I found some that directly related to the "notability" topic. And more references and ISBN numbers etc. also someone has added something again, another user - so I'm not touching those. So 2 outside sources now (although how does the Wikipedia know I didn't add them??

The references are quite long at times, and has been quite complicated to construct. Please let me know if its getting close now. I need help at this point - All is uploaded to the Jen delyth page (not the sandbox anymore). thanks. scott SSilverberg (talk) 10:40, 13 August 2008 (UTC)
 * It's definitely looking better now. Good work.  To find out who has added what, and when, select the history tab at the top of the page (two tabs to the right of edit this page.)  It shows the entire history of the article.  It is now 10:30 pm here on the east coast of Australia and I'm off to bed.  Regards  Dolphin51 (talk) 12:30, 13 August 2008 (UTC)

Thanks.. I'm glad its starting to look more editorial. I can see why it was not ok in the beginning, although I did follow the example of other artist and musician pages on Wikipedia.. Nonetheless, I understand the need for references and so on, its been a good excercise. I have run out of things to add/change for now I think. So do I leave it alone? What is the process of asking for a review to keep the page? Didn't know you're in Australia. Wikipedia is amazing how everyone is all over the world. Best wishes, Scott —Preceding unsigned comment added by SSilverberg (talk • contribs) 00:01, 14 August 2008 (UTC)

Dolphin, I need your help/advise with RHaworth's posting of the "conflict of interest" tag. I have responded on the Jen delyth talk page. []. Please advise..

thanks, ScottSSilverberg (talk) 19:30, 14 August 2008 (UTC)

Dolphin, As you requested on my user page, I have responded to you on the Jen delyth page. and here..

(in response to comment on my user page..) Thanks Dolphin, I didn't see those comments (regarding making CTofL be main focus). Very helpful.. I'll get on with responding to them, although its worrying that all the work may be for nothing.. But keeping my fingers crossed, and either way have learned much of interest, and all will not be lost whatever the outcome. Thanks for your time, much appreciation across the world - ScottSSilverberg (talk) 00:16, 15 August 2008 (UTC) Scott SSilverberg (talk) 02:01, 15 August 2008 (UTC)

Just to say thanks again for your generous advice and support. I think I must let things go as they will now. I suppose it could take some time? much appreciation for some sanity in all this.. Scott —Preceding unsigned comment added by SSilverberg (talk • contribs) 00:07, 16 August 2008 (UTC)

Review & Status
Hello Dolphin. I would like to know what the process for review is, how long it could take to remove the tags on the page. Jen Delyth is a featured artist at a large upcoming conference, with a main stage presentation and featuring of her new work. The tags are not exactly positive. Can the page be taken down until the review is done? What is the procedure? thanks, Scott SSilverberg (talk) 03:36, 20 August 2008 (UTC)

Thanks again Dolphin for helping get this page appropriately edited and acceptable to Wikipedia. Could not have managed this without your support. And have learned how articles are written now, and what is considered a positive contribution. Thanks... Scott —Preceding unsigned comment added by SSilverberg (talk • contribs) 20:54, 3 September 2008 (UTC)

Bernoulli and lift #2
OK, much simpler thoughts this time.

Newton - A wing produces lift by applying a downwards force on the air, via a combination of forwards speed and effective angle of attack. This downward force results in a downwards acceleration of air, which responds with an equal and opposing force (Newton's 3rd law).

Bernoulli - The downwards acceleration of air results in an increase in kinetic energy of the air. Most (or almost all) of this increase in kinetic energy occurs via a Bernoulli like transition where the pressure energy is decreased by the increase in kinetic energy.

Wings are not 100% efficient, so there is drag, which occurs whenever a solid passes through a gas of fluid. I'm not interested that much in distinguishing between parasitic and induced drag, partly because induced drag has multiple definitions, and since parasitic drag can be reduced, but not eliminated. The efficiency is pretty good in the case of high end, 80 foot or more (some 100 foot) wingspan, gliders with glide ratios of 60:1 at around 60 knots.

My main question is about high force situations, such as a propellor or turbine (non-combustion, such as electric powered ducted fan turbines used on radio control models). The increase in kinetic energy in these situations is well beyond the total pressure energy of the air, negative pressure doesn't exist, so it would appear there has to be a very significant non-Bernoulli like transition in these cases. There's a huge increase in kinetic energy in the direction of "lift", which seems like a conflict because how can work be done if the force is perpendicular to the direction of travel? The answer seems to be that there is a force applied in the direction of travel, if you take into account the perpendicular component of distance from the leading edge to the trailing edge of the airfoil used, the sin of the angle of attack times chord length. The work done for lift would be the integral of the force over the perpendicular component of the distance from leading to trailing edge of the wing, propellor, or turbine, plus possibly some "effective" perpendicular distance due to coanda like or similar effects.

I assume that a wing is behaving in the same manner, the main difference being that a lot of the work done in the direction of lift is conversion from pressure energy into kinetic energy, until the speed and angle of attack reach a point where there's a significant increase in total energy, both pressure and kinetic. I assume that a wing under a high load factor, such as a 9 g turn in a F16, or a 40 g turn in a radio control model (like rc gliders dynamic soaring) would result in a significant increase in total energy of the air.

Assuming all of this is correct, then is there a way to "describe" when producing lift transitions from a mostly pressure to kinetic energy conversion into an overall increase in total energy of the air (a conversion of energy from the source of power for an aircraft)?

Jeffareid (talk) 13:48, 16 August 2008 (UTC)


 * Hi Jeff. You have asked some good questions that set me thinking.  It took me a while to be comfortable with my answers so I apologise for the delay in replying.

Total energy is constant along a streamline, but only providing there is no energy added from an external source. In the cases you mention - a propeller (or turbine), significant energy is added to the fluid as it flows through the disc of the propeller. As fluid ahead of the propeller accelerates towards the propeller its speed increases and its pressure decreases so that its total pressure remains constant in accordance with Bernoulli. As this fluid emerges out the downstream side of the propeller disc its speed is about the same as on the upstream side of the disc but its pressure has increased significantly and so has the total pressure. The pressure difference across the propeller disc is the source of the thrust generated by the propeller.

As the fluid flows away from the propeller disc its speed increases as the pressure falls towards atmospheric but total pressure remains constant at the value throughout the plume exiting the propeller disc. When the pressure falls to that of the surrounding atmosphere the plume exiting the propeller ceases to accelerate further. (The energy acquired by the plume as it flows through the propeller disc is ultimately dissipated by the action of viscosity and is manifest as a very small rise in temperature of the air.)

Bernoulli’s principle applies upstream of the propeller disc, and also downstream of the disc, but there is a significant increase in total pressure (ie total energy) as the fluid passes the propeller disc and acquires extra energy from the propeller. This is often explained using simple momentum theory. My favourite book is Aerodynamics (by L.J. Clancy) and it is explained in section 17.4 The Rankine-Froude Momentum Theory of Propulsion.

The lift on an airfoil is defined to be perpendicular to the vector representing the airfoil’s velocity relative to the stationary atmosphere, so lift does no work on the air although it does alter the direction of movement of the air close to the airfoil. (The change of direction of the air leads to the Newtonian explanation of lift.) However, in the case of a propeller (or turbine) it is as though there are multiple airfoils following one behind the other. Each blade is constantly moving through the downwash caused by the blade ahead of it.

As a wing approaches a parcel of air the parcel accelerates and rises to meet the wing (this is called the upwash, ahead of the wing). After the wing has passed, the parcel is decelerating downwards (this is downwash behind the wing, but not the full downwash caused by the trailing vortices) and eventually returns to the stationary state it had before the wing arrived. In the case of a propeller or turbine, there is not sufficient time or distance for the air to return to the stationary state before the next blade arrives. So each blade of a propeller or turbine is not meeting stationary air. Each blade is operating in air that is still moving “downwards” as a result of its interaction with the preceding blade. The lift force on each blade is perpendicular to the direction of flow of air past the blade, but that direction is different to the direction of the blade relative to the atmosphere remote from the blade. As a result, the lift on the blade does work on the air, and the kinetic energy of the blade increases as it passes through the propeller disc. (It is similar to lift generated by a three-dimensional airfoil. The trailing vortices cause an induced-component of angle of attack and the lift vector is rotated by an angle equal to the induced-component of angle of attack.  The lift does negative work on the air, resulting in what we call induced drag.)

I hope this helps. Cheers! Dolphin51 (talk) 03:02, 30 August 2008 (UTC)

Dolphin, Jeffareid writes:
 * "Newton - A wing produces lift by applying a downwards force on the air, via a combination of forwards speed and effective angle of attack."

My question is:

Doesn't only half the wing's surface produce an downwards force on the air, and doesn't the other half produce an upward force?


 * "This downward force results in a downwards acceleration of air, which responds with an equal and opposing force (Newton's 3rd law)."

My question: On the upper half the wing, isn't the force unsuccessfully opposing, rather than 'resulting in' the downwards acceleration of the air?

Mark.camp (talk) 23:11, 6 February 2009 (UTC)


 * Hi Mark. When a flat object, such as a book or sheet of metal or a wing, is stationary there is air pressure acting on the lower surface and an equal air pressure acting on the upper surface.  The result is that the force on the lower surface exactly matches the force on the upper surface.  The two forces cancel each other.  When this flat object is moving relative to the air, and is inclined to the air at some angle of attack, the air pressure on the lower surface is approximately equal to atmospheric pressure but the air pressure on the upper surface is significantly less than atmospheric pressure.  This occurs because the air is passing the upper surface at much faster speed than the speed of the air passing the lower surface.  (Why does this happen?  The answer is that this happens whenever the Kutta condition exists with a body with a sharp edge, such as the trailing edge of a wing.)  Where the air is moving faster than the speed of the atmosphere generally the air pressure is less than atmospheric pressure &mdash; Bernoulli's principle.


 * As the result of the above, the force on the upper surface is less than the force on the lower surface. There is a resultant force acting upwards on the wing because the force on the upper surface is not sufficient to cancel the force on the lower surface.


 * The atmosphere is exerting an upwards force on the wing, called aerodynamic force or lift. Newton's Third Law says that if body A exerts a force F on body B, then body B also exerts a force F on body A, but in the opposite direction.  Seeing the air is exerting an upwards force on the wing, the wing is exerting the same force on the air, but in a downwards direction.  As each parcel of air passes close to the wing it is affected momentarily by this downwards force. This causes the parcel of air to accerated downwards.


 * The downwards momentum gained by each parcel of air is exactly equal to the force acting on it, multiplied by the time for which that force acts.


 * Does this explanation help? If not, let me know what point you have reached and I will try to clarify further.  Happy editing.  Dolphin51 (talk) 11:25, 7 February 2009 (UTC)


 * I think so. Did I understand correctly that the answers to my questions, above, are "yes" and "yes"?   This talk page is great, thanks!
 * Mark.camp (talk) 21:55, 9 February 2009 (UTC)


 * Yes, the answers to your two questions are yes and yes. It is customary to think of lift as a single force acting on an airfoil as a result of the difference in air pressure acting on the upper and lower surfaces, but it is equally correct to think of the upwards force on the lower surface, and the downwards force on the upper surface.  The lower surface is the one that provides the downwards force on the air, causing the downwash immediately behind the airfoil.  Dolphin51 (talk) 05:09, 10 February 2009 (UTC)

Center of pressure
Dear Dolphin51 : Thank you for your comments. Is it possible to have a discussion outside this page ? What I need to discuss may not be quite relevant for this page. may I request you send me your e-mail address where i can communicate withyou direct. My e-mail addreess is cgibwn@gmail.com. After we communicate, if you think it is ok, we could shift the entire conversation here for the benefit of all. Thanking you, regards,CGI BWN (talk) 14:43, 17 August 2008 (UTC)

Dear Dolphin51 : Can you please explain what will happen if the CofG of an aircraft and its CofP were co-located by design ? There will be no nose up / down moments. Then what will be the function of the tailplane ? What would happend when the weight of an aircraft reduces due to consumption of fuel, external or internal stores carried in / on the aircarfat ? Or if the engine fails during flight ? Will the tail plane be able to control / stabilize the aircraft in level flight ?CGI BWN (talk) 07:20, 10 August 2008 (UTC)
 * As you correctly imply, it would be possible to design an aircraft, and load it, so that the weight and lift coincide at a particular airspeed, and there would be no nose up/down moment. However, if it is a conventional aircraft it would be longitudinally unstable.  If the airspeed increased a little, or the angle of attack decreased a little, the airspeed would continue increasing, or the angle of attack would continue decreasing, and without a tailplane the pilot would have no control to prevent the airspeed and angle of attack from "running away".  Similarly, if the airspeed decreased a little, or the angle of attack increased a little, they would "run away" and the pilot would have no way to stop that from happening.Tailless aircraft can be designed but they are not conventional.  They need to either have a swept wing (with the function of elevators carried out by moving surfaces near the wing tips) or have "reflex camber" (upside-down camber with the function of elevators carried out by moving surfaces at the trailing edge of the main wing.)
 * Also, be aware that the CofP on a cambered airfoil moves as angle of attack changes. See Movement of center of pressure.  With a conventionally cambered wing the CofP moves in a direction which causes longitudinal instability.  It is only with a reflex cambered wing that the CofP moves in a stabilising direction.  Let me know if this doesn't clarify your question.  Regards  Dolphin51 (talk) 07:18, 13 August 2008 (UTC)

Starting vortex
Hello. I noticed that you moved the Spanish text out to the talk page. Have you contacted the author Hazebrouck about transwikiing it to the Spanish Wiki? He seems best suited to insert it over there. Have a look at the entry at "Pages needing translation into English", we've been discussing the general matter over there. De728631 (talk) 20:01, 27 August 2008 (UTC)


 * Hi De728631! Yes.  Indirectly.  On 11 August I left a message on WP:Help desk asking for someone familiar with Spanish Wikipedia to arrange for the text to be made immediately available to Spanish readers; and to contact User:Hazebrouck (Talk) to explain how Spanish Wikipedia works.  User:PeaceNT responded on WP:HD saying he had listed the article at WP:Pages needing translation into English, and had also left a message on the Editor's Talk page.  If you check Hazebrouck's Talk page, you will see PeaceNT has welcomed Hazebrouck to Wikipedia, and also left a bi-lingual message for him/her about Starting vortex and Spanish Wikipedia. Cheers  Dolphin51 (talk) 23:33, 27 August 2008 (UTC)


 * Ah, right, I remember seeing that message on Hazebrouck's talk page - I was going to put it there myself. By the way, I also read your comment on Talk:Wingtip vortices. Now I see the difference between the two phenomena, merging wouldn't help here. De728631 (talk) 23:42, 27 August 2008 (UTC)

Bernoulli and lift #3
Thanks for the previous response, continuing from #2, I think I have an idea here:

"The lift force on each blade is perpendicular to the direction of flow of air past the blade". Wings and propellors do have an effective angle of attack, so there is a direct mechanical force applied to the air by a wing or propellor over a small perpendicular component of distance, approximately the sin(angle of attack) times chord distance, so although the force is perpendicular to the direction of the overall wing, it's not perpendicular to the direction of the surface of the wing, so a significant amount of work can be done in the direction of "lift". A wing or propellor is literally pushing the air (via collisions with the surface), on the downflow surface. On the upflow side, it's possible that Coanada like effect could allow for some mechanical interaction via friction and viscosity, but most of this is the production of a low pressure area which accelerates air in a Bernoulli like fashion (conversion of pressure energy into kinetic energy with virtually no increase in total energy). On the upflow side of an airfoil, the pressure energy can't be reduced below zero, but on the downflow side, there's no such limiting factor.

Even in the case of a wing, a very high g-force turn or loop could probably create a similar situation where the total energy increase of air is very large. I've read that radio control gliders pull about 40g's while dynamic soaring (link to video of a 333mph run 333mph dynamic soaring, a 357mph run done later that day. Last I read was the record was 365mph.

What started me thinking about this was reading that sound waves in the air are limited to about 190db. Above that, the pressure peaks are more than double atmospheric pressure, while the valleys can't be less than zero pressure, and these higher energy, imbalanced waves are shock waves. It's not possible to produce such waves without a non-Bernoulli like mechanical interaction, like a supersonic aircraft, or an explosion. A more common experience that triggered this in my mind is that prop wash is easily felt in comparason to any air flow in front of a prop (at a reasonably safe distance).

Jeffareid (talk) 06:03, 31 August 2008 (UTC)

Update - I found a reference regarding Bernoull's equation and propellers on a NASA web page:  ... but we cannot apply Bernoulli's equation across the propeller disk because the work performed by the engine violates an assumption used to derive the equation. from this NASA web page: Propeller_Thrust. The point here is that work is performed in a non-Bernoulli like manner across the propeller disk in the direction of thrust. I don't see why a wing shouldn't operate in the same way except that the amount of work peformed by a wing is usually less than the case of a propeller.

Also, somewhere along the line I confused a pressure differential of 1 psi with 1 atm. Some eletric ducted fans (turbines) get a bit over 1 psi jump, like a 120mm screw type propeller in a tube, generating 19 lbs of thrust across 17.5 in^2 of area. A F-16 has 77 lbs / ft^2 wing loading at 1 g, or .5347 psi and can pull 9 g's for about 4.8 psi of pressure differential.

Jeffareid (talk) 07:18, 5 September 2008 (UTC)

Balanced Flight
Dolphin51: I am not a pilot (but an aero engineer). While your physics seem to be correct, I do not enough about the pilot term for balanced flight to comment. I recently was traveling and read severl books on flying (for pilots). It seems that pilots must think of things in the steady-state. So my earlier comment about flight mechanics and the gliders might not be appropriate for a general audience. I spend most on my time thinking about things that are not in a steady condition. Skimaniac (talk) 13:42, 2 September 2008 (UTC)


 * Thanks for your note. Hmmm...interesting article. Let me find some references and see what they say! - Ahunt (talk) 12:24, 12 September 2008 (UTC)


 * Okay I think I succeeded in making it worse!! Talk:Balanced flight - Ahunt (talk) 14:40, 12 September 2008 (UTC)

Canard (aeronautics)
Nice work fixing up this article, including refs, it makes good sense now! - Ahunt (talk) 11:30, 12 September 2008 (UTC)

Turning flight stall
Hi there. The rework of the accelerated stall section makes sense to me, although I think the followings should be addressed: I'm happy to work on these points - when I have a minute - if there are no objections. Giuliopp (talk) 00:48, 7 October 2008 (UTC)
 * The section now doesn't even mention the term accelerated stall, while this is a common expression in aviation, albeit used to mean turning flight stall. John Brandon's website, after all, still presents the 'old' definition first (accelerated stall = stall at n > 1). In my opinion, the section heading should read Accelerated and turning flight stall and the text should explain the usage of both expressions, beside their rigorous definitions.
 * The sentence at the bottom, after "lift coefficient" is a bit unclear to me; I would reword and expand it, to make it clearer.
 * The notable example is best placed at the bottom of the section.


 * Hi Giuliopp. I have no objections to you working on the points you have raised. I will also have a look at the points to see if I can clarify.  Dolphin51 (talk) 01:08, 7 October 2008 (UTC)

Flight Dynamics
Hi Dolphin51. Yes I had put 'three axis control' as it is a term coined by the Wrights themselves. But basically I made the amendment because the article accurately describes the three axis' of which a fixed wing aircraft must be controlled. 'Three Axis Control' is somewhat of an archaic term but accurate and to the point of fixed wing aircraft controle.Im okay with the deletion as it may confuse people. So, you have it from me, it's okay. Thanks Koplimek (talk) 07:41, 16 October 2008 (UTC)

Bernoulli
Thanks for the help on the Bernoulli page I'll read over the Kutta conditions. It just feels like the explanations I've heard for lifts are snow jobs. When I think of things like aspirators I don't imagine the Bernoullie principle; I think of molecules being stripped out of an atmosphere and into the liquids flow. If this wasn't the case then an aspirator would quickly reach an equilibrium when attached to a closed container. I realize I'm probably missing something there... My point is thanks for suggestions at an appropriate level.--OMCV (talk) 05:00, 14 December 2008 (UTC)


 * Thanks for the acknowledgement. I'm pleased to be able to help.  Best regards.  Dolphin51 (talk) 09:15, 14 December 2008 (UTC)

Lift doing work
I am sometimes unclear on what is meant by statements about work done on "the air", or changes in momentum or energy of "the air", which speak of "the air" as if it were a single body with a single momentum, position, or energy, or of the wing as if every part of it were doing the same work or subject to the same pressure. Example, you wrote above "Consequently, lift does a small amount of work". (1) Does work on what body, what parcel? In which cases of a parcel undergoing a change in kinetic energy does the lift do work and in which does it not? For example, (2) a parcel in a lower streamtube moving from one place in front of the wing to another in front of the wing and increasing in kinetic energy as it becomes part of upwash? (3) A parcel moving over the high point of the wing, whose acceleration is down, but with that acceleration being opposed by the force from the wing? (4) A parcel above the wing which has no contact with the wing (does Newton's second law about two bodies exerting a direct force on each other also apply when the two bodies exert no direct force on each other?) (5) A parcel which was accelerated downward in the trailing vortex and is now moving vertically upward and thus accelerating laterally? Mark.camp (talk) 03:36, 13 January 2009 (UTC)

Hi Mark. Thanks for sending me your questions.

When a solid body is moving in a straight line, without rotating, it is easy to calculate, and visualise, its kinetic energy and momentum. Every gram (or ounce) of material in the body has the same kinetic energy and momentum. I agree it is not so easy with a fluid because, in most fluid flow situations of interest to us, every gram of fluid has a different kinetic energy and momentum.

It might make it easier to begin the transition from a solid body to a fluid by considering a solid body that rotates, such as the propeller on a stationary airplane. The kinetic energy and linear momentum of a gram of material at the outer tip of the propeller is very high. The kinetic energy and linear momentum of a gram of material at mid-radius is only half that at the tip. The kinetic energy and linear momentum of a gram of material at the center of the propeller is zero.

With a fluid, the kinetic energy and linear momentum are likely to vary around the flow field, not with a simple mathematical relationship like the various positions on a propeller, but in a more complex fashion.

With a solid body it is easy to see that the work performed on the body by the resultant force acting on the body exactly equals the change in kinetic energy (KE) of the body. (Positive work causes an increase in KE; and negative work causes a decrease.) With a fluid the same principle applies, but it is usually not possible to identify any boundary to the part of the fluid whose kinetic energy has changed – in one region of the fluid the KE changes significantly; surrounding that region is another region where the KE changes a smaller amount; surrounding that region is another region where the KE changes only a little; and surrounding that region is another region where the KE barely changes at all. When a propeller is generating significant thrust it is causing major increases in the KE of each gram of air close to the propeller. Several propeller diameters away the increase in KE of each gram of air is much less. Theoretically, the propeller is increasing the KE of each gram of air in the entire atmosphere!

User:Jeffareid wrote about the lift force doing work on the air. My view is that, when we are viewing an airplane in flight from the inertial reference frame attached to the atmosphere, lift never does work because it is, by definition, the component of the aerodynamic force perpendicular to the velocity of the airplane. (Work is only done by a force when that force has a component in the direction of movement. A force that is perpendicular to the displacement vector, such as a centripetal force, does no work and hence causes no change in kinetic energy.)  Seeing Jeffareid held the view that a lift force does work on the air, I conceded that lift can do a small amount of work. What I had in mind was that the induced drag is actually a component of lift. Induced drag certainly does work because it is parallel to the velocity vector. Therefore it is reasonable to say that the component of lift that is the induced drag does work. (However, it is simpler to avoid this complexity and say that lift never does any work when viewed from the inertial reference frame attached to the atmosphere.)

Drag does work on the atmosphere. Consider a stationary atmosphere, and an airplane flying from right to left. The drag force acts on the airplane, in a direction from left to right, retarding its motion. The reciprocal force (the equal and opposite force) is the force on the air, in a direction from right to left. This latter force on the air does positive work on the air and causes its KE to increase as some of the air begins to move from right to left. After the airplane has passed (and disappeared to the left) the wake remains, moving from right to left as though it is trying to follow the airplane. The work done on the air by the reciprocal of drag exactly equals the increase in KE of the air in the wake. There is KE in the wake, but the remainder of the atmosphere is unaffected by the passage of the airplane, and its KE remains zero.

The reason the air moves through a complex path around an airfoil – such as first moving upwards in the upwash, then in a circular path around the nose of an airfoil, then downwards in the downwash, is all caused by the varying pressure around the airfoil. Air near the nose of the airfoil is strongly influenced by the pressure gradient near the nose, but much less influenced by the pressure further away near other parts of the airfoil. Similarly, air near the trailing edge of the airfoil is strongly influenced by the pressure gradient near the trailing edge but much less influenced by the pressure near the nose. The vector sum of all these small pressure forces on the airfoil is the aerodynamic force on the airfoil. Lift is the component of aerodynamic force perpendicular to the velocity vector, and drag is the component parallel to the velocity vector.

Finally, some ideas on the important question of the reference frame. When thinking about aviation there are three obvious reference frames.
 * Firstly, there is the reference frame attached to the atmosphere. In this reference frame the velocity of an airplane is its true airspeed, and the velocity of the atmosphere is generally zero.  In this reference frame, lift does no work.
 * Secondly, there is the reference frame attached to the earth. In this reference frame the velocity of an airplane is its ground speed, and the speed of the atmosphere is the wind speed.  In this reference frame lift does work on the airplane (and the reciprocal of lift does work on the atmosphere.)  The work done by the horizontal component of lift on the airplane in a turn is what causes the ground speed to increase when turning downwind, and the ground speed to decrease when turning upwind.
 * Thirdly, there is the reference frame attached to an airplane in the special case of straight flight at constant speed V. In this reference frame the velocity of an airplane is zero, and the velocity of the atmosphere is generally V.  (The earth below is also moving at velocity V.)  In this reference frame, lift also does no work because the displacement (and velocity) of the airplane is zero.

I have rambled quite a bit here, and I probably haven’t answered all your questions. Don’t hesitate to ask some more and I will try my best to give a satisfactory answer. Dolphin51 (talk) 00:20, 14 January 2009 (UTC)


 * Not rambling at all--I appreciate the time and ideas shared.


 * You mention that each volume of air has its own physical state, rather than "the air" having a single physical state (momentum, energy, velocity, pressure).  One conclusion I draw from that is that one must be careful when making a statement about the physical state (momentum, pressure, velocity, energy) of "the air", or of "work done by the air" or "work done on the air".  One must  specify exactly WHICH body of air is being referred to.  Otherwise, the statement is meaningless.


 * Correct?


 * Mark.camp (talk) 16:05, 10 February 2009 (UTC)


 * Correct. Fluid flow is similar to the rotating propeller &mdash; each gram of material is likely to have a slightly different velocity to its neighbours so its KE and momentum will be different to those of its neighbours.


 * Consider an airfoil moving at speed V through a stationary atmosphere. At most points in the atmosphere the velocity is zero so each gram's KE and momentum is also zero.  Close to the airfoil the air is moving at some non-zero speed.  Close to the leading edge on the upper surface of the airfoil the air could be moving at twice V or faster.  As the airfoil passes and disappears into the distance the KE and momentum of the affected air falls close to zero, except in the wake where there is residual KE as a result of the work done by the drag force.  The KE in the wake eventually returns to zero as the result of viscous forces.  Dolphin51 (talk) 22:36, 10 February 2009 (UTC)


 * Jeffareid wrote about the lift force doing work on the air. My view is that, when we are viewing an airplane in flight from the inertial reference frame attached to the atmosphere, lift never does work because it is, by definition, the component of the aerodynamic force perpendicular to the velocity of the airplane. Even though lift is perpendicular to the direction of an aircraft, it's not perpendicular to the surfaces of the wings which have an effective angle of attack and divert the air downwards. There is a non-zero vertical component of distance that the surfaces of a wing (both upper and lower) interact with the air. It would seem that the work done would equal lift times this non-zero component of distance. Using the air as a frame of reference, after an aircraft flies through a volume of air, most of the resultant air flow is downwards, corresponding to lift, and some forwards, corresponding to drag. Note that the downwards force applied by gravity onto the aircraft, and from the aircraft onto the air, is eventually transmitted through the air onto the surface of the earth (spread out over a much larger area), which "reacts" with an equal and opposing upwards force. The downforce of the atmosphere onto the the earths surface includes the weight of the air and any object that the air is supporting (after taking into account vertical components of acceleration). Without getting into how it happens, a wing works because it diverts (accelerates) the air downwards (lift), at the cost of diverting some air forwards (drag). Jeffareid (talk) 11:12, 16 February 2009 (UTC)

Transparent materials
Dear Dolphin51:

I recently submitted a new article on "Transparent Materials". While I was in the process of edting it, I was interrupted by an Editing Conflict which redirected my page to the page entitled "Transparency (optics)". I wasn't sure what to do, so I copied the majority of my material on light transmission over to the page "Transparency (optics)" where it is now firmly in place.

My concern is for the material on light transmission in glasses and ceramics which was also on the original page. It has apprently disappeared altogether (?) I would like to know how to retrieve that information for the purpose of building a new page on Transparent Ceramics.

Please advise...and thanks for your time and energy !

logger9 (talk) 20:08, 20 January 2009 (UTC)


 * Hi Logger9. I see your predicament, and I sympathise.  While you were editing "Transparent Materials", RHaworth created a Re-direct to Transparency (optics) so that Transparent Materials is effectively no longer an active article in Wikipedia.


 * Fortunately, nothing is ever lost from Wikipedia (unless the article is deleted. Transparent Materials has only been re-directed, not deleted.)  If you select "Transparent Materials" you will be re-directed to Transparency (optics); however, two lines below the heading Transparency (optics) you will see, in small print, Redirected from Transparent Materials.  If you click on the blue link saying Transparent Materials you will be taken to that article (which now consists of nothing more than the re-direction.)  But if you then click on the History tab you will see the historical evolution of Transparent Materials,  right from your first save up to RHaworth's creation of the re-direct.  By clicking on the date on your last save you will see your text as you last remember it.  You can then select the Edit tab, copy what you want, and paste it wherever you want.


 * Common courtesy dictates that RHaworth should have contacted you to explain why he re-directed Transparent Materials, thereby effectively rendering all your good work invisible, except with the ingenuity described above.


 * Please don't hesitate to contact me again if you run into further problems. Happy editing!  Dolphin51 (talk) 22:13, 20 January 2009 (UTC)
 * My apologies. The article screamed "student essay" at me so loudly that I did not bother to explain. I have now done so at Talk:Transparent materials. &mdash; RHaworth (Talk | contribs) 03:04, 21 January 2009 (UTC)

Invite to Canberra Meetup #2
--.../Nemo (talk • Contributions) 14:28, 22 January 2009 (UTC)

_

Bernoulli "demonstration", straw versus static port
I've found several examples of Bernoulli princicple being "demonstrated" by having a stream of air blow across the top of straw with the other end drawing up water from glass implying that the pressure in the stream of air is below ambient.

Realizing that aircraft use static ports to sense the pressure of moving air, I decided to create my own static port using by inserting the end of the straw through a spool of thread and attaching it to a piece of carboard. Links to pictures of my "static port":

static_port_1.jpg

static_port_2.jpg

If the breeze is strong, then you'd want to cut down the size of the cardboard, or use wood. However at this point, note that real static ports can be purchased for less than $20 (USA):

static_ports.htm

I then repeated the pressure measurement test using a blow dryer and a straw in water. With just the straw, the water rises indicating lower pressure in the straw. With the static port there was virtually no movment of the water.

I then noted a surface tension and friction effect was resisting vertical movement within the straw, so I mixed in a small amount of liquid soap into the water. This changed the surface within the straw from convex to concave, and for some reason raised the water a slight amount (capillary like effect?). Retesting with the "static port" the water receded a small amount, indicating a slighly higher than ambient pressure in the output stream of the blow dryer.

The blow dryer source is also problematic, because it has a tapered nozzle, acting as a venturi to cause a Bernoulli type exchange of speed for pressure.

If the nozzle wasn't tapered, then the wash from the fan would have higher than ambient pressure, unless there is some special design of fan or propeller that reduces pressure fore of the prop more than than it increases pressure across the prop disc. This Nasa link explains what I'm getting at (prop increases pressure, air continues to accelerate after the prop as it's pressure returns to ambient):

propeller_analysis.htm

I'm not sure what is going on with the exposed end of the straw in a stream other than it interferes with the stream while the static port doesn't (apparently it's "hiding" in the boundary layer of air near the surface around the port). It's how the exposed end of the straw inteferes with the stream that has me puzzled, does it generate a vortice with corresponding low pressure? Jeffareid (talk) 04:11, 26 January 2009 (UTC)


 * Hi Jeff. I will be very interested to look at your web sites in the next day or two.  The experiment with the drinking straw is an interesting one.  If you blow a plume of air close to the straw, but far enough away so that the end of the straw doesn't interfere with the plume, you will find the water is not drawn upwards, indicating the pressure in the straw is not affected.  But if you blow the plume at the end of the straw so that the straw interferes with the plume, the plume must flow around the end of the straw.  In curving around the top of the straw the plume of air follows a path that represents a segment of a vortex.  (With any vortex, pressure decreases towards the center of rotation, and where the pressure is lowest velocity must be highest, in accordance with Bernoulli's principle.)  The outside of the vortex is exposed to the atmosphere so the air at the outside is at atmospheric pressure.  The inside of the vortex is only exposed to the interior of the straw and its pressure is lower than atmospheric because its speed is faster than the outside of the vortex.


 * A similar phenomenon can be seen on a much, much larger scale, with the tropical cyclone. Towards the center of the cyclone the air speed increases progressively and the pressure falls progressively, in accordance with Bernoulli's principle.  A tropical cyclone is an atmospheric vortex on a giant scale.  Dolphin51 (talk) 11:28, 26 January 2009 (UTC)


 * I thought it might be related to vortex generation, but I wasn't sure. I will be very interested to look at your web sites in the next day or two. - My links are just to two pictures (1 jpeg image per link). The prop analysis site is a single NASA educational web page, with fairly simple explanation of prop wash. My issue is that I've seen "vertical straw (or tube) in a horizontal flow" used at a lot of web sites explaining Bernoulli, implying it was the horizontal speed, and not the vortex (or vortex like) interaction with the straw. Do a web search for "bernoulli water straw" and you get a lot of hit's about Bernoulli atomizer. Jeffareid (talk) 14:18, 26 January 2009 (UTC)


 * Thanks for the photographs, and the link to the two web sites. The standard static ports regularly used on aircraft are flush with the surface of the fuselage.  If the static port consisted of a hollow tube, perpendicular to the surface of the fuselage, ending about 1 inch (2.54 cm) above the surface it would make an interesting experiment.  This arrangement would set up a segment of an elementary vortex over the end of the hollow tube, and lead to a pressure in the static system that is lower than the pressure of the freestream.  I think the altimeter would over-read the altitude of the aircraft; and over-read the indicated airspeed.  Dolphin51 (talk) 01:57, 27 January 2009 (UTC)

Much Appreciated
Dear Dolphin51,

Thanks mate. Of all the Gin Joints in all the places... who should i meet but a fellow Aussie! I wholeheartedly agree with your intro and truly believe there is more to what's going on here at Wiki than meets the eye. It truly is a brave new world now that the shackles to knowledge have been so thoroughly loosened at last. Knowledge needs to be free if the human race is to reach it's full potential, i believe.

Thanks for all the advise and your kind offer re Wikipedia usage also. I will look it up post haste and familiarize myself better with Wiki protocol.

Will stay in touch and let you know if my 'thought experiment' goes anywhere interesting.

TTFN, Walt

Outofthewoods (talk) 22:25, 26 January 2009 (UTC)

New Article Advice
Thanks for your contributions --Bl00513 (talk) 03:24, 29 January 2009 (UTC)
 * I've just submitted my first article Hopeulikit, Georgia. Please review my article and point out anything you think I should improve upon. Thanks!!!
 * I noticed that you took a look at my article and made a few changes that were much needed. Thanks Alot for your time and assistance.
 * I did not realize my spelling was as bad as it was. Again, thanks for your help!!!
 * I've improved upon my article's notability(in my opinion). Please let me know if there is anything you would like to differently as I would really like to ensure the article is not deleted.

Welcome!
Thanks for the welcome. keeping to jets etc. ghostshipred is a craft much slower to what I'm use to. Lack of thrust!--GhostShipRed (talk) 12:11, 1 February 2009 (UTC)