Talk:Angle of attack/Archive 1

Archive 1

AOA is more of a geometric idea

AOA is a geometric parameter. It has large effects on how fluid flows around a body, that's why it's important. But it's fundamentally geometry. It gets trickier in 3D when a reference frame needs to be defined rather than just a reference line (and Beta gets into the mix as well).

AOA is a geometric idea. All else is example or application or illustration of why it's important. I would like to add (or see added) better description of AOA geometrically and more examples other than so much mush about stalling of airfoils and wings. Stalling of airfoils is an important and fundamental example, but, there are lots more examples out there. The usefulness of AOA indication to STOL is a good example, as are the other examples near the bottom. I can think of other examples too like sideslip of a boat, local flows around smaller parts like propellers. Hmmm... Helicopters have AOA for the individual sections of the rotor blades AND an AOA for the whole machine as it moves through the air. Swimmers have an intuitive sense of AOA as they move their flattened hand through the water and adjust its angle for maximum "lift" or pull. I'm just brainstorming to myself here. I'll bet you-all have lots of great examples in addition to the tired old stalled airplane.

Maybe the examples (including stalled airfoils) should all be under an "Examples" heading to show that they are NOT definitions of AOA.

I agreed with 68.48.226.95 (in the "Support the weight?" section) about his problem with the words that discussed the dynamics of an airplane in a stall. Not just because they are incorrect (which they are), but because they are even more off-topic than all the detail about wing stalls. I deleted them.

I'm guilty of contributing to the mush myself. I got caught up refining the details of just exactly how an airfoil/wing stalls. I'm so ashamed now.  :-)

Some potential opening words: "Angle of Attack is one parameter along with Angle of Sideslip describing how a body moving through a fluid is oriented to the angle the fluid is arriving at the body." -- Gummer85 (talk) 06:12, 11 March 2009 (UTC)

Those are some pretty significant changes. I can't judge the accuracy and/or appropriateness because of my lack of knowledge in this field. Enigma^msg 20:05, 11 March 2009 (UTC)

Yup. That's why I haven't made them (yet :-) ). I'm new and testing my "boldness". I didn't want to go that far because I don't know how I would be stepping on toes, making it just too abstract, etc. I want to let the idea(s) set for a while so it isn't too much of a shock to other editors of this article if I rewrite it a few months from now.

I am an AOA "expert" though (as if it's even that complicated - it's not). In two dimensions, it's really a piece of cake. In three dimensions, with zero Angle of Sideslip, it's still piece of cake. When sideslip is nonzero, AOA isn't as easy to define without another diagram showing AOA and Sideslip and the Body/Aircraft's axis system (I have a bunch of copyright-free axes diagrams that I could paste in).

So, if we want to define AOA fully, if we want a full and correct definition to be in scope for this article, then some number of paragraphs and a diagram or two would be needed to settle it. At that point we would have a significant body explaining what AOA is. You can see now perhaps how I see AOA as just a geometric thing and how describing it geometrically is (should be) the core of the article.

The second thing I see is that after the core is in place, The next thing to assert is the fact that AOA is important because it affects the fluid flow around and the forces on a body/airplane in important ways. Showing some of those ways is good (as is already done)

The last thing I see for it is listing of "AOA in action!"  :-) like the application to STOL, High AOA, etc.

I think that's a pretty good way to organize it. I don't see as much of a sense of organization as it is now.

-- Gummer85 (talk) 01:29, 14 March 2009 (UTC)

Support the weight?

I have a problem with this statement:

"At the critical angle of attack the wing is unable to support the weight of the aircraft, causing the aircraft to descend which, in turn, causes the angle of attack to increase further. This leads to stall of the aircraft."

1) The wing stalls, not the aircraft.

2) The wing can stall even if it is not supporting the weight of the aircraft (e.g., in a vertical climb or dive).

3) Even the Wikipedia article for "stall" talks about it in terms of flow separation. —Preceding unsigned comment added by 68.48.226.95 (talk) 1 December 2008

It is true that the dramatic separation of airflow that indicates the stall is separation of the flow over the wing rather than the flow over the fuselage. However, it is common to see the stall described in comments such as "at a weight of X kg the aircraft stalls at 60 knots" or "extending wing flaps will reduce the stall speed of the aircraft".

There is always separation near the trailing edge of any body moving in a fluid, including a wing moving through air. At low angles of attack the separation point on a wing may be only one centimetre ahead of the trailing edge. As the angle of attack increases the separation point moves ahead of the trailing edge towards the leading edge. At high angles of attack the separation point may be twenty centimetres ahead of the trailing edge but the aircraft is still flying level - the boundary layer and its accompanying airflow have separated from the wing near the trailing edge, but the aircraft has not stalled.

Stall of an aircraft occurs as the angle of attack passes its critical value. At angles of attack greater than the critical angle, any increase in angle causes a REDUCTION in lift coefficient. (Below the critical angle, any increase in angle causes an INCREASE in lift coefficient so the aircraft is able to continue in steady flight.) An aircraft cannot maintain steady flight at angles of attack above the critical angle - the aircraft stalls and, hopefully, pitches nosedown in a manner that quickly reduces the angle of attack.

When a wing is mounted in a wind tunnel it is possible to steadily increase its angle of attack and observe the flow pattern. It is possible to investigate the wing at angles of attack much higher than can be experienced in an aircraft in flight. In a wind tunnel, even though the airflow is mostly separated from the wing, the wing doesn't pitch down or fall - it is rigidly mounted in the tunnel. In contrast, an aircraft cannot fly steadily at an angle of attack greater than the angle for maximum lift coefficient (the critical angle). As the angle for maximum lift coefficient is exceeded the wing can no longer produce lift equal to the weight of the aircraft, and the aircraft falls or pitches down. It is this dynamic manoeuvre, the aircraft falling or pitching, which signifies the stall. A wing mounted in a wind tunnel does not display a sudden stall, although it does display a progressive forward movement of the separation point.

When the stall speed of an aircraft is to be determined, it is done by slowly decelerating until there is a sudden change of body angle or altitude. The stall speed is the speed at which the aircraft displays this sudden manoeuvre. The stall speed is not determined by attempting to assess the amount of separation of airflow over the wing, or by attempting to determine where the separation point occurs on the wing surface. Dolphin51 (talk) 02:18, 2 December 2008 (UTC)

Suggestion

This would make a lot more sense if somebody could say what u, v and w are, and Vt GRAHAMUK

Formulas clipped from main:

$\alpha \ =\tan ^{-1}\ \left({\frac {w}{u}}\right)$

Where $Vt={\sqrt {u^{2}+v^{2}+w^{2}}}$

The diagram says it all. Meggar 03:22, 2005 August 7 (UTC)

Well, not really. The diagram doesn't include u, w or v, nor Vt. However, you're right in the sense that the diagram is all you need, not really sure what the formulae are meant to add to the article. However, if they stay, they need fully explaining. Graham 08:23, 7 August 2005 (UTC)

defining the formula terms....

alpha = angle of attack

Vt = total aircraft velocity (magnitude of velocity vector of the aircraft)

u,v,w are the components of the aircraft's velocity that make up the Vt vector.

u is the velocity of the aircraft along its longitudinal axis, also known as the intertial x-axis, which runs from tail to nose in the positive direction

v is the velocity of the aircraft along its lateral axis, also known as the intertial y-axis, which runs from left wing to right wing in the positive direction

w is the velocity of the aircraft along its vertical axis, also known as the intertial z-axis, which runs from top of aircraft to belly in the positive direction

this axis system is fixed (intertial) to the aircraft, and its origin is usually near the aircraft's center of gravity

furthermore, the sideslip angle, greek letter Beta, may be calculated from.... beta = asin (v/Vt) but this probably deserves its own wiki page

Now that the terms are defined: The first formula gives alpha as already shown in the diagram but in rectangular coordinates. The second gives total velocity that has no place in this article at all. Maybe they will fit into some other future page that lays out the whole system. Meggar 21:04, 2005 August 12 (UTC)

I removed something about a record angle of attack of 123 degrees. Unreferenced and hard to believe, as the wing would be flying backwards at that point. DJ Clayworth (talk) 02:37, 18 June 2008 (UTC)

There have been recorded AOA > 90 deg indeed, typically based on dynamic effects. , so you are allowed to believe the claimed 123 deg, seriously. Would be nice if we could add this with proper references and maybe even some explanation how this high 195.176.0.55 (talk) 02:08, 30 October 2008 (UTC)

I like this idea! "How high is high?", the cobra stuff, thrust vectoring and the F-22 making very high AOA routine. A lot has changed in the last 20 years for AOA. High AOA has arrived! -- Gummer85 (talk) 02:05, 14 March 2009 (UTC)

Critical AOA (stall)

There was a statement in the text, claiming that stall always occurs at the very same AOA. This is incorrect:

a) Re dependence, e.g. at lower speeds, say vs the critical AOA would be lower than at high speeds (for most airfoils)

b) Turbulence dependence

c) Dynamic stall (generally dynamic effects, pitch)

d) HLD's (I am aware that this was not meant in this statement, implicitly. I just think then it should be explicitly stated.)

e) Effect of jet or propeller stream hitting the wing

etc.

These may easily be underestimated...

Now, I think the author of those lines just had a very limited set of circumstances in mind, as it may hold for a private pilot operating a Piper - as opposed to some more intricate thing as a high performance glider, fighter or experimental machine. Yet, even for the Piper pilot the differences are significant: the critical AOA at vs and engine off will significantly lower than at full speed and full power.

Just my two cents. contribs)

British usage

In traditional British usage, the term angle of incidence is used instead of angle of attack.

This is incorrect. In UK usage the angle of incidence is the rigged angle of the plane (wing or tailplane) as built-in by the designer - see the Armstrong Whitworth Whitley article for an aircraft with a wing with a designed high angle of incidence. Angle of attack is used in the normal usage, the angle at which the airflow meets the wing/flying surface. —Preceding unsigned comment added by 213.40.254.26 (talk) 11:55, 24 September 2009

Agreed, I have removed the unreferenced statement from the article. Nimbus (Cumulus nimbus floats by) 14:45, 24 September 2009 (UTC)

I disagree. I have two excellent books by British authors and both use the term angle of incidence in the way that many authors use angle of attack.

(g) The attitude of the aerofoil, as expressed by the angle between the chord line and the freestream velocity vector. This angle, denoted by alpha, is called the incidence, or angle of attack. L.J. Clancy (1975), Aerodynamics, Section 5.2, Pitman Publishing, ISBN 0 273 01120 0 (After acknowledging the equivalence of incidence and angle of attack, Clancy then uses incidence consistently throughout the book. Clancy was Head of the Department of Aerodynamics at RAF College Cranwell.)

The angle between the chord line of a given aerofoil section and the direction of flight or of the undisturbed stream is called the geometric angle of incidence, alpha. E.L. Houghton and P.W. Carpenter (1993), Aerodynamics for Engineering Students, Section 1.4.1, page 33, (4th edition), Butterworth-Heinemann, ISBN 0 340 54847 9

However, there is not a clear distinction based on which side of the Atlantic the author comes from. In Mechanics of Flight, (Chapter 3, 8th edition), A.C. Kermode writes:

We call the angle between the chord of the aerofoil and the direction of the airflow the angle of attack. This angle is often known as the angle of incidence; that term was avoided in early editions of this book because it was apt to be confused with the riggers’ angle of incidence, i.e. the angle between the chord of the aerofoil and some fixed datum line in the aeroplane. Now that aircraft are no longer “rigged” (in the old sense) there is no objection to the term angle of incidence; but by the same token there is no objection either to angle of attack, many pilots and others have become accustomed to it; it is almost universally used in America, and so we shall continue to use it in this edition.

In Wikipedia, Angle of incidence#Angle of incidence of fixed-wing aircraft concludes with the advice that The use of the term "angle of incidence" to refer to the angle of attack occurs chiefly in British usage.

Angle of incidence is still used in lieu of angle of attack by some authors, chiefly British, so my position is that it is important for Wikipedia to continue to acknowledge this use of the term incidence. I have restored the comment about angle of incidence, albeit re-worked from its most recent form. I have also added a citation of Kermode's comment. Dolphin51 (talk) 23:41, 24 September 2009 (UTC)

Removed citation tag

I removed the citation tag for the "Confusion between AOA and Pitch angle" section. There is essentially no new citable information introduced there except for the idea of Pitch Angle. Pitch angle is cited via a wikipedia link. It could be cited with an inline citation I suppose, especially since the the WP link is so weak. The idea that AOA and pitch angle both (usually) have the same reference line is new and I suppose reference-able. Although that's not the kind of fact that is stated explicitly in texts. It's just obvious. Also, the statement that they use the same reference can actually be removed and lay readers won't miss it, they might even assume it, and not being distracted, understand better. The fact that they are often confused isn't referenced. Is that what you want referenced? I suppose a "popular" text might mention that common confusion, but still, the "fact of the common confusion" seems silly to reference. So what about it needs referencing?

Part of the problem is that the wording of the that particular tag is threatening and bullying, I think, and I rankle at it. It makes me want to say "okay, if you're going to threaten to remove this material because you judge it to commit the heinous sin of insufficient inline citations then do it right now dag nabbit. Do it right now and you can put your money where your mouth is." Implied by the tag is that the article is better without the text than with the text, but no citations. IS IT REALLY? If it is, then make the article better right now by deleting the text right now.

It the wording of the tag wasn't so bullying, "unsourced material may be removed!", I might be more inclined to look for something. But, this is an example of the downside of rabid citationism. Text is made to look bad regardless of it's actual usefulness to the reader. And, yes, text is made to look incorrect regardless of its correctness.

I wrote the section because indeed lay people are often confused. You "demoted" the section because it wasn't cited. That's a bad reason. I don't mind the explanation being moved around if it's for a good reason, like fitting in with the flow, or being next to other similar things, etc. If you think the section doesn't do a good job explaining, that's fine with me, we can fix that. But, it's unproductive to sit up on one's high horse and add another bullying little tag. The awful wording of that tag sucks the joy out of making it better (including finding references!).

I'm not going to add references to this section. They're not needed. You can either add the references you want, or change it so it doesn't need them. While you're at it, improve the explanation if you think it could use it, I'd love to see another perspective on how to de-tangle the ideas for lay people. Really, my explanation is strained.

I suggest you don't just revert. I don't wrestle pigs, I won't edit war. But I'll quit, I'm tired. And, that'll be one more actual knowledgeable editor gone, chased away by rabid citationism. There will be even fewer to guard against the same constant renewal of entropy that took down so many "former featured articles" and continuously erodes at all articles. Soon enough, in the edit history, it will be difficult to see that I ever had anything to do with a now muddled, well-cited, mush of an article.

Gummer85 (talk) 07:04, 1 October 2009 (UTC)

Hi Gummer85. I see here a serious misunderstanding about the nature of Wikipedia. When you and I and everyone else contributes to Wikipedia our contribution will quickly be subjected to peer review. Others will look at what we have written. They may accept it and say nothing; they may edit it to improve it; or they may add Fact tags, Dubious tags, or Reference required tags. That is all legitimate, and part of what makes Wikipedia the encyclopedia it is. If someone is not willing to have his or her edits subjected to peer review that someone should write for some other document.

You wrote a paragraph about confusion between AoA and pitch angle. Good start. I added a banner saying some reference was required to support your paragraph. My addition was part of the peer review. Others are entitled to disagree with my banner, and remove it. Others, including you, are entitled to add references and in-line citations to make the paragraph more robust, intellectually. You wrote the paragraph so you are not entitled to remove the banner. Doing so indicates you are not willing for your contribution to be subjected to peer review.

I accept that you disagree with the current wording of the "unreferencedsection" banner. You are entitled to dislike it. The appropriate course of action is to raise your concern at one of the forums for discussing these banners. I suggest WP:Village pump. Your comments above suggest you believe I personally composed the wording of the "unreferencedsection" banner. That is not correct. That banner has been in use for a long time, has been inserted by thousands of editors, and read by millions of others. If you don't like it, raise your concern in a forum where something positive might come from it.

I see that not only have you deleted my "unreferencedsection" banner, you have deleted the whole paragraph. This raises another problem. When we make a contribution to Wikipedia, it then belongs to Wikipedia. It no longer belongs to us. Deleting a whole paragraph from Wikipedia without good reason is vandalism, even if you were the original editor of the paragraph. The paragraph doesn't belong to you. Please return to Angle of attack and restore the text, including my "unreferencedsection" banner. Others will decide whether the paragraph warrants being retained, amended, supported by in-line citations, or something else. You are welcome to participate in this improvement process in a constructive manner.

The reason I demoted two paragraphs from near the top of the article to near the bottom had nothing to do with their perceived quality or lack of supporting references. It was because, in my view, the technical content of those two paragraphs belonged, logically, further into the article than their original location. I accept that someone might disagree with my decision and move those two paragraphs higher up on the page. I will accept that as part of the peer review process and I won't revert it. I might argue about it on the Talk page, but I won't revert it. In the same way, when I moved your paragraphs lower down the article you should accept that as part of the peer review process. Feel free to argue about it on the Talk page but don't revert the change. Leave that to others. Dolphin51 (talk) 22:34, 1 October 2009 (UTC)

Removed uncited sections

I decided to put my money where Dolphin51's mouth is. I "challenged" and deleted the offending sections myself. Oh! I can see now! It's SO MUCH BETTER! Now the ever-misinterpreted, lowly regarded, yet somehow highly vaunted "verifiablility, not truth" inclusion criterion is satisfied! So encyclopedic! So professional!

Gummer85 (talk) 07:28, 1 October 2009 (UTC)

This looks like petulance. See my comments immediately above. Dolphin51 (talk) 22:41, 1 October 2009 (UTC)

Diagram is inadequate

As the article says, "The angle of attack can be simply described as the difference between where a wing is pointing and where it is going." The diagram implies that the angle of attack is the angle above horizontal that the wing is pointing. If the wing is moving horizontally, then the diagram is correct, but the diagram doesn't even show the direction the wing is moving. A better diagram would show the wing moving in a direction other than horizontal, and clearly display the angle of attack as as the difference between where a wing is pointing and where it is going. —Anomalocaris (talk) 04:37, 15 May 2012 (UTC)

The diagram was created by User:Theresa knott. Theresa is still active on Wikipedia so if you discuss this with her on her TALK page she might be willing to fix the problem. Dolphin (t) 06:11, 15 May 2012 (UTC)

The arrow in the diagram shows the direction of the air moving past a stationary wing (as it would in a wind tunnel). In real life it is the wing doing most of the movement but as far as the physics is concerned, it's the relative motion that matters. Burninthruthesky (talk) 10:41, 8 December 2012 (UTC)

I promptly left a message on Teresa's talk page. Nothing happened. It's been almost two years and the same wrong, misleading graphic remains.—Anomalocaris (talk) 10:00, 25 February 2014 (UTC)

I see Theresa has been inactive since May 2012, about the time of your request. I agree the diagram is misleading. I'm not able to manipulate the graphics but I can adjust the caption. I have changed it and hopefully it makes the whole diagram more accurate. See my diff. Dolphin (t) 12:20, 25 February 2014 (UTC)

The angle α is the angle of attack only if the wing is moving horizontally, not rising or falling. For this drawing, we need to say that the wing is moving horizontally, but even then the drawing is inadequate and needs to be replaced. —Anomalocaris (talk) 18:05, 25 February 2014 (UTC)

The article explains that the diagram represents the relative motion of air, which in this case is clearly flowing horizontally, past a stationary wing. The diagram is similar to ones given in the references (e.g. Langeweische, NASA).

Although I wouldn't object to replacing this graphic with one that shows the air approaching at a different angle, I don't feel it would improve the article. The diagram is correct and, I believe, adequate as it is. Burninthruthesky (talk) 22:13, 25 February 2014 (UTC)

I agree that the diagram makes some sense if we consider the airfoil is stationary relative to the earth's surface. I say this because the vector represents the velocity of the free stream, not the velocity of the airfoil.

If it was a diagram of a stationary atmosphere and a moving airfoil, the vector would point in the forward direction of a moving airfoil, and ideally it would be attached to the airfoil itself. Dolphin (t) 00:50, 26 February 2014 (UTC)

If the diagram was drawn with a stationary atmosphere, you couldn't show the streaklines being deflected as the wing accelerates the air in order to create lift. Burninthruthesky (talk) 08:12, 26 February 2014 (UTC)

Correct. But streaklines being deflected don't contribute to the concept of angle of attack. Dolphin (t) 11:06, 26 February 2014 (UTC)

The diagram illustrates the text, "Angle of attack is the angle between the body's reference line and the oncoming flow". The same diagram is used in the closely related topic of lift. Burninthruthesky (talk) 14:55, 26 February 2014 (UTC)

Someone comes across the terminology "angle of attack" and goes to Wikipedia. Either they read the explanation and don't understand it, so they look at the diagram, or they just look at the picture. They see a side view of an airplane wing and fuselage pointing upward at an angle labeled the angle of attack. The naive, logical, but incorrect understanding is, "Angle of attack is the angle that the airplane points to (the pitch angle)." The diagram at What is AOA , angle of attack? correctly shows the angle of attack as the difference between the pitch angle and the flight path angle. Streaklines are needed and appear in the diagram at Lift_(force)#Newton's laws: lift and the deflection of the flow. They are not needed here. The diagram should help someone understand the definition of angle of attack, not the whole science of aerodynamics and lift.—Anomalocaris (talk) 22:42, 26 February 2014 (UTC)

I completely agree the diagram should help someone understand the definition of angle of attack. The diagram linked above illustrates the relationship, in an aeroplane under certain conditions, between its pitch angle and angle of attack.

The diagram in the article illustrates the definition of angle of attack, "the angle between the body's reference line and the oncoming flow". This is is not limited to whole aeroplanes, or even wings. One or both of the directions in the diagram can vary at different cross-sections of the same aerofoil. This is essential to understanding AOA in other contexts such as Washout, Adverse yaw, and Propeller, for example. Burninthruthesky (talk) 13:45, 22 July 2014 (UTC)

Simple non-technical explanation?

The angle of attack is, by definition, the angle between the chord line and the relative wind. The article goes on to say, "or between the chord line and the flight path." That's only true in still air. Is this additional statement more likely to clarify or confuse?

I see several issues in the remainder of this section:

• "there will not be enough lift generated for flight" is incorrect.
• The fact stalls occur at different speeds is covered elsewhere in the article.
• The critical angle of attack is not exceeded simply, "because of gravity".
• Stall speed is generally determined from straight and level flight.
• It doesn't explain how "poor aircraft design" affects the stall.
• Gravity is not momentum.
• Accelerated stalls are covered in Stall_(flight)
• Momentum makes an object continue in a straight line, not "go down"
• Aircraft are quite capable of flying when the the wings are "pointing up but the direction of travel is down", without stalling.
• Standard stall recovery is to push the stick before applying power.
• In many aircraft, applying power will generate a nose-up force which can make things worse.
• I'm not aware of any stall recovery technique which involves only applying power.

Does this section add anything to what's already present?

Burninthruthesky (talk) 15:42, 7 December 2012 (UTC)

After removing questionable, uncited material there isn't much left. The definition of AOA is given in the article. Although the butterfly picture is pretty, the explanation in the caption is questionable and I'm not convinced it helps explain the topic. I propose deleting the section. Burninthruthesky (talk) 07:52, 8 December 2012 (UTC)

Mushing flight

On 17 Feb 2018 a new sub-section titled “Mushing Flight” was added - see the diff. Only one source was cited - Langeweische’s Stick and Rudder.

The content of this new sub-section is not technically sound and does not deserve to be published in any encyclopaedia. For example, the new text says control forces become soft and mushy at high angles of attack. It is true that control force gradients change during flight, but they increase with increasing speed, and decrease with decreasing speed. They don’t change with angle of attack! This article is about angle of attack; it isn’t about airspeed.

The handling qualities of an aircraft change with airspeed - usually proportionally to the square of the airspeed. In some aircraft they also change slightly with angle of attack. In sound technical explanations of handling qualities there is no suggestion of the sudden onset of a new regime called mushing flight that is related to angle of attack.

Langeweische’s book Stick and Rudder was written for trainee pilots and people who are new to the field of aviation. It is not an authoritative source of state-of-the-art information about fixed-wing aeronautics. My view is that Langeweische’s coverage of something he calls mushing flight doesn’t justify this topic being retained in Wikipedia. It should be removed. Dolphin (t) 13:54, 18 February 2018 (UTC)

There has been no response in a week so I erased the section titled "Mushing Flight" - see the diff. Dolphin (t) 00:26, 26 February 2018 (UTC)

No, airplane pilots do talk about that, even ones who fly for commercial carriers … — Preceding unsigned comment added by Ll1324 (talk • contribs) 04:59, 13 March 2018 (UTC)

The fact that pilots talk about mushing flight does not meet the criteria for inclusion in Wikipedia. Inclusion here requires that it can be verified in at least one reliable, published source. Langeweische’s “Stick And Rudder” doesn’t appear to be reliable on the matter of mushing flight. If Langeweische is saying control force gradients are directly related to angle of attack he is clearly in error because control force gradients in subsonic flight are directly related to equivalent airspeed. Dolphin (t) 22:40, 13 March 2018 (UTC)

Can Somebody Provide a More "Typical" lift-curve slope ?

The present lift-curve slope, described as "typical", is far from typical. Its maximum lift coefficient of 1.71 (unflapped) is considerably above the values used for design of present civil light aircraft, and might lead wanna-be desigers to make unjustifiable assumptions. FWIW, that data came from [1], which summarized the work of specialists to develop a specialized airfoil shape for a particular high-performance glider (sailplane). Can somebody cue in a copy of a NACA 2412, or 66-215, or similar? Please?--Spray787 (talk) 21:25, 8 July 2018 (UTC)

Good point. It's definitely not "typical" as stated in the caption (for the reasons you say). It would be worth fixing. It should be easy enough, give it a try. Alufergrbgtb78459 (talk) 17:40, 22 July 2018 (UTC)

Seeking the typical lift coefficient curve is as futile as seeking the typical human being. I have eliminated the word “typical” - it was unnecessary. Dolphin (t) 22:15, 17 September 2019 (UTC)

Sailing

I removed the following unsourced sentence:

A boat's angle of attack is the angle between the boat's course and the wind direction. See points of sail.

I've never seen it defined this way and a quick Google search didn't turn up anything. Most discussions of a boat's angle of attack concern the centerboard or daggerboard or keel, which are simply hydrofoils with their angle of attack defined conventionally, i.e. the angle between the oncoming fluid and the chord line. Note that the fluid in question is the water, not the wind. Not sure if it makes sense to add something about the centerboard and it's angle of attack here, so I'll leave it to another day. The rudder also has an angle of attack, which may or may not deserve a mention. The boat as a whole? Unless someone comes up with a reliable source we should leave that out. Mr. Swordfish (talk) 11:58, 1 June 2019 (UTC)

Thanks for making that removal. I agree with your explanation. Applying the expression angle of attack to the angle between the boat’s course and the wind vector was incompatible with the definition of angle of attack on an airfoil. Dolphin (t) 12:35, 1 June 2019 (UTC)