Talk:Angle of attack

message: 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)
replies: text: Those are some pretty significant changes. I can't judge the accuracy and/or appropriateness because of my lack of knowledge in this field. Enigmamsg 20:05, 11 March 2009 (UTC)
thread_title:  AOA is more of a geometric idea 

message: 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)
thread_title:  Support the weight? 

message: 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)
thread_title:  Suggestion 

message: 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)
replies: text: 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)
thread_title:  defining the formula terms.... 

message: 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)
thread_title: British usage

message: 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)
replies: text: This looks like petulance.  See my comments immediately above. Dolphin51 (talk) 22:41, 1 October 2009 (UTC)
thread_title:  Removed uncited sections 

message: 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)
replies: text: 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)
thread_title: Simple non-technical explanation?

message: 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)
replies: text: 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)

text: 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)
replies: text: 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)
thread_title:  Mushing flight 

message: 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 , 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)
replies: text: 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)
replies: text: 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)
thread_title:  Can Somebody Provide a More "Typical" lift-curve slope ? 

message: 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)
replies: text: 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)
thread_title:  Sailing