Talk:Dihedral (aeronautics)

message: Guys, I'm adding the cleanup tag because the explanation of the stability effect in this article is simply wrong.  It's not about the amount of aerodynamic force, it's the direction that matters.  When an aircraft with dihedral rolls, the wing that's closer to horizontal will generate the same lift as the other wing, but the lift vector is closer to vertical, opposing gravity more directly than that of the other wing.  It's not related to the angle of attack, or any sideslip.  The stabilizing effect is there as soon as the wingtips aren't at the same height relative to the horizon.   I'll come up with some corrected diagrams and fix the text as well.
:Sorry, but you are simply wrong. Any authoritive book on the subject will use the sideslip/AoA explanation, and be at great pains to point out that the explanation you're proposing is incorrect. Dihedral in itself doesn't change the lift vector angle from being exactly vertical. Also, you have not signed your comment. I will remove the cleanup tag - feel free to discuss this further if you wish, but please refer to a decent textbook on the topic before making yourself look foolish. (One I recommend is "Mechanics of Flight" by A.C. Kermode, which is a very accessible and well respected textbook on the topic). Graham 11:29, 12 April 2006 (UTC)
replies: text: The difference in angle of attack due to sideslip causes a rolling moment which tends to roll the body to point the lift vector so as to oppose the sideslip. The fundamental purpose of dihedral is the cancellation of sideslip.  It is therefore nonsense to claim that sideslip has no effect. Dihedral does not control the inertial roll angle, but tends to keep the plane of incidence in the plane of symmetry of the aircraft,  Much of the above discussion confuses inertial roll with aerodynamic roll. In analysing the stability of aircraft, the reference point is taken as the centre of gravity, so that all gravitational moments are identically zero. Shifting the cg changes all the values of stability derivatives used in the analysis.  With stick fixed the lateral modes consist of roll subsidence, Dutch roll and spiral instability, and dihedral is important for the latter two. I suggest reading Arthur Babister's  Aircraft Dynamic Stability and Response. Elsever 1980, . Gordon Vigurs 19:50, 27 June 2006 (UTC)
thread_title:  Erroneous explanation of stability 

message: I removed the sentence about "cathedral" having the same derivation as "dihedral". Cathedral comes from the Latin word Cathedra for "chair", referring to the chair in which the bishop sits when presiding over the liturgy in his cathedral. The derivation has nothing to do with the structure of the ceiling. See Cathedral and Catholic Encyclopedia: CathedralSbreheny (talk) 04:42, 7 August 2008 (UTC)
thread_title:  Etymology of Cathedral 

message: This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:48, 10 November 2007 (UTC)
thread_title:  WikiProject class rating

message: This article muddles an important difference between Dihedral Angle and Dihedral Effect.
*References to fixed-wing aircraft geometry should always refer to Dihedral Angle.
*References to aircraft stability should always refer to Dihedral Effect.
*Dihedral Angle is the angle the wings meet (of course).
*Dihedral Effect is a rolling moment produced in proportion to sideslip angle.
Dihedral Effect is called "Dihedral Effect" because increasing Dihedral Angle increases the rolling moment produced by sideslip.
BUT!  A gazillion other things also change the rolling moment created by sideslip.  Such as:  Wing sweep, Vertical CG, height of sideforce-producing  surfaces like fins, fuselages, etc., etc.
Such things should be made clear in the article.  I will set out to do that.
-- Gummer85 (talk) 03:57, 3 April 2009 (UTC)
thread_title:  Muddled!  :-) 

message: This article (but mostly the discussion) digresses too much toward Lateral-Directional Stability.  Dihedral Effect is a subset of Lateral-Directional Stability.
Perhaps a new article could be created for "Lateral-Directional Stability" if we really want to include the whole miasma.  That would be the proper place where everyone could post all their MAD THEORIES!  :-)
The article "Dihedral" should be kept and renamed "Dihedral (flight)" or something like that.  It should be small with a few pretty pictures of dihedral and anhedral like it already has.  It should have the distinction between angle and effect of course and the fact that effect is important for Lateral-Directional Stability which it refers to and be done with it!  :-)  
--Gummer85 (talk) 06:03, 3 April 2009 (UTC)
replies: text: << I've changed my mind on including a little L-D stability by discussing DE effect on Spiral Mode.  It's a little redundant w/ Spiral Mode, but material to the main subject.  And, now that it's discussion is correct, it doesn't scream "delete me!" to experts.  It's okay to keep now in my new (but not humble :-)) opinion. Gummer85 (talk) 16:40, 20 May 2009 (UTC)

text: Don't forget to cite your additions and changes from relialble souces. The article has none, so if you are able to cite some of the other items at the same time, that would be very helpful. - BillCJ (talk) 08:21, 3 April 2009 (UTC)
thread_title:  Not the place for Lateral-Directional Stability 

message: This is an explanation for Spiral Mode which is important, but it is a superset and it isn't dihedral anything.  However, it does contain within it "How Dihedral Angle creates Dihedral Effect" which is useful.  The section should be retitled "How Dihedral Angle creates Dihedral effect" and rejiggered to explain just only that.  I'll do that later if someone doesn't get to it first...
Also perhaps some other sections would be good like "How [fill in the blank] creates Dihedral Effect" for some of the other effectors (like wing sweep and all that other stuff).  Please help here!  :-)
--Gummer85 (talk) 06:55, 3 April 2009 (UTC)
thread_title:  "Simple Explanation" describes "Spiral Mode", not "Dihedral Effect" 

message: The explanation isn't referenced and isn't "common knowledge of experts".  It's also inconsistent with the fact that there is SO MUCH ANHEDRAL on the "horizontal" tail.  There is so much anhedral on the tail, it looks like a Viper from Battlestar Galactica!
The story I heard years ago was that they had to tip up the wing tips to provide wing clearance for landing on aircraft carriers (as the F-4 was originally to be both a Navy as well as Air Force airplane).  The increase in polyhedral angle has the same effect as an increase in Dihedral Angle.  That is, it increases Dihedral Effect.  The airplane then had too much Dihedral Effect.  To reduce it, they made Anhedral on the tail.
That's what I heard.  It's much more plausible than the explanation in the article, but I don't have a reference (yet).  The current entry really should be removed, but I don't want to "lose the space" and then forget to add the "correct" explanation after it is confirmed.
Also, I probably won't get around to confirming "my" story very soon.  Can someone else look into it?  (Is anyone out there? :-)  )
-- Gummer85 (talk) 18:36, 4 April 2009 (UTC)
thread_title:  Explanation for polyhedral on F-4 is wrong I think. (Nope, it's right.)

message: I plan on changing the name of this article pretty soon if there aren't any objections.  It'll take me a while to be sure anything that references it isn't broken, and to figure out exactly how to do that.
--Gummer85 (talk) 16:27, 20 May 2009 (UTC)
thread_title:  Change name to Dihedral (aircraft)? 

message: Hi Mike52,
I'm glad to see someone's actually watching and actually cares!  :-)  This whole time I've been essentially having a conversation with myself.  I reverted your edits though, for the reasons explained here.
Rolling moment caused by yaw rate is not Dihedral Effect, which by definition is Rolling moment due to Sideslip.  Rolling moment caused by yaw rate is actually a different Stability Derivative called, well, "Rolling moment due to yaw rate" (funny how that is).  These two ideas are very commonly mixed up.
The force couple (the difference in lift force on wings) is a moment as that is  the definition of a moment.  Moments and Couples are one and the same.  I initially wrote "produces" myself, then I realized it was the moment.  It's a small point, but more correct I think and makes it so we don't need to explain exactly how the couple produces the moment.  Hmmm, maybe I didn't need to italicise the is, (less teachy that way). (I've rejiggered and improved this sentence to be a little clearer I think.)
The differential drag under sideslip conditions you speak of is a contributor to yet another stability derivative (Cn-Beta) called "Yawing moment due to sideslip".  This is an important stability derivative which is also called "directional stability", but it is unrelated to Dihedral Effect except how they both contribute (in their own different ways) to the stability of the spiral mode.
The geometric definition of "dihedral" is covered elsewhere in wikipedia.  The disambiguation note at the top points to the geometric definition.  It would be good though to rename the article "Dihedral (aircraft)" to make it more clear.
--Gummer85 (talk) 15:50, 27 May 2009 (UTC)
thread_title:  Why I reverted changes by Miket52 

message: I added a "Common Confusions" section.  I see these misunderstandings all the time in my pilot world and even among flight instructors and other near-experts.  I thought it would be good to head them off at the pass.
--Gummer85 (talk) 16:49, 27 May 2009 (UTC)
thread_title: "Common Confusion" section added

message: I changed the name from "Dihedral" to "Dihedral (aircraft)" and properly rewired the references and redirections.  All non-specific references go to Dihedral (disambiguation) whereas before they went here.  This is to help people see that there is more on dihedral than this page and to help direct them to the most suitable location for their particular POV on dihedral (be it geometric, aircraft, etc.)
--Gummer85 (talk) 18:26, 27 May 2009 (UTC)
replies: text: At my tagged request, an admin has moved Dihedral (disambiguation) to Dihedral, since there is now no need to disambiguate the DAB page's title. Please take this into considertation when you move an article from the primary topic to a DABbed title. In this case, an admin had to perform the move, since the original title was moved elsewhere. (This is a housekeeping role for admins, not because of something done wrong.) - BillCJ (talk) 22:24, 5 June 2009 (UTC)
replies: text: Cool.  :-)  --Gummer85 (talk) 03:58, 8 June 2009 (UTC)
thread_title:  Article name changed from "Dihedral" to "Dihedral (aircraft)" 

message: Hi, 
Please don't think I'm possessive about this page.  I thank you for your comments about admin actions for the name change.  Also, I did indeed wonder what to do regarding capitalizing "Angle" and "Effect" and other editorial things like that.  I gratefully seek guidance and improvement in that regard.  There were some important changes in meaning you made that would have been better discussed here before making them.  I reverted because that is the best way to correct them with no fuss nor muss.
In the last few months, I made changes and corrections to this article and explained every major change along the way here on this discussion page (and in detailed 255-character Edit Summaries).  It was a discussion with myself, no one seemed to be responding so I had no choice but to see the changes as "acceptable" and "good".  I am an aeronautical engineer and the changes are correct.  The distinction between Dihedral Angle and Dihedral Effect is important and often confused.  The main citation given (Roskam) is a well known reliable source and it verifies my explanations.  I know people always like to see more citations.  I can and will easily include some.  However, the Roskam citation does indeed cover the corrections I made.  In my opinion, it is quite adequate to justify the removal of the refimprove tag (although, I recognize that these questions are judgement calls).
In the future, I would love to discuss proposed major technical changes here before risking introduction of technical errors.  I'm up for "explanatory" improvements too.  My technical explanations are, I think, usually much better than those made by other technically-oriented people, but it sure does help to have a layperson's point of view to spot possible confusions that we don't see because things are just too "obvious" to us.  :-)
Gummer85 (talk) 03:38, 8 June 2009 (UTC)
replies: text: Unfortunately, I found the article was somewhat confusing and inaccesible to an average reader with no engineering background. (Style issues aside - a reading of the Manual of Style might help with the basics on that.) However, I am fairly well-read in the aviation field in general, and usually the term "dihedral" is used to mean "dihedral angle," as far as I can tell, and that is what I was trying to make clear. Probably the best thing to do is to raise the issue at the WP Aircraft Project talk page, and get some broader input from other editors with more of a aviation/aeropace backgraound than I have. (There are several such editors active in the project.) They may have some solutions neither one of us have thought of, and was to make the article more clear without being confusing too (something my edits probably did not help.) - BillCJ (talk) 17:07, 8 June 2009 (UTC)
replies: text: Neat.  I've added the WP Aircraft Project talk page to my watch list.  :-)   -- Gummer85 (talk) 05:19, 9 June 2009 (UTC)
thread_title:  Why I reverted edits by BillCJ 

message: Should this be noted in the article?
69.250.53.240 (talk) 07:17, 11 July 2009 (UTC)
thread_title:  Isn't longitudinal dihedral more commonly referred to as decalage? 

message: This article uses the term "polyhedral" to describe what is elsewhere (e.g. here) called a cranked wing. Is there any precedent for that, and if so then which should we standardise on? — Cheers, Steelpillow (Talk) 20:48, 16 April 2012 (UTC)
thread_title:  Polyhedral or cranked? 

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thread_title:  External links modified 

message: Reading this article was like having someone wave their finger at me and tell me how wrong I am about everything. I came here to learn about this stuff, not to be lectured. What's worse, some of these explanations of the stability imparted by a positive dihedral contradict what I have read in textbooks by reputable publishers (e.g., Jeppesen Sanderson), yet these strongly worded and condescending explanations (contradictions) are not sourced. I came to learn about anhedral wings, and I got what I came for, but I could have done without the lecture. Dcs002 (talk) 06:29, 18 October 2019 (UTC)
replies: text: Sorry, man.  The truth is that info in pilot publications about the technicalities of aero engineering is often very wrong.  Often maddeningly so for me I would say.  You probably aren't wrong about everything, but about some things if you think Jeppesen is a reliable source for this kind of information.  Check out the sources in the ref list.  They're extremely well relied on by engineers -- and by you when you fly in a plane designed by those engineers.  The article does lack specific inline citations, but the refs it's based on are solid.  Usualzukor (talk) 01:10, 28 May 2020 (UTC)
replies: text: Referencing aside, this page is written more like a lecture than an encyclopaedia. GraemeLeggett (talk) 07:12, 28 May 2020 (UTC)
thread_title:  I feel like I've been scolded