Talk:Three-surface aircraft

3 lifting surfaces ?

1. The common sense of lift is positive vertical lift (against the gravity).

2. if "lifting means positive vertical lift", the Avanti is not a three surfaces : the stabiliser is non lifting in cruise (AVL analysis).

3. if "lifting" means physical lift, the Avanti provides much more than three lifting surfaces : canard, fuselage (the fuselage lift is important), wing, aft low stabilizers, horizontal and vertical tail : 6 lifting surfaces. Engines fairings and props are lifting devices, too.

I think this is really about what to call the wing configuration comprising a central main wing with both forward and rear auxiliary surfaces. There was some discussion here, before one editor went on to create this article. I am not sure whether that person chose a good or bad name. — Cheers, Steelpillow (Talk) 21:29, 11 April 2013 (UTC)

Three surface

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: moved Tiggerjay (talk) 03:26, 23 April 2013 (UTC)

---

Three lifting surface aircraft → Three surface aircraft – Along researches for "canard/stabiliser", I looked for "three surface" designations.

1) Abzug/Larrabee (Airplane stability and control) gives "three surface case", "three surface configuration".

2) Roskam (Airplane Design) : "three-surface configuration".

3) Mason (Configuration aerodynamics) gives "Three surface concept".

4) Kendall, E.R.. The Aerodynamics of Three-Surface Airplanes, AIAA-84-2508

5) Owens, D. Bruce & Coe, Paul L., Jr. Exploratory Wind Tunnel Investigation of the Stability and Control Characteristics of a Three-Surface, Forward-Swept Wing Advanced Turboprop Model. AIAA-90-3074 August 1990

6) Agnew, J.W., and Lyerla, G.W., and Grafton, S.B. The Linear and Non-Linear Aerodynamics of Three-Surface Aircraft Concepts. AIAA-80-1581 October/November 1984

7) Strohmeyer, D., Seubert, R., Heinze, W., Osterheld, C., Fornasier, L. Three Surface Aircraft – A Concept for Future Transport Aircraft. AIAA-00-0566 January 2000

8) Agnew, J.W., Hess, J.R., Jr. Benefits of Aerodynamic Integration to the Three Surface Configuration. AIAA-79-1830 August 1979

9) Bill Husa, Orion Technologies, "Three surface design"

10) Chris Conrad, Elizabeth Craig, Matt Eluk "Three surface aircraft"

11) Ilan Kroo, Stanford, Design and Analysis of Optimally-Loaded Lifting Systems, "Three-surface designs"

12) Three surface aircraft - A Concept for future large aircraft [1]

13) Wichmann, G., Strohmeyer, D., Streit, Th. Investigation of a Three-Surface Airplane Configuration. Proceedings ODAS 99, 1st ONERA - DLR Aerospace Symposium, Paris, France, 21-24 June 1999

So, "Three surface" + aircraft (or airplane, configuration, design, concept) seems to be a general/basic designation, including "Three lifting surface", when the reciprocal is not true (because the tail is not a lifting (conventionally speaking) surface. Do you agree this article be renamed "Three surface aircraft" ? Plxdesi2 (talk) 13:56, 13 April 2013 (UTC)

I am happy for this change, but it is perhaps important enough to ask the wider editorship. [updated] For example others may prefer "three-surface aircraft" with a hyphen (I don't mind either way). I'll post notices on a couple of Project talk pages, in case anybody objects. — Cheers, Steelpillow (Talk) 14:18, 13 April 2013 (UTC)

• Support - simpler and seems well supported by the refs. - Ahunt (talk) 14:27, 13 April 2013 (UTC)
• Support I concur with Ahunt's assessment FOX 52 (talk) 18:13, 13 April 2013 (UTC)

• Comment this isn't a proper WP:RM request. -- 70.24.250.103 (talk) 05:49, 14 April 2013 (UTC)
  • Now it is. - The Bushranger _{One ping only} 06:43, 14 April 2013 (UTC)

I propose "Three-surface (aircraft)"; three-surface is the hearth of the expression, and (aircraft) in brackets because other names exist (design, concept, layout, configuration, airplane) and because one can say : "It is a three-surface", like "it is a canard", without telling "aircraft". Plxdesi2 (talk) 07:15, 15 April 2013 (UTC)

That fails both WP:COMMONNAME and WP:MOS. (brackets) indicate a disambiguation, not a clarification. - The Bushranger _{One ping only} 21:40, 16 April 2013 (UTC)

• Support per nom, WP:COMMONNAME and WP:COMMONSENSE. - The Bushranger _{One ping only} 21:40, 16 April 2013 (UTC)
• Support "Three-surface (aircraft)". I am happy to see articles related to static stability maturing like this... Ariadacapo (talk) 07:16, 17 April 2013 (UTC)
  • Three-surface (aircraft)" is inappropriate per the MOS standards for disambiguation. - The Bushranger _{One ping only} 05:29, 19 April 2013 (UTC)

• Support. One can make a case for other names, such as "Three-surface aircraft", or "Three-surface (aeronautics)" (after Canard (aeronautics)) but we have not been wholly consistent in the past so I wouldn't lose sleep over that argument. Removing "lifting" is more important. — Cheers, Steelpillow (Talk) 08:58, 17 April 2013 (UTC)
• Strong oppose. The operative word is "lifting". All aircraft have three surfaces – the fuselage, the wings, and the tail. Apteva (talk) 06:30, 21 April 2013 (UTC)

• Comment - consensus appears clear, requesting G6 to complete move. Tiggerjay (talk) 04:39, 22 April 2013 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Foreplane

"The aerodynamic function of the small forward wing on a three surface design is different than the small forward wing on a canard aircraft."

If the aerodynamic function is to provide lift, there is no difference. Difference is in secondary items, in pitch trim or control : there are flaps in lieu of elevators

"is not a canard, according to Piaggio Aero. It is, instead, a forward wing. The difference between the two, is that the forward wing, while a lifting surface, is not a controllable one. There is no “elevator” in it; hence, it’s not a canard."

Avanti is equipped with wing flaps, to be controlled, of course. The aircraft is not a canard (configuration), but the foreplane is commonly reffered to as a canard surface.

The foreplane of thh Saab Viggen IS controllable.

"The canard configuration has no rear surface but a small forward mounted wing: this is sometimes used to stabilize the aircraft".

A foreplane (forward of CG) is a balancing and always destabilizing surface.

Do you have authoritative reference that the foreplane is called a canard surface, even when referring to the 3-surface configuration?

1) Jan Roskam, Airplane Design, Part II, Unusual configurations, p. 85-87 Three surface configurations, Piaggio P-180 : "...by a geared flap on the canard (front wing). This canard flap is..."

2) Abzug-Larrabee, Airplane Stability and Control, Modern Canard configurations, "...if the configuration is actually a three-surface case : main wing, canard, and aft horizontal tail. Examples of three-surface configurations are the Piaggio P-180, the Sukhoi..."

3) Cambridge University Press, Aircraft Design, Stability considerations, Pitch plane, "Figure 12.9 (a P-180 Avanti view) shows the generalized forces and moments (including the canard) that act in the pitch plane."

4) H. Mason, Configuration Aerodynamics, Aircraft Configuration Design Options, Three-surface considerations, "Note that the X-29 should also be considered a three-surface configuration since it uses a flap at the end of what is known as the aft strake in the control system in addition to the canard." Plxdesi2 (talk) 10:09, 13 April 2013 (UTC)

5) Peter Garrison, Flying magazine dec 2002, p.86, "For the Avanti..., the division of upward lift between the canard and the wing...". Plxdesi2 (talk) 14:14, 13 April 2013 (UTC)

The article on the Saab 37 Viggen currently says that its canard foreplane is not controllable, but is fitted with landing flaps only. Do you have an authoritative reference which states otherwise?

The point about stabilisation is whether we consider the action of the surface in isolation or in conjunction with the main wing. If the lifting forewing is removed from a stable canard type and the craft re-trimmed, it will be unstable. In this circumstance the forewing is commonly called a "stabiliser" because that is the net outcome of adding it. This issue has in the past been very extensively discussed on other talk pages.

In all these things, remember that Wikipedia puts verifiability above truth. — Cheers, Steelpillow (Talk) 22:05, 11 April 2013 (UTC)

Copying this rationale, "If the lifting wing is removed from a stable conventional type and the craft re-trimmed, it will be unstable" : so the wing would be called a stabiliser too ? This "cutting area" rationale seems to me correct only about balance, not about stability. For a fixed CG, pitch stability increases with the tail area, and decreases with the foreplane area : the foreplane acting the opposite of the tail, how can we call it a stabiliser ?

According to top level aerodynamicist Mark Drela [2], MIT aero proffessor, the main wing of a canard aircraft IS the tail :

"A canard is really an extreme conventional configuration with the following features: 
1) a small highly-loaded wing
2) the c.g. WAY back, at 538% chord or whatever
3) a huge lifting tail to give enough stability with this extreme aft c.g."

A drawing telling the same (in every configuration, the Srear = tail) [3]. Plxdesi2 (talk) 12:05, 12 April 2013 (UTC)

Verifiability above truth. Sufficient references have been found describing a canard forewing as a "stabiliser", that we should accept this usage and if need be explain it. If you can find adequate references for a different usage, then by all means add it alongside.

In the quoted post from Mark Drela, he is evidently talking about lifting-canards and not control-canards, which are not "highly loaded"; on a forum post that probably doesn't matter, but it does illustrate why on Wikipedia we do not take such forum posts as authoritative. It is also tempting to paraphrase him:

"A conventional tail is really an extreme canard configuration with the following features: 
1) a foreplane which is so large that, even though moderately-loaded, it contributes most or all of the lift.
2) the c.g. WAY forward, at -538% chord or whatever
3) a pathetic little main wing which is all that is needed to give stability with this extreme forward c.g."

which I hope also illustrates how differing technical approaches can say the same thing in wildly different ways. — Cheers, Steelpillow (Talk) 14:14, 12 April 2013 (UTC)

About Drela phrase and your paraphrase : in both texts the stabiliser is the aft surface. I quoted this forum post because I do not remember the original source; I understand you do not consider Drela, MIT aerodynamic expert, as an authoritative person... oups (just have a look on his Fluids lectures [4]). I have to find the source ( this text is in Canard (aeronautics), without telling the source, only the author). Other quotes :

1) In AIR International may 1999, p.311 : Foreplanes foremost, "thus a tailplane, being aft of the CG is stabilising, a canard is highly destabilising."

2) In Hoerner and Borst, Fluid Dynamic Lift (THE aerodynamic reference book), page 11-29, about Curtiss XP-55 canard fighter : "Stability contributions : ...To balance this pitching moment at a certain lift coefficient the canard has to provide a positive (destabilising) moment. Stabilization in any canard configuration can thus only be obtained from the wing".

3) Same document, Page 11-33 Delta canard, "While the moment arm of the canard is found to be ..., the fact remains that this surface always contributes a destabilizing moment". (in italic in the text).

4) Nasa TM 88354, A look at handling qualities of canard configurations, p. 14, "...the canard carrying a geater unit load than the wing... to reduce its destabilizing effect;"

5) Piaggio P-180 Avanti US Patent : "As a matter of fact a lift surface placed in a front position has the same balancing ability as a conventional stabilizer in a rear position but its effects on the stability are reversed. While a lift surface rear placed has a stabilizing action, a lift surface placed ahead has a destabilizing action."Plxdesi2 (talk) 13:56, 15 April 2013 (UTC)

Where can I find your references describing a canard forewing as a stabiliser ? thanks, Cheers, Plxdesi2 (talk) 22:09, 12 April 2013 (UTC)

To clarify the status of Drela: when he writes authoritatively, e.g. in a peer-reviewed publication, then he is an authoritative reference, but when he writes informally, e.g. on a newsgroup, then he is not an authoritative reference. This should not stop us quoting his news posting if it helps clarify something, as his post reproduced above is (slightly mis-)quoted at Canard (aeronautics)#Lifting-canard.

For some references supporting the description of a lifting-canard as a "stabilizer", see Stabilizer (aircraft) references 1, 7 and 8 - cited in the section on the Canard foreplane.

— Cheers, Steelpillow (Talk) 10:16, 13 April 2013 (UTC)

Lifting-canard described as a "stabilizer" :

1) Garrison (paper in Flying) uses the word "stabilizer" 3 times and "canard " 18 times. The first use of "stabilizer" is to introduce the subject, with the same meaning as "tail first" : "The stabilizer in the front, how can that work ?". Then Garrisson explains the stabilizer is the wing, not the canard : "The role of the feathers of the arrow is now taken by the main wing rather than by the small auxilliary surface you think of as the stabilizer." The third and last time Garrisson uses "stabilizer" is to explain the fonction of a stabilizer, including a forward position without seing the opposition with the previous sentence (or probably using the term "stabilizer" with the meaning of secondary surface). Because of this contradiction, this quote is not valid to support the sentence : "But in some cases the foreplane acts with the other horizontal surfaces to provide longitudinal (or "pitch") stability, in which case it acts as a stabilizer."

2) Nasa ref 7 : "On the Wright brother's first aircraft, the horizontal stabilizer was placed in front of the wings." That is a historic designation, valid for pioneers time, not a physical aerodynamic comment.

3) Nasa ref 8 : "On some aircraft, the pitch stability and control is provided by a horizontal surface placed forward of the center of gravity (a tail in the front). This surface is called a canard." This sentence is false (the canard may provide lift and/or control only), but exists.

This only false but verifiable reference does not balance the 4 above true and verifiable quotes telling the opposite. I propose the wording as follows : "But in some (rare) cases the foreplane, probably by geometric (or apparent) symmetry with a conventional layout, is named a stabilizer." Plxdesi2 (talk) 16:41, 13 April 2013 (UTC)

What all three references do show is that the lifting foreplane is sometimes called a "stabilizer". Technical analysis may show that this is unwise, but it is what people say and Wikipedia should be clear that people do so. Of course, Wikipedia should also summarise any verifiable technical explanation, which is that the stabilising action is provided by the rear surface. I am not sure where you are proposing to add your comment, but can I suggest some small changes? Firstly, we should not make value judgements like "rare", especially when several references have been found. Secondly, we should not speculate about things such as why some people call it a stabiliser. So I would suggest the modified version: "A lifting foreplane is sometimes called a horizontal stabilizer". I would love someone to dig out a good reference criticising this, so we could write something like this: "A lifting foreplane is sometimes called a horizontal stabilizer, although this is not strictly correct." At the moment we can't do that because no authority we know of has explicitly said it is incorrect, and we ourselves must avoid original research. It's frustrating, but that's the way Wikipedia works. — Cheers, Steelpillow (Talk) 20:18, 13 April 2013 (UTC)

Garrison has never used the phrase "canard stabilizer" at any time in any article he has ever written. I suggest you contact him. I did. Nor does he believe that canards are stabilizing in any context. Stodieck (talk) 04:30, 25 June 2013 (UTC)

Better to put aside value judgements, ok, that's why I wrote rare between ( ). If "sometimes" means rare, it works. The second part of the sentence, "probably by geometric etc...is also an hypothesis difficult to assert. "Although this is not strictly correct" asks for an explanation of what is behind "strictly"; I would write "physically" instead, so : "A lifting foreplane is sometimes called a horizontal stabilizer, although this is not physically correct according to some aerodynamic experts." - above quotes following.

Trying to go to the roots and understand why some educated people call "stabilizer" a destabilizing lifting plane : In Nasa TP 2382, Wind -Tunnel Investigation of a Full-Scale Canard-Configured Airplane (Rutan VariEze), a comparison was done between two canards of different airfoils. As this canard is a highly loaded surface of low chord, the original canard airfoil (GU 25 ---) is thick (20 %) and cambered. Nasa team choose to compare it to a Naca 00012, "typical of airfoils sections used on conventional horizontal tails." As foreseeable, the naca 0012 results were poor, with a much lower lift coefficient and an abrupt stall. A Naca 4415 canard airfoil testing should have been more instructive. This unhappy airfoil choice by aerodynamics professionals shows the very weight of more than 60 years of aft stabilizer monopoly on mental process. Paraphrasing "Britannia rules the waves" : "Inertia rules the minds".Plxdesi2 (talk) 08:59, 14 April 2013 (UTC)

Why a lifting-canard is called a "stabiliser"

This discussion has moved to Talk:Stabilizer_(aircraft)#Why a lifting-canard is called a "stabiliser".

3 surfaces efficiency

"This allows the total surface area of all wing surfaces of a three surface design to be less than that of an equivalent 2-surface aircraft."
To be asserted. Any performance sailplane is a three surfaces configuration. 3 surfaces means one surface in excess; as a general rule a single surface is better than two (less structural and control weight, less aerodyn. drag. The (Avanti) interest of the 3 surfaces is any wing spar-cabin intersection, providing a better cabin layout and a structural advantage for pressurization. This is not an aerodynamic advantage.Plxdesi2 (talk) 15:23, 11 April 2013 (UTC)

You failed to read any of the Piaggio references. It is all about surface area reduction. Stodieck (talk) 04:26, 25 June 2013 (UTC)

X-29A is a 3-surface

Discussion moved from Talk:Canard_(aeronautics)

"X-29A is not really a 3-surface design, as the rear projections are integral with the main wing surface."

A close examination of the X-29 wing plan shows that the arm lever of aft control surfaces is 2 times the MAC of the aicraft, and 2 times the foreplane arm lever too (ref. point being 1/4 MAC chord). As the aft control surfaces are situated more than one chord (MAC) aft of the MAC rear end, one can hardly say they are integral with the wing.

Jan Roskam and WP X-29 article agree with 3 surface denomination. Plxdesi2 (talk) 07:50, 22 April 2013 (UTC)

Jay Miller (The X-Planes, 2nd Printing, Speciality Press, 1985) calls the rear extension variously a chine or a strake. He calls the movable tip merely a "trailing edge surface". Does the craft behave like a 3-surface design? Yes. Does it look like one? No. So when we designate its configuration, do we name it after how it looks or the way it behaves? I would suggest the former - how it looks. For example a tailless configuration may be stabilised in either of two ways - by adding negative camber such that the rearmost part has reduced incidence, or by sweeping the wing back and "washing-out" the outer section such that the rearmost section has reduced incidence. Reducing incidence is just how a conventional stabiliser works, so really a tailless type has stabiliser surfaces after all. But the stabiliser is integral with the main wing surface, so the plane looks tailless. The Lockheed Blackbird had long forward chines but that did not make it look like a canard so it isn't called that. Similarly the X-29 has rearward chines but that does not mean we call it a 3-surface type. — Cheers, Steelpillow (Talk) 10:53, 22 April 2013 (UTC)

A "close examination of..." is not the same as "X says" for referencing. If the issue is disputed (which it seems to be) then we need explicit sourcing one way or the other - or both ways if expert opinion is divided. GraemeLeggett (talk) 11:19, 22 April 2013 (UTC)

Except, you cannot source "Nobody says that ...". If I were to claim that the X-29 is a type of helicopter, you would not find a source explicitly denying it! The burden of sourcing lies with those who make the claim. — Cheers, Steelpillow (Talk) 13:07, 22 April 2013 (UTC)

Though one might not find a source that says it isn't a three-surface, one might find a source that said the X-29 is a two-surface design. GraemeLeggett (talk) 13:30, 22 April 2013 (UTC)

I agree that tailless are conventional aircraft, their common look and type being that the H-tail is integrated into the wing. No problem. What "strake" means ? it is an all-purpose term, describing different surfaces/functions : front high AoA VG, or leading edge wing large VG (Concorde, F-18), ventral high angle of yaw VG (for better spin recovery), aft stabilising lifting surfaces like tail added surfaces (Piaggio Avanti). In short "strake" means what you want or what you dont know of the purpose : better to use another term. In the X-29, the "strakes" are rearward placed stability/control surfaces ; that is a "tail", of low aspect ratio, yes, and definitively not integrated into the wing; moments arms tell clearly that is a 2 control surface + 1 wing = 3 surface. About ref., Jan Roskam is an authoritative author, that's important. Plxdesi2 (talk) 14:57, 22 April 2013 (UTC)

"Jay Miller calls the rear extension variously a chine or a strake."

Another example of what-you-want wording. "Chine "in WP gives "narrow extension to the leading edge wing root, extending far along the forward fuselage". Is this definition well suited to X-29 aft surfaces ? Plxdesi2 (talk) 15:59, 22 April 2013 (UTC)

WP is not a reliable source. I note also that its example fails to notice that the Lockheed A-12 precedes Blackbird. It always struck me that the wing extension chine as in the Blackbird et al is more of an exagerration of the chine of the fuselage - the line where the curve changes. Flight in the 1960s etc refers to the chine of the fuselage of several aircraft being around floor level. Wading through all the references to flying boats slows down the process of actually finding a definition. GraemeLeggett (talk) 17:45, 22 April 2013 (UTC)

Found a mention finally "Blackbirds from the skunk works" uses the phrase "fuselage strakes" to describe the chines. Very interesting technical article on the flight characteristics of the family and how the chines contribute. GraemeLeggett (talk) 18:14, 22 April 2013 (UTC)

I think we need to revisit our understanding of the term "chine". I have started a discussion at Talk:Leading-edge extension — Cheers, Steelpillow (Talk) 18:48, 22 April 2013 (UTC)

Coming back to X-29 "3 surface" : NASA Dryden FRC gives "use of three-surface longitudinal control" . Nasa paper cites "close-coupled canards" (so "canards" as surfaces, but not as a configuration). — Preceding unsigned comment added by Plxdesi2 (talk • contribs) 07:29, 23 April 2013 (UTC)

Looks like you are right, that first quote does support the 3-surface description. And the same reference also describes the foreplanes as "canards". Nice one, Plxdesi2, I'll bake myself a cake hat and eat it, provided nobody discredits the authority of that NASA source.  ;) — Cheers, Steelpillow (Talk) 11:13, 23 April 2013 (UTC)

Nice to see we have quite the same expression : "je vais manger mon chapeau" (I will eat my hat). Unconnected with, do you know the reason why Nasa report server is closed ? Plxdesi2 (talk) 12:52, 23 April 2013 (UTC)

Minimum wing surface design

"Doing so, the forward wing lift directly reduces the amount of lift the main wing must produce, and reduces the downward force the horizontal stabilizer needs to produce - further reducing the amount of lift the main wing must produce."

"The forward wing lift directly reduces the amount of lift the main wing must produce" seems ok at first glance, but counting the canard downwash effect on the wing behind, that is not so evident. Canard aircraft (of conventional stability) have the same characteristic (loss of some rear wing lift). In every case, the max lift is get putting all the surface in a single wing, not in two splitted wings (as a three-surface). If it was THE best layout, gliders and liners should be all 3-surface aircraft. The second part of the sentence looks better, but as the tail has to be larger to cope with the destabilising effect of the canard, may be there is no final advantage at all. The Piaggio Avanti design seems first to be a structural/accomodation layout optimisation.Plxdesi2 (talk) 12:41, 23 April 2013 (UTC)

Trying to verify the 3 surface claimed advantage, I did some computations with AVL (vortex lattice) sofware on Piaggio model. Conversely to some affirmations, the 3S (three surface) global lift efficiency seems not to be higher than a 2S (two surface) equivalent aircraft (same wetted area, same stabiliser, same pitch stability at cruise : Cma = -1.30). At landing conditions, following are the Lift coefficients of canard - wing - stabiliser :

3S : 2.33 - 1.92 - 0 with canard flap 45°, wing flap 40°, AoA 3.6°

2S : ---- - 2.02 - 0 with wing flap 40°, AoA 2°

Canard flaps at 32° balance the nosedown moment of 40° main wing flaps. Because of the canard downwash, the 3S wing lift is lower. The 3S needs more AoA for the same lift (less efficiency). It appears also that the would-be higly negative lift of the 2S stabiliser is a myth.Plxdesi2 (talk) 13:59, 18 June 2013 (UTC)

The lift coefficients of the stabilizer are never 0 or positive in stable aircraft. You have made a basic error. Stodieck (talk) 22:39, 24 June 2013 (UTC)

So can you explain how a tandem wing aircraft can apparently be stable? — Cheers, Steelpillow (Talk) 10:05, 25 June 2013 (UTC)

If you can provide suitable technical references for a tandem wing aircraft that is actually stable, you will have answered your own question. Stodieck (talk) 01:08, 26 June 2013 (UTC)

No, I specifically asked for your explanation - of an observed fact which appears to contradict your assertion. — Cheers, Steelpillow (Talk) 09:41, 26 June 2013 (UTC)

Verifying the claim

I have not yet found a demonstrably independent and unbiased verification of the minimum wing surface claim, only explanations of the theory it is based on. It may be generally true, it may apply only to certain designs, or it may be wholly false, but whatever the case we need it to be verified by an authority who is wholly independent of the Piaggio Avanti and similar aircraft. Also, the drag and performance benefits need offsetting against the inherent inefficiencies of having multiple surfaces, such as destructive interactions and multiple tip losses, and I can find no unbiased analysis of this aspect. On the technicalities, one may note that the wing is most loaded near the stall. This tends to occur at takeoff and often landing, and at maximum altitude. The elevator downforce story is in general not borne out by historical fact - for example both canard and tandem configurations require upward lift of the rear surface yet remain statically stable within the flight regime. It is really only at rotation (the point when the nose lifts just before takeoff) that a downforce is almost always required of the conventional tailplane, and at this point static stability is not an issue. So I am concerned that "proofs" of the minumum surface claim are being offered by people close to the Avanti or similar projects, who have an axe to grind and are distorting the technical arguments to further their claims. This is why independent references are so important before Wikipedia can accept these claims as fact. Does anybody know of such a reference? — Cheers, Steelpillow (Talk) 10:00, 6 July 2013 (UTC)

We suggest reading the references in the article. Including Burt Rutan's comments on his three surface Triumph design, "it had the potential for enormous improvements in efficiency compared to the King Air. It was as fast as the Citation II (jet), but had 60% better fuel economy."

and from the Naval Post Graduate School. http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA227604

Since you are starting one of your confabulation sessions again I am asking Mr. Hunt and others to do his job and start trimming your wings as he was supposed to do in the first place. I will be detailing your use of the meat puppet "Biker Biker" to revert edits and to make claims of 'abusive editing' in your name. I suggest that other editors not allow themselves to be used this way.

Stodieck (talk) 15:21, 7 July 2013 (UTC)

Hi, if you can provide unbiased references, preferably not drowned out by noise, that is the end of the matter. Patent applications and company sales literature are not adequate to prove the claims made in them. Nor are casual observations made by the designer: they stand as claims, no more. The paper you mention above is interesting, but it is a primary reference not secondary, and written by an unqualified student. It also notes the Piaggio "claim" as such (Page 2) and, in the normalised performance comparisons at the end pretty much leaves the 3-surface as a slow, heavy also-ran. As for your torrent of abuse (much now thankfully deleted), I have asked others to intervene - see here and here. — Cheers, Steelpillow (Talk) 18:59, 7 July 2013 (UTC)

This is the wrong problem to solve. It is not our job to verify claims or find the truth among the different theories. If Piaggio claims something (and it is not entirely foolish) all we have to do is indicate that Piaggio claims that. The real problem with the article, in my view, is that manufacturer/designer claims are not all identified as such (e.g. "This aircraft's top speed and service ceiling are comparable to lower end jets", of course this sentence does not come from Cessna). A lot of interesting research and calculations in the article and this talk page are just original research. Having independent sources will not help with that. Ariadacapo (talk) 11:03, 8 July 2013 (UTC)

True, as you say "It is not our job to verify claims or find the truth among the different theories". But it is our job to verify anything we write about them, such as blandly presenting them as facts and backing that up with inadequate references. Maybe I didn't make it as clear as I should what the issue is here: Stodieck and I disagree over whether we should represent this particular statement [Update: by Piaggio] as a claim or a fact. Adequate references would quickly resolve that in Stodieck's favour. The four references offered to date (two in the article and two above here) are demonstrably inadequate.

Also, if you think that more statements in the article might fall foul of WP:OR, please either tag them too or delete them. I am sure there is OR on this talk page, but I assume that is OK as long as it is recognised as such and relevant to the discussion. — Cheers, Steelpillow (Talk) 20:42, 8 July 2013 (UTC)

Ok! I just made some edits in this spirit to the Piaggio section. I think the Triumph and Catbird need to be in a section called "Examples of three-surface aircraft", not "Examples of minimum surface design". I have tagged this accordingly. Ariadacapo (talk) 12:01, 11 July 2013 (UTC)

This is the wrong problem to solve. It is not our job to verify claims or find the truth among the different theories. Thank you Ariadacapo.

Thank you, and again the claims are not mine they are from the references. In the case of the P180 they verified not just by the manufacturers data but a dozen references that can be found on the on the P180 page including the "Flying" article referenced here. That the performance of the P180 stands way out from the competition, is obvious as was stated in this article and many many others. The paper "written by an unqualified student" is a master's thesis for a Master of Science in Aeronautical Engineering. And "casual observations made by the designer" apparently refers to statements made by Burt Rutan about the documented actual performance of his three surface Triumph. The performance of Rutan's Catbird was documented by the FAI as stated in the article. Maybe you have heard of Burt Rutan? No?

The references here the are the best of the best available in any article on the Wiki. SP your first paragraph, "I have not yet found a demonstrably independent and unbiased verification . . . . " is all original research, you have no valid references for any of the statements.

I am going to ask you to do something that I know you absolutely cannot do. I want you to go back and revert your own last edit sequence. I know there isn't a chance in hades that you can do that. It is not within your power.

- Disruptive Editor Stodieck (talk) 03:58, 11 July 2013 (UTC)

You have good references. They enable us to describe the claims (a Rutan statement is a Rutan statement). They don’t make the claims true. Whether the claims are true, intelligent, casual, or not, is not the point. Ariadacapo (talk) 12:08, 11 July 2013 (UTC)

NB: writing "I am going to ask you to do something I know you absolutely cannot do" is not an acceptable attitude here. Ariadacapo (talk) 12:12, 11 July 2013 (UTC)

Broken link to reference

The url is broken in this reference used in the article:

<ref name="3-Lifting-Surface design">
[http://www.smartcockpit.com/docs/P180_Avanti-Specification_and_Description.pdf]
</ref>

Does anybody know the correct url? — Cheers, Steelpillow (Talk) 16:58, 26 June 2013 (UTC)

Found it, took about ten minutes. YSSYguy (talk) 07:53, 27 June 2013 (UTC)

Many thanks. — Cheers, Steelpillow (Talk) 14:51, 27 June 2013 (UTC)

Centre of lift

The thing about the wing's centre of lift is, it moves as the angle of attack, flap settings and so on change. The elevator (typically) is then adjusted or "trimmed" to move the aircraft centre of lift back to restore equilibrium. Saying that in a design "X is placed relative to the centre of lift" has no meaning. Rather, one should say, "The centre of lift can move such that X is placed relative to it". — Cheers, Steelpillow (Talk) 19:30, 11 July 2013 (UTC)

Aha, it’s an interesting problem! I understand better your edit now. We really need to write this article on Aircraft longitudinal equilibrium...

There are two distinct reasons why the CG may not coincide with the wing centre of lift.

1. As you explain, the wing centre of lift moves when equivalent air speed is varied, and when flaps are deployed (trim);
2. Static stability is increased when the CG moves forward (stability).

In other words, even if the wing centre of lift did not move (say, a flapless wing with symmetrical profile) we would still want the CG ahead of the wing. Otherwise we would need a disproportionate (zero-lift) stabilizer to provide the required stability. That is the reason why airliners still generate negative tail lift in cruise, where the trim conditions are most favourable (high equivalent speed, clean wing).

So, does the wing centre of lift move ahead of the CG, or do we position the CG ahead of the wing centre of lift? Both, I guess =) In this light, I think each of our article versions is too categorical. I’ll try to find a better compromise, but feel free to edit right away. Ariadacapo (talk) 11:08, 12 July 2013 (UTC)

OK, I have made a bold rewrite. What do you think? — Cheers, Steelpillow (Talk) 19:52, 12 July 2013 (UTC)

Great work! (I couldn’t help but add a link to longitudinal static stability in the final sentence, where I hope it is most relevant). Ariadacapo (talk) 09:08, 13 July 2013 (UTC)

Advanced combat manoeuvres

I don't think the bit I wrote about the three-surface configuration "allowing" Pugachev's Cobra and the Kulbit is quite right, but I can't think of a neat form of words. It was using this type of aircraft that these manoevres were originally performed, but since then other configurations have performed these manoeuvres. Any improvements welcome. — Cheers, Steelpillow (Talk) 10:11, 13 July 2013 (UTC)

I believe that we should not over-think it, and simply state what we know. I have just moved the sentence in the history section ("Some advanced combat manoeuvres ... were first performed on Sukhoi three-surface aircraft but have since also...") down to replace the controverted statement. If a reference shows up to support the original statement (which I believe is almost correct), we will restore it. Thank you for re-structuring the article, by the way! Ariadacapo (talk) 08:25, 14 July 2013 (UTC)

Paragraph titled "Wing area reduction"

I do not understand what the point of the paragraph titled "Wing area reduction" exactly is. In my view, the main point seems to be that "Once sized for takeoff and landing, both the main wing and stabilizer are larger than required for all other points of flight. This excess surface area creates unnecessary drag." but that is true for all aircraft configurations. I suggest that we delete this paragraph entirely. Am I missing something? Ariadacapo (talk) 08:45, 14 July 2013 (UTC)

I don't have time to address this right now, but in brief, the idea is that adding the third (foreplane) surface allows the other two to be reduced in size sufficiently to effect an overall reduction in area and hence weight and drag. Care is needed in the wording, for example the maximum altitude condition is also limited by wing area, and a given criuse altitude and speed could set the limit on area, as with the Lockheed U-2 spy plane, rather than takeoff as currently stated. — Cheers, Steelpillow (Talk) 09:06, 14 July 2013 (UTC)

OK I have gone for broke and done a massive rewrite. I have tried to create a logical progression from each factor to the next, moving stuff around where it had been in the wrong section and deleting detail on things like wing flaps which are not specific to the three surface configuration. Hope it now makes more sense. Probably needs the odd inline citation too, but I'll leave it to others (possibly your good self?) to challenge. — Cheers, Steelpillow (Talk) 12:40, 14 July 2013 (UTC)

I really appreciate your work, most especially the re-structuring. Nevertheless, I still cannot see the difference between the point made in this paragraph and the point made in the first paragraph, titled "pitch equilibrium". The argument seems to be {less tail downforce + foreplane lift} = less wing lift = smaller wing. Could we perhaps make this argument clearer in the first paragraph clearer and avoid repetition? Ariadacapo (talk) 18:24, 15 July 2013 (UTC)

Bunch of unsatisfacory edits?

I should like to revert the recent batch of edits by Ariadacapo (talk) for a number of reasons, my primary reasons being:

1. "Contemporary examples of minimum-area three surface aircraft include..." was deleted. These craft appear important in the development of the theory, and I think there is more to say about them. In fact more was said by another editor but it got whittled away for one reason or another. Rather, we should reinstate mention of these craft and expand on their relevance to the theory.
2. "These aircraft were designed to expose a minimum of total surface area to the slipstream; thus reducing surface drag for speed and fuel efficiency." was deleted. OK it needs references, but it is a useful mention of minimising not just the lifting surface area but the total wetted area.
3. "On a canard design, to achieve static pitch stability the foreplane must provide lift" was deleted. Not all canard surfaces are lifting canards. The sentence "In order for a canard aircraft to have safe stall characteristics, the foreplane must stall before the main wing" is only true for lifting canards, so the deleted sentence needs restoring in order to explain this context.
4. The implications of the stall safety margin were moved forward a paragraph. They are directly relevant to the design discussion in the earlier paragraph and need to be moved back. Stating them in the next paragraph is too late.
5. Stability constraints on the size of the foreplane were moved to the discussion on pitch equilibrium. This is inappropriate.

Some other parts of those edits were good, such as correcting the claim about "Minimum wing surface" from the references provided, but I think it is easier to reinstate these after indiscriminate undoing of the whole bunch. Way ahead? — Cheers, Steelpillow (Talk) 21:38, 15 July 2013 (UTC)

I should hold on to point #3. I’m fine with reverting all the other edits! Comments:

1. OK. I think "contemporary" is wholly inadequate, though.
2. OK. {{citation needed}} =)
3. The second sentence you quote is correct all the time (except for fly-by-wire, artificial pitch-down-input-upon-stall aircraft, but then any mention of stab characteristics is irrelevant). Stability is completely independent of whether a surface generates lift. A zero-force tail is stabilizing, a zero-force force foreplane is destabilizing. What matters is what moment they and the wing generate when there is a pitch disturbance. (the first sentence you quote is incorrect, but that is not the point, see my remark below)
4. OK. I wanted to avoid using the word "oversize" (implies undesirable, implies existence of optimum, both of which are not NPOV).
5. OK. I wanted to express that these trim drag/wing weight reductions may not be carried through all the way.

A final comment: static pitch stability has different requisites in steady flight and in the stall condition. A stable three surface aircraft (3SA) or canard may pitch up during stall. An unstable 3SA or canard may pitch down during stall. So, we must be careful not to mix our explanations of the phenomena. Ariadacapo (talk) 06:36, 16 July 2013 (UTC)

Thank you for your understanding and good manners. I have kind of merged our two versions, except for properly considering your point 3. Usually your "all the time" corresponds to the lifting canard type, while your "fly-by-wire" corresponds to the control canard type. But "all the time" is a dangerous assumption with any principle of canard design! There is another, older way to achieve a control-canard, using a free-floating surface. This can be designed to automatically adjust its angle of incidence for zero lift, except when control forces are applied. Consequently in normal flight it is not destabilising. It was tried on the Curtiss-Wright XP-55 Ascender, with unhappy results (ISTR something about unexpected trim conditions destabilising it), but in principle it remains an option. So it is important to set any comment about high-lift regimes in context. I agree that stable behaviour in the stall is different from stable behaviour in level flight, but I was concerned that this is the wrong place to present the reader with two kinds of "stability", so I tried to present the stall as a dynamic event and not go into that much detail, simply comparing design requirements for normal stable flight with stall dynamics. How does my edited version read now? Do you need some more of your edits restoring? — Cheers, Steelpillow (Talk) 11:24, 16 July 2013 (UTC)

Good. It looks fine to me except for #3, naturally =). I understand your point better with the XP-55 example, but I think free-floading surfaces make for a very special case that does not deserve mention in the general statement. It’s very much like stick-free trim and stability (when the pilot releases the controls) which are also super interesting but treated as a special case. I think it is implicit that when we say "canard" or "foreplane" in the context of trim/stability, unless specified we mean a surface that only moves/changes shape with pilot inputs.

In my view, the sentence "On a canard aircraft, to achieve static pitch stability in normal flight the foreplane must provide lift." needs to be deleted for three reasons:

• It is misleading. The reason why the aircraft is stable is that the wing stabilizes it, thus the wing is behind the CG, thus the canard must bear lift. The generation of canard lift in itself is not the stabilizing factor. It’s as if I said "for me to have a weight my car also needs to have a weight", that statement is correct but would not really help someone approach/understand the Earth’s gravity.
• It is formally incorrect. On a classical canard aircraft we could have the CG so far aft that even though the canard bears lift the aircraft is unstable (wing not stabilizing enough). With a negative-camber wing, the canard could have zero lift yet the aircraft could be stable. "Most stable canard a/c generate canard lift" is different from "to achieve stability a canard a/c must generate canard lift".
• The term "however" in the following sentence implies that there is a direct causal relation between {loaded canard in steady flight} and {static stability in stall}. As we seem to agree, stall and steady-flight stability are different occurrences.

To conclude, I believe this sentence should be deleted. We can go straight into stall stability without risking inaccuracy covering steady-flight stability too quickly. If we want to cover it (I’m not sure it’s wise, 3-S and canard aircraft are similar in this respect), it needs a paragraph of its own. The XP-55 and stick-free cases can be mentioned in a footnote. I might attempt an edit in this direction later today.

Other sentences relating to stability need some tuning, but one step at a time. :-) Ariadacapo (talk) 08:59, 17 July 2013 (UTC)

Just did a bold edit re:#3. Comments? Ariadacapo (talk) 20:09, 17 July 2013 (UTC)

Have to say I disagree strongly:

I changed the bullet list to a numbered list so addressing points is easier -- Ariadacapo (talk) 06:17, 21 July 2013 (UTC)

1. Many modern canards, especially combat aircraft, have fly-by-wire artificial stability with relaxed or negative static stability. We have to be clear that this discussion does not apply to them. While we are at it, a form of words which also excludes the floating type can at worst do no harm and is in fact more technically accurate.
2. Saying that the main wing "stabilises the canard" is the misleading view if any. While some authorities say that such a canard is "like" having a small main wing and a huge conventional stabiliser, none (to my knowledge and despite many vehement claims in these discussion pages) actually treats this as the correct analysis. A designer does not create a fuselage with a canard and then think, "oops, this is unstable, I must add a big lifting wing behind it". Rather, the designer creates a fuselage with a wing and then thinks, "oops, this is unstable, where shall I put the horizontal stabiliser?" For example consider a tailless design having a conventional (i.e. unstable) aerofoil. By adding a suitable forpelane and adjusting the CG position accordingly (e.g. by locating the main wing a little further back on the fuselage) the design can be stabilised. In this sense it is common enough for authorities to refer to such a foreplane as a "horizontal stabiliser" or "putting the tail at the front".
3. Sure, the main wing's lifting moment acts to aid stability but the key is the relationship between the lift coefficients of the two surfaces. The key to such a forward stabiliser is that its change in lift coefficient with angle of attack must be less than that of the main wing - just as a tail stabiliser requires a change more than that of the main wing. This may be achieved by rigging the angle of incidence, using a different aerofoil section, etc. It is this relationship, not either surface in isolation, which stabilises the aircraft.
4. Your claim of formal incorrectness is based on the idea that the main wing could be stable in its own right. This does not use a conventional wing design, requiring negative camber, sweep plus washout, huge elevators (which equate to negative camber when trimmed) and suchlike. This is a tailless aircraft design topic. Sure, such craft have been modified by adding canards - the many such modifications of the Dassault Mirage III spring to mind. But this is done for entirely different reasons and should not intrude in the principles of design for static stability. For this reason I was at pains to limit the scope of the discussion to a "conventional" wing design. You argue for this advanced special case which is technically excluded from the core discussion, yet you don't like me introducing the floating canard which is technically included!
5. Having established that static stability requires a lifting canard, I then explain the main caveat to the lifting canard. The causality is not a direct mapping, but nevertheless if the canard is not lifting then its stall characteristics will be irrelevant. The causality goes {loaded canard in steady flight} and {affects static stability in stall}. "However" is an accurate and grammatically correct preposition which helps express this causality; the accompanying text then explains its contingent nature.
6. FWIW discussion of the Curtiss-Wright Ascender is more relevant to Canard (aeronautics) and should not clutter up the discussion of three surface aircraft. Here, we need at most only allow in our phrasing that such things might logically exist.

Revert? — Cheers, Steelpillow (Talk) 17:57, 20 July 2013 (UTC)

Well. I am yielding all I can; at this point I’ll risk getting the satisfaction of a difficult-yet-constructive team edit over that of a satisfactory article. Please also try to contend with remixing edits you don’t like rather than keeping your finger on the revert trigger...

1. Yes. We need to do a better job at this.
2. That is just point of view (you: I load the canard so I can shift the wing behind the CG | me: I move the CG ahead of the wing so I need a canard). Suggesting there is "a correct analysis" is absurd, math does not care how you read the equation, a good equation will not even state whether the stabilizer is ahead or behind of the CG.
3. No, that’s all wrong, I’m sorry. The wing’s moment about the CG does not contribute to stability (only the change does). Changes in CL with angle of attack absolutely no not need to be different for the aircraft to be stable. The statement in the article that I removed, "its lift force acts against the aircraft’s pitch stability", has no meaning. Phillips has a good coverage of this (a search for "canard with no control surface deflection" will land you p.385 here. See eqs. 4.6.9, 4.6.13 and the discussion thereafter), with several worked-out examples of stable canard a/c that have identical CL slopes. But that is not the point. We do not need to cover steady-flight static pitch stability of canard or three-surface aircraft. For instance, it is not required to cover stability in stall.
4. OK, good point. We can change "On a canard aircraft, to achieve static pitch stability in normal flight the foreplane must provide lift" → "On a canard aircraft, in normal flight the foreplane must provide lift so that static pitch stability may be achieved".
5. There is no relationship between how much lift a surface carries in flight, and how it will affect stall behaviour. What determines a surface’s contribution to stall behaviour is what moment it generates around the CG as the aircraft accelerates, once the first surface has stalled.
6. Yes, thus the footnote. Writing a legible sentence allowing for constant-alpha mechanisms sounds difficult. Do you have suggestions?

I’ll try steering towards something we can agree on. Ariadacapo (talk) 06:19, 21 July 2013 (UTC)

Much better now, but still a couple of issues (and my apologies if the word "revert" gave unwelcome connotations. I'm not reverting indiscriminately, nor even proposing to as you seem to suggest, but if I see a single edit as containing multiple flaws and no good bits, that is effectively what happens - a "selective" retraction where 100% is selected is logically just a reversion. And I am not criticising your other edits which surrounded the one in question - those were all good.) Let us pass by the no-longer-relevant discussion points. As the article now stands I have issues only with one paragraph: "Since it is positioned ahead of the centre of gravity, a foreplane reduces the aircraft’s static pitch stability. If the aircraft is to be naturally stable, surfaces aft of the centre of gravity, the wing and tailplane, must then have sufficient moment arm and lift slope to restore overall stability. This constraint may limit the size of the foreplane, and in turn its ability to share pitch trim forces."

• I have explained above how the foreplane is placed there in order to stabilise an otherwise unstable main wing. To say that it "reduces the static pitch stability" is to deny the reason the designer put it there. We just have to find a more sensible form of words, I see this as a no-brainer. Hence my (now deleted) version, "A lifting foreplane acts ahead of the aircraft centre of gravity so its lift force acts against the aircraft’s pitch stability." I think you criticise this briefly above somewhere, but I can't seem to find that now. Can you be more specific about the problem and maybe give a better alternative?
• "This constraint may limit the size of the foreplane". This only applies if the centre of mass is held constant. There is a continuous morphology of form from canard to tandem wing to Delanne tandem to conventional. Nobody says that the forward surface of a tandem wing (Delanne or otherwise) or conventional craft is limited in size by stability constraints - one simply adjusts the centre of mass accordingly. The same is true of canards. I had added this context to the article but you deleted it. I would suggest that it needs to be restored.

— Cheers, Steelpillow (Talk) 10:11, 21 July 2013 (UTC)

Ooooh, I understand what your thought pattern has been all this time now! Addressing your remarks:

1. The foreplane is still destabilizing. It’s like an investment. It might be key to making the overall operation a profit-making one, but it’s still an expense, and it’s contributing to reducing profit. There is nothing such as a "stable wing"; the wing is stabilizing or destabilizing depending on where it is relative to CG. The canard reduces stability, but it enables the wing to increase it by a larger amount.
   If we can agree on stability being "the sum of each surface’s {derivative of the moment about the CG with respect to alpha}", then the sentence I deleted is incorrect. It says "...its lift force acts against the aircraft’s stability" but stability is simply increased or decreased, not acted upon, and by moment derivatives, not lift forces.
2. Neatly phrased! I agree about the continuity, and about the fact that "nobody says" that the forward wing of a tandem is limited by stability. Indeed once the airplane flies, we know that it’s both trimmable and stable, and the "currency" for stability is the permissible range for CG position.
   Nevertheless, on the drawing board, all of these forward surfaces reduce stability and this limits their size and distance to CG. It’s very easy to draw a canard aircraft in which the centre of mass position required for attaining stability is so far forward that the canard then cannot sustain the required lift (stability and trim then being exclusive). Okay what I wanted to express in the last sentence is what Phillips (linked above, p.386) says much more clearly:
   
   "From Eq. (4.6.11) [that states "aircraft is trimmed"] we see that trim requires a canard volume ratio large enough to counter the negative pitching moments generated by the lift of the main wing and any camber in the wing and/or canard.
   On the other hand, from Eq. (4.6.12) [that states "aircraft is stable"], stability requires a canard volume ratio small enough so as not to overpower the stability provided by the main wing.
   Thus, the trim and stability analysis for the design of a canard configuration is more critical than it is for the design of an aft tail. With the aft tail, pitch control and pitch stability are both improved by increasing the volume ratio of the horizontal tail. However, sizing the volume ratio for a canard requires a trade-off between pitch control and pitch stability, which makes sizing a canard more critical than sizing an aft tail."
   
   As it applies to our article, I wanted to translate this into something like "Increasing canard trim capability (more surface, greater arm) is tempting, but then it may have to be compensated by increased rear surfaces to maintain stability". Three surface aircraft are advantaged compared to canard aircraft here because of the extra faraway tail, but they still may not be fitted with just any canard.

Whew! Sorry for the wall of text. I’ll try to clarify the article sentence. Ariadacapo (talk) 18:17, 21 July 2013 (UTC)

No aircraft can ever be fitted with "just any" auxiliary surface, whether fore or aft. It all depends. Philips does not appear to state that the size of a canard is limited, only that it is somewhat critical. The Miles Libellulla designs were tandem wings with such a small forewing that they are sometimes called canards - the Miles M.35 Libellula had a forewing smaller than the aft wing and the Miles M.39B Libellula had a smaller forewing still. Both were trimmable and statically stable. If the design for either of these had started as a canard and someone had said, "don't make the foreplane bigger or it will become unstable," they would have been proved wrong. To emphasise, there is no direct link between plane size and stability, it is all contingent on other design factors. Philips is wise not to claim that such designs as the Miles types cannot have the properties they exhibited in the air. We should be careful to follow his lead. — Cheers, Steelpillow (Talk) 21:05, 21 July 2013 (UTC)

Your latest edit is if anything worse than before and is taking us back round in circles.

The section title has reverted to specifiying stability in the stall. I previously explained why it needs to cover the stall condition more generally, including the onset of stall, and that had apperaed to be accepted. Now I see it being rejected once more.

"The three surface configuration can then present an advantage compared to the canard configuration." As has been fought over in a previous discussion, this is a claim which has not been confirmed as true by a reliable source, and that needs to be clarified. Since the claim is already noted and referenced elswehere, I am not sure why it bears repeating here anyway.

"Since it is positioned ahead of the centre of gravity, a foreplane reduces the aircraft’s static pitch stability. If the aircraft is to be naturally stable, the foreplane’s size, lift slope and moment arm must be chosen so that it does not overpower the stability provided by the wing and tailplane. Stability constraints thus limit the foreplane’s volume ratio, which may in turn limit its ability to share pitch trim forces as described above."

• I repeat, the designer typically puts a lifting foreplane there in order to achieve static stability. To say that such a foreplane "reduces static stability" is absurd. This has not changed.
• "the stability provided by the wing and tailplane" does not exist. For an aircraft to be stable it must be trimmed. The wing and tailplane alone do not provide the required trim condition, so stability cannot follow. Both trim and stability also require the lifting forplane.
• "Stability constraints thus limit the foreplane’s volume ratio...": You seem to be trying to introduce that articifial size limit by the back door, still without explaining the conditional assumptions. Why not say that the CG range is limited by the size of the foreplane, or that the lift coefficient of the foreplane depends on X,Y,Z? It is unreferenced and smacks of PoV editing. I think the best thing is just to avoid all mention until someone can produce a technically sensible analysis backed up by adequate referencing. [Update 11:09, 23 July 2013 (UTC): but it was felt important by another editor so perhaps a corrected version should stay for now]

So all in all, you have had several stabs at addressing my concerns but seem unable to get there, maybe it's my turn now. — Cheers, Steelpillow (Talk) 10:40, 23 July 2013 (UTC)

I have now made that edit. Are there any specific changes you would like to see? — Cheers, Steelpillow (Talk) 11:01, 23 July 2013 (UTC)

Hey sure, I was in good faith trying to move the article your way. I’m happier without the introduction that I added, and also happier when claims about 3-S configuration advantages are getting removed (this article still sounds like it promotes the configuration).

• Regarding a component "increasing/decreasing", "providing" stability, that’s just the standard way that it’s treated. Stability is quantified as a sum of contributions, just like trim, just like vertical equilibrium. It’s much like saying that a lifting canard provides a pitch-up moment, even though the aircraft does not pitch up. A foreplane is destabilizing even if it was added to make an aircraft stable. You may say also that it "makes a negative contribution to the overall/total stability".
• "The stability provided by the wing and the tailplane" is the same point, see Phillips page 385 (linked above), "Thus it is the main wing and not the canard that provides stability for the wing-canard configuration" (emph. removed).
• Ok, let’s be rigorous then, the limit is not just on the surface of the foreplane, nor just on CG distance relative to it. It is on the term

$-{\frac {S_{c}l_{c}}{S_{w}{\bar {c}}_{w}}}{\frac {dC_{Lc}}{d\alpha }}(1+\epsilon _{u,\alpha })$ as described in Eq.4.6.9 in Phillips, whose (positive) value has to be small enough that the equivalent term for the wing (and tailplane) still make the total sum negative enough. For a given wing (given $S_{w}$ and ${\bar {c}}_{w}$) there is thus a limit on the multiple of all of the remaining terms in this equation. We’re bound to disagree about which terms to describe in a readable sentence. I see the same problem is present in the Canard (aeronautics) article.

Overall, with my last two-word edit, while I still feel a bit let down by the treatment of this (difficult) topic in the article, and uncomfortable with the statements made regarding stability, I am feeling satisfied enough that I am going to slowly retire from editing it. I think given our strong disagreements we did a good job at finding common ground. Ariadacapo (talk) 16:52, 25 July 2013 (UTC)

Yes, you have always shown good faith - and assumed the same in me, which I much appreciate. I take your point about Phillips, and if that is what he says then that should be recognized in the article, whatever my own ideas. I will try and restore it to save you the trouble. FYI for my own sanity I have been working on an explanation of the stability issues and collecting together some references on my user page at User:Steelpillow/Aircraft#Canard stability. If you can bear to take a look, I'd be interested to know what you think. — Cheers, Steelpillow (Talk) 17:54, 25 July 2013 (UTC)

Categorising the canard

I notice there has been a bit of a tiff over whether an article on a certain three-surface aircraft should be in Category:Canard aircraft. Now that Category:three-surface aircraft has been created, might it be sensible to make it a sub-category of Category:Canard aircraft (on the basis that a 3SA has a canard but a canard may not have three surfaces)? There is also the contrary argument that a canard foreplane does not nessarily make a canard-configuration aircraft, and only aircraft of true canard configuration should go in Category:Canard aircraft (because that's what it says on the tin, as they say) - and that excludes all 3SA. This is my own view. Either way, we could/should then remove all 3SA articles from Category:Canard. What do folks think? — Cheers, Steelpillow (Talk) 20:17, 15 February 2014 (UTC)

I think that if it has a canard then it should go in Category:Canard aircraft and if it is a three surface aircraft then it should go in Category:Three-surface aircraft and if it has both then it should be categorized as both. No need to make one a subset of the other. If we do make "three-surface aircraft" a sub-cat of "Canard aircraft" then I am sure that someone will dig up an obscure three surface aircraft that has no canard! - Ahunt (talk) 20:27, 15 February 2014 (UTC)

I'd agree with Ahunt here - if it's either, it should be categorised as either, if it's both, it should be categorised as both. Some of the Sukhoi Flanker variants, for instance, are technically three-surface aircraft - but the third surface is the forepart of the wing/body chine instead of a 'proper' canard. - The Bushranger _{One ping only} 20:54, 15 February 2014 (UTC)

Really? I have to say I am extremely surprised at this view. Do you two truly think that the canard wing configuration is not definitive of what makes a "canard aircraft?" References tying "canard aircraft" to the canard configuration are ten a penny - just google "canard aircraft" if you don't believe me, ah, and first grab from my bookshelf, Wragg, D.; Historical Dictionary of Aviation, History Press (2008) defines canard as as "An aircraft with a tail-first layout." If you two are right then I would expect to see some cast-iron references describing a 3SA as not just having a canard foreplane but of actually being a "canard aircraft." So - where are those refs? — Cheers, Steelpillow (Talk) 21:14, 15 February 2014 (UTC)

So what I get is that you are saying that the categories are exclusive, an aircraft can be one or the other, but not both? - Ahunt (talk) 13:55, 16 February 2014 (UTC)

Yes. An aircraft can only be of one configuration, and that is what the present categories are capturing. — Cheers, Steelpillow (Talk) 14:19, 16 February 2014 (UTC)

Well I would argue that some aircraft can be of two configurations, such as a biplane that is also a canard. I guess the real issue here is whether Category:Canard aircraft is for aircraft that have canard surfaces fitted or are true canard configuration aircraft. In this regard I am thinking of aircraft like the B-1 bomber. - Ahunt (talk) 21:48, 16 February 2014 (UTC)

Here is what Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 86. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2 says:

canard (type of airplane)

A type of airplane in which the horizontal auxiliary control is mounted ahead of the main lifting plane.

canard (aircraft component)

A horizontal control surface mounted ahead of the main wing to provide longitudinal stability and control.

14 CFR Part 1

“The forward wing of a canard configuration and may be a fixed, movable or variable geometry surface, with or without control surfaces.”

canard configuration. 14 CFR Part 1

“A configuration in which the span of the forward wing is substantially less than that of the main wing.”

My read of those definitions would lead me to think that a three surface aircraft with a canard surface would also be considered a canard aircraft. - Ahunt (talk) 00:04, 17 February 2014 (UTC)

My read is quite to the contrary. To clarify Crane's first definition, a canard airplane or aircraft is one in which the horizontal auxiliary control surface is mounted ahead of the main lifting plane. Note this is "the" horizontal auxiliary control surface, there is no room for a second copy behind the main plane. One may safely say that the "canard configuration" describes the wing configuration of a "canard aircraft".

Since your logic is to the contrary, I am assuming that you are seeking get-outs such as "14 CFR does not explicitly forbid a tail surface" and similar. But many of these forms of words were laid down when 3SA were not at issue and everybody knew perfectly well that canard means tail-first and not two-tailed. Nobody felt it worth writing-in such caveats. What about a sesquiplane with backward stagger, or an inverted sequiplane with forwards stagger? Those both meet the 14 CFR wording for a canard, are you going to argue for them too? Crane's wording elsewhere has similar lapses of rigour (e.g. are we talking "auxiliary surface" or "smaller wing" here?), but his "the" which I discuss above is consistent with universal usage.

Still sceptical? You might like to check out these references, all of which contrast "canard aircraft" with "three surface" as mutually exclusive:[5][6][7][8] For the pdf, read page 2, para 1. — Cheers, Steelpillow (Talk) 11:39, 17 February 2014 (UTC)

It seems to me to all come down to how you want to use the category, as "aircraft that have canard surfaces fitted" or "true canard configuration aircraft". I think we just have to decide, unless we want to create two cats to cover both cases. - Ahunt (talk) 14:31, 17 February 2014 (UTC)

Yes and no. Yes it comes down to how we use the category but no, we do not need to decide, just to look around us. Those four references I linked to above are unequivocal, I did not cherry-pick, and there are plenty more. There can be no room for doubt: the meaning of "canard aircraft" is not up for grabs. If you feel the need you could canvass support for a new Category:Aircraft with canard foreplanes or whatever, just don't put 3SA in the wrong one. — Cheers, Steelpillow (Talk) 17:38, 17 February 2014 (UTC)

I think extra cats would just muddy the waters. Checking page hits always shows that readers make very low usage of cats on Wikipedia in general and that aircraft cat pages like this are rarely read at all, so I am not sure it is worth spending any more time on. I think you have proven your case sufficiently for me and if you want to consider three surface and canard aircraft mutually exclusive categories I won't debate it further. One thing remains and that will be policing the two cats to fix up spurious inclusions. - Ahunt (talk) 17:55, 17 February 2014 (UTC)

Establishing claims

When someone makes a claim about their aeroplane (or about anything else for that matter), Wikipedia's policy on verification, WP:VERIFICATION, requires that the claim be backed up by an independent reliable source (WP:RS). In particular, self-published sources (WP:SELFPUBLISH, WP:SELFSOURCE) are not reliable. Edit warring and abusive posts are no substitute and are likely to get one blocked, and I would ask all parties involved in the current dispute to discuss it here in a civil manner.

In the present edit warring, claims about the performance benefits of the Piaggio Avanti and other three-surface types need to be verified by citations from independent RS if they are not to be treated as mere claims. — Cheers, Steelpillow (Talk) 09:56, 1 October 2014 (UTC)

In the disputed section I'm not sure it could even be claimed that Rutan praised the design. Of the Triumph, the scaled composites page says "confirmed the performance and operating characteristics of both the airplane and the engines." which doesn't even say that it met the design spec. And the page 30 cited from the Flight article says Rutan didn't want to discuss the performance of the Triumph. p32 does mention performance but only to the extent that the FAA examination found it "..better than other business jets in some areas" (and gives example of not needing yaw damper). GraemeLeggett (talk) 21:33, 1 October 2014 (UTC)

Performance figures

Should this article start giving performance figures for individual aircraft types if they are not notable as a record of for similar reason? I think it would be unnecessary clutter here and such mundane figures are best kept for the individual aircraft articles, but another editor is persisting. — Cheers, Steelpillow (Talk) 09:35, 6 October 2014 (UTC)

It's partly a question of what is said. At one point we had "Flight testing validated the targeted performance range of 41,000 ft (12,497 m) at speeds up to 0.69 Mach" The source says " The subsequent test program, which consisted of over 100 hours of flight tests, confirmed the performance and operating characteristics of both the airplane and the engines. The Triumph was tested to over 41,000 ft at speeds up to .69 Mach". Which is not the same thing; it could have (though I doubt it was) been rattling like a collection tin and drinking fuel rather than operating at the planned cruise conditions for the planned production version. Without more context it's hard to tell if the quoted numbers mean anything. GraemeLeggett (talk) 15:39, 6 October 2014 (UTC)

Performance is the whole point of the subheading of the article. Thus the figures are central not mundane. The original article was only about performance. This article has been so mauled since I created it that it no longer correctly expresses the technical advantage of the wing format. It does mention the issue under 2 differently titled headings and includes 2 separate incoherent attempts to discuss three surface stability. The article has become mush. — Preceding unsigned comment added by Stodieck (talk • contribs)

"Performance is the whole point of the subheading of the article." - but as GraemeLeggett points out, without context any actual figures are meaningless. And here the context needs to be the principle of the three-surface design. The context to these figures in the source is just some arbitrary aircraft's measured performance, it says nothing about the performance contribution made by the three-surface configuration. Thus the figures are indeed wholly mundane. Following the logic of including such meaningless figures would just clutter the article with irrelevancies, they are out of place here. — Cheers, Steelpillow (Talk) 19:04, 6 October 2014 (UTC)

I think it is useful to present the figures, but I do agree it would be best to present them in relation to something, like more conventional layout aircraft of the same weight and power, where possible. - Ahunt (talk) 19:57, 6 October 2014 (UTC)

Yes. In the ideal world, there would be sentences that said things like "the [aircraft name] achieved a 10% improvement in [speed/range/whatever] over a conventional layout aircraft of the same [weight/wing area/other parameters]". GraemeLeggett (talk) 20:06, 6 October 2014 (UTC)

Indeed that was ideally what I was thinking we need, if refs can be found!! - Ahunt (talk) 20:14, 6 October 2014 (UTC)

Except, none seems to have been found. Until then, the numbers mean nothing. While we are waiting for Godot, my original question remains unanswered: Should this article start including performance figures for individual aircraft types if they are not verified as relevant to the article? Or, put it another way, should the existing numbers be deleted unless and until their relevance can be verified? — Cheers, Steelpillow (Talk) 11:16, 8 October 2014 (UTC)

• Delete: we could be waiting for ever. Performance figures should not be included unless their relevance is cited. — Cheers, Steelpillow (Talk) 11:18, 8 October 2014 (UTC)
• Delete: I have to agree, with nothing to compare them to they don't really add much of value. - Ahunt (talk) 12:10, 8 October 2014 (UTC)

Pitch equilibrium of 3-surface aircraft, bending moments, and PoV-pushing

User:Stodieck, you have added two statements that have no physical basis (emphasis mine):

• "However, on canards, the trailing edge flaps on the main wing are located far behind the center of gravity, at aft end of the aircraft. Consequently the flaps produce extreme negative pitching moments when deployed."
• "On a three-surface aircraft, the main wings trailing edge flaps are located near the center of gravity, and produce relatively low negative pitching moments when deployed."

If you want to maintain these two statements you need to add references. The burden is on the author to support their statement, not on other editors to disprove it.

All of this comes in the context where every two months or so, you reappear on this article to explain to the world why this aircraft configuration is the best in the world. Your enthusiasm is appreciated but you must bring in independent references. Otherwise, please move on to something else. Ariadacapo (talk) 10:38, 20 April 2015 (UTC)

Wing area reduction

Stodieck (talk · contribs) has done a bold and extensive rewrite of the section on wing area reduction. I made some change to the opening paragraph. Ariadacapo (talk · contribs) was unhappy with at least some aspects of the bold edit and reverted it wholesale. Bold edits are of course welcome in principle, but they can be dangerous because they may get reverted. If that happens, as it did here, it is customary for the bold editor to open a discussion (see for example WP:BRD). Instead, Stodieck undid the revert, which is an act of warring (see WP:EDITWAR). Attempting discussion through edit comments while warring is not acceptable. My edit got reverted along the way, too. So, rather than risk sanctions for bad behaviour, can we get the content issue resolved amicably? Several points of disagreement seem to be (and correct me if I am wrong here):

• Some aircraft may have other limiting factors on the theoretical minimum wing size.
• The condition of a downforce from the tail plane may only apply during takeoff.
• The description of "excessive" pitching moment from flaps far from the centre of lift may be inappropriate.
• Some or all of the new material may not be verifiable in reliable sources (WP:RS).

So first, are these criticisms justified, and second, is it easier to revert the bold edit and start again or to improve on the bold edit? — Cheers, Steelpillow (Talk) 10:47, 20 April 2015 (UTC) Updated — Cheers, Steelpillow (Talk) 11:14, 20 April 2015 (UTC)

The statement I disagree about is that the pitch-down moment generated by the deployment of flaps about the CG is somewhat dependent on their position relative to the CG.

Surely we do not need to roll back entirely to before the contentious edits to find a satisfactory solution. Nevertheless, what I am unhappy about is not the physics, but the current editing process. I would like this article to start moving less with "let me explain to you why this is good/bad" and more as a series of reference-supported statements. Ariadacapo (talk) 11:09, 20 April 2015 (UTC)

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