Abrial's Tailless Designs (and the Caudron C.260 mystery)

Retrofit said:

Is there more information available on that Caudron C260- tailless glider?

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My dear Retrofit,


here is a very small info about Caudron C.260,But only by French language.


TU magazine

Thank you very much, Hesham

Rush translation:
"C-260 (?), In 1930, Abrial realized at Caudron workshops a tailless monoplane powered by a Salson 9 AErs rated 75 hp. C-260 is its alleged appelation. No caracteristic known by the writer."
I read somehere about an Abrial A-260: Probably the same aircraft.

My dear Retrofit,


the Abrial A-260 was developed from Caudron C.260.

hesham said:

the Abrial A-260 was developed from Caudron C.260.

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This is just a repeat of what is said on Wikipedia and reproduced all over the web... but there never was a C.260 as such and no books on Caudron mention any such aircraft, even in projected form.

Apparently Caudron's "260" slot was simply allocated to Abrial's tailless aircraft built by Caudron, which was called the A.260 (and perhaps C.260 at Caudron for record purposes).

If anyone has pictures of the A.260, that would be appreciated.

Here is a three-view arrangement of the Abrial A.8, which I believe is the same as the A.260.

It was presented in mockup (or just model?) form on the Caudron stand at the Paris Salon Aéronautique in 1932 but was never built.

It was to be powered by a 95 hp Renault Pb engine. , Length was 5.06 m, wingspan was 8.5 m, wing area was 18 sq. m.

Hi Stargazer,


here is the Abrial A.8 in two variants from TU,but I don't see any relationship between
A.8 and A.260,except they were a tailless aircraft.

hesham said:

here is the Abrial A.8 in two variants from TU,but I don't see any relationship between
A.8 and A.260,except they were a tailless aircraft.

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Thanks hesham. But do you have a picture of the A.260?

Sorry Stargazer,


I haven't a drawing or a picture for it,even from Internet,it's hard to find it.

hesham said:

I haven't a drawing or a picture for it,even from Internet,it's hard to find it.

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Exactly what I'm saying. No picture of the A.260 anywhere on the web, and the only mentions are just a word for word repeat of only one source, which is the Wikipedia entry. We know Abrial designed a small tailless general aviation aircraft for Caudron... The fact that the A.8 was presented in 1932 on the Caudron stand makes me think that it must have been that... and also that A.8 may have been Abrial's initial designation for Caudron's C./A.260. That is why I need to be sure that the two are one and the same design, but unless I can see a picture that is clearly labeled as the A.260 I can't be sure (actually there is one on the web but it's a mistake as it in fact shows the Abrial "Air 60" glider).

hesham said:

here is the Abrial A.8 in two variants from TU

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Actually the caption says that the two top pictures represents the scale model of the larger A.8 show to the right. The model is very likely the one that was shown in 1932 on the Caudron display stand.

May be you are right Stargazer.

hesham said:

May be you are right Stargazer.

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Maybe I'm wrong too... I probably am, actually, as I will show just below.

Here is the transcription of the small item on the would-be "C.260" from Le Trait d'Union which you shared previously:

En 1930, Abrial réalisa chez Caudron, un avion monoplan sans queue, à moteur Salmson 9 AErs de 75 ch. C260 est son appellation présumée. Aucune caractéristique connue du rédacteur.

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Which translates roughly as:

In 1930 Abrial built a tailless monoplane at Caudron, powered by a 75 hp Salmson 9 AErs engine. C260 was its alleged designation. No specs are known by the author.

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Here is the transcription of the small item on the A.8 from Alain Pelletier's description in his book Les Ailes Volantes:

Grand spécialiste du vol à voile, Georges Abrial (1898-1970) étudia un avion biplace sans queue à train tricycle et moteur propulsif. Quoique présentée sous forme de maquette sur le stand Caudron du Salon Aéronautique de 1932, cette machine demeura au stade de projet.

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And here's a rough translation:

Great sailplane specialist Georges Abrial (1898-1970) studied a two-seat tailless aircraft with a tricycle gear and pusher engine. Although presented as a model on the Caudron display at the 1932 Paris Air Show, the machine remained a project.

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Now here is a set of reflections/interrogations/conclusions to ponder.

• The "C./A.260" is said to have been powered by a 75 hp Salmson engine (powerful enough for a single-seater but a bit feeble for a two-seater). The A.8 would have used a 95 hp Renault 4 Pb. Unless T.U.'s claim that the 1930 aircraft was allegedly called the C.260 is wrong, this is proof that the C./A. 260 and the A.8 CAN'T be the same machine.
  
• There apparently WAS a tailless aircraft prototype built by Abrial in 1930. However I find the use of the French word "réalisa" by the T.U. author puzzling. I translated it as "built", although it makes it a lot less ambiguous than it really is in fact. The word conveys the idea that the 1930 "C.260" was more than just a project but an actual built type of some kind. If so, why can't we find any trace of it in any Caudron source? Why do no photos exists? For some reason no images or photos of this machine seem to have popped up. Did it just hop? Did it crash?
  
• If this "C.260" was powered by a 75 hp engine, then it must have been a single-seater. Was it produced independently and then taken over by Caudron? Or was it done at Caudron from the start, as the words "chez Caudron would indicate? At any rate, it must have been interesting and/or successful enough for Caudron to to endorse the project and even consider building a larger tandem-seat version, shown in model form on their 1932 stand at the Paris Air Show.
  
• Considering Abrial had done mostly tailless gliders before, and how radical the A.8 project was for the time, it seems unlikely Caudron would have had a full-scale aircraft built without some proof-of-concept vehicle built beforehand. Was the "C.260" a subscale flying proof-of-concept model for the larger A.8 two-seater?
  
• Why Caudron eventually carried on with Fauvel's design and shelved Abrial's is another matter... especially when we know that Fauvel acknowledged that he relied on Abrial's own research at the beginning. A website specialized in gliders claim that Abrial was more interested in gliding and returned to designing sailplanes, but I find that explanation a bit lacking...
  
• T.U.'s original document shows two distinct designs as both pertaining to the A.8. The top view shows a seemingly disproportionate front wheel and a strange square dorsal fin, while the lower image shows a suggested cutaway view with seat arrangement, engine placement, etc. This gives the impression that the bottom one is the real one, BUT that would be misinterpreting the document (Pelletier unfortunately made that mistake by reproducing that configuration in his book as showing the planned full-scale article!) Why? Because the undergear of the second design would be far too feeble to sustain the actual aircraft (Pelletier must have thought that too, as he thickened the wheeltrain rods!), and also because it is fixed (as opposed to retractable in the top views). That bottom design carries the captions "Epure de centrage" and "Maquette au 10e - échelle 1/5 soit 1/30e grandeur". Although I can't quite figure out these scales (1/10th? 1/5th? 1/30th?) it seems clear here that the lower design, despite being more detailed, does not depict the projected full-scale version but a very small scale-model used to test weight balancing.
  
• The full-scale tandem seat version, designated A.8 by Abrial (and presumably granted another inhouse designation by Caudron), would have had a small square tail fin, retractable front wheel and wheel spats as shown in T.U.'s top version. The dimensions which are quoted by both T.U. and Pelletier applied to the full-scale, unbuilt article.
  

Comments and constructive criticism will be appreciated!

Below you'll find another document from another issue of Trait d'Union (n°170), by Charles Claveau.
The translation is: "At the 1932 Salon, one could see on the Caudron booth a model of the A.8, a two-seat tailless tourism aircraft with closed cabin. The project was shown at the Security Congress in Dec. 1930. With small dimensions, its lift-to-drag ratio was 14. The engine planned at the time was a Salmson 80hp. It should attain 190 km/h, 6000m and land at 62 km/h, reaching 1000m in 5 min. Total weight was 600kg with fuel for 4 hours."

Stargazer2006 said:

• The "C./A.260" is said to have been powered by a 75 hp Salmson engine (powerful enough for a single-seater but a bit feeble for a two-seater). The A.8 would have used a 95 hp Renault 4 Pb. Unless T.U.'s claim that the 1930 aircraft was allegedly called the C.260 is wrong, this is proof that the C./A. 260 and the A.8 CAN'T be the same machine.

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It can, those light aircraft often received a variety of engines. See the many variants of the C.270 or Farman 230 families. If the aircraft were actually built, the engine variants would have been distinguished by sub-designations.

Stargazer2006 said:

• There apparently WAS a tailless aircraft prototype built by Abrial in 1930. However I find the use of the French word "réalisa" by the T.U. author puzzling. I translated it as "built", although it makes it a lot less ambiguous than it really is in fact. The word conveys the idea that the 1930 "C.260" was more than just a project but an actual built type of some kind. If so, why can't we find any trace of it in any Caudron source? Why do no photos exists? For some reason no images or photos of this machine seem to have popped up. Did it just hop? Did it crash?

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Because the author has no other information about the aircraft, I think that the word "réalisa" was a bit over-enthusiastic, and it was perhaps a project only, or maybe construction started and was not finished.

Stargazer2006 said:

• If this "C.260" was powered by a 75 hp engine, then it must have been a single-seater. Was it produced independently and then taken over by Caudron? Or was it done at Caudron from the start, as the words "chez Caudron would indicate? At any rate, it must have been interesting and/or successful enough for Caudron to to endorse the project and even consider building a larger tandem-seat version, shown in model form on their 1932 stand at the Paris Air Show.

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It was not necessarily a single seater. See the Farman 230 two-seater with Salmson 40hp. Also it is not clear that Caudron fully endorsed the project. It seems possible that it merely rented its factory and workforce (same thing for the Fauvel and Viscaya designs built by Caudron, I think.)

Stargazer2006 said:

• T.U.'s original document shows two distinct designs as both pertaining to the A.8. The top view shows a seemingly disproportionate front wheel and a strange square dorsal fin, while the lower image shows a suggested cutaway view with seat arrangement, engine placement, etc. This gives the impression that the bottom one is the real one, BUT that would be misinterpreting the document (Pelletier unfortunately made that mistake by reproducing that configuration in his book as showing the planned full-scale article!) Why? Because the undergear of the second design would be far too feeble to sustain the actual aircraft (Pelletier must have thought that too, as he thickened the wheeltrain rods!), and also because it is fixed (as opposed to retractable in the top views). That bottom design carries the captions "Epure de centrage" and "Maquette au 10e - échelle 1/5 soit 1/30e grandeur". Although I can't quite figure out these scales (1/10th? 1/5th? 1/30th?) it seems clear here that the lower design, despite being more detailed, does not depict the projected full-scale version but a very small scale-model used to test weight balancing.

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I think that "Maquette au 10e - échelle 1/5 soit 1/50 [not 1/30] de grandeur" applies to the two upper views. These drawings would depict the 1/10 wind tunnel model. The drawings itself were surely five times smaller than the 1/10 model, hence at 1/50 scale when compared to the real-scale aircraft ("grandeur"). I don't think that the gear is retractable, it seems to have fairings on the main wheels. Retractable gear would have been too heavy and complex at the time for such a low-powered aircraft.
Conversely, I think that the words "Épure de centrage" apply to the lower view. They depict the internals of the actual aircraft, for calculation of the CG location. None of those are actual construction drawings.

For the designations, I believe that the project was designated A.8 by Abrial, successively or indifferently planned with a radial Salmson or an inline Renault. One wind tunnel model was built at 1/10 scale, based on the upper two drawings.
I guess that Abrial approached Caudron for the construction of the actual aircraft in their works. A Caudron designation slot was registered, C.260 or perhaps A.260 with Abrial's initial (like the P.V. 200 by Pierre de Viscaya). The model was exhibited in 1932 at the Caudron booth but I guess that nothing further emerged.

Adrien

Très intéressant Adrien !

So according to you these may still all be one and the same project, as I initially thought? Let's not rule out that possibility.

When I talked about a retractable gear, I meant for the front wheel only. The main gear, as I said, has spats, so not retractable. Initially I also thought (like you do) that the top views represented the model (perhaps a wind-tunnel model) but what made me change my mind about it was 1°) the fact that the dimensions of the planned real aircraft were applied to it, and 2°) the fact that it had a fin (if the wind tunnel is there to prove the design is sound, the fin would not be necessary). I believe fins wereusually added to tailless prototypes as a way to reassure the pilot and/or the investors! But on a wind-tunnel model I have my doubts... Still, as I also remarked, the front wheel does seem abnormally big... So I guess the mystery of the Abrial/Caudron A./C.260 is far from being solved, but it's a captivating and fun one, so I'm all in!

Not simple indeed, Stéphane,

Several test reports from the wind-tunnel facility of "St Cyr l'Ecole" concerns Abrial works on auto-stable profiles and tailless aircraft:
Report n° 349/B, dated January 1st 1928, concerned only auto-stable profiles (Abrial n° 4 and 5)
Report n° 609/A, dated ???, concerned the 1st model of Abrial A-8
Report n° 669/A, dated May 1931, concerned the 2nd model of Abrial A-8 (and mentioned with a Gipsy engine).
Report n° 736/A, dated Feb. 3, 1933, concerned the abrial A-83 and mentioned 2 types of wings.

An abrial -83 is mentioned in Rudolf Stork's book "Flying wings" with cropped delta wing. In German language so I don't kown the details (other source mentioned the same drawing as dated 1929).

The list of Abrial designation is (needs to be corrected/complemented:
A-1 Levasseur-Abrial, 1922, glider destroyed during her 4th flight.
A-2 "Vautour" glider
A-3 "Oricou", 1927, 2-seat tourism aircraft
A-4 Flying wing project
A-5 Peyret-Abrial "Rapace" glider, world record altitude holder
A-6 ?
A-7 ?
A-8 Tailless aircraft project
A-83 Tailless aircraft project derived from A-8
A-9 ?
A-10 ?
A-11 ?
A-12 "Bagoas" 1932, tailless glider
A-13 "Buse" 1946, tailless glider (not built)

Superb contribution! I believe a separate Abrial topic is in order. I'm splitting this one right away...

From Rudolf Storck "Flying Wings", a photo of the A.12 "Bagoas"

About the A.83 it is said, that it was a shoulder wing with a trapezoidal wing and
a tractor (!) propeller, quite similar to the Lippisch Delta-I. So the drawing is either
an alternative design, or an earlier or later one, or there's something wrong .. :-\

Old Informations from Internet,


Abrial A-7 and A-9 were a glider projects,but there's no existing to that site
now,and I forgot to record any data about them,can anybody help.

Details and photo of the Abrial A-83. The model has a swept wing but no central vertical fin.
Source: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930094623_1993094623.pdf

Thanks a bunch, Retrofit.

The documents you shared in the two posts confirm that the configuration tested in the model is the one that appears in the detailed drawing ("Épure de centrage") and is also the one designated as A.83 (and probably also the one that was shown on the Caudron display in 1932).

My concern is whether the wheeled extension below the engine was only for model purposes or would have been part of the full-scale design. Looks a bit awkward, but at the same time it could help the wingtip fins and blades not to touch the airstrip at take-off. Thoughts?

IMHO it replaced the upper rectangular fin of the first A-8's 1/10th model, with a dual function as propeller guard.

Hi,


and here is a 3-view to Abrial A-13 project.

Like-mindedness or uncredited inspiration? Here is Paul E. Best's Superdart project of 1956, which showed uncanny resemblance to the Abrial A.8 design, especially in plan view. Best had previously designed and built a tailless glider, also shown in attachment.

hesham said:

Old Informations from Internet,

Abrial A-7 and A-9 were a glider projects,but there's no existing to that site
now,and I forgot to record any data about them,can anybody help.

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Abrial A-4,A-6,A-7,A-9,A-10,A-11 and A-12 were a glider Projects,but no more details are known.

From,Premier_Congrès_international_de_la_[...]Congrès_international_bpt6k98051650

Retrofit said:

Details and photo of the Abrial A-83. The model has a swept wing but no central vertical fin.
Source: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930094623_1993094623.pdf

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My dear Retrofit,

I can solve this problem now,from Onera Archive,there was two variants
of A8,one have two-seat and anther have three-seat as I guess.