Identification needed

YavorD · 15 July 2009, 02:26 AM

Quote:

Originally Posted by Varese2002

There is also an 'incision' in the topwing at the back, just above the tailboom. The only rason why this should be done is to give a crewmember / gunner a clearer view above. It could be that there were MG's in the tailbooms operated by crew members in the tail booms.

The machine was possibly devised as a battle ship escorting bomber squadrons. Be aware this is only conjecture, no factual data.

Paolo and Yavor, I presume that the pieces taken out of the topwing at the back are not the best in aerodynamics? Also the wings grow longer from lower, to middle to topwing.

Escorting battle ships (planes) were envisaged at the end of the war in the USA, I think for example by Burgess, but not really built.

Cheers

Kees

As an afterthought. The relatively small size of this three-engined triplane might hint at the fact that the machine is not designed as a bomber, but primarily as an escort battle-ship.

After attempts with a cannon-armed Voisins, a typical bomber escort "battle ship" was Caudron R.11 with two gun positions.
Different wingspan is quite common for a biplane / triplane. There is a classic example of R.A.F. B.E.2c vs B.E.2e, B.E.12 vs B.E.12a, R.E. series.
Different chord for upper / lower wing is not unusual too (Nieuport sesquiplanes; Albatros D.III/V/Va; SSW D.III).
The real problem is when two surfaces are too close to each other (gap-to-hord ratio below 1). Partial remedy can be obtained by using positive / negative stagger (as shown on illustrations provided by Paolo). Such data with sound explanation were available for all interested parties from about 1916. There are British (e.g. Flight magazine, Hunsaker and Huff, 23 November 1916, pp. 1029-31) and German (Technische Berichte, Band I.) sources. No doubt, there is French, American, Russian and Italian research too.
Regards,
Yavor

Rbailey · 15 July 2009, 05:32 PM

Quote:

Originally Posted by Varese2002

Interesting hint, the only reference I could find till now is from the NASM Directory of Airplanes here. At least there exists another trimotor in France, unfortunately no date given.

Cheers

Kees

The only information I can find on the Van den Born is from Davilla and Soltan, who say it was tested in late 1917. Intended for 3 230hp Salmson radials but fitted initially with 80 hp Le Rhones - I don't see how it could have flown on 1/3 the design power so presumably it got something better for the tests. Crew of 5. They give nothing else.

Varese2002 · 16 July 2009, 04:53 AM

Quote:

Originally Posted by Rbailey

The only information I can find on the Van den Born is from Davilla and Soltan, who say it was tested in late 1917. Intended for 3 230hp Salmson radials but fitted initially with 80 hp Le Rhones - I don't see how it could have flown on 1/3 the design power so presumably it got something better for the tests. Crew of 5. They give nothing else.

Thanks for the reference to Davilla and Soltan. Unfortunately they give no reference to archive documents and/or contemporary sources. So we are left with the following text of which the accuracy cannot be verified (p.539) -

Quote:

The French F category called literally for an aircraft that would be a flying fortress. It was hoped that it would be able to destroy enemy aircraft and airships simply by the strength of its armament. The Van Den Born F5 was intended to meet this specification. It was a trimotor and carried a crew of five. It was originally intended to use three 230-hp Salmson radial engines. However, it was initially fitted with three 80-hp Le Rhônes, presumably due to a lack of availability of the Salmsons. The decrease in planned power by almost two-thirds cannot have done much to help the aircraft's performance, and after flight testing at Villacoublay in late 1917 it was rejected for use.

Given this information, there at least a fit with the mysterious tri-engined triplane. From the picture it is possible to define the machine as a battle-plane with 3 to 4 MG's [1 in each tailboom and two in the central nacelle - firing fore and aft, hence the cutout in the upper wing], making a crew of 5. Engines are not recognized, but can perhaps be counted by the number of cylinders.

The description of Davilla does not mention a triplane or the way the three engines were mounted.

The way to go would be in an ideal world:

search for the French specifications for the 'flying fortress' - the French F category - maybe somewhere in the French SHA archives

any records of tenders for this specification

as the machine was (Davilla) rejected for use, it would be logical to assume an official authority (STAé - Service Technique de l'Aéronautique) made that verdict, which might be documented and archived

Although not proven there is at least a possibility that the mystery 3-engine triplane and the Van den Born F5 are one and the same. If we only could have the references of Davilla and the archival pieces

By the way I had never heard about the French F-category aircraft. I also found out that Van den Born quit his job with the Belgian military aviation school (L'École militaire belge d'aviation) in 1916, leavig without pay. This could mean that he had something important to attend to for the war effort at another place (designing the F5 machine ?)

Cheers

Kees

paolomiana · 16 July 2009, 05:12 AM

Hi Kees, I run again trough the STAè reports from 1917-18 that survived the (in)famous VISTA crash on my laptop. Unfortunately no mention of this machine nor of the F-class projects.....

cheers

Paolo

Varese2002 · 16 July 2009, 05:39 AM

Paolo, this is a mystery thread, logically the French F class designation is also a mystery

Thanks for looking through STAé reports, never seen them myself though.

In the meantime I have done some research about the engines of the Van den Born F5

Le Rhône 80 hp 9-cylinder

Salmson Z-9 230 hp 9-cylinder

Engine on the mystery 3-engined triplane

Unfortunately the picture of the engine of the mystery plane is not very sharp, so the distinguishing bougie at the side of the Le Rhône cylinders cannot be distinguished. Looking at the 'pipes' I have a slight preference for the Le Rhône, but this is no fact. Perhaps the engine experts can do a sure identification?

Cheers

Kees

Rbailey · 16 July 2009, 07:26 AM

Attached s a photograph of a Z9 engine. Looks possible.

YavorD · 16 July 2009, 10:48 AM

Hi!
I do not see any hint of radiators, necessary for a Salmson. We are looking for an air-cooled engine, in my humble opinion. My choice is Le Rhône 9C.
Regards,
Yavor

Varese2002 · 16 July 2009, 03:24 PM

Thanks Yavor, I think you are right. The 260 hp Salmson 9Z is quoted as 'one of the rare kind of liquid-cooled radial engines'. So we seem to be looking at a machine powered by three 80 hp Le Rhône radials, total of 240 hp (when working absolutely correctly).

There is some more light that the mystery plane is the Van den Born F5. It would be great if we knew that the Van den Born F5 was a triplane. Still more closing of the net is necessary.

Cheers

Kees

Rbailey · 16 July 2009, 03:55 PM

Quote:

Originally Posted by YavorD

Hi!
I do not see any hint of radiators, necessary for a Salmson. We are looking for an air-cooled engine, in my humble opinion. My choice is Le Rhône 9C.
Regards,
Yavor

Looking at the cowlings, it appears that the bottom part is open, which would be consistent with an air-cooled rotary. Doesn't solve the machine's identity problem though.