Poll/Forstmann Giant Triplane

[Breguet]

From the pen of Ljubomir Petrovic:

During 1919 an Inter-Allied Aeronautical Control Commission team reported on the partially-finished remains of a fantastic ten-engined triplane found in a hangar at the Poll airfield near Cologne. For many years the only information regarding this mystery aircraft was that described in the I.A.A.C.C. report dated 29 September 1919. From an engineering point of view the report was fairly comprehensive and was entirely in keeping with the I.A.A.C.C. objectives - not only to control but to describe new German aviation developments. Unfortunately, virtually nothing was mentioned regarding the history of this machine, so that for many years speculation has surrounded its existence. The only clue to the identity of the aircraft was that the designer's name was Forstmann. But the following important statements appeared in the report: "It appears that the 'Forstmann' Giant was intended to carry petrol for 80 hours flight, to have a speed of about 130 km.h. and to land at about 90 or 100 km.h." Then later on: "Function-heavy bombing, long distance machine, alleged to have been intended to bomb New York. No trace of any gear or bomb release gear found." These statements were to be significant in the search for the Poll Giant's true identity, because they established a connection with a document in the German Naval Archives.
While searching through the voluminous Naval archives a memorandum dated 18 October 1917 came to the author's attention, quite by chance. It had no heading and ostensibly was a short information note prepared for some high-ranking officer. It read:
A transport aircraft with ten engines capable of flying to America was financially supported by Bruning and the Deutsche Bank. The Navy became interested in the project because of its potential military application. The construction work has lagged behind and costs have risen so that further financing has been refused. The Company approached the Navy for funds, but the Navy declined because its interest was only of technical nature. Mannesmann was ready to re-finance the project, but the Navy considers it worthwhile to inhibit further construction due to the scarcity of material and labour.
The signature was unintelligible.
It is now known that the Poll triplane and the Bruning-Deutsche Bank project were identical. From the outset, the Poll Giant was intended as a long-range transport not bomber. Its designer was Villehad Forssman, creator of the early SSW-Forssman R-plane. Forssman enjoyed a close working relationship with Bruning & Sohn A.G. owner of "the four largest factories in Germany for the manufacture of quality plywood" and operated Fahrzeugbau Bruning at Grossauheim (near Hanau) for manufacturing transport vehicles, including aircraft. In fact Fahrzeugbau Bruning's registered trademark was an exact front view of the Poll triplane. To utilize Bruning's woodworking skills and sell plywood, Forssman actively promoted the company through his design and patent office in Berlin. In this connection, in April 1916 Forssman contacted Anthony Fokker and offered to have Bruning build several plywood wings, at no cost, according to Fokker specifications. Fokker quickly submitted the required wing drawings. Also involved with Fahrzeugbau Bruning was engineer Thorsten von Carlheim, a fellow Swede, who worked for Forssman in Berlin and Grossauheim.
Hptm. Krupp, now an Rea staff officer, recalled in pecting the Poll Giant at the request of Admiral Lahs and felt certain that Villehad Forssman was the designer. According to the Illustrated London News (p. 992, 1920), the Poll Giant was "intended to fly to America and drop propaganda leaflets over the United States before that country enter the war." Such a far-fetched proposal was entirely in keeping with Forssman's creative fantasy. The "Mannesmann" of the German Navy report was the Mannesmann Wafffen & Munitions Werke in Westhoven near Cologne who, in 1918, were constructing a small radio-guided flying missile designed by Forssman. Although no proof exists, Mannesmann was surely involved in the construction of the Poll Giant.
Waldemar Roeder recalls visiting the Poll Giant construction site as follows:
A very interesting project, under construction in 1918, was the one by Forssman. During my service with the Rea in Cologne, I learned of a huge triplane being built near Kahl (between Hanau and my home, Aschaffenburg; there was no airfield in the vicinity). Naturally, I went there as soon as I could and found a rather primitive building almost in the middle of the woods. Unfortunately, I do not remember who took me through the workshop, but I was impressed by the clean workmanship. Wings and nacelles were made of plywood, the former not yet covered with fabric. The very handsome engine nacelles were intended for a tractor and pusher engine each.
Since not all of the Poll Giant's components were found (engines, engine bearers, control surfaces, undercarriage and sections of the tail were missing), it is likely that this aircraft was constructed in at least two locations. The engine nacelles and other part had not yet been shipped to the Poll airfield site when it was inspected by the Allies.
The triplane wing was characterized by a middle wing with a much greater span than the outer two wings. The ribs were set fairly wide apart, and the box-section compression ribs were spaced at approximately 20 foot intervals. These thickened between the spars so that some 5 inches projected below the curve of the camber. The entire wing surfaces were covered with three-ply wood reinforced by a layer of fabric applied to the top veneer. The I.A.A.C.C. considered the workmanship good, but thought the structure to be weighty and disproportionately weak. Ailerons were to have been fitted to the middle wing only. Eight tandem engines were located at the strut intersections on the middle wing. The remaining two tandem engines were located below the fuselage at the centre of the lower wing. No information is available as to the type and horse-power of the contemplated engines.
The rectangular centrally-mounted fuselage was built of wooden longerons and cross-members reinforced with diagonal cable bracing. Although the fuselage was covered with three-ply wood, the I.A.A.C.C. team stated that the fuselage appeared weak and felt the three-ply covering added unnecessary weight. Because cable bracing across the fuselage interior was omitted, the inner (9 feet 3 inches square) fuselage was free from obstruction. The inner sides of the fuselage were covered by a second plywood layer. If strength were uppermost in the designer's mind he had no regard for weight, and the impression was that the Poll Giant was quite heavy in structure. When one considers that the fuselage was 150 feet long, some 12 feet longer than the wingspan of the Staaken R.VI, the designer's preoccupation with strength and rigidity is perhaps excusable.
Only a portion of the tailplane was available for inspection by the I.A.A.C.C. team. The elevators, fin and rudder were missing. A point of much interest to the Commission was that the leading edge of the tailplane was hinged and connected in a manner to assist in working the elevators. A recommendation was made by the I.A.A.C.C. team to test this arrangement in a British wind tunnel.
All that was found of the undercarriage was one of the huge, 7 foot 9 inch diameter wheels, which were entirely built of wood with the exception of the steel hub. For many years this wheel was on exhibition at the Imperial War Museum in London, where it is now in storage along with a section of the fuselage.
While there is no question that the Poll Giant was immense in concept, the naivete of its construction betrays the designer's inexperience in methods of aircraft design and fabrication. It is hoped that future research will bring to light the full history of this fascinating but forgotten aircraft. The accompanying provisional general arrangement drawing is based on all available data.
SPECIFICATIONS
Type: "Poll" Giant Triplane
Manufacturer: Unknown (initially financed by Bruning and the Deutsche Bank)
Engines: Ten tandem engines
Dimensions:
Span: middle, 50•3 m. (165 ft.)
top and bottom, 31•1 m. (102 ft.)
Chord, 6•7 m. (22 ft.)
Gap (upper and lower), 55 m (18 ft.)
Fuselage length, 45•7 m. (150 ft.)
Maximum fuselage depth, 2•8 m. (9 ft. 3 in.)
Wheel diameter, 2-4 m. (7 ft. 9 in.)
Performance (Est.):
Maximum speed, 130 km.h. (80•8 m.p.h.)
Landing speed, 90-100 km.h. (56-62•5 m.p.h.)

[Volker_Nemsch]

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... was probably simply oversized for it's time. Stangely enough the British tried something comparable (the Tarrant Tabor) and their experiment was a failure (although, unlike the Poll machine, it was completed and flew some metres).

My guess would be that position of the engines of the "Poll giant" was much more suitable for operating the machine. On the other had it is obvious that the Germans had no (or not sufficient) +400hp engines and so they needed more smaller ones. In both cases, the design was pretty average if compared with the Zeppeln-Staaken E-4/20 of 1920...

Anyway, thank you for this thread.

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[Barry Hickson]

Thanks for that interesting info Adrian.
I had heard of the Aircraft but not in detail & had never seen those pictures.