O.Thetford, P.Gray German Aircraft of the First World War (Putnam)

Siemens Forssman (first version)
   Designed by Forssman, this four-engined machine was obviously influenced by Russian Sikorsky bombers. Construction commenced in October 1914, and completion was in spring of 1915, but although a speed of 115 km.hr. (71.8 m.p.h.) was attained on test, the aircraft was generally under-powered and modifications were put in hand. In its very first appearance the aircraft had no nose turret; this was added later to give better weight distribution. Engines, four 110 h.p. Mercedes. Span, 24 m. (78 ft. 9 in.). Length, 16.5 m. (54 ft. 1 3/4 in.). Area, 140 sq.m. (1,512 sq.ft.). Weights: Empty, 3,250 kg. (7,150 lb.). Speed, 115 km.hr. (71.825 m.p.h.).

Siemens Forssman (final version)
   After extensive modification, this version first flew in September 1915. The nose had been converted to an enclosed, streamlined cabin, the inner engines were now eight-cylinder 220 h.p. Mercedes D lVs, and the outer engines were suspended between the wings. The machine was finally accepted by Idflieg (Inspectorate of Flying Troops) in April 1916 for training purposes only. Further development was discontinued, as the type was by then obsolescent. Engines, two 110 h.p. Mercedes, 2 x 220 h.p. Mercedes. Span, 24 m. (78 ft. 9 in.). Length, 16.5 m. (54 ft. 1 3/4 in.). Area, 140 sq.m. (1,512 sq.ft.). Weights: Empty, 4,000 kg. (8,800 lb.). Loaded, 5,200 kg. (11,400 lb.). Speed, 120 km.hr. (75 m.p.h.). Climb, 2,000 m. (6,560 ft.) in 29 min.

G.Haddow, P.Grosz The German Giants (Putnam)

In contrast to the successful Steffen-designed R-planes, the Forssman R was doomed from the start to be a failure, despite the fact that it was modified at least five times to improve its performance. The final version of the Forssman R was the result of such extensive reconstruction that its appearance bore little resemblance to the original.
   Villehad Forssman, a Swede, made his first appearance as a builder of airships in Russia during the years 1910-12. He then moved to Germany, where he designed and built the "Bulldog" monoplane for Prince Friedrich Sigismund in early 1914. Forssman has been described as a "Jules Verne type", a man with a vivid imagination who invented among other things a one-man submarine, a shell-proof tank and was responsible for the design of the ambitious transatlantic "Poll" Giant project.
   At the outbreak of hostilities Forssman joined SSW to construct improved versions of his "Bulldog" monoplanes, which were, however, rejected by the military services due to their overall poor performance and handling characteristics.
   It is entirely possible that Forssman had an opportunity to examine early versions of Sikorsky's four-engined aircraft during his Russian sojourn; at any rate, the Forssman R was a rough copy of Sikorsky's famous design. The construction of the Forssman R was begun in October 1914, and it was completed some time in the first half of 1915.
   In its original form the aircraft mounted four uncowled 110 h.p. Mercedes engines spaced along the lower wing, each of which drove a single tractor propeller. The pilots' cabin was located in an abbreviated nose that was amply supplied with transparent panels for a magnificent view. Early flight tests, believed to have been limited to short exploratory hops, revealed a serious lack of fore-and-aft trim. This required additional weight in the form of an observer/gunner's pulpit fitted to the nose, and this was crudely braced by a strut running from the pulpit floor to the top longerons. The wings were rigged in a peculiar fashion - instead of a pair of struts between the second and third bays, only a single front strut was fitted. Tests proved this arrangement to be unsatisfactory, and the missing strut was added along with diagonal struts to support the overhang of the upper wing. Modification followed modification. The large side area of the fuselage and its relatively short moment arm required the addition of another rudder to improve control. The wings were also re-rigged with slight dihedral to improve lateral stability.
   Besides being structurally weak, although some parts, such as wing struts and landing gear were far too strong, the handling qualities of the Forssman R were notoriously bad. In addition, the aircraft was underpowered, and It is doubtful if any flights other than short hops were attempted. One wonders how the speed of 115 km.h. claimed for this version was arrived at. In any case, the Forssman R was in no condition to fulfill the Idflieg acceptance specifications. By this time, Villehad Forssman had severed connections with SSW owing to the failure of his design.
   In an attempt to make something of the machine, it was extensively modified by Harald Wolff and fitted with higher-powered inboard engines. These were mounted on a strengthened and faired structure. The original outer engines were retained, but to improve propeller efficiency they were raised to mid-gap position supported by the faired second-bay wing struts. As before, the engines were fully cowled, but the propellers were fitted with spinners.
   To improve streamlining, the fuselage nose was rebuilt to a sharp point. It was fitted with incongruous bull's-eye windows and surmounted by a fully enclosed teardrop-shaped pilot's cabin. The fuselage was given openings for gun positions in the nose ahead of the cockpit, in dorsal and in ventral locations. There is no evidence of machine-gun rings having been mounted.
   After one pilot declined to fly the machine following a few ground runs, the famous pre-war pilot and later Pour-le-Merite holder, Lt. Walter Hohndorf, decided to make an attempt. In September 1915 he took the controls, and it is said that he made a short hop (or two) when the machine capsized during a landing run. The Forssman R turned almost completely over, coming to rest on its crushed nose and upper-wing leading edge, which was neatly fractured span wise in the process.
   Reluctant to write off their ever-increasing investment in the machine, SSW once again rebuilt the Forssman R in hopes that it would finally be accepted by Idflieg. As the crash had not been too serious, it was a comparatively simple matter to fit a new nose and repair the wing. The nose was rebuilt into a rounded, blunt shape fitted with a circumferential window. An opening for a future gun position which remained covered for flight trials was located atop the nose. The pilots' cockpit was either situated behind the window or in an open position under the leading edge of the wing. Outwardly these represented the only major changes. In its final form the Forssman R, with its modern glassed-in nose, fully cowled engines and handsome paint job, presented a sleek appearance which belied the weakness the gloss concealed.
   By this time, the Forssman R had achieved a universally bad reputation, known as the Ladenhuter, freely translated as "White Elephant". No pilot could be found to fly the machine. Consequently, for the major part of its life the Forssman R sat in a great hangar at Johannisthal collecting dust and taking up valuable space while damaging the prestige of SSW. But the aircraft belonged to SSW, and they understandably were anxious to deliver it to the military services and in turn recapture a portion of their investment.
   The technical director of the SSW aircraft section, Dr. Reichel, approached the Steffen brothers and offered them 10 per cent of the delivery price if they would perform the acceptance flight. In return for a price reduction, Idflieg reduced the delivery specifications, which now called for the machine to reach 2000 meters in 30 minutes carrying a useful load of 1000 kg. and enough fuel for 4 hours. Bruno Steffen accepted the challenge, but only after thoroughly convincing himself that the Forssman R was reasonably safe to fly. The tail surfaces were so large that he feared he did not possess the strength to move them. He considered the landing gear and wing struts far too robust, whereas other parts appeared too weak. One change which he made was to install a device so that all throttle levers could be operated in unison when necessary. Steffen felt that the lack of this feature was the reason why other pilots had such poor luck trying to fly the Forssman R. Meanwhile, Franz Steffen had carefully studied the construction drawings and the engineering calculations. He concurred with his brother that the aircraft was safe and strong enough to fly, but warned him that the fuselage immediately behind the wings was dangerously weak, and that caution must be taken during landing and taxiing. Everything considered, Bruno decided to perform the acceptance flight despite final warnings from his associates and friends. All that remained was to convince himself that he could control the machine in the air, and he prepared to make a short test hop. He found the steerability on the ground good by alternately revving opposite outer engines. After a hop of 300 meters he landed, satisfied that he could control the aircraft in the longitudinal direction at least. Although the hand-wheel control column was massive and the ailerons huge, he did not think he would experience any difficulties, for he felt he could always maintain lateral control by means of throttling the outer engines. All was ready for the acceptance flight in October 1915.
   Steffen decided to fly the Forssman R on the next day with five persons aboard as he had in the SSW R.I. But everyone whom he invited to go along, including members of the Idflieg acceptance commission, politely declined, leaving him no choice but to fly alone. For the flight, the Forssman R carried 725 kg. ballast and 275 kg. extra fuel to make up the required 1000 kg. useful load.
   Once in the air, he found the loaded aircraft tail heavy, which so increased the angle of attack that there was a danger of stalling. He was able to achieve correct climbing trim with the hand-wheel control column pushed far forward, a position which normally should have caused an aircraft to descend. During the flight, Bruno Steffen experienced only one updraft, but a violent one which threw the machine into a bank. With the control column held far forward, Steffen did not have the strength to turn the hand-wheel to correct the bank with the ailerons.
   Although in a climb, he was forced to pull back on the control column, causing the machine to nose up and then turn the hand wheel - one and one-half turns! Then in a fraction of a second he pushed the controls forward again. Slowly the aircraft righted itself, but now the time came to return the ailerons to neutral position. Quickly the control column was pulled towards the chest, the hand-wheel was turned and instantaneously pushed forward again. Steffen knew that he had to maintain absolute control of the aircraft lest it develop uncontrollable oscillations. The remainder of the flight was uneventful, and Bruno Steffen reached 2000 meters in 28 minutes, but to be sure he climbed another 100 meters. He was descending when one of the outboard motors stopped, through lack of fuel-tank pressure. Steffen pumped vigorously, but to no avail, and shortly all engines stopped. Steffen, who had experienced many close shaves in five years of flying, felt that this time his luck had finally run out. But by pushing the control column even farther forward, and half out of his seat, he was able to maintain a reasonable glide angle and managed to land safely. The ballast and fuel were weighed, and the barometer checked, with the result that the Forssman R was finally accepted by Idflieg in April 1916 for training use. All further development of the design was stopped. Later on the ballast or useful load was relocated to balance the tail-heavy condition but the machine was still next to impossible to fly.
   Shortly after the aircraft's acceptance the fuselage broke in two (just aft of the wings) due to vibrations while running the engines on the ground. The Forssman R was dismantled. Bruno Steffen was glad when he heard the news,- for now the danger that the machine could crash and claim human lives was past.
   The Forssman R was constructed before the R designation was actually applied to large aircraft. Consequently, if it did have a designation the Forssman R probably fell into the G category. Later German records refer to the machine as the Forssman R, although strictly speaking, it did not meet the R specification that the engines must be serviceable during flight.
   The Forssman R did not add anything to the development of the R-plane as a fighting weapon nor as an aircraft. It was a misconceived design from the start, and perhaps its only contribution to R-plane history was that it gave engineers an opportunity to learn from a failure.
  
Color Scheme and Markings
  
   The original aircraft had an overall dull buff appearance. Large Patee crosses on white backgrounds were painted on both sides of the upper wings and on the underside of the lower wings at half-span position. Similar markings were applied to the rudders. The redesigned version was painted a light color and the edges of the fuselage were outlined in black.
  
  
Manufacturer: Siemens-Schuckert Werke G.m.b.H., Siemensstadt, Berlin
Type: SSW Forssman R (first version) SSW Forssman R (second version)
Engines: Four 110 h.p. Mercedes engines Two 220 h.p. Mercedes D.IV engines
   Two 110 h.p. Mercedes engines
Dimensions:
   Span 24 m. (78 ft. 9 in.) 24 m. (78 ft. 9 in.)
   Length 16.5 m. (54 ft. 2 in.) 16.5 m. (54 ft. 2 in.)
Areas:
   Wings 140 sq. m. (1506 sq. ft.) 140 sq. m. (1506 sq. ft.)
Weights:
   Empty 3250 kg. (7166 lb.) 4000 kg. (8820 lb.)
   Loaded 5200 kg. (11,466 lb.)
Performance:
   Max speed 115 km.h.(71.5 m.p.h.) 120 km.h.(75 m.p.h.)
   Climb to 2000 m.(6562 ft.) 28 mins.
Service Use: None Training duties
  

J.Herris Siemens-Schuckert Aircraft of WWI (A Centennial Perspective on Great War Airplanes 12)

SSW Forssman "R"

   Construction of the Forssman "R", SSW's first experience with R-plane building, began in October 1914. Its design was clearly inspired by the Sikorsky Il'ya Muromets and construction was completed in the first half of 1915. The initial configuration had four uncowled, 110 hp Mercedes D.I engines independently mounted on the lower wing, each driving its own propeller. The cabin was fully glazed for an excellent field of view and, like its Sikorsky inspiration, projected just a small distance in front of the wings.
   Early test hops quickly revealed the design was seriously tail heavy, and an observer's/gunner's pulpit was added in front of the pilot to add weight to the nose. The biplane wing cellule had three bays, but the aft strut was omitted from the middle bay, probably in an attempt to save weight. This weakened the cellule and the 'missing' strut had to be installed. To improve directional control and stability a second rudder had to be added. Although the wing struts and landing gear were too strong and heavy, overall the structure was weak. In addition to poor handling qualities and a weak structure, the Forssman R was also under-powered. The design was a failure and SSW and Forssman parted ways.
   This should have been the end of the story. Unfortunately, SSW was reluctant to accept failure and tried to salvage the design, resulting in a painful, protracted development process that was foredoomed to failure. To improve performance the inboard engines were replaced with 220 hp Mercedes D.IV engines and the outboard engines were cowled and moved to a higher position thought to improve propeller efficiency. In addition, the nose was rebuilt to a more streamlined form. In its modified form the machine was tested by Lt. Walter Hohndorf (later to become a fighter ace awarded the Pour le Merite), but the Forssman over-turned on landing.
   Despite the resulting damage, SSW again rebuilt the aircraft, adding a more rounded nose. By now the Forssman had acquired the reputation of being a white elephant and no pilot wanted to fly it. Anxious to sell the aircraft to the Army, SSW offered the Steffen brothers 10% of the delivery price if they would perform the acceptance flight. Idflieg agreed to reduced specifications in return for a lower price. The Steffen brothers examined the aircraft and determined it was flyable.
   In October 1915 Bruno Steffen flew the aircraft on its acceptance flight. He flew alone,- all of the people he invited to accompany him declined, including members of Idflieg’s acceptance commission! The flight was an adventure. The aircraft was very tail heavy and Bruno struggled to control it. After exceeding the required 2,000 meter height in 28 minutes, Bruno was descending when one of the outboard engines failed due to inadequate fuel pressure. While trying to restart the engine by manually pumping fuel, all the other engines stopped! Despite total engine failure, Bruno was able to land the aircraft safely and it was accepted by Idflieg in April 1916 for training. However, further development was cancelled.
   While running the engines on the ground shortly after acceptance, the fuselage broke in two just aft of the wings due to excessive vibration and the aircraft was scrapped. A relieved Bruno Steffen was glad no one had been killed in the aircraft. Despite extensive development, being modified at least four times, the Forssman was a complete failure.


Siemens-Schuckert R-Plane Specifications
Forssman R.I R.II (Orig.) R.II (Reblt.) R.III (Orig.) R.III (Reblt.)
Engines Mercedes(1) 3 x 150 hp Benz Bz.III 3 x 240 hp Maybach HS 3 x 260 hp Mercedes D.IVa 3 x 240 hp Maybach HS 3 x 200 hp Benz Bz.IV
Span 24 m 28 m 28.22 m 38.0 m 28.22 m 34.33 m
Wing Area 140 m2 138 m2 156 m2 233 m2 156 m2 177 m2
Length 16.5 m 17.5 m 17.7 m 18.5 m 17.7 m 17.7m
Height - 5.2 m 4.6 m 4.6 m 4.6 m 4.6 m
Empty Weight 3,250 kg 4,000 kg '5,350 kg 6,150 kg - 5,400 kg
Loaded Weight - 5,200 kg 7,150 kg 8,460 kg - 6,820 kg
Max. Speed: 115 km/h 110 km/h 130 km/h 110 km/h - 132 km/h
Climb: 2,000m - 35 min. - 23 min. - 35 min.
3,000m - - - 45 min. - -
Ceiling: - 3,700 m - 3,800 m - 3,000 m
Duration: - 4 hours 5 1/4 hours 4 hours - 4 hours
Notes: 1. Originally 4x110 hp Mercedes D.I, rebuilt to 2x110 hp Mercedes D.I + 2x220 hp Mercedes D.IV.

M.Dusing German Aviation Industry in WWI. Volume 2 (A Centennial Perspective on Great War Airplanes 85)

Siemens-Schuckert-Werke, Abt. Flugzeugbau, Siemensstadt b. Berlin (SSW)

Aircraft Development:

Siemensstadt:

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  After the outbreak of World War I, the aircraft designers Villehad Forssmann and the Steffen brothers from Neumunster offered their experience and plans to the SSW. Since the army administration also suggested a resumption of aircraft construction, an aircraft department was set up at the Siemens-Schuckert dynamo plan under the direction of Prof. Reichel. Forssmann immediately began designing a four-engine R airplane, while Franz Steffen went to work on an R airplane with a central engine system, in which the Idflieg was very interested.
  Forssmann left at the beginning of 1916, after engineer Harald Wolff had previously taken over as head of the design office.
  Under the leadership of Professor Reichel, Forssman began designing a four-engine R airplane as early as the end of 1914, while Franz Steffen turned his attention to an R airplane with a central engine arrangement and a split fuselage. After various modifications, both aircraft were accepted by the Army Administration. The design developed by Franz Steffen was used for series production.
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