Siemens - Schuckert Forssman The Siemens - Schuckert Forssman was a prototype bomber aircraft designed and built in Germany in 1914 and 1915 . When its performance proved inadequate for its intended role , even after numerous modifications , the German Inspectorate of Flying Troops ( the " Idflieg " ) eventually accepted it into service as a trainer . Shortly after its acceptance into military service , the aircraft ' s fuselage fractured while on the ground , ending its career . The aircraft is sometimes known as the Siemens - Schuckert Forssman R , the " R " alluding to the designation that the " Idflieg " assigned to multi - engine aircraft in late 1915 . However , the Forssman did not meet all the criteria of the " R " designation — for example , its engines were not serviceable in flight — and the " R " designation only came into use after the Forssman was built . If the Forssman received any military designation at all , that designation is not now known . Design and development . The Forssman was a large , four - engined , thee - bay biplane with an extensively glazed , fully enclosed cabin . The wings were unstaggered and of uneven span , and the undercarriage consisted of two mainwheels carried on a common axle , plus a tailskid . The tail was of conventional layout with a single fin . Power was supplied by Mercedes D . III engines mounted on short struts on the lower mainplane . The design bore such a strong resemblance to the contemporary Sikorsky Ilya Muromets bombers produced in Russia that " Jane ' s Encyclopedia of Aviation " describes it as " virtually a copy " of that aircraft , and in their book on German multi - engine types of World War I , Haddow and Grosz comment that designer Villehad Forssman " was content to copy the Sikorsky configuration almost line - for - line " . Construction commenced in October 1914 , and was completed by spring 1915 . Early test flights , probably limited to short hops , revealed multiple shortcomings in the design . As originally completed , the wings were braced between the second and third cell by only a single strut . Reinforcements to the wings added a second strut aft of this position , together with a set of diagonal struts to support the overhang of the upper wings Other modifications at this time included rigging the wings with a slight dihedral to improve lateral stability , adding a second tailfin and rudder to improve control , and grafting an open gun position onto the front of the fuselage to improve the aircraft ' s centre of gravity . Even with these modifications in place , the Forssman could not fulfil the " Idflieg " ' s acceptance criteria , and Villehad Forssman severed his connections with Siemens - Schuckert owing to the failure of his design . With Siemens - Schuckert still eager to recoup its investment in the design , the firm assigned Harald Wolff to improve the aircraft . Wolff deleted the tacked - on pulpit from the nose and redesigned the forward fuselage to taper to a sharp point , surmounted by a teardrop - shaped cupola for the pilot . The redesign also replaced the two inner D . III engines with more powerful Mercedes D . IVa engines mounted on faired struts . The outer engines remained unchanged , but were moved from their original position to mountings on faired struts midway in the interplane gap , to improve propeller efficiency . Gun positions were added in the nose and in dorsal and ventral locations in the fuselage , although all these positions remained faired - over during testing and there is no evidence that armament was ever fitted . In September 1915 , and after another pilot had refused to fly the aircraft following some ground tests , Lt Walter Höndorf agreed to test the redesigned Forssman . After a one or two hops , the aircraft turned over on its nose while alighting . The nose was crushed , and the leading - edge spar in the upper wing was fractured . Despite all setbacks , Siemens - Schuckert still wanted to sell the aircraft , and commenced another rebuild . The nose was redesigned again , into a rounded , blunt configuration with a gun position atop . The pilot ' s position was relocated either behind the nose windows or to an open cockpit on top of the fuselage . By now , the aircraft had acquired the nickname " Ladenhüter " ( literally , " shelf warmer " or , idiomatically , " white elephant " ) and pilots refused to fly it . Siemens - Schuckert director Walter Reichel negotiated a price discount for the " Idflieg " if they would accept the aircraft to a lower specification . The " Idflieg " accepted , and reduced the acceptance criteria to the aircraft reaching in 30 minutes while carrying a useful load of and enough fuel for an endurance of 4 hours . Reichel now offered Bruno and Franz Steffen ten percent of the sale price if they could perform an acceptance flight to meet the " Idflieg " ' s requirements . The Steffen brothers examined the Forssman and Bruno agreed to make the flight , against the recommendations of friends and associates . Franz ' s calculations based on the construction drawings showed the aircraft safe to fly , although the fuselage to be structurally weak immediately aft of the wings . After a successful hop , Bruno Steffen planned to fly the Forssman on its acceptance flight with four passengers aboard , as he had for his own R . I design . However , everyone whom he invited declined , including the members of the " Idflieg " acceptance committee , and so he made the flight alone . Carrying the required 1 , 000 - kilogram payload , Steffen reached 2 , 000 metres in 28 minutes , and then climbed another before returning to the ground . While descending , one engine failed , followed shortly by the other three . Nevertheless , Steffen made a safe landing and the acceptance criteria were verified . Although now obsolescent , the " Idflieg " accepted the Forssman into service in April 1916 as a trainer . Further development of the design was halted , although the aircraft ' s ballast was moved to counter tail heaviness that Steffen encountered on the acceptance flight . Shortly after acceptance , the aircraft ' s fuselage fractured just aft of the wings , due to engine vibrations while running the engines on the ground . The Forssman was dismantled at that point , and Bruno Steffen expressed relief at the news , as the aircraft would not be able to endanger other lives .