A.Weyl Fokker: The Creative Years (Putnam)
While the M.7 was giving so much trouble, Fokker was doing some thinking about fighting in the air. Firms were encouraged to fit a machinegun to the observer’s cockpit of their two-seat types. Such armament was purely defensive; what was needed was an offensive fighter aircraft.
Fokker decided to build such an aircraft without official guidance or advice. He confidently expected to achieve quick results by using components of existing types.
Two M.7 fuselage structures, engineless but each with its individual standard tail group, were joined by a biplane structure. Between these fuselages a nacelle was mounted centrally on the lower wing. In this the pilot sat, sandwiched between two 80-h.p. Oberursel rotaries, one driving a tractor airscrew, the other a pusher. Outboard of the fuselages the equal-span wings had two-bay bracing. Two gunners were to be carried, one in the front of each fuselage; no armament was ever fitted, however, and there was no provision for rearward defence.
By the standards of its time the basic idea of the Fokker M.9 was reasonably promising, and the aircraft might have proved better than the A.E.G. K.I, apart from its lack of rear defence. But the execution of this interesting experiment was utterly unsatisfactory. It was a makeshift, hastily assembled without any attempt at engineering; and its tests by Fokker were correspondingly slapdash.
For the first take-off, six men were posted along the intended run armed with fire extinguishers; others sat in two motor-cars and on motorcycles with engines running, ready to rescue the pilot in the event of mishap. The take-off run was rather long. On landing, Fokker complained that the fuselages moved when the wings were warped. He made another flight alone, and finally took up two passengers (military mechanics) in the gunners’ positions in an attempt to correct the M.9’s tail-heaviness. Henze recalls that all these flights took place within the space of a few days and were quite short.
After this perfunctory testing of a radical new design Fokker gave up. The M.9 was put aside for dismantling, and its development was completely abandoned. Any aeronautical engineer could have foreseen that the lack of any rear connexion between the fuselages would permit flexing and lead to unsatisfactory control. If Fokker had had more patience he might have made something of the M.9. However, his attention was then fully taken up by the work on the M.5K/MG single-seat fighter, which began when the M.9 was abandoned.
J.Herris Fokker Aircraft of WWI. Vol.1: Spinne - M.10 & Watercraft (A Centennial Perspective on Great War Airplanes 51)
Fokker M.9
The M.9, work number 129, was Fokker's first design after the outbreak of war. The Army wanted an airplane that could defend itself against Allied fighter attack, which was then just hypothetical. Fokker's response was an unusual two-engine, twin-boom biplane. The booms were M.8 fuselages without engines; in their place was a cockpit for a gunner with flexible machine gun. The pilot sat in the central nacelle with two 80 hp Oberursel U.0 engines mounted in push-pull configuration. The booms and nacelle were held together by strengthened center sections and the outboard wings were derived from M.7 wings but were of equal span.
The construction was standard Fokker; welded steel tube fuselages and tail surfaces and wooden wings, all fabric covered.
Fokker flew the prototype and quickly discovered it had poor flight characteristics and was tail heavy. In addition, the center section was too flexible. A second flight was made with mechanics in the gunner's cockpits to correct the tail heaviness, but the other problems were not resolved and Fokker dismantled the M.9.
Fokker M.9 Specifications
Engine: 2 x 80 hp Oberursel U.0
O.Thetford, P.Gray German Aircraft of the First World War (Putnam)
Fokker M 9 (K1)
April 1915 saw the appearance of the M 9, the only twin-engined Fokker aircraft of the First World War. The twin fuselages were modified M 8s, each with its own tail surfaces, there being no rigid connecting surface aft. The central nacelle housed a crew of three, and 80 h.p. Oberursel rotaries were mounted at either end. The Kl designation implied Kampfflugzeug but was soon modified to the G classification. Only one M 9 was built, and relatively few flights were made.
W.Green, G.Swanborough The Complete Book of Fighters
FOKKER K I (M 9) Germany
Original in concept in having a push-pull engine configuration and twin fuselage booms, the M 9 was developed without official encouragement as an offensive fighter, the sole prototype being completed in April I 1915. Also known by the designation K I (the "K” prefix indicating Kampfflugzeug, or ‘‘Battle Aircraft”), the M 9 utilised two fuselages, complete with tail assemblies from conventional M 7 two-seat sesquiplanes. These I were married by means of a biplane structure to a central nacelle which carried single 80 hp seven-cylinder rotary Oberursel U O engines fore and aft, with the pilot seated between. The nose of each M 7 fuselage accommodated a cockpit for a gunner. No rigid structure connected the two fuselages aft of the nacelle and, in consequence, the booms tended to twist when the wings warped. The M 9 was perfunctorily flight tested by Anthony Fokker. He complained of the flexing of the tailbooms and the marked tail heaviness which rendered control difficult. As Fokker was by then preoccupied with testing the M 5K/MG (E I) monoplane, further development of the M 9 was abandoned. No data relating to this short-lived experimental fighter have apparently survived.
