The first Distance Diamond for a flight in a powered sailplane was issued by the German Aero Club to Willibald Collé, who on Jflew his SF-27M from Elz, Germany to Le Rabot airfield, France, a distance of 334 mls (537 km). The fuel tank, capacity 5.28 gal (20 l), is mounted in the fuselage behind the pilot. A specially designed ignition system facilitates easy starting. The engine is started by a hand-operated cable. The power plant comprises a 26 hp Hirth Solo vertically-opposed four-cylinder engine, driving a propeller of about 53 in (1.36 m) diameter through a reduction gear of 1:186. The whole process is extremely simple, requiring only 31 turns on the crank, and can be completed in 5 seconds. The fuselage doors over the engine and propeller bay are automatically opened and closed when the engine is raised or retracted. The engine is raised and retracted manually by a crank-driven draw chain-pushrod system, swinging upward and forward into the operating position. The fuselage center section has also been modified, increasing the overall length to accommodate the engine which, when retracted, lies inside the fuselage behind the wings. The wings and control surfaces are strengthened internally.
The construction of the SF-27M is similar to that of the SF-27. In addition, the main wheel tire size is increased to 5.00 x 5. The main difference arises from the additional weight of the engine installation, amounting to approximately 88 lb (40 kg).
Since the power plant is retractable, the SF-27M has about the same soaring performance as the normal SF-27 Zugvogel V high-performance sailplane. Remarks by Johan Visschedijk: "The SF-27M is a single-seat powered sailplane with a retractable power plant which makes it capable of self-powered take off as well as normal launching by winch or aero-tow.
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