12/31/2010. Remarks by Johan Visschedijk : "The Helikopter Technik Wagner of Friedrichshafen, Germany, was formed by Josef Wagner with the objective to develop a torque-free basic vehicle which could be fitted with a variety of cabins and specialized equipment for different applications. Development was started in 1960 and designed by Chief Engineer Alfred Vogt, the earliest simple two-seat pod-shaped test models with coaxial rotors and skid landing gear were fairly rudimentary machines built to test the concept, and one design was a roadable machine titled the Rotocar III.
Each of these designs utilized a contra-rotating rotor system in which the lower three-blade rotor was attached to the crankcase of a 95 hp three-cylinder rotary engine, rotating around the rotor pylon, with the upper two-blade rotor driven by the crankshaft. The first production-standard prototype to fly in July 1965 was the Wagner Sky-Trac 1 (D-HAJE c/n 10), which still had a frame structure but the rotary engine was replaced by a conventional drive from a 260 hp Franklin 6AS-335-B horizontally-opposed six-cylinder engine, and had a sliding canopy forming an enclosed cabin for the single pilot.
A second machine was built (D-HARB c/n 12) which was fitted with a pontoon landing gear and a longer boom with a V-tail. The subsequent three-seat Sky-Trac 3 (D-HAJI), also flown in 1965, had a more complete cabin structure and was fitted with spray bars and under-slung tanks for agricultural chemicals, and could also be fitted with a pontoon landing gear. After extensive development work had been carried out, the Wagner designs were passed to a new company, Helikopter Technik München (HTM) of Munich in 1971.
The Sky-Trac 1 and Sky-Trac 3 were used by HTM to demonstrate the concept, and a new prototype of the Sky-Trac (D-HHTM) was built in tandem two-seat configuration, as a utility helicopter with a 260 h.p. Lycoming IO-540 engine. This still had the coaxial rotor system but was extensively redesigned to accommodate the new engine and cockpit layout.
HTM then went on to build two examples of the Skyrider (D-HTMS and D-HHTF) which reverted to the configuration of the Sky-Trac with a four-seat cabin and a fully enclosed streamlined structure. The Skyrider was an attractive machine with a skid undercarriage and V-tail, which commenced flight testing on February 21, 1974.
Unfortunately, HTM was forced to abandon further development in 1975 through lack of further funding."