Rieseler RI


Henrich Focke and Anton Flettner are pre-war Germany's must famous helicopter pioneers, but there was a third pioneer whose name has all but disappeared from the history books. Walter Rieseler was born in Berlin in 1890. Rieseler became interested in flight at an early age. With his brother he started a small aircraft company in Breslau in 1920. On the 24th of January 1926 with his friend Walter Kreiser was given a patent for an autogyro (This was two days before Cierva was issued a patent for his autogyro in England). In 1927 Rieseler and Kreiser build their first autogyro. Financed by a Hamburg banker, the autogyro which was conventional in design, but featured a four-leaf rotor. Unlike Cierva's design, Rieseler's autogyro had blades that could be adjusted in flight. The first flight showed a strong oscillation that could not be eliminated. At this setback the banker withdrew any further funding.

Rieseler work had drawn the attention of Professor Alexander Kleimin of the Daniel Guggenheim Institute at the University of new York. At his urging Rieseler and his partner Walter Kreiser, left for the United States in 1930. It was there that Riesler and Kreiser were to form a partnership with E. Burke Wilford. The new company was called the Pennsylvania Aircraft Syndicate (PAS). On August 5th, 1931 PAS flew their first autogyro. This was a small autogyro powered by a 62 KW (85 PS) Continental engine and was flown by American pilot F. P. Brown on August 1931. After further modification to both more powerful engine, widened wing and shorten chassis they christened the autogyro the WRK (Wilford Rieseler Kreiser) Autogyro.

Rieseler had a more adventurous idea in mind for vertical flight and returned to Germany in 1934. With the idea of a new type of aircraft that would feature two coaxially mounted rotors moving in opposite directions that would rotate around their longitudal axis. With a patent for this idea issued on February 16th 1935 Rieseler founded his own company, Rieseler und Company in Berlin.

Rieseler soon succeeded in interesting the RLM in his ideas for controlled vertical flight and managed to get a contract to develop the RI, a simple helicopter design with a pair of contra-rotating coaxial rotors powered by a 90 hp HM504 engine. Construction of the RI was done by Rieseler's engineer Otto Steue. By the Spring of 1936 Rieseler began testing the RI in tethered flights and by the Summer it was ready for its first free flight. Riesler invited his friend Flugkaptain Johannes Mohn to fly the RI. Mohn reported that the RI the helicopter was unlike anything he had ever flown before. Be adjusting the engine throttle he soon succeeded in hovering the RI to a height of 49 feet. The R1 was tested almost daily. Mohn claims to have reached a top speed of 99 mph. Engine overheating problems prevented flights from lasted any longer then 15 to 20 minutes. Mohn was not happy with the flight characteristics in the horizontal flight which led to re-designs and to changes of the tail unit.

A demonstration was arranged for the benefit of Ernst Udet on September 3rd, 1936. Mohn took off vertically to a height of 197 feet, turned the helicopter 360 degrees and landed after a flight of 16 minutes. After the engine had cooled, Mohn took off again to demonstrate a full circuit flight. When Mohn throttled the engine down to land, the engine stalled and the R1 crashed into a heap of twisted metal. Udet joked, "You can't impress me with that! I am quite capable of producing a crash myself". Mohn survived the crash with broken ribs.

It is believed that the R1 was rebuilt and handed over to the DVL, where testing was carried out in 1937. Little else is known on the faith of the RI.

Rieseler was not dismayed by the crash of the R1 and immediately began work on his next helicopter, the RII. The RII was a two seat helicopter powered by a pair of coupled Sh 14a engines. The twin engines were envisioned to ensure sufficient power to land safely on one engine.

The initial test flights done by Mohn were satisfactory, however on a later flight on December 18th, 1937, the connecting bolts and pylons between the fuselage and rotor head gave out and the RII crashed. Though slightly injured in the crash this was to be Mohn's last helicopter flight. He decided that two crashes were enough helicopter flying for him.

Work on the third helicopter, the RIII did not reach the construction stage as Walter Rieseler died in January 1938 at the age of 47 of an heart attack. Consequently, no further work was done on the RIII and the work of Walter Rieseler passed into obscurity.