The Baumgärtl Heliofly III/57 and Baumgärtl Heliofly III/59 were 1940s experimental backpack helicopters designed and built by the Austrian-designer Paul Baumgärtl. Following on from his earlier experiments with strap-on autogyros the Heliofly III/57 was powered by two Argus As 8 piston engines each driving a single-blade of the contra-rotating rotors.
A problem with the supply of the As 8 engine forced a re-design to use one engine, powering two rotors on a common co-axial shaft, with the engine driving one rotor directly and the other through gearing to overcome the torque effects.
Specifications (16hp).
"Data from" 
General characteristics* Crew: 1* Length: ()* Empty weight: ()* Gross weight: ()* Powerplant: 1 × piston engine , () * Main rotor diameter: 2 × ()
References.
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