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The H3 Sprinter was a light experimental helicopter that originated in West Germany. It was produced in by the VFW-Fokker joint venture that began in 1969. The H3-E model was built as either a three-seat executive transport, a two-stretcher ambulance or and agricultural aircraft. The H3 employed a single-engine design and a distinctive compressed air tip-drive rotor. Separate forward thrust came from a set of fuselage-mounted fans. Amazingly for the time, the H3 made extensive use of aluminum and glass-fiber reinforced plastic laminate. The aluminum mostly went into a load-bearing keel which served as support for the cabin, landing gear and engine bay. The composite plastics were used for the cabin’s skin. The sole engine was made by Allison and produced 400 shaft horsepower. However, not all of those horses actually went to the shaft. Thanks to the unique propulsion system of the H3 it would also have to drive the compressor system when hovering. The air followed a winding path through ducts until it was passed via a rotor-mounted distributor into the blades themselves and to the tip jets. The rotor itself had a three-bladed design. This is where the remarkable cold blade tip drive system could finally express itself as thrust. Alternatively, the air could be ducted to the forward-thrusting fans instead, all seamlessly handled by then state-of-the-art gearbox. Originally the idea was that the H3 would be the start of an entire family of tip-jet aircraft, but after only a few flights it became clear that this method of propulsion was not effective for an aircraft at this size. All in all, only two H3 prototypes were ever built and today this unique and technically impressive helicopter is nothing more than a small but significant footnote in the history of helicopters.
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