The H-3 Kolibrie (“Hummingbird) was a very small helicopter of origin made by the NHI (the Dutch Helicopter Industry) and was developed in the 1950s.
Hailing from the early days of helicopter design, the H-3 is quite a Spartan machine, with little in the way of cabin, having to make do with a basic windscreen only. The H-3 certainly lives up to its lightweight namesake.
This helicopter was designed as a general-purpose machine. The entire airframe is made from duralumin tubing. Interestingly, the H-3 was ramjet-powered. At the tip of each of the two rotor blades a ramjet provided thrust to turn the blades. The mechanical motion of the blades was also the source of power for the tail rotor.
One of the main advantages of the ramjet approach is that they would run on a variety of fuels, making the Kolibrie very cost effective and versatile. Apart from this, the decision to design the helicopter around ramjets meant that expensive and complex engine and gearbox components were not necessary. To get the ramjet system going it was necessary to make use of a 2 horsepower starter system. This small motor would bring the rotors to 70 rpm at which point the jets would be ignited.
Unfortunately, the whole mechanism of ramjet propulsion was judged to be too dangerous and unreliable for a production helicopter. Only nine units were ever built as production versions and were then exported to Israel, Germany, the UK and Netherlands New Guinea.
Historically the H-3 is considered a technical triumph, but a commercial failure. Despite the very low purchase price at the time. Although it was versatile, light and cheap the H-3 consumed a relatively large amount of fuel and the jets themselves were not easy to produce at production scale. To further dash the chances of the H-3, the USA provided the Hiller H-23 Raven to the Royal Netherlands Air Force free of charge, making it a poor decision to spend money on H-3 helicopters.