While we are on these little 'ram jet' types I don't suppose (for the sake of posterity) that we should overlook the industry's first 'Kolibri' helicopter.
The SOBEH Foundation (Stichting voor de Ontwikkeling en Bouw van een Experimenteel Hefschroefvliegting) was established in the early 1950's to research and build small ramjet-powered helicopters designed by J. Meyer Drees. The SOBEH-1 helicopter, which flew in 1954, was an open-frame single-seat machine with a skid undercarriage. Two small ramjets were fitted at the tips of the two-blade rotor which embodied an automatic pitch adjustment system. The pilot controlled the machine through a suspended overhead cyclic stick.
The SOBEH-1 was written off through ground resonance, but was succeeded by the SOBEH H-2 (PH-NFT) which was flown in May 1955. The H-2 was an improved version with a large windshield and a tiny strutted tail unit with a small anti-torque tail rotor. It was taken over by Nederlandse Helicopter Industrie N.V. (NHI) which was formed by Aviolanda and Kromhout and based at Rotterdam. There they refined the design into the two-seat NHI-3 (H3) Kolibri.
The Dutch NHI (Nederlandse Helicopter Industrie) Kolibri H3 PH-NHI being test flown near Rotterdam in May 1956
The Kolibri showing its 'subtle' tip jets
All of the early European 'ram jet' helicopters, including the Kolibri, offered spray gear installations
The cockpit arrangement of the H3 Kolibri (Photo: André de Heus)
The photo above is of an example of the Kolibiri which is now housed in the 'Aviodrome' at Lelystad airport in Holland.
And .. courtesy of our friends at British Pathé, a short clip of the Kolibri in action .. being looked upon by a somewhat bemused Prince Bernhard of Holland:
