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90 Years of Helicopter Design, Development and Testing in the Netherlands

K. Bakker
Apart from a brief period during the 1950's the Netherlands never possessed an indigenous helicopter industry. Yet the helicopter has been on the Dutch agenda for almost 90 years. At three different points in time in the last century helicopter projects started, two purely national, and one in which the Netherlands is a participant in an international project. The paper focuses on the two national projects, the Von Baumhauer helicopter and the Kolibrie project. Both emanate from the personal interest in helicopters of young people. Albert Gilles von Baumhauer, who from 1910 onwards, even before he became a mechanical engineer, is thinking of technical solutions for helicopters. He concludes that a single rotor helicopter with cyclic blade pitch control offers better stability and control than a multi rotor helicopter. This concept as well as that of a separate tail rotor to counteract rotor torque is patented. He has the skill to work out his ideas into models and prototypes based on detailed calculations, sketches and drawings. He also is able to make others enthusiastic for his ideas. In 1924 the Dutch Helicopter Association is founded. The task is to study the scientific and operational aspects of helicopters. An excellent opportunity to bring this task into practice is the building and testing of the so called Von Baumhauer helicopter, which contains the above mentioned design novelties. In the period 1924 - 1930 the helicopter is built and tested. Von Baumhauer in 1921 becomes deputy director of the Government Service for Aeronautical Studies (RSL), at that time a government body. In view of his position he formally has to stay at a distance from the association. In practice he is the driving force behind the project and there is a continuous involvement of the RSL with the project. Some 40 RSL test reports are available in the NLR museum, covering the whole test period from 1925 to 1930. A number of those is referred to in detail to give an impression how the very complex problem of helicopter vibrations is dealt with, some 85 years ago. Twenty years later two other young men, like Von Baumhauer graduated from Delft University of Technology, meet each other. One is Gerard Verhage, who is thinking of a helicopter rotor type, which automatically reduces the blade pitch angle to make a safe autorotation possible. The other is Jan Meijer Drees, working for the National Aeronautical Laboratory (NLL), which since 1937 is the name of the former RSL. He is an expert on helicopter rotor flow. A growing interest for the helicopter is emerging in the Netherlands. The Helicopter Foundation is established and a Sikorsky S-51 helicopter is acquired to assess the operational capabilities. NLL is assigned to set up and execute the test program. The outcome is promising and a new foundation with the name SOBEH is created to build and develop an experimental helicopter. Verhage and Meijer Drees later join SOBEH. This project is financed with the remaining funds from the S-51 test program. The first SOBEH helicopter uses the soft-in-plane rotor of Verhage and is fitted with tip jets. The paper describes the development steps made by the very enthusiastic and almost autonomously operating design team, their success and setbacks. Sometimes the latter are a result of inherent characteristics of the new rotor type or the ram jet engines that so far are not known or not taken into account in the design phase. In 1955 the development work leads to the H-3 helicopter configuration, which is successfully demonstrated to government officials. The decision is made to start the production of this helicopter with the name Kolibrie. However the original development funds are depleted. In that year the Netherlands Helicopter Industry is founded with the aim to finance the trajectory leading to certification and production. The Netherlands Institute for Aircraft Development (NIV) from that moment on has a more prominent role, as it provides the funds for further research of the helicopter. NLL is assigned by Professor Van der Maas, the chairman of NIV, to do much more fundamental work on the helicopter which is already common practice for the Fokker aircraft development programs. The certification process is successfully completed in 1958. Some 100 NLL reports cover the Kolibrie project. This does not become a commercial success, primarily because of the high fuel consumption, which leads to a short range and endurance.
35th European Rotorcraft Forum 2009,
Conference Paper
21,0 x 29,7 cm, 16 Seiten
DGLR-Bericht, 2009, 2009-03, 35th European Rotorcraft Forum 2009 - Conference Proceedings; S.1-16; 2009; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn
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35th European Rotorcraft Forum 2009 - Conference Proceedings