September 2019

Von Baumhauer Helicopter

First flight: September 1925

In 1924, the British Ministry of Aviation announced a contest for a helicopter that could complete a closed circuit flight at a speed of 54 kt (100 km/h), make a vertical take-off and climb to up to 1970 ft (600 m), and glide to a safe landing with no engine power. The prize of £50,000 attracted many contenders, with an end data of May 25, 1925, which was later extended by one year.

In response to this British contest, Dutchman A. G. von Baumhauer built a helicopter in 1925 that flew, however in a very limited fashion. Able to stay in the air only briefly, this machine had a single 2-bladed main rotor and a small vertical tail rotor to offset torque. A separate engine powered the tail rotor, which operated independently of the main rotor.

The first flight was made in September 1925 by Lt. F.H. van Heyst in Soesterberg (near Amsterdam). On Feb. 10, 1926, van Heyst was able to keep the machine several meters off the ground for 5 minutes.

After these first test flights, the helicopter was transferred to Schiphol in 1926, where B. Grass and later Peter J. Six acted as test pilots. On Aug. 28, 1930, von Baumhauer himself made a half-hour flight. The next day however, a hinge bolt of one of the rotor blades failed due to a fatigue crack, and the helicopter crashed. The helicopter was completely destroyed, but von Baumhauer was unharmed. Due to lack of funds this machine was not rebuilt, but Von Baumhauer's interest in helicopters continued until the end of his life.

Von Baumhauer's design made some major achievements which greatly influenced further development of helicopters, such as:

  • The use a single main rotor, as opposed to two counter-rotating rotors typical for that time period.

  • One of the first uses of a tail rotor to counteract the torque produced by the main rotor. Note that the tail rotor in this helicopter was powered by a separate engine and its angle of incidence could not be adjusted during flight.

  • The use of collective and cyclic pitch control via the use of the swashplate principle. Below the rotor, two concentric rings were mounted, connected to each other with bearings. The non-rotating inner ring could be tilted and moved along the rotor shaft. The outer ring rotated with the rotor and adjusted blade angles via pitch rods. This enabled adjustment of blade pitch according to the blade's current angle, a mechanism which is still used in modern helicopters.

 Photo: via Wikimedia.org

Text: Peter Noell

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