Dutchman A. G. von Baumhauer built a helicopter in 1925 that flew in a very limited fashion. Able to stay in the air only briefly, this unsuccessful machine had a single main rotor and a small vertical tail rotor to offset torque. It needed the weight of dangling chains at each corner to keep level. A sepa-rate engine powered the tail rotor, which operated independently of the main rotor.

J.P.Spencer "Whirlybirds: A History of the U.S. Helicopter Pioneers", 1998