Return

THE DE LACKNER AEROCYCLE –
An early “Flying Platform”

     One of the most prominent concepts in military aviation in the 1950s and 1960s was the "flying platform."  These platforms were designed to carry one combat-ready soldier to perform reconnaissance missions.

    Charles H. Zimmerman, engineer for the National Advisory Committee on Aeronautics (precursor to NASA), proposed that if the rotors of a helicopter were placed on the bottom of the aircraft, a pilot would be able to steer it just by shifting his weight.  This concept became known as 'kinesthetic' control. 

    After initial tests by NACA proved the idea valid, three companies developed prototypes: De Lackner, Hiller, and Bensen.

First Test Flight of the Aerocycle – Brooklyn Army Terminal, 1955

    The HZ-1 Aerocycle was designed by De Lackner Helicopter Company of Mount Vernon, New York.  It's first test flight was at Brooklyn Army Terminal with a combat-ready test pilot.

    The tests were successful, and the US Army ordered twelve of these for further evaluation.

    The Aerocycle was powered by a 4-cylinder, water-cooled 43hp Mercury outboard motor located on a circular platform.  Just under the platform were two belt-driven, counter-rotating 15-foot rotor blades.

    With a top speed of more than 70 mph, it was faster than others evaluated by the Army. 

Testing at Fort Eustis – 1956

    Captain Selmer Sundby was the test pilot for this Aerocycle at Fort Eustis in 1956.  An Army pilot with 6 years of experience and more than 1500 hours in fixed and rotary winged aircraft, Sundby volunteered for numerous test flights, some lasting seconds long and one almost 43 minutes long.

    Designed to require only about 20 minutes of instruction before actual flight, Sundby said, ". . . it only took me one flight to realize that a non-flyer would have considerable difficulty operating it."

    Standing to the rear of the center platform, secured by safety belts, Sundby used the motorcycle-like handlebars to turn, varying the speed of the rotor blades thereby changing torque.  Lift was obtained by increasing the rotor blade rpms.

Above, then Captain Sundby testing the Aerocycle, 1956.

   Captain Sundby said, "I had two accidents while testing this machine - one in free flight from about 40 feet in the air, doing 30-35 mph, and another during tethered flight." 

     "Both accidents were similar in that the counter-rotating blades flexed and collided, shattering the blades.  This resulted in immediate loss of lift and control."  Further studies could not pinpoint the exact speed or conditions that caused the blades to flex, and eventually the concept was abandoned.

    For his efforts, Sundby was awarded the Distinguished Flying Cross by the Chief of Staff of the Army in 1958.

Sundby as a lieutenant colonel

   Of the original twelve ordered by the Army, the only one remaining is the one on exhibit at the Transportation Museum.