THE DE LACKNER
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
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
The tests were successful, and the US
Army ordered twelve of these for further
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
With a top speed of more than 70 mph, it
was faster than others evaluated by the
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
"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
Of the original twelve ordered by the
Army, the only one remaining is the one on
exhibit at the Transportation Museum.