De Lackner HZ - 1 Aerocycle The HZ - 1 Aerocycle , also known as the YHO - 2 and by the manufacturer ' s designation DH - 4 Heli - Vector , was an American one - man " personal helicopter " developed by de Lackner Helicopters in the mid - 1950s . Intended to be operated by inexperienced pilots with a minimum of 20 minutes of instruction , the HZ - 1 was expected to become a standard reconnaissance machine with the United States Army . Although early testing showed that the craft had promise for providing mobility on the atomic battlefield , more extensive evaluation proved that the aircraft was in fact too difficult to control for operation by untrained infantrymen , and after a pair of crashes the project was abandoned . A single model of the craft was put on display . Design and development . During the early 1950s , Charles H . Zimmerman of the National Advisory Committee for Aeronautics ( NACA ) developed a system for control of a rotorcraft in which , with the rotors mounted on the underside of the aircraft , the machine could be steered by the pilot through the simple shifting of his weight , and kept stable through the actions of his natural reflexes . Known as kinesthetic control , and similar in principle to the mechanics of riding a bicycle or a surfboard , it was hoped that the concept would allow for pilots to operate an aircraft with little to no training time . NACA testing proved that the idea had merit , and several companies , including Bensen Aircraft , Hiller Aircraft , and de Lackner Helicopters , began development of rotorcraft using the concept . The concept proposed by de Lackner Helicopters was a one - man flying platform , and it received the company designation " DH - 4 " . The DH - 4 was expected to be able to carry up to of cargo or an auxiliary fuel tank to extend its range up to in addition to its pilot ; in addition , a cargo lifting line could be threaded through the rotor shaft for the carrying of slung load s underneath the craft . The machine was a simple , cross - shaped frame , with the pilot standing on a platform , secured by a safety harness . The harness also secured the aircraft ' s engine , which was an outboard motor manufactured by Mercury Marine . The engine was controlled by a twist - grip motorcycle - style throttle and transferred power to the diameter , contra - rotating rotors via belt drive with a chain reduction unit . The aircraft ' s landing gear consisted of airbags at the end of each arm of the frame along with a large rubber float in the middle , allowing for amphibious capability , although this arrangement was later replaced by a pair of conventional helicopter - type skids . Testing . Originally designated YHO - 2 by the U . S . Army , then later re - designated HZ - 1 and named " Aerocycle " , the prototype made its first tethered flight on 22 November 1954 , with its first free flight taking place in January 1955 at the Brooklyn Army Terminal . Over 160 flights totaling more than 15 hours of flight time were conducted , and the results of this early test flight program were considered promising enough that a dozen examples of the type were ordered ( serial numbers 56 - 6928 to 56 - 6939 ) . Predictions were made that the craft could provide transport to a modern version of the old horse cavalry , providing airborne " eyes and ears " for the Army . In 1956 , the test program was transferred to Fort Eustis , Virginia , where Captain Selmer Sundby took over test - flying duties . The HZ - 1 had been designed to be very easy to fly , and early testing indicated that untrained soldiers could learn to operate the craft in less than 20 minutes , and some claiming that only five minutes of instruction were required . In addition , the HZ - 1 proved to be faster than other flying platform designs evaluated by the Army . Sundby , however , quickly determined that the craft was much more difficult to fly than had been expected , and would not be safe in the hands of an inexperienced pilot . In addition , the low - mounted rotors proved to be prone to kicking up small rocks and other debris . Over a series of tethered and free - flying test flights lasting up to 43 minutes , the HZ - 1 suffered a pair of accidents . Both crashes occurred under similar conditions – the contra - rotating rotors intermeshed and collided , the blades shattering , causing an immediate loss of control resulting in a crash . Aerodynamic testing was conducted in the full - scale wind tunnel at the Langley Research Center , and it was discovered that the Aerocycle ' s forwards speed was limited by an uncontrollable pitching motion , but rotor - tip clearance was always sufficient . The inability to determine the precise cause of the intermeshing , combined with the fact that the " personal lifting device " concept was failing to live up to its expectations , led to the decision to terminate the project . Sundby was awarded the Distinguished Flying Cross for his test - flying work with the HZ - 1 , going on to test - fly the H - 21 and H - 34 helicopters , as well as seeing combat in the Vietnam War before retiring with the rank of colonel . Parachute development . An entirely new type of parachute with extremely fast opening characteristics , the " Ultra - Fast Opening Personnel Parachute Type XMP - 2 " , was developed for use in testing of the HZ - 1 and Hiller VZ - 1 flying platforms . Designed for use from and at altitudes as low as , the XMP - 2 proved to have insufficient reliability for use as a personnel parachute . Aircraft on display . Of the dozen examples of the type ordered by the U . S . Army , only a single example of the HZ - 1 has survived , and this aircraft is currently on display in the U . S . Army Transportation Museum at Fort Eustis , Newport News , Virginia .