Many unusual military vehicles have been developed throughout history, yet there are few as strange as the de Lackner HZ-1 Aerocycle. Designed to be piloted by someone with little (or no) flight experience, it initially showed great potential – that is, until some obvious flaws were uncovered.
Development of the de Lackner HZ-1 Aerocycle
The concept for the Aerocycle first came about in the early 1950s, thanks to Charles H. Zimmerman of the National Advisory Committee for Aeronautics (NACA). He came up with the idea of the rotorcraft, an aircraft with rotors on its underside that could be controlled by a pilot shifting their weight. It was intended to be flown by those with little-to-no flight training, and initial tests showed merit. This prompted aircraft manufacturers to begin developing their own designs.
de Lackner Helicopters presented a design that featured a one-man platform atop helicopter rotors. Known under the company designation “DH-4,” it was intended to carry up to 120 pounds of cargo or a five-gallon fuel tank.
It was a relatively simple design, consisting of a cross-shaped frame, upon which the pilot stood before bicycle-like handlebars. They were secured to the aircraft by a safety harness, which itself was attached to the 32kW outboard motor. This powered the Aerocycle’s 15-foot-long contra-rotating rotors.
The DH-4’s landing gear consisted of airbags attached to arms, which themselves were connected to a rubber floatation device in the middle. This would allow the aircraft to operate in amphibious settings, if necessary. This feature was later replaced by a pair of helicopter type-skids. The craft also had a special parachute developed for it – the “Ultra-Fast Opening Personnel Parachute Type XMP-2” – which was later proven to be unreliable.
Testing was successful… At first
The DH-4 was eventually named the “HZ-1” by the US Army. Testing of the Aerocycle began on November 22, 1945 with the tethered flight of a prototype. This was soon followed by a free flight at the Brooklyn Army Terminal in January 1955. Over 160 test flights were conducted in total, amounting in over 15 hours of in-air experience, and the results were promising – so much so that the Army requested a dozen examples be produced.
The Army believed the Aerocycle could become the modern version of the horse cavalry, and it was alleged someone could learn to pilot the aircraft after less than 20 minutes of instruction. de Lackner Helicopters’ design also proved to be the fastest out of those presented to the service.
Testing was transferred to Fort Eustis, Virginia in 1956, falling under the purview of Capt. Selmer Sundby. However, while the initial results had proved promising, Sundby quickly determined the Aerocycle had numerous flaws. Firstly, it was a lot more difficult to control than initially thought and therefore wouldn’t be safe in the hands of an unexperienced pilot. As well, the rotors kept kicking up debris from the ground.
Crashes led to the de Lackner HZ-1 Aerocycle’s abandonment
During the testing period, the de Lackner HZ-1 Aerocycle experienced a pair of crashes that eventually led to the project being abandoned. Both occurred under similar conditions, after the contra-rotating rotors became intermeshed. This caused the blades to break and the pilot to lose control of the Aerocycle.
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Following the crashes, testing was conducted in the wind tunnel at the Langley Research Center, where it was discovered the Aerocycle’s forward speed was limited by a pitching motion. Its rotor-tip clearance was found to be sufficient, so experts were unable to determine why the rotors kept intermeshing. This, paired with the overall concept of the HZ-1 failing to live up to expectations, led the Army to terminate the project.