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.