Ott, W., "HELIos, a VTOL Flying Car," SAE Technical Paper 985535, 1998, doi:10.4271/985535.
HELIos is a single seat, three wheel, vertical take-off and landing (VTOL) flying car concept. It uses duct enclosed counter-rotating propellers. This technology eliminates the need for a tail rotor and makes the vehicle more compact. It needs no modification to switch between drive mode and flight mode. It uses a modified motorcycle or snowmobile engine for road travel and a two-stroke, aircraft, diesel engine for air propulsion. It is flown by wire for directional control, and a helicopter pitch control is used for vertical motion. HELIos is equipped with a guidance control system for safe and precise flying. In emergency cases, the driver/pilot can employ a ballistic parachute, which allows the vehicle to float safely down to earth. It will be street legal under the rules of the Department of Transportation (DOT); its three-wheel design categorizes it in the motorcycle and scooter category.