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The Williams X-Jet, created by Williams International, was a small, light-weight Vertical Take Off and Landing (VTOL) system powered by a modified Williams F107 turbofan aircraft engine. It was designed to be operated by and carry one person and controlled by leaning in the direction of desired travel and adjusting the power. It could move in any direction, accelerate rapidly, hover, and rotate on its axis, staying aloft for up to 45 minutes and traveling at speeds up to 60 miles per hour (100 km/h). It was evaluated by the U.S. Army in the 1980s, and was deemed inferior to the capabilities of helicopters and small unmanned aircraft.
Due to aerodynamic effects in the duct within which the propellers rotate, the platform was dynamically stable even though the pilot and center of gravity of the platform were fairly high up. In testing, the prototypes flew well enough but the US Army judged them to be impractical as combat vehicles as they were small, limited in speed and only barely flew out of the ground cushion effect.
The Springtail EFV-4A is a fourth generation single engine powered-lift research vehicle. This craft was built for the express purpose of testing and proving our core technology. This was accomplished on November 5, 2003 when transition to forward flight was achieved. This vehicle is still in service and is being employed as a test bed for further enhancements and refinements to the technology. We are currently using this vehicle for expansion of the flight envelope.