The Starship
Everyone thought the Starship would come out to be quite impressive, but it was anything but that. Its carbon-composite construction and turboprop engines had engineers thinking it would be flawless, but it actually was very slow and difficult to fly. In 1989, 53 of these designs were created, but only a handful got sold.
The Hiller VZ-1
This aircraft was horrible in reality, so our only hope is that people thought on paper that it would be impressive. The concept of this aircraft is actually terrifying; there are no gears, but the pilot is expected to steer with his bodyweight. The highest speed it could reach was 16 miles per hour, and everyone hated it once they saw it in action.