A mono tiltrotor aircraft is different from a conventional tiltrotor in which the proprotors are mounted to the wing tips, in that the "coaxial proprotor" is mounted to the aircraft's fuselage. As a result of this structural efficiency, a mono tiltrotor exceeds the transport efficiency (speed times payload) of both a helicopter and a conventional tiltrotor. One design study concluded that if the mono tiltrotor could be technically realized, it would be half the size, one-third the weight, and nearly twice as fast as a helicopter.