 As a result of this reduced payload, some estimate that a tiltrotor does not exceed the transport efficiency (speed times payload) of a helicopter, while others conclude the opposite.Additionally, the tiltrotor propulsion system is more complex than a conventional helicopter due to the large, articulated nacelles and the added wing; however, the improved cruise efficiency and speed improvement over helicopters is significant in certain uses.Speed and, more importantly, the benefit to overall response time is the principal virtue sought by the military forces that are using the tiltrotor.