DARPA Wants a New X-plane that can Hover

DARPA’s new X-plane VTOL illustration
Defense Advanced Research Projects Agency (DARPA) announced earlier this week that it is interested in developing an experimental program that will be able to take off and hover like a helicopter but fly like an aircraft and perform both these tasks at very high efficiency – much higher than any similar vehicle in existence.
DARPA has just released a requirement for a new experimental aircraft (also known as an X-plane) with some groundbreaking capabilities. According to the agency: “one of the greatest challenges of the past half century for aerodynamics engineers has been how to increase the top speeds of aircraft that take off and land vertically without compromising the aircraft’s lift to power in hover or its efficiency during long-range flight”.
While fixed wind aircraft became faster and faster and helicopters enjoyed better control over hovering and maneuvering, vertical take-off and landing (VTOL) aircraft which are meant to combine both capabilities progressed slowly and became more and more complex in their designs. This is where the new DARPA X-plane initiative come into place. Opening the door for the industry to push forward unorthodox thinking and out of the box innovation that might not have developed otherwise.
The DARPA specs for the new VTOL call for a craft capable of reaching more than 300kt (or 555km/h)  –  higher than existing conventional helicopters while having the ability to hover with greater efficiency than current rotorcraft.

This is of course not the first time engineers are trying to tackle this issue. However in the past they have encountered many problems, including low fuel efficiency, reduced lift capacity, control issues, structural complexity, general reliability and more.
According to DARPA, unlike previous attempts at an efficient high speed VTOL aircraft, this time around: “rather than tweaking past designs, we are looking for true cross-pollinations of designs and technologies from the fixed-wing and rotary-wing worlds. The elegant confluence of these engineering design paradigms is where this program should find some interesting results.”
DARAPA is said to be pushing the new X-plane extremely aggressively, hoping to have the first test flight of the craft in 3.5 years time (modern aircraft design typically take many years to develop). It also believes that unlike previous attempts several key pieces of technology are now mature enough that they can help make the program a success.
More information can be found on the DARPA website.

An American Dynamics 2010 video showing the AD-150 VTOL concept