Boeing Begins Work On DARPA DiscRotor

By Graham Warwick

Boeing has kicked off work under a 30-month U.S. Defense Advanced Research Projects Agency program to study a high-speed rotorcraft design called the DiscRotor.

The concept promises helicopter-like hover efficiency, but speeds in excess of 350 knots in fixed-wing mode. This compares with 150 knots for a typical helicopter and 250-300 knots for a tiltrotor.

The DiscRotor would takeoff and land like a helicopter, slowing the rotor and retracting the blades into the disc as it accelerates, until it morphs into a swept-wing aircraft powered by ducted fans.

DARPA program manager Phil Hunt says the DiscRotor’s combination of high speed for ingress and egress and good high-altitude hover performance would fit the combat search-and-rescue role. The initial concept has a UH-60 Black Hawk-size fuselage.

The 30-month effort is aimed at validating the capabilities of the DiscRotor rather than defining a flight demonstrator configuration. Hunt believes too early a focus on designing the demonstrator caused problems in previous programs, including Boeing’s X-50 “Dragonfly” Canard Rotor Wing — another concept that sought to combine vertical takeoff and landing capability with fixed-wing speed. The X-50 was abandoned after crashes ruined both flight prototypes.

Under the DiscRotor program, the Boeing-led team will build a small-scale model of the aircraft for wind tunnel testing to determine lift-to-drag ratio and stability, and a small model of the rotor system to investigate transition between rotary-wing and fixed-wing modes.

Boeing will also design and build a larger retractable-rotor test rig that will be installed in a 20-foot wind tunnel later in the program. Lightweight airframe and transmission technologies will also be investigated.

Once the study is complete, Hunt says, DARPA will decide whether the results are promising enough to proceed to a flight demonstrator, at which point the agency plans to reopen to program to competition.

Image: DARPA