Boeing X-50 Dragonfly

Background

The X-50A was conceived by Boeing to fill a requirement for a VTOL aircraft capable of escorting the V-22 tiltrotor. The program was a joint effort between Boeing and DARPA, with each covering half the development costs. Two proof-of-concept aircraft were built. The maiden flight occurred on 24 November 2003.

The design featured a canard foreplane and a conventional tailplane, both contributing lift during forward flight and offloading the main rotor wing. For vertical takeoff, hovering, low-speed flight, and vertical landing, the main rotor was driven by tip jets that directed exhaust from the jet engine through nozzles in the rotor tips. Because the rotor was driven directly by jet thrust, no tail rotor was needed to control torque.

For high-speed forward flight, exhaust was redirected through an ordinary jet nozzle and the rotor was stopped and held in a fixed position, functioning as a conventional wing. The first prototype crashed on 23 March 2004 during its third flight due to cross-coupling in the controls. A second, improved prototype (Ship 2) was built but was destroyed in a crash at the Yuma Proving Ground on 12 April 2006 during its sixth of eleven planned test flights. Investigation revealed that the fuselage was subject to an aerodynamic pitching moment of extreme sensitivity; both airspeed and rotor wake produced a nose-up pitching motion greater than the flight controls could compensate for.