The Boeing X-50A Dragonfly, formerly known as the Canard Rotor/Wing Demonstrator, was a

VTOL A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-wi ...

rotor wing A rotor wing is a lifting rotor or wing which spins to provide aerodynamic lift. In general, a rotor may spin about an axis which is aligned substantially either vertically or side-to-side (spanwise). All three classes have been studied for use as ...

experimental

unmanned aerial vehicle An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controll ...

that was developed by

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...

and

DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the A ...

to demonstrate the principle that a helicopter's

rotor Rotor may refer to: Science and technology Engineering * Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator *Helicopter rotor, the rotary wing(s) of a rotorcraft ...

could be stopped in flight and act as a fixed wing, enabling it to transition between fixed-wing and

rotary-wing A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft with rotary wings or rotor blades, which generate lift by rotating around a vertical mast. Several rotor blades mounted on a single mast are referred to as a rotor. The Internati ...

flight. The X-50A built upon the work of the Sikorsky S-72 X-Wing program of the 1980s by designing the vehicle as a multi-mode aircraft from the ground up. The X-50A was one of two projects funded by DARPA in its "Heliplane" program. Neither of the two prototype aircraft ever successfully transitioned to full forward flight. DARPA withdrew funding for the X-50 program in late 2006 due to inherent design flaws.

Development

Boeing initially proposed using the CRW configuration to fill a requirement for a VTOL aircraft suitable for escorting the

V-22 The Bell Boeing V-22 Osprey is an American multi-mission, tiltrotor military aircraft with both vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) capabilities. It is designed to combine the functionality of a convention ...

tiltrotor A tiltrotor is an aircraft which generates lift and propulsion by way of one or more powered rotors (sometimes called ''proprotors'') mounted on rotating shafts or nacelles usually at the ends of a fixed wing. Almost all tiltrotors use a trans ...

. The X-50A was a joint program between Boeing and DARPA, with each paying for half the development costs. The X-50A was powered by a single conventional

turbofan The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...

engine. For rotary-wing mode, the engine's exhaust was diverted to nozzles in the tips of the rotor blades. When the aircraft transitioned to full forward flight, the engine exhaust was directed through a nozzle at the rear of the aircraft and the rotor was locked into a fixed position and functioned as a conventional wing.McKenna, James T. "One Step Beyond", ''Rotor & Wing'', February, 2007, page 54 Two proof-of-concept aircraft were built as part of the program. The X-50A's maiden flight took place on 24 November 2003.

Design

The X-50 had a "canard" foreplane as well as a conventional tailplane, allowing both to contribute lift during forward flight and to offload the main rotor wing. For vertical take-off, hovering, low-speed flight, and vertical landing, the main rotor wing was driven by tip jets, by directing the exhaust from a

jet engine A jet engine is a type of reaction engine discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include Rocket engine, rocket, Pump-jet, water jet, and ...

through thrust nozzles in the rotor tips. Because the rotor is driven directly by jet thrust, there is no need for a

tail rotor The tail rotor is a smaller rotor mounted vertically or near-vertically at the tail of a traditional single-rotor helicopter, where it rotates to generate a propeller-like horizontal thrust in the same direction as the main rotor's rotation. Th ...

to control

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

as in a conventional helicopter. For high-speed forward flight, the exhaust is redirected through an ordinary jet nozzle and the rotor wing is stopped and held in a fixed position, as in a conventional airplane.

Operation

Crashes

During the third flight of the prototype X-50A, on 23 March 2004, the vehicle crashed, as a result of cross-coupling in the controls. A second, improved prototype ("Ship 2") was then built. On its sixth of 11 planned test flights, Ship 2 was completely destroyed in a crash at the

Yuma Proving Ground Yuma Proving Ground (YPG) is a United States Army series of environmentally specific test centers with its Yuma Test Center being one of the largest military installations in the world. It is subordinate to the U.S. Army Test and Evaluation ...

on April 12, 2006. Subsequent investigation revealed that the aircraft's

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

was subject to an aerodynamic

pitching moment In aerodynamics, the pitching moment on an airfoil is the moment (or torque) produced by the aerodynamic force on the airfoil if that aerodynamic force is considered to be applied, not at the center of pressure, but at the aerodynamic center o ...

of extreme sensitivity. Both airspeed and rotor wake would produce a nose-up pitching motion that was greater than the flight controls could compensate for.

Outcome

Neither aircraft was able to achieve transition to full forward flight mode during the portions of the test flight program that were completed. In September, 2006, DARPA recognized the inherent design flaws and withdrew funding for the program.

Specifications

References

External links

Boeing press release
*
Additional technical information
{{DEFAULTSORT:X-50 Unmanned aerial vehicles of the United States X-50, Boeing Canard aircraft DARPA X-50 Dragonfly Stoppable rotor helicopters Cancelled aircraft projects 2000s United States helicopters Aircraft first flown in 2003