Boeing X-50
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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 takeoff and landing, 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- ...
rotor wing experimental
unmanned aerial vehicle An unmanned aerial vehicle (UAV) or unmanned aircraft system (UAS), commonly known as a drone, is an aircraft with no human pilot, crew, or passengers onboard, but rather is controlled remotely or is autonomous.De Gruyter Handbook of Dron ...
that was developed by
Boeing The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...
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 Adva ...
to demonstrate the principle that a helicopter's
rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...
could be stopped in flight and act as a fixed wing, enabling it to transition between
fixed-wing A fixed-wing aircraft is a heavier-than-air aircraft, such as an airplane, which is capable of flight using Lift (force), aerodynamic lift. Fixed-wing aircraft are distinct from rotorcraft, rotary-wing aircraft (in which a Helicopter rotor, r ...
and
rotary-wing A rotary-wing aircraft, rotorwing aircraft or rotorcraft is a heavier-than-air aircraft with rotor wing, rotary wings that spin around a vertical mast to generate lift (force), lift. Part 1 (Definitions and Abbreviations) of Subchapter A of Chapt ...
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
tiltrotor A tiltrotor is an aircraft that generates lift (force), lift and thrust, propulsion by way of one or more powered Helicopter rotor, rotors (sometimes called ''proprotors'') mounted on rotating shaft (mechanical engineering), shafts or nacelles ...
. 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 A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the add ...
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 may 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. ...
to control
torque In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...
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 on April 12, 2006. Subsequent investigation revealed that the aircraft's
fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...
was subject to an aerodynamic
pitching moment In aerodynamics, the pitching moment on an airfoil is the Moment (physics), moment (or torque) produced by the aerodynamic force with respect to the aerodynamic center on the airfoil . The pitching moment on the wing of an airplane is part of ...
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


See also

* Sikorsky X-Wing


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 Aircraft with fixed tricycle landing gear Single-rotor helicopters Single-turbine helicopters