PAUL LEWIS / MESA, ARIZONA
First flight in third quarter could pave way for vehicles able to switch between helicopter and fixed wing model
Boeing Phantom Works planned to start ground testing of the X-50A Canard Rotor Wing (CRW) Dragonfly demonstrator as Flight International closed for press, in preparation for a first flight in the third quarter. The programme could finally allow the development of manned and unmanned vehicles capable of conversion between helicopter and fixed-wing modes using a reaction-drive propulsion rotor system.
Boeing and the Defense Advanced Research Projects Agency (DARPA) have provided $31 million for the CRW advanced technology demonstration over the last four years. Vibration and structural mode interaction testing was completed in March and the next step will be restrained ground tests of the X-50A at full power to measure lift and cruise nozzle thrust.
The 3.5-month test schedule calls for the first four flights to validate rotary-wing flight control and to expand the envelope to 60kt (110km/h). The following five flights will be in compound mode, blending rotary and fixed wing lift in the 60-120kt range. The final two flights will be full conversions into aeroplane mode. "The flight cards we have right now indicate we can achieve our objectives in 11 flights," says Clark Mitchell, CRW Dragonfly programme systems integration team lead.
Up to 60kt the rotor is maintained at 100% maximum revolutions per minute (RPM) and provides more than 90% of lift with 30% of thrust directed out through two side directional control nozzles for anti-torque control. At conversion speed, the aft cruise nozzle is opened, the rotor is slowed to 70% RPM and the canard and horizontal stabiliser begin to provide lift. In aeroplane mode, the rotor is stopped and the ducted gas flow from the X-50A's Williams F112 turbofan is diverted away from the blade tip nozzles to the jet nozzle.
While DARPA has yet to commit funding for a follow-on programme, Boeing is looking at a transition study. A number of potential applications have been identified for CRW, including a manned high-speed escort for the Bell Boeing V-22 Osprey tiltrotor, as well as unmanned platforms such as the US Army's planned Unmanned Combat Armed Rotorcraft.
Source: Flight International
