GUY NORRIS / LOS ANGELES
Canard Rotor Wing demonstrator may prove concept's suitability for range of applications
Test flights of the delayed X-50A Dragonfly Canard Rotor Wing (CRW) technology demonstrator are expected to start this month following the completion of rotor bearing repairs that were required after ground tests in December.
The Boeing Phantom Works and US Defense Advanced Research Projects Agency CRW programme aims to prove the viability of a vehicle capable of transitioning between helicopter and fixed-wing flight using a reaction-driven stopped- rotor system.
If successful, the CRW concept could be developed for applications ranging from unmanned combat armed rotorcraft to larger utility vehicles. Boeing had planned to start flight tests in the third quarter of last year, but encountered swash plate and rotor bearing issues. "We did a tear down during a ground check out and had to get new bearings," says Dragonfly programme manager Clark Mitchell. "We had higher dynamic loads coming down through the rotor system, so we made a change and added elastomeric bearings to take the centrifugal forces. We ended up clocking that bearing to get the loads down to an acceptable level," he adds.
Although the loads were reduced to allow test flights to start, "we still didn't have enough fatigue life".
The subsequent modifications are expected to double the bearings' fatigue life, enough to complete the 11-flight, three-month test programme. The initial flights will see the envelope expanded to 60kt (110km/h) and an eventual altitude of 5,000ft (1,525m), which provides a 96% chance of recovering the CRW in a glide in fixed-wing mode, or in an autorotation in case of engine failure.
Source: Flight International
