A US Navy-backed project which aims to dramatically improve rotor blade efficiency, especially for the Bell Boeing V-22 Osprey tiltrotor, has been boosted by the restoration of funding after a lean period lasting three years.
Development of the reconfigurable rotor blade (RRB) stalled after 2002 when the USN restricted its funding to just 40% of that requested, delaying the project by two years to 2008. However, navy support has returned and almost 90% of the funding requested for fiscal years 2005 and 2006 has been approved, says Boeing RRB programme manager Rick Bussom.
The programme’s goal now is to develop a quarter-scale actuator system in FY06 to support windtunnel testing by January 2007. The results of this work will be critical in persuading USN rotorcraft programmes to invest in reconfigurable blades, says Bussom.
While the most likely candidate is the V-22, he says any helicopter could benefit from the technology at some level. “It works for any mission that requires you to do long dashes with heavy loads.”
The new actuator uses a 1960s- era alloy called NiTinol, which can be trained to reshape itself into a pre-determined configuration as heat is applied, then return to its original shape as it is cooled. The NiTinol tube is heated to apply a twist to the rotor blade, which for the V-22 would change shape as the aircraft transitions from hover mode to forward flight, matching the more efficient blade angle for each mode of flight. The reconfigurable system is designed to cost $6,000 a blade, although a large upfront cost will be incurred while integrating and qualifying the new system.
The US Navy has launched a mishap investigation following an April incident during which a CV-22 suffered damage estimated at between $20,000 and $200,000 when both its engines ingested ice during a transit flight to Edwards AFB, California.
The aircraft flew into a weather front at 18,000ft (5,500m) before descending to 10,000ft when its full authority digital engine control system initiated an automatic recovery cycle.
STEPHEN TRIMBLE/WASHINGTON DC
Source: Flight International
