First full conversion of the Bell/Agusta Aerospace BA609 between helicopter and aeroplane mode is expected later this month after the civil tiltrotor returned to flight on 3 June. The 1.3h flight was the first since 2003, and followed changes to bring the six- to nine-passenger aircraft up to certification standard.
Over a series of flights from Bell Helicopter’s XworX research and development centre in Arlington, Texas, proprotor nacelle angle will be reduced in steps from 90° (vertical) to 0° (horizontal). “We will do level flight, climb, dive, turns and stalls at each nacelle angle,” says Jack Gallagher, Bell/Agusta engineering vice-president. “After 10h we will get to 0° and aeroplane mode.”
On the 3 June flight, Aircraft 1 was flown forward, backwards and sideways in hover mode, “demonstrating excellent handling”, says Bell/Agusta. Nacelle angle was varied from 95° to 75°, the aircraft reaching a forward speed of 86kt (159km/h). The BA609 is expected to exceed 260kt in aeroplane mode.
The first BA609 was returned to flight after a series of configuration changes including the upgrade of flight-control software, separation of electric systems to meet certification requirements, modifications to ease engine starting and installation of retractable landing gear. “The aircraft is now conformed,” says Gallagher.
The resumption of flight testing was slowed by delays in developing the definitive software for the BAE Systems triplex digital fly-by-wire system and by the need to replace bearings on the input shafts to the proprotor gearboxes after chips were detected during ground runs, says Gallagher.
Aircraft 2, meanwhile, is being assembled by joint-venture partner AgustaWestland in Italy, and is scheduled to fly in the fourth quarter. The first two BA609s are assigned to basic handling qualities testing and flight envelope expansion. Aircraft 3, for icing tests, is scheduled to begin ground runs in Italy by the end of this year. Aircraft 4, for avionics and service-ready testing, will begin ground runs at Bell in the second quarter of 2006. Certification is “still on target for 2008”, says Gallagher.
Bell/Agusta plans to certificate the BA609 for operation in instrument meteorological conditions and will offer the basic aircraft with optional utility or executive interiors. Gallagher says vibration levels in the first aircraft, with no treatment of the cabin, are “amazingly low”, similar to those in a business jet, while the noise level “allows normal conversion”.
GRAHAM WARWICK/WASHINGTON DC
Source: Flight International
