Bell’s bold vision of a civil tiltrotor takes flight

 - January 16, 2008, 11:03 AM

Like the old blues song goes, “It’s been a long time coming. But a change is gonna come.” That change–the possible revolution that is the promise of civil tiltrotor flight– took to the air on March 7 with the first flight of Bell/Agusta Aerospace’s BA609 tiltrotor prototype.

As with most rotorcraft first flights, the test card was deliberately kept modest. The BA609 hovered at an altitude of 50 feet, performed left and right pedal turns, both forward and aft flight maneuvers, four takeoffs and landings, nacelle position changes and stability testing for 36 minutes before setting down. The tiltrotor’s retractable tricycle landing gear was not retracted and won’t be until the successful conclusion of the first 10-hour block of test time. Conversion to fixed-wing mode is due by the end of the year. The first flight follows seven weeks of ground runs and taxi testing conducted at Bell’s Flight Research Center in Arlington, Texas.

At the controls for the first flight was Bell/Agusta senior flight test pilot Roy Hopkins, the world’s high- time tiltrotor pilot with more than 1,000 flight hours in the V-22 Osprey and XV-15 tiltrotor experimental testbed aircraft. Bell test pilot Dwayne Williams flew as copilot.

Within the modest dimensions of the six- to nine-passenger BA609 is an aircraft packing an extensive array of firsts. Given its 25,000-foot cruise altitude (when in fixed-wing mode), the BA609 will be the first pressurized rotorcraft. (Since the hybrid convertiplane must perform two of the most critical flight maneuvers–landing and takeoff–as a helicopter, it is considered by most defining regulatory agencies primarily as a rotorcraft).

The BA609 also has a triple-redundant fly-by-wire system, a first among general aviation aircraft. And, of course, when officially approved for civil flight, it will be the first convertiplane so approved.

The BA609 will also be fully de-iced and eventually approved for flight into known icing.

Hopkins and Williams flew the BA609 at a weight of 12,400 pounds, two-thirds of its mtow of 16,800 pounds. Weather conditions were close to ISA. The men reported the aircraft, powered as it is by a pair of 1,940-shp Pratt & Whitney Canada PT6C-67A turboshafts, to be quite lively, with takeoff achieved while pulling very little torque and both engines “running very cool.”

The squawk sheet filed after the historic first flight revealed how minor the problems detected were. Pilots reported the nose-gear steering to be too stiff, and that the glare from the windshield was excessive.

Neither pilot wore a parachute for the first flight, principally due to the fact that the altitude was so limited. Subsequent flight tests will require the men to wear them, however.

The first prototype will soon be joined by another, which is just being completed at the Arlington facility. Later this year another pair of prototypes will bring the BA609 fleet to four. At the completion of the first 10 hours of flight test, prototype number one’s powertrain and rotor dynamics will be torn down for inspection, with flight test due to resume by the beginning of summer.

Bell chairman and CEO John Murphey has pledged that the V-22 Osprey tiltrotor will enter service with the U.S. armed forces before the BA609 is certified. For this reason, delays in the Osprey project could produce ripple effects throughout the BA609 certification program, pushing its service entry date well beyond its present 2007 mark. For its part, the Osprey has been receiving high marks from Pentagon officials as it proceeds through its second round of operational tests, evaluations ordered in the wake of a pair of fatal accidents in 2000 and 2001.