The first Bell/Agusta BA609 tiltrotor made full conversion to airplane mode near Fort Worth, Texas, in late July. On the eve of returning to Italy to take the reins of aircraft two, Agusta test pilot Pietro Venanzi briefed AIN on what the companies learned from this fundamental expansion of the flight envelope.
“During the first conversion flight we stayed at 100-percent rpm, to assess all the aeroelastic modes and torsional stability in that regime. In fact, we consider that full airplane mode is achieved when the rpm has been reduced to 84 percent, and we achieved that soon afterwards.
“We have been able to appreciate the exceptional smoothness of this machine. It’s quiet and vibration-free up to Vcon (200 kcas at zero degrees nacelles and 100-percent rpm). We’ll see what happens when we reach higher speeds and higher density altitudes, but so far so good, and I don’t see why that shouldn’t continue.”
According to Venanzi, “Performance has been outstanding. The Citation we’re using as a chase aircraft can’t keep up with our eye-watering rates of climb, which exceed 2,500 fpm at 140 kcas.” During testing the BA609 has been taking off at close to its 16,800-pound maximum design weight.
Venanzi continued, “Handling qualities are also good. Besides some marginal directional stability issues at 60-degree nacelle while descending at high sink rates (but only there and then), the aircraft shows well harmonized flight controls, excellent stability in all axes, well tuned sensitivity and control power. It flies just like the simulator.”