SOMEWHERE BETWEEN THE SPEED OF AN AIRPLANE and the maneuverability of a helicopter lies the Bell/Agusta Aerospace Co. BA609 civil tilt-rotor. This sleek, futuristic aircraft has the fuselage and tail of a fixed-wing jet, the wings and engines nacelles of a turboprop, and the mammoth blades of a tandem-rotor helicopter.
Producing an aircraft to fly like both a helicopter and an airplane presented extensive challenges. Recognizing the need for ground-based simulations and engineering models, the Bell/Agusta engineering team developed two BA609 simulators. One was a full-motion, full visual simulator for training the program test pilots. The other was a small, stationary engineering model, which made an appearance at the National Business Aviation Assn.’s 2006 convention in Orlando in October. The idea was to show the flight-handling qualities of the BA609 using the software that drives the actual aircraft in flight test. This was the simulator I had the good fortune to fly.
Entering the simulator was a simple matter of climbing two steps to a small, railed platform. Access to the cockpit was similar to climbing onto a corporate jet flight deck. I had to duck my head while maneuvering between and over pilot seats and instrument consoles. I took the pilot-in-command seat on the right. Roy Hopkins, a former U.S. Marine Corps AH-1 driver and Bell Helicopter’s chief BA609 experimental pilot, took the left seat. He’d be my instructor pilot.
"The nacelles are pitching for you. All you have to do is maintain a level attitude, especially when the nacelles are in transition. Use the power lever to increase your speed."
Everything was laid out as it would be in any corporate-size helicopter. The panels had the usual switches, levers and instruments found in almost any helicopter, except that many were non-functioning mock-ups and graphic representations installed to cut costs. After all, the purpose of an engineering model is to evaluate flight characteristics, not to conduct initial flight training.
Outside the glassless windows were a series of panels that provided a nearly seamless, 240-deg field of view of a small, virtual airport. We were positioned and holding on Runway 26R under clear skies with calm winds. Looking to my left and right, I could see the engine nacelles pointed vertically on the ends of the wings.
The BA609 is powered by two 1,940-shp Pratt & Whitney Canada PT6C-67A turboshaft engines. Its span from rotor tip to rotor tip is 60 ft (18.29 m), and its tail stands 15 ft (4.5 m) high. The 44-ft (13.31-m) long aircraft is designed for a max takeoff weight of 16,800 lb (7,631 kg) and a useful load of 5,500 lb (2,500 kg). It has space to carry 6-9 passengers, with a 50-cu-ft (1.41-cu-m) baggage compartment.
The BA609 is designed to cruise at 25,000 ft (7,620 m) and a max speed of 275 kt (509 kph), with a max range of 1,000 nm (1,852 km) with no reserve. It is also designed to hover out of ground effect at 5,000 ft (1,150 m) at ISA and max gross weight.
The first BA609 prototype made its maiden flight in March 2003 at Bell’s Flight Research Center in Arlington, Texas. It has accumulated more than 100 hr of flight test time and has operated at 25,000 ft and speeds up to 304 kt (563 kph). The second prototype took to the air Nov. 9 at AgustaWestland’s facility on the Italian air base at Cameri, Italy. Two other prototypes are to join the flight test program.
Hopkins, who was the first pilot to fly the BA609 prototype, immediately began my lesson by correcting me when I referred to the flight controls.
"We don’t call them the ‘cyclic’ and ‘collective,’" said Hopkins. "They’re the ‘center stick’ and ‘power lever,’ and serve as the cyclic and the collective when the aircraft is in helicopter mode, and like a yoke and throttle when in airplane mode."
Thanks to the BA609’s twin, counter-rotating rotor design, there is no torque to counteract with pedal inputs, so they retain the name "rudder pedals" and are used to control movement about the yaw axis.
Hopkins pointed out a grey thumb control on the power lever. Called the conversion switch, it rotates the nacelles simultaneously from 0 deg (straight ahead) through 95 deg (slightly aft of vertical). The latter position allows for rearward flight and landings on slight nose-down slopes.
For my takeoff, I rolled the nacelles to 90 deg, thus giving me a pure vertical launch. Once airborne, about 100 ft off the runway, I clicked the conversion switch forward to rotate the engines to their 75-deg position for a "normal" tilt-rotor departure angle.
"Don’t push the nose over," said Hopkins patiently as my helicopter habits kicked in. "The nacelles are pitching for you. All you have to do is maintain a level attitude, especially when the nacelles are in transition. Use the power lever to increase your speed."
At the 75-deg position, beeping the conversion switch forward just one additional time rolled the engines non-stop into their 0-deg position, putting the BA609 into airplane mode in which maximum forward airspeed can be attained. As the airspeed indicator rose, I retracted the landing gear at about 100 kt and pulled in more power.
While not a motion simulator, this simulator’s fidelity in portraying the world outside provided the proper illusions during each maneuver around the "airport."
After several enjoyable minutes of tilt-rotor fun and mayhem, I entered a 7-nm final for 26R. At that point, I tapped the conversion switch once, which pulled the engine nacelles back into their 75-deg angle, thus slowing us down. Again, I had to fight the urge to pull back on the center stick to bleed the airspeed off.
As I approached the ground, repeated taps on the switch shifted the nacelles back 3 deg at a time until the rotors were at about an 80-deg angle, which was excellent for a steep approach that felt exactly like that of a conventional helicopter. At 1 nm out and about 120 kt indicated, I dropped the wheels, lowered the power lever, and plopped us somewhat gently on the ground.
While not the real thing, or a full-motion simulator, the engineering model of the BA609 was a kick to fly. It has excellent fidelity, and is a great vehicle for becoming acquainted with the nuances of tilt-rotor flying.
Dual FAA and European certification of the BA609 is not expected until 2010, but the manufacturer reports the order book remains at more than 60 aircraft. Click here for more BA609 news from Rotor & Wing.