Seven suppliers provided composite parts for the Scorpion, and Textron AirLand produced more than 700 composite parts in house. The Scorpion’s primary structure, fuselage, wings, empennage and control surfaces are made predominantly from composite materials. The primary structure includes a mix of unidirectional and woven carbon fibers, depending on the specific needs of the parts. The aircraft utilizes the HexPly® 8552 epoxy resin system, which has already been used for commercial aircraft at Cessna. “Since the development schedule was so tight, we wanted to use a proven material,” says Dale Tutt, chief engineer for the Scorpion program.
The Scorpion’s composite structures have a high level of corrosion resistance and address fatigue characteristics that can occur with metal structures. “We were looking for a 20,000-hour life span, and composites helped us achieve that,” says Ben De Putter, fuselage team lead for the Scorpion program. “It’s not unachievable with metals, but you have to keep adding weight to get there, which is not desirable for overall operation costs.”
De Putter and his team discovered another advantage. “Composites have proven to be very robust in our manufacturing environment,” says De Putter. “For example, when manufacturing a typical solid laminate, we can’t vary too much from the specification. But the composites we used are not overly sensitive. They are reasonably tolerant of variation in cycle time, temperature and pressure, within spec. It gives us more flexibility from a quality control standpoint.”
Composites were also chosen for their life-cycle costs, adds De Putter. “In the design methodology we chose, large laminate structures made of composites can be easily maintained and repaired – on the assembly line or out in the field,” he says. “We can repair rather than replace a whole wing.”
The Scorpion passed its initial flight test in December with flying colors. Test pilot Dan Hinson, a former U.S. Navy pilot, indicated the jet is very nimble and responsive but solid and stable as well. Since its first flight, it has made at least five additional flights, and ground vibration testing was conducted during the first two months of 2014.
Textron AirLand’s next challenge is to identify buyers for the Scorpion. The company considers the U.S. Air National Guard as a potential fit. They are also targeting allied nations that may require tactical aircraft but not at the price of high-end fighter jets. Some countries could see it as a cost-effective alternative to replace turboprop reconnaissance aircraft with a capable jet aircraft.
But for now, the project team celebrates each flight the Scorpion makes. “Our initial success definitely has us feeling good,” says De Putter.