June 17, 2013
Credit: Hawker Beechcraft
Aviation Week jumped at the chance to fly AT-2, the second AT-6C prototype. We were accompanied by Daniel “Shaka” Hinson, Beechcraft Corp.’s AT-6 research, development, text and engineering manager.
The AT-6C is powered by a 1,600-shp Pratt & Whitney Canada PT6A-68D engine that has 45% more power than the basic -68 engine that powers the T-6 Texan II trainer. It also has a new wider chord Hartzell four-blade prop to convert the extra torque into thrust. The upgraded engine and prop add weight to the nose of the AT-6C, but that’s offset by removing ballast from the engine compartment.
The 500-shp increase helped the AT-6C better meet the conditions of the LAS system requirements document issued by the U.S. Air Force. It stipulated that candidate aircraft must be able to carry two crew, two 50-caliber machine guns, two GBU-12 Mk 82 500-lb bombs and an electro-optical/infrared sensor ball, in addition to cockpit and engine armor, a chaff and flares dispenser and enough fuel to complete a three-hour mission profile.
Other requirements include a HUD, NVG-compatible cockpit displays, zero-zero ejection seats, front and rear multifunction displays and the ability to cruise at at least 250 KTAS at 10,000 ft with the prescribed LAS weapons load.
While the basic AT-6B had a sufficiently robust airframe and excellent aerodynamics that enabled it to meet contract requirements, its 1,100-shp engine lacked the muscle to meet the payload, equipment and performance requirements of the LAS contract. For the AT-6C, Beechcraft not only added more power, it also embarked upon a major drag-reduction program for the aircraft and the external stores. In addition, internal wing fuel capacity was increased by 325 lb to 1,525 lb, thereby eliminating the need to carry two external fuel tanks for the three-hour LAS mission profile. The AT-6C now easily exceeds mission requirements, says AT-6 program director Derek “Turk” Hess. “Those changes have dramatically improved performance,” he says.
For our demo flight, AT-2 had no external stores, unlike the heavily laden aircraft we flew for our 2010 AT-6B report. That aircraft was handicapped by having only 1,100 shp. With AT-2’s “clean wing” we expected performance to be sprightly, and we were not disappointed.
With 1,094 lb of fuel aboard, two pilots and test equipment, our ramp weight was 8,460 lb. Airport performance tests with the new engine had yet to be completed; thus a computed takeoff distance was not available.
Departing Wichita, Kansas’s Beech Field Runway 18, we noticed that the trim aid device, a system that compensates for power-induced yaw, has yet to be fine-tuned to handle the extra 500 shp of the -68D engine. However, modest right rudder pedal pressure kept the aircraft on centerline. Hinson recorded a ground roll distance of 800 ft and we headed east, climbing at 140 KIAS and in excess of 3,000 fpm. In level flight at 10,000 ft with full power in ISA conditions, the aircraft accelerated to 257 KIAS, resulting in 302 KTAS. Clearly, AT-2 was a much stronger performer than the first prototype.
We also flew a series of aerobatic maneuvers, including loops, barrel rolls and Immelmanns, along with clean and dirty stalls, plus three spins. As it did during our first demo flight last year, the AT-6 impressed us with its stability and handling ease. But further development of the trim aid device will be required to reduce the amount of rudder input to keep the aircraft in balanced flight.