50-year Old PT6 Engine Upgraded With Latest Technologies
Pratt & Whitney Canada is here with the recently certified PT6A-140, the latest version of a turboprop engine that will celebrate next year the 50th anniversary of its first delivery. The -140 is will power Cessna’s new Grand Caravan EX turboprop single, with 867 shp at takeoff. That represents a 28-percent increase over the -114A used in the Grand Caravan. Transport Canada certified the -140 last July. The FAA’s equivalent approval is expected “in the next few months,” according to Denis Parisien, P&WC vice president for general aviation.
The PT6A-140 provides better takeoff, climb and hot-and-high performance for the improved Grand Caravan EX, which is slated to enter into service later this year. Nevertheless, the new engine is the same length as the -114A, and thus has a very high power-to-weight ratio, Parisien pointed out. Specific fuel consumption is lower, too, by 5 percent.
The PT6A-114A uses technologies that have been employed on larger PT6 variants. For example, the hot section enables higher thermal power because “we’ve incorporated the latest in high-temperature nickel alloys and single-crystal blade materials,” Parisien told AIN. These alloys have demonstrated excellent durability properties, added Nick Kanellias, general manager for P&WC’s utility and general aviation programs.
In the compressor, engineers introduced on the first stage a wide-chord “integrally bladed rotor.” This feature is also known as a “blisk” and increases flow and improves aerodynamic efficiency. There is no additional stage in the PT6A-140, compared to the PT6A-114A.
Another feature on the -140 is its flight data acquisition storage and transmission system, which enables automated transfer of engine parameters, wirelessly to P&WC’s network, once the aircraft has landed. “A customer will always know where he stands as for predictive maintenance,” Kanellias said. The PT6A-140 features a 3,600-hour TBO.
The engine also benefits from the greener production techniques P&WC is developing. “We have optimized the test cell sequence for running an engine in pre-shipment tests,” Parisien explained. Over the last couple of years, this has enabled a cut in fuel consumption by 28 percent for these tests. In addition, “materials of concern” in the manufacturing process have been identified and have either been removed or being researched for suitable replacements. These are, for instance, chromic acid anodizing, chrome 6-containing paints, chrome plating, conversion coatings and leaded-bronze bushings.
The company invests $400 million in research and development every year, and the two P&WC officials hinted the industry should stay tuned for more PT6 enhancements. While they would not give annual production numbers, Parisien said PT6 engines generally account for “approximately 50 percent of our annual engine production.” The current trend is said to be a slight ramp-up.