July 22, 2013
Credit: Pratt & Whitney Canada
On a chilly December day in 1963, when Pratt & Whitney Canada's turbine engine design group celebrated certification of their diminutive new PT6 turboprop, they had no idea they had given birth to one of the world's most successful propulsion concepts.
Fifty years later, with more than 51,000 engines delivered and new ones rolling off the production line at more than 1,000 per year, the PT6 is accepted as a design classic to be admired, imitated and challenged. “It is the only engine in the world that can be found in an aircraft sitting on a mountain peak, ready to take off at 15,000 ft., or just as easily next to a [Boeing] 787 on the ramp of a busy airport,” says P&WC President John Saabas.
In a world where the term “design classic” is frequently abused, the notion that classics cannot be invented but have to evolve is epitomized by the PT6. From humble beginnings with the delivery of the first production PT6A-6s to Beech 50 years ago, the family has branched out to include a bewildering range of turboprops and turboshafts which are flown by over 7,200 operators in more than 180 countries. The trunk of the family tree has grown to include 69 turboprop versions covering the 500-2,000-shp power range, while three other main branches—the PT6T Twinpac, PT6B and PT6C—are formed by a variety of turboshafts covering the 1,000-2,000-shp range.
In all, the PT6 has evolved to include over 135 different build specifications, more than fulfilling its developers' original dream of providing a turbine replacement for light pistons, and sparking the birth of an entire generation of new fixed- and rotary-wing aircraft. “A whole network has been created to support it,” says Saabas, who notes that the engine has accumulated an unprecedented 384 million hours of flight time.
“The PT6 is more than just an engine; it is a culture,” he says. “Physically, the engine has changed very little. The barrel diameter has grown one inch, but the power has gone up four times, the power-to-weight ratio increased by 40%, and it now has 20% better performance in terms of specific fuel consumption. So the PT6 is a living, breathing family of engines.”
The PT6 played a fundamental part in establishing P&WC as a global player in its own right, helping to provide a development springboard for the company's growth through the 1970s, '80s and '90s, into a broad range of markets ranging from military trainers to regional airliners. Spinning off from the PT6 experience, P&WC went on to develop a family of turbofans, as well as larger turboprop and turboshaft engines. The Canadian manufacturer has certificated a remarkable 74 new engines in the past 19 years—including new versions of the PT6, such as the most recently certified PT6A-140 for the Cessna Caravan EX.
While its product line has been more recently bolstered by other new engines—including the PW300 and PW800 business-jet turbofans, as well as the PW210 turboshaft family—the PT6 continues to provide a solid foundation for the company as it recovers from the market downturn of the late 2000s. This saw overall engine deliveries fall to a low of 2,617 in 2011, the bulk of which was made up of turboprops, from a high of more than 3,963 engines in 2008. Now, as production continues to recover toward the 3,000-engine mark, around a third of it is sustained by the ever-popular PT6.