Pratt & Whitney Canada’s PT6A turboprop is the most popular engine in its class in the world today, powering thousands of high-performance airplanes and helicopters. But in its early days, the engine (or, more precisely, an industrial version called the ST6) appeared in a number of surprising applications.
One quick look at what was done with the PT6A’s predecessor, the ST6TM engine, by our engineers back in the ’60s and 70’s and you’ll gain a whole new appreciation for the expression “we’ve got an app for that!”
Ocean Racing Boat (1966)
The Thunderbird was a 10-metre boat designed by racing-boat champion Jim Wynn. It boasted two ST6 engines and two Chevrolet truck transmissions. On the day of its launch, it clocked 109 km/h. In the February 22, 1966, Sam Griffith Memorial Race, it was one of only two boats out of 31 to complete the challenging circuit. Although it won the race with a time of four hours and 43 minutes, it was denied official recognition because of its “experimental” nature.
Turbo Train (1967)
The turbine engine Turbo Train was first introduced in the United States to provide high-speed passenger transportation between Boston and New York. In Canada, it was meant to be one of the centrepieces of Expo ’67 but wasn’t completed on time. In fact, the Canadian-made train encountered several snags – related to cold weather and its complex and sensitive electrical and control systems – in its early permutations. By 1973, it was back on the tracks on the Montreal-Toronto corridor, regularly travelling at speeds of nearly 193 km/h. It was retired in 1982 and replaced by a new type of diesel train.
Indianapolis 500 Race Car (1967–1968)
The ST6 was first built into an Indy car in 1967 upon the request of Andy Granatelli, president of STP, the manufacturer of fuel and oil additives. In its inaugural race, the car was well in the lead until eight miles before the end of the 500-mile race, when a $6 transmission bearing failed and stopped it in its tracks. (The engine performed perfectly.) Following new restrictions imposed by the United States Automobile Club (USAC), the engine was modified and installed in three Lotus 56 cars the next year. All three qualified for the 1968 race, although none completed it. Shortly thereafter, the USAC imposed additional restrictions on turbine cars that essentially removed them from competition.
Formula 1 Lotus 56B (1971)
The Lotus 56B was the first turbine-powered car to compete in a Grand Prix race. Minor modifications to the Indy Lotus 56 were all it took to make it suitable for the Grand Prix circuits. That said, the look of the car was quite different, with rounder sides to accommodate a larger fuel tank. (An Indy race requires 189 litres of fuel, whereas an F1 needs 283 litres.) It was also outfitted with extra-powerful brakes to deal with the ST6, which idles at 112 km/h. The car raced in several Grand Prix events throughout the 1971 season; it performed well but never took home the trophy.
The “Jet Vett” (1978)
Granatelli may have lost his battle to keep the ST6 on the Indy racetrack, but nothing could stop him from having one installed in a custom-made Corvette. Known affectionately as the “Jet Vett,” the car can travel up to 320 km/h and has to go to the airport to gas up. In 1998, the car’s current owner, Cliff Martin, brought it to P&WC headquarters to display it during the Open House. Pierre Hamel, from Plant 1 Assembly & Test, got to drive visitors around in the supercar!
Other Offbeat Applications of the ST6
- Roadside wood chipper
- Anti-submarine hydrofoil
- Mobile oil-well fracturing unit
- Electrical plant
Special thanks to Pierre Hamel for his invaluable assistance in compiling the information for this article and for lending us photos from his extensive collection of PT6 memorabilia. Also, thanks to retired Service Engineer Fred Cowley for sharing his firsthand experience in working on these unconventional applications of our famous PT6.
This text first appeared in P&WC Magazine, Spring Issue, 2010, p.32-33.