Pratt & Whitney Canada PT6T

The PT6T Twin-Pac is a turboshaft engine for helicopters from Pratt & Whitney Canada, and the company's first turboshaft. Two PT6A-derived power sections are coupled to a combining reduction gearbox, and a clutch system lets the helicopter fly on both power sections or on one alone. Bell Helicopter placed the first order in 1968 for a twin-engine version of the UH-1, the Bell 212, and the engine entered service in 1970. The United States military ordered 294 of these helicopters as the UH-1N, and designates the engine T400, with engines assembled in West Virginia from 1971. About eleven models have been built, covering roughly 1,800 to over 2,200 shaft horsepower, and later Bell 412 variants use improved versions up to the PT6T-9 with electronic engine control.