PT6E: A Classic Turboprop Goes Digital

Pratt & Whitney Canada
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Pratt & Whitney Canada (Booth K67) has unveiled the latest member of its perennial PT6 turboshaft family.

Known as the PT6E-66XT, the engine’s first application is the Daher TBM 960 single-engine turboprop. Indeed, the 66XT was developed specifically with the TBM 960 in mind on the back of more than 30 years of PT6 integration. Both engine and aircraft debuted during the Sun n’ Fun Aerospace Expo held at Lakeland in Florida in April.

The PT6E-66XT is a very different powerplant from the original PT6A that first ran in 1960. The family—which now numbers more than 50,000 engines with over 400 million flying hours—has expanded to cover a wide power range and has benefitted from repeated improvements. The latest major innovation is the integration of advanced digital control, resulting in the PT6E series. This is the first engine family in the general aviation sector to offer a dual-channel integrated electronic propeller and engine control system (EPECS).

Drawing on more than 100 digital data inputs, the EPECS delivers optimized performance, fuel efficiency, and precision, while greatly simplifying pilot control. The system monitors and refines engine performance throughout the whole flight, as well as aircraft data, making continuous alterations to fuel flow and propeller pitch to extract maximum efficiency and optimal power.

All of the gathered data is available for post-flight downloading by wireless connection to a variety of devices for analysis. Improved design has allowed PWC to extend the engine’s scheduled maintenance intervals from 3,500 to 5,000 hours compared with earlier, similarly-rated models. The adoption of the EPECS also permits a number of redundant components to be removed, combining with the time-between-overhaul increase to produce an overall reduction in scheduled maintenance requirements of 40 percent.

For the pilot the PT6E delivers a simpler flying experience, reducing the workload and freeing time for other tasks. The start-up and shut-down procedures are greatly simplified and ensure consistency. The single-lever digital control allows for combined operation of both the engine and the propeller (five-blade Hartzell Raptor in the TBM960), while the EPECS delivers highly precise auto-throttle control.

Other benefits of the 895-shp rated engine, which incorporates single-crystal compressor turbine blades, include a take-off and climb power increase of 45 shp over the non-EPECS PT6A-66D, while cruise thermodynamic power is increased by up to 4 percent under ISA conditions. Noise levels are also reduced due to lower propeller rotation speeds. The engine’s green credentials are underlined by being certified for use with sustainable aviation fuels, while a new system recovers all unburnt fuel after shutdown.

Maintenance and operation of the PT6E-66XT is much simpler and will help reduce operating costs.

Maintenance and operation of the PT6E-66XT is much simpler and will help reduce operating costs.