Allison Engines has revealed details of a new variant of the 250 turboshaft for the Bell 407.

The C47M is based largely on the C40, launched recently on the new Bell 430. The C47M's compressor incorporates a new high-flow impeller, which increases airflow by 7%, and a brush seal to reduce leakage. The turbine includes an air-cooled first-stage nozzle, allowing higher-temperature operation, better first-stage turbine-blade clearance control, and optimised first- and third-stage turbine-nozzle flow areas.

Rated at 590kW (790shp) for take-off and 525kW maximum continuous power, the engine will have a single-channel full-authority digital electronic-control system based on that used on the C40 engine. The 500kW transmission is based on the system used by the US Army's OH-58D Kiowa Warrior.

The twin-engined Bell 407T will be powered by two Allison 250-C22Bs rated at 320kW maximum continuous power and driving a Soloy combining gearbox.

Poland's PZL-Swidnik has selected the Allison 250-C20R/2 turboshaft for its PZL-SW4. Flight tests of the utility helicopter are expected to start in the third quarter of this year. International certification is to be completed in July 1997 with initial production due to start in 1996.

Source: Flight International