Texas-based Blackhawk Modifications is working on FAA STC approval for a Beechcraft King Air 350 engine upgrade that replaces the original 1,050-shp Pratt & Whitney Canada PT6A-60A engines with 1,200-shp (flat-rated to 1,050 shp) PT6A-67As. The engines and new, five-blade composite propellers from MT were recently installed on the company’s King Air 350 testbed and, according to Blackhawk, initial performance has been “promising.”

In hot conditions, the company has seen climb rate more than double from sea level to the FL350 service ceiling, reducing time-to-climb to 18 minutes. Cruise speeds have also increased by as much as 37 knots, up to a maximum of 340 knots at engine power limits. The STC will include a new flight manual supplement with full performance specifications for flight-planning purposes.

The company expects the initial certification to cover all Rockwell Collins Pro Line II equipped 350s with analog engine instruments, and it is working with Garmin on G1000 compatibility on the initial STC. A separate STC is intended for King Air 350s equipped with the Pro Line 21 avionics suite.

Blackhawk said the Hartzell 105-inch-diameter five-blade composite propeller will be available as an option, while Raisbeck Engineering is working to upgrade its newly certified swept, four-blade aluminum propeller assembly to be compatible with the PT6A-67A installation.