Blackhawk Modifications has taken legacy King Air 90 series and vastly improved them with the replacement of the original Pratt & Whitney PT6A-21 engines with the new PT6A-135A engines. This provides a significant boost in power at altitude and a reduction in fuel flow. Blackhawk says the replacement of the -21 engines will cost about the same as an overhaul to the old engines. The new engines come with a warranty as well.
New Hartzell propellers can be added. The new blades, with squared-off tips, reduce hi-frequency prop noise. The new props are longer with a higher twist to produce more thrust and better airflow into the engines. The Blackhawk C90 XP135A will have the same performance as the new Hawker Beechcraft PT6A-135A C90GT series.
As of 2010, the Blackhawk XP 135A modification is available for the King Air C90, C90A, C90B, E90 and F90.
