5,332 hp (3,976 kW) Allison YT40-A-6 turboprop engine driving three-bladed contra-rotating propellers.

Full VTOL testing at Edwards AFB was delayed pending the availability of the 7,100 shp Allison T54, which never materialized.

mpty weight: 11,599 lb (5,261 kg)

No turbo prop will beat a wankel on power to weight ratio.

http://www.rotaryeng.net/VTOL.html

Paul Lamar