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1950's Army Prototype VOTL Aircraft
The Doak VZ-4 (or Doak Model 16) was an American prototype VTOL aircraft built in the 1950s for service in the United States Army. The aircraft was originally powered by an 840 shp (630 kW) Lycoming YT53 turboprop engine. It was replaced with a 1,000 shp (750 kW) Lycoming T53-L-1 turbine. The turbine engine is mounted in the fuselage driving two wing-tip mounted tilting ducted fan propellers.