Abstract: A modular rotary wing aircraft includes a modular cockpit, central frame section, tailboom assembly, landing gear, flight control components and other modular parts so that those parts can be interchanged and interconnected to form differing helicopters to accommodate the requirement of differing tasks. A drive train platform is releasably mounted atop the fuselage formed by the interconnection of the cockpit, central frame section, and tailboom assembly. Modular hydraulic servos, a transmission and rotary propulsion unit, a gas turbine engine, and an engine oil cooling system are releasably mounted to the drive train platform. The drive train platform and all components mounted on it are removable as a unit from the fuselage so that inspection, repair, and maintenance can be performed at bench top level in a controlled environment.