Modern air transport powerplants

The convertible rotor (CR) is a means that provides lift in the hover mode and propulsion in the cruise mode of a VTOL aircraft. In the wide disk loading spectrum of this family of aircraft, ranging from 2-2000 psf, various aspects are examined, especially that of noise. The need for a balanced VTOL is demonstrated. Such various solutions are feasible depending on operational requirements, namely, the helicopter rotor (for low cruise speed and prolonged hover) and the fan lift engine (for supersonic cruise speed). The convertible rotor with a disk loading of approximately 25 psf is shown to be the best solution when economy at high subsonic cruise speed is required. This loading is also near the maximum that can be tolerated on account of noise, for operation in builtup areas. The aerodynamic mechanism of the convertible rotor is explained and reasons for its high efficiency given. Operating costs, together with journey times between city centers, of a typical convertible rotor VTOL aircraft are given in comparison with those of helicopters and fixed-wing transport aircraft. It is concluded that, subject to technical problems as yet unresolved, the convertible rotor can win an important domain in the field of air transportation.