The application of vertical take-off and landing principles to modern aircraft is receiving increasing attention. Airfield restrictions compromise performance; conventional landing gears limit design flexibility; and there is a growing need for greater operating flexibility. Necessary scientific progress is being made in the fields of powerplants, dynamics of flight, and structural and component design to support this new concept. The methods of obtaining direct lift are fundamental in principle but varied in application. Direct lift by means of rotor, propeller, ducted propeller, and jet are compared on the basis of lifting ability, range, speed, altitude, and operating cost. A short take-off run is shown to be advantageous for overload operation where vertical ascent is not mandatory. A description is given of a medium-range transport with VTOL capabilities and its performance is compared with conventional aircraft.
