Analysis of conceptual parameters of lift-fan VTOL aircraft in transition

Lift-fan VTOL aircraft is a special type of fixed wing aircraft, whose three modes are: helicopter-like hover, fixed-wing, and special transition. Among these three modes, aerodynamic lift system and direct lift system share only one engine system. The working conditions of the two lift systems differ apparently. Consequently, the relationships among conceptual parameters of lift-fan VTOL aircraft are different from those of conventional aircraft. On the basis of classical momentum theory, we established a preliminary model for analyzing characteristics of lift, drag and power. Then we assessed the impacts of the conceptual parameters exerted on characteristics of total drag and power consumed. We gave feasible methods for so selecting and weighing the conceptual parameters as to meet the requirements of reducing surplus power and saving more fuel during transition for cruising efficiency. The three conclusions in section 4 of the full paper, in our opinion, can provide effective guidance for the preliminary design of lift-fan VTOL aircraft.