Design Synthesis and Optimisation of VTOL Personal Air Vehicles

Abstract

Personal Air Vehicles (PAVs) are envisaged to be the next logical step in mobility to alleviate modern transport problems. PAVs could combine the freedom of point-to-point personal mobility with the higher speeds of air travel. Hence the principal aim of this research programme was to develop a preliminary design and optimisation methodology for an innovative vertical take-off and landing (VTOL) PAV with a ducted fan propulsion system driven by a single turboshaft engine. A feasibility study conducted at the start of the programme concluded that a ducted fan powered VTOL PAV provides a flexible, quiet and safe point-to-point mobility platform free from runway constraints and any problems associated with jet efflux or exposed rotating components. To satisfy VTOL and forward flight requirements a design and optimisation methodology for ducted fans and contra-rotating lift fans was developed from a series CFD tests. With a single engine driving all the fans, a methodology was developed for the design of a system of interconnecting gears, gearboxes and shafts. To accommodate the propulsion system and all the other internal components of the aircraft, an innovative tri-surface configuration was generated by adopting a systems packaging approach. Weight minimisation through the use of composites and appropriate prediction methods was crucial to reducing the power requirements and fuel consumption. The aerodynamic surface interaction was explored and optimised using a vortex-lattice method. The same approach was also used to estimate the stability derivatives of the aircraft. The overall performance was analysed utilising the data produced from the above methodologies and that also included an analysis of the transition from hover to forward flight. All the above methodologies were integrated to form an automated PAV design synthesis which in combination with a MATLAB global optimiser is capable of producing variants of the baseline aircraft that are capable of meeting different mission and passenger capacity requirements while maximising a specified merit function.