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1 Introduction
Currently, the smart unmanned aerial vehicle (UAV), which has been developed by Korea Aerospace Research Institute, is a tilt‐rotor type UAV that uses two propellers positioned at both starboard and portside main wings for vertical take‐off/landing and then forwarded horizontally for forward flight like a conventional fixed wing airplane. The propulsion system for this purpose vehicle is composed of a turboshaft engine mounted on the centre fuselage and two propellers driven by the link shaft system connected to the main engine drive shaft.
The fuel system for the smart UAV is divided into several subsystems such as fuel tanks, fuel feed and transfer system, vent system and refuelling/defuelling system. The fuel system should supply safely the flow rate as well as pressure required by the engine at given flight conditions. Design of the fuel system needs an optimization process through lots of re‐designs to satisfy the aircraft system requirements as well as to keep light weight, high reliability, simplicity, maintainability, etc.
In this study, a specific design procedure for the smart UAV fuel system was established, and preliminary design was carried out to meet the system requirements. Finally, target operational reliability of the proposed fuel system was confirmed through reliability analysis.
2 Fuel system for the smart UAV
A specific design procedure of the fuel system is proposed as shown in Figure 1.
The fuel system design for the smart UAV has followed to this proposed procedure. Among those design activities, because the experimental verification process will be performed at the next development phase, it was not included in this work.
2.1 Design specification and fuel system layout
The system requirements for the fuel system are as follows: total fuel capacity less than 300 kg, fuel system weight less than 20 kg and total fuel tank volume is limited to 0.382 m2. Layout configuration of the fuel tank system is composed of left and right wing tanks, forward and rear tanks and a collector tank as shown in Figure 2.
Based on this fuel tank layout, the preliminary fuel system layout, as shown in Figure 3, was designed. According to the proposed fuel system, fuel is transferred from each wing and fuselage tanks to the collector tank in the centre fuselage, then the collected...