2018) 'Review of unmanned aircraft system technologies to enable beyond visual line of sight (BVLOS) operations'. Abstract-The need to develop and deploy Beyond VisualLine of Sight (BVLOS) aerial vehicles has intensified over the last decade. As the demand for Unmanned Aircraft Systems (UAS) has increased, so too has the regulations that surrounds the industry. Strict regulations are currently in place but differ from country to country. Due to these regulations BVLOS innovators have been posed the task of exploring the means of operating flight missions with the UAV out of the sight of the pilot. Autonomous flight capability is not only fundamental to BVLOS operations for UAS but also likely to have a significant impact on the future development of passenger carrying autonomous aircraft. This review explores the technologies that have been developed to date that enable BVLOS applications. BVLOS flight operations have the potential to open a huge area of commercial opportunity however, there remain many concerns about the current capabilities of UAS to detect and avoid manned and unmanned airborne hazards that may pose a significant safety risk.

This paper provides a review of the state-of-theart in aircraft electrical propulsion (AEP). Initially, the limitations of on-board energy storage devices are highlighted and contextualised. The definitions of useful measures for determining the suitability of motor design, namely specific power and motor torque per unit rotor volume (TRW), are discussed and relevant examples are provided. The classifications of motors used for terrestrial vehicle applications are reviewed and their limitations highlighted regarding their suitability to AEP applications. A discussion on motor configurations for aerospace applications is provided which includes: synchronous motor stator winding configurations; axial flux motor configurations and the causes of energy losses. Additionally, the topologies and performance characteristics of existing aerospace motor technologies are examined. It was concluded that electrical motors provide an ideal means for achieving aircraft propulsion and that higher motor speeds are likely to be required for future commercial aircraft motor designs.

Aircraft propeller performance is significantly reduced when tip speeds become sonic causing the maximum attainable airspeed of the vehicle to be limited by the propeller diameter. There are also performance losses attributable to miniature Unmanned Aerial Vehicles as the propeller to hub diameter ratio is reduced. The research conducted indicated that re-arranging a Brushless DC Motor and propeller configuration, so that it becomes rim-driven rather than hub-driven, would provide some performance and operational advantages and could inspire the design of novel high-speed Unmanned Aerial Vehicle configurations powered by hub-less, multi-stage contra-rotating electrical fan-compressors. This investigation involved analysis, design and testing a prototype, low cost, concept demonstrator Rim Driven Fan device in order to assess the feasibility of applying this technology to Small Unmanned Aircraft. It was demonstrated that Rim Driven Fan technology could be successfully applied to lift and propel a Small Unmanned Aircraft. However, the performance testing of the Rim Driven Fan demonstrated that in its prototype configuration it would not be as efficient as a conventional Brushless DC motor and propeller. Keywords-rim driven fan; small unmanned aircraft; unmanned air vehicles; drone; brushless dc motors; hub-less fanI.

This paper presents a review of the state-of-the-art in aircraft electrical propulsion technology. A comparison is provided of differing propulsion mechanisms such as propellers, open fans, ducted fans, multi-stage rim driven fans and distributed thrust designs and their suitability to particular flight profiles and mission applications. Electrical motor architectures are also reviewed with particular attention being given to synchronous machines, such as Brushless Direct Current (BLDC) and Switched Reluctance Motor (SRM) technologies, and the recent advances that have been made in solid-state switching and High Temperature Superconducting (HTS) material applications. Present day electrical power generation, storage and control technologies are also reviewed including hybrid and fuel cell technologies and regeneration techniques. Electrical storage capabilities with regard to specific power and energy characteristics are discussed and the extent to which existing system technology can be integrated onto a Hybrid-electric and an All Electric Aircraft (AEA) is also investigated. Finally, a conclusion is provided highlighting the current technological challenges facing the development of commercial aircraft in terms of performance, airframe configuration and legislative and operational infrastructural requirements. , all electric aircraft, hybridelectric aircraft, more electric aircraft, unmanned aircraft, rim driven fan, high speed electrical flight, aircraft batteries, fuel Keywords-electrical propulsion cells, PV cells, supercapacitors(3)

Electrical Rim Driven Fan (RDF) technology is a novel application to aircraft propulsion, and there are many factors that play a part in determining its optimal achievable performance, for example, the electrical, magnetic and thermal properties of the rim driven motor architectures; the mechanical strength, mass and friction properties of the materials used; the aerodynamics of the fans and the efficiency of the motor drive and control circuitries. Each of these factors could easily warrant their own lengthy and indepth analyses. The aims of this paper are to provide a starting point from which to get a feel for the rough-ordermagnitude of an RDFs performance and to elucidate a conventional calculative methodology suitable for a quick and easy reality-check before undertaking more accurate numerical analysis techniques. Initially, the properties of an existing aerospace fan design, namely that of the IAE V2500-A5 turbo-fan engine, is used to validate this approach and then the same methodology is used to estimate a first-guess performance prediction for a range of single-stage RDFs of varying sizes from 100mm to 500mm diameter, operating over a range of speeds from zero to 25 kRPM. Finally, a comparison between a single-stage and a dual-stage (contrarotating) 200mm diameter RDF for a UAV application is conducted. The performance limits of the RDFs considered in this analysis have been established to ensure that the fan blades are always operating within the subsonic flow regime.