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Within aircraft electrical network designs, energy storage systems (ESS) provide a means of decoupling the electrical-mechanical interactions between the aircraft electrical power system and the aircraft engine, meeting peak load demand and maintaining power quality during network disturbances and variable load conditions. Within the literature to date, control and management strategies of ESSs for such applications has primarily focused on normal network operation with only limited coverage on the behavior of such technologies under abnormal conditions and the subsequent impact on the operation of the wider power system. Through modeling and simulation of a generic aircraft electrical system, this paper will highlight the potential risks of the inherent, sub-optimal operation of certain existing control strategies during fault conditions.

This paper analyses the behaviour of a highly-capacitive DC UAV network under fault conditions. Through simulation, the nature of overvoltage transients caused by the redistribution of stored energy following the clearance of a fault is illustrated. It is found that clearance of fault currents at or around their peak magnitude can result in substantial quantities of inductive energy being redirected into the smaller load capacitors, causing severe overvoltages across these loads. Recommendations for a protection strategy are given on the basis of the results presented, with consideration given to the use of surge arrestors to provide additional overvoltage protection to sensitive loads.

Increasingly complex and challenging mission requirements for Unmanned Aerial Vehicles (UAVs) may in the future place demands on the vehicle electrical system. Direct current and high-frequency alternating current have been proposed as alternatives to conventional AC approaches in manned aircraft which may contribute to meeting these requirements. The paper reviews the advantages and disadvantages a number of power distribution options across a range of metrics likely to be of interest to UAV designers and operators including factors such as weight, fault management and electrical losses. Important technical challenges in the application of these technologies are identified.

Complex certification issues aside, aircraft electrical systems possess a number of attributes that present good opportunities for the implementation of adaptive protection systems. Rather than experiencing the complex upgrade process faced in the application of adaptive protection to grid based networks, the opportunity to incorporate their functionality at the design stage of new aircraft systems encourages their use and even offers the potential to implement highly integrated protection and control systems. The physically compact nature of aircraft electrical systems and the presence of an existing communications infrastructure should permit the use of both local and remotely obtained power system data within the adaptive protection systems, maximizing the opportunities for achieving highly capable systems.

NASA has compiled a set of research goals for five year periods starting 2015, 2020 and 2025 for three classes of future subsonic aircraft, N+1 (2015), N+2 (2020) and N+3 (2025). With the intention of progressively making reductions in noise emissions, greenhouse gas emissions, fuel burn and energy consumption at each of these points to achieve Technology Readiness Levels (TRL's) of between 4 and 6. In the last few years much progress has been made towards achieving these goals through the development of new technologies and designs. This paper assesses how the current More Electric Aircraft (MEA) design concepts are advancing to allow the near term, N+1 goals of reducing 32 dB of noise emissions, 60% of the landing and take-off (LTO) NOx emissions, 55% of cruise emissions and 33% saving of fuel burn and energy consumption, relative to single aisle B737-800, could be met and eventually surpassed.