March 2020 - Aerospace Science and Technology: Rotorcraft are commonly required to fly at low altitudes and this places them at a high risk of striking various types of obstacles. Wires, in particular, are very difficult to discern and easily blend in the background which explains why wire strikes are a major cause of helicopter accidents. In the context of helicopter operations, a wire hazard is any wire or structure supporting those wires that presents a danger to the aircraft. Data from the National Transportation Safety Board (NTSB) shows that wire strikes were responsible for 124 fatalities between 1994 and 2018. Data on civil helicopter wire strikes further show that the majority of helicopter models involved fall in the lightweight category. In this study, existing aircraft-mounted and ground-based wire strike prevention and protection technologies are reviewed, along with some other potential technologies that have not been specifically developed for use on helicopters but that might be able to prevent wire strikes. In particular, commercially available wire detection systems such as laser scanning systems, database-dependent warning systems, wire cutters, radar scanners and aerial markers are surveyed and evaluated against each other. Publicly available databases of transmission lines in the U.S. are identified and documented for the development of wire strike prevention technologies for lightweight helicopters. The feasibility of creating useful maps of wires from tabulated data or image data is discussed and various Electronic Flight Bag manufacturers are surveyed and compared to determine the feasibility of integrating and displaying such information in the cockpit. Challenges of implementing safety devices, in particular wire cutters, on lightweight helicopters are also discussed and recommendations are provided to improve helicopter wire strike safety. Finally, a multi-criteria decision-making analysis is carried out to rank wire strike safety devices and compare the robustness of their rankings with respect to various operator's preference scenarios. It is shown that the Electronic Flight Bag (EFB), the Wire Strike Protection System (WSPS), the Obstacle Collision Avoidance System (OCAS), and the wire markers perform best regardless of the scenario.
March 2020 - Aerospace Science and Technology https://doi.org/10.1016/j.ast.2019.105665