Hazards Caused by Volcanic Ash on Avionic Systems

Volcanic ash can have a serious impact on flight safety. A safety risk assessment is currently accepted as a means to increase air operation in areas contaminated with volcanic ash while minimising risks. Several aircraft systems can be affected by volcanic ash; safety analyses should thus consider hazards associated to all of them. This paper provides an overview of interfering mechanisms and modes of failure of avionic systems of aircraft exposed to volcanic ash. A focus is laid on navigation and communication systems, for which possible disturbing processes are discussed, in particular the electrostatic discharges caused by triboelectric charging. Examples are shown to stress the severity of possible failures of avionic systems. In addition, important aspects to be considered in a safety risk assessment of flights in areas contaminated with volcanic ash are presented.