AIRCRAFT VIBRATION AND THE READABILITY OF AN ELECTRONIC FLIGHT INSTRUMENT DISPLAY

An advanced turboprop aircraft encountered icing conditions in flight and developed severe airframe vibration during which the pilot observe d image break-up on the Electronic Flight Instrument System (EFIS) dis play. This effect was investigated using whole body, hand transmitted and direct head vibration. When vibration was applied directly to the head, the reported pattern of EFIS image break-up was observed if the vibration frequency was close to the display refresh frequency. It was concluded that vibration had caused retinal image motion, and that th e observed effect occurred because spatially adjacent components of th e display were written at separate times within the refresh cycle.