Material Failure Analysis of Three In-flight Wing Fractures of Wooden Aircraft

Wooden remains of a training acrobatic aircraft, a glider, and a single-seat tailless glider were investigated using visual inspection, microscopic techniques, infrared spectroscopy, mechanical testing, and heat flow thermography. The causes of the three in-flight wing fractures include deviations in wood quality, craftsmanship, and maintenance. During the investigations, several aspects of wood failure analysis were addressed: compression failure, fiber deviations, fatigue of wood, wood-discoloring fungi and wood-destroying fungi, the influence of iron salts, and the failure of bond lines. The article presents a brief overview of some techniques and approaches, presents knowledge gaps in wood failure analysis, and discusses differences in wood failure analysis as compared to the failure analysis of metals and plastics.