How can compression failure in a wooden aircraft spar be identified?

Identifying compression failure in a wooden aircraft spar is crucial for maintaining the integrity and safety of the aircraft. The presence of streaks that run perpendicular to the wood fibers is indicative of the failure mode known as compression failure. This type of failure often occurs when the wood is subjected to excessive loads, causing a crushing effect.

When the fibers of the wood are compressed, they can buckle or deform, leading to visible streaks that manifest as lines crossing the grain direction. These streaks are often a sign that the wood fibers have not merely split or cracked but have experienced structural failure due to overload conditions. Recognizing these patterns during inspections allows for timely maintenance and replacement, which is essential for ensuring that the spar maintains its strength and load-bearing capabilities.

Other options relate to different types of wood damage but are not specific indicators of compression failure. For instance, cracks running parallel to the grain might indicate other issues such as drying or shrinkage, while separation of wood fibers near the end might suggest tension failure or fatigue. Rough textures could be a sign of surface damage but do not specifically point to compression-related issues. Understanding the unique characteristics of compression damage is key for effective inspection and maintenance of wooden structures in aviation.