What is a primary indicator of potential fatigue in aircraft structures?

The presence of notches or holes serves as a primary indicator of potential fatigue in aircraft structures due to the fact that these geometric irregularities can significantly affect the stress distribution within the material. When the aircraft undergoes cyclic loading—such as during takeoff, flight, and landing—areas around notches or holes can become stress concentrators. These regions are more susceptible to developing fatigue cracks due to their inability to evenly distribute stresses. Over time, even small variations in shape or discontinuities can lead to fatigue failure, which is a critical concern in aircraft maintenance and safety.

In comparison, while corrosion can adversely affect the structural integrity of an aircraft, it does not inherently signal fatigue in the same way that notches and holes do. Repeated inspections are vital for identifying fatigue issues, but they are more about monitoring and less about direct indicators of fatigue. Increased airframe weight can result from additional repairs or reinforcements but is not a direct measure of fatigue in the material itself. Thus, identifying and addressing notches or holes is crucial for predicting and managing fatigue-related issues in aircraft structures.