How can you differentiate a FOD damaged engine blade from a repaired one?

FOD (Foreign Object Damage) can significantly impact engine blades, leading to specific characteristics that differentiate damaged blades from those that have been repaired. When examining a FOD damaged blade, it may have irregular edges, which can appear jagged or twisted due to the impact of debris or foreign objects. This distortion typically alters the original geometry of the blade, suggesting that it has been compromised structurally.

In contrast, a repaired blade—assuming it has been properly restored—will have undergone processes such as grinding or reshaping, which might make its surface appear more uniform but do not typically lead to the same jagged or twisted features that signify damage. Thus, the observation of jagged and twisted edges is a key indicator of FOD damage, making it the most definitive way to differentiate it from repaired blades.

Other options, while they may contain elements of truth, do not provide the same clarity regarding the characteristics associated with damage versus repair. For instance, not all repaired blades necessarily exhibit discoloration, and the appearance of blade length or smoothness can vary widely based on specific repair methods or damage types.