Widespread Fatigue Damage 

WFDWidespread Fatigue Damage is the simultaneous presence of multiple fatigue cracks in an aircraft structure that are of sufficient size and density such that the structure will no longer meet its residual strength requirements. 
The sources of WFD are multi-site damage (MSD – see May’s What the Hec?!) and multiple element damage (MED – see June’s What the Hec?!).

For more information on WFD see:

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