What is WFD (Widespread fatigue damage) ?
How is it keeping Aircraft manufacturer & Airlines always under watch ?
✔WFD in an aircraft structure is known by simultaneous presence of cracks at multiple structural areas that are enough in size & density so that structure will no longer be under damage-tolerance limits & could catastrophically fail.
✔In April 1988, aeging Aloha Airlines flight 243 suffered major structural damage to its pressurized fuselage with 18-foot section of upper fuselage separated.
✔Alarmed FAA required roll out of a program to preclude WFD into the FAA-approved maintenance or inspection program of each operator of large transport category airplanes.
✔The rule required a limit of validity-LOV (in FC/FH) of the structural maintenance program, where additional inspections/ modification/replacements must be incorporated into the operator’s maintenance programs in order to allow continued operation on or beyond design service goal.
✔Sources of WFD are
👉Multiple site damage (MSD) is a source of WFD known by the simultaneous presence of fatigue cracks in the same element .
👉Multiple element damage (MED) is a source of WFD Known by the simultaneous presence of fatigue cracks in similar adjacent structural elements.
Author – Tanmay Palei
Sr. Aircraft Structure Engineer