Incident Summary
On May 17, 2010, an Atlas Air Cargo Boeing 747-400F, registration N498MC, was on approach to Miami International Airport (KMIA), Miami, Florida. The cargo flight had originated from Rio de Janeiro-Galeão-Antonio Carlos Jobim International Airport (BGL) in Rio de Janeiro, Brazil. During the approach, after selecting 30 degrees of flaps, the flight crew heard and felt a large impact. A section of the left fore-flap separated from the aircraft. The flap portion struck the fuselage, resulting in substantial damage. The flight crew was not injured, and the aircraft landed without further incident.
Inspection Findings
A postflight inspection revealed that approximately twelve feet of the right wing inboard fore flap was missing. The missing section had caused substantial damage to the aft fuselage. The separated fore flap section was subsequently recovered for examination.
Examination Results
Examination of the recovered fore flap section showed that a large portion of the enamel was missing from the fore flap attachment fitting of the carriage assembly. There was a large amount of contamination and grease buildup around the lubrication fitting. Extensive corrosion byproducts covered the lubrication passage in the attachment, which prevented the passage of grease to the bearing. This resulted in extensive corrosion in the bore, which propagated by fatigue before the final ductile separation of the flap section.