Boeing 747 N498MC accident near Miami, Florida

Probable cause

impact of the fore flap with the aft fuselage after fatigue failure of the right wing fore flap carriage assembly attachment fitting at position 6.

NTSB analysis

On May 17, 2010, an Atlas Air Cargo Boeing 747-400F, N498MC, lost a section of the left fore-flap while on approach to Miami International Airport (KMIA), Miami, Florida. The airplane was substantially damaged when the flap portion impacted the fuselage. There were no injuries to the flight crew and the airplane landed without further incident. The cargo flight originated from Rio de Janeiro-Galeão-Antonio Carlos Jobim International Airport (BGL), Rio de Janeiro, Brazil.

According to the operator, the flight crew heard and felt a large impact after 30 degree flaps was selected during the approach. Postflight inspection revealed that approximately twelve feet of the right wing inboard fore flap was missing and had caused substantial damage to the aft fuselage.

The separated section of the fore flap was recovered and examined. The examination revealed that a large portion of the enamel was missing from the fore flap attachment fitting of the carriage assembly and that there was a large amount of contamination and grease buildup around the lubrication fitting. Extensive corrosion byproducts covered up the lubrication passage in the attachment, which prevented passage of grease to the bearing, causing extensive corrosion in the bore and propagated by fatigue before final ductile separation.

Text from the NTSB. Open the NTSB docket for DCA10CA061 for the full record.