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Germany issues safety recommendations after two Boeing 747-400F cargo aircraft lost flap parts
29 April 2018

BFU Germany issued three safety recommendations after two Boeing 747-400F cargo aircraft lost flap parts.

On May 8, 2009 an Asiana Airlines Boeing 747-400F was on approach to Frankfurt International Airport, Germany. When the landing flaps were moved to the 30° position,  the crew heard an impact sound and noticed vibrations. The aircraft landed normally. It appeared that part of the left wing flap (Inboard Fore Flap) with dimensions of about 4.5 x 1 m had broken away and impacted the fuselage.

On October 8, 2014 a Korean Air Cargo Boeing 747-400F was on approach to Frankfurt International Airport, Germany. When the landing flaps were moved to the 30° position,  the crew heard a noise and subsequently, the aircraft rolled 8° to the left. The captain switched off the autopilot and continued the approach manually. A safe landing was carried out. After landing it appeared that a 4,5×1 m part of the ‘Inboard Fore Flap’ of the left wing had broken away.

It was concluded that in both cases the flap fitting broke due to pronounced oscillation/vibration fractures,  originating in a corrosion cavity.

As a result the BFU recommended Boeing to improve the corrosion resistance of the landing flap attachment fittings. The airlines were recommended to check and, if necessary, replace the landing flap attachment fittings installed on Boeing 747-400 type aircraft in accordance with the revised Manufacturer Service Bulletin (SB) 747-27-2366R3 and Service Letter 747-SL-57-085-C.

Missing flap part on the Asiana B747-400F (BFU)