What happened
On May 19, 2017, at 07:48 local time, a Boeing 747-400F cargo aircraft was on final approach to Munich Airport, operating under instrument flight rules from Frankfurt. The crew, consisting of two pilots and one flight mechanic, was flying toward runway 26R.
As the aircraft was approximately 12 km from the runway threshold, the crew extended the flaps to 30°. At an approach speed of 146 knots, the crew reported hearing an unusual noise. Despite the occurrence, the aircraft landed on runway 26R without further incident and taxied to its parking position.
The investigation
Upon arrival at the parking stand, a post-flight inspection revealed that the fairing for the outer flap drive (number 8) was missing from the right wing. The investigation by the BFU involved examining the flap track area, where several brackets and connecting rods were found to be broken or bent. The underside of the trailing edge flap near the outer drive was also slightly dented.
Investigators located the missing fairing in a field near Wartenberg, approximately 2 km southwest of the aircraft's flight path, roughly 12 km east of the runway 26R threshold. Analysis of the fairing and the aircraft's attachment points revealed that the bolt through-holes at the forward attachment points showed significant scratch and friction marks. Furthermore, the rear support fitting of the fairing mechanism was found to be twisted nearly 180 degrees and torn, with the bolt receptacle forcibly ripped out.
Findings
- The loss of the fairing was caused by the failure of the attachment hardware.
- Both bolts at the forward attachment points were missing from the aircraft.
- The rear support fitting and the bolt receptacle for the adjustable rod had suffered severe structural damage, including tearing and twisting.
- The aircraft had recently undergone a C-check, during which the outer flap drive fairing had been removed and reinstalled.