What happened
On 4 December 2001, a Boeing 767-323, registration N7375A, was operating a scheduled passenger flight from Brussels, Belgium, to Chicago, USA. During the climb through 13,700 feet, the forward pylon strut fairing located above the right engine detached from the aircraft. The commander initially noted a minor noise, but the situation became clear when a passenger reported seeing a piece of metal fall from the engine area. Upon inspection, the crew discovered that the fairing was missing and that the adjacent leading edge slat had sustained damage.
Following the incident, the flight crew reduced the airspeed to 280 knots and, after consulting with company operations, decided to divert the flight to London Heathrow Airport. The aircraft performed an overweight landing at Heathrow without further incident. There were no fatalities and no injuries to the 12 crew members or 65 passengers on board.
The investigation
Investigators analyzed radar and flight recorder data to pinpoint the location of the detachment. The fairing was eventually recovered near Gent, Belgium, which matched the aircraft's flight path at the time of the event. While the Flight Data Recorder showed no operational anomalies or asymmetry in the slats, the Cockpit Voice Recorder had been overwritten by subsequent recordings after the aircraft parked.
Examination of the aircraft revealed that the detached panel was the No 2 forward pylon strut fairing. Scrape marks on the engine cowling indicated the panel had rotated and struck the leading edge slat, causing a 0.4m area of damage. Although the fairing's hook latches were found in the engaged position, the left-hand side button was not flush with the surface, suggesting the hooks had not properly seated on their pins. Maintenance records showed no recent work had been performed on this specific area of the pylon since an engine change in September 2000.
Findings
- The detachment of the forward pylon strut fairing was likely caused by improper latching of the component.
- Although the hooks appeared engaged, the non-flush button indicated the mechanism was not fully secured to the retainer pins.
- The operator had previously implemented a cautionary stencil to prevent such occurrences, but this did not prevent the current incident.
- The fairing design allows for a configuration where the panel appears secured even if the latches are not correctly engaged with the pins.