What happened
On February 11, 2011, an Avro RJ85, registered OO-DJK, was climbing through approximately 10,000 feet after departing from Marseille Airport (LFML) for Brussels (EBBR). During this phase of flight, the crew heard a loud bang accompanied by slight vibrations. The flight crew continued the mission to Brussels, where the aircraft landed without further incident. Upon arrival, a post-flight inspection revealed that a composite wing leading edge fairing panel, located above the center tank, had detached from the aircraft. The panel was not recovered.
The investigation
Investigators examined the aircraft's attachment structure and found that while the bolts remained on the airframe, the auxiliary attachment structure had suffered secondary damage, including cracked angles and broken grommets. The investigation focused on the steel grommets (part number SL51 .83) used to reinforce the composite holes.
Analysis of the hardware revealed that the design of these specific grommets was inherently vulnerable. The process of peening the grommet flanges during installation or maintenance could easily lead to material thinning or cracking. Furthermore, the investigation looked into the maintenance history, noting that the aircraft had been repainted in 2007 and had undergone a grommet inspection in 2009. The investigators also reviewed historical data regarding similar incidents in the Avro RJ fleet, including a previous occurrence involving a similar panel detachment.