Factual Information
On 3 November 2015, a Boeing B757-236(SF), registration unknown, operated by DHL Aviation on a cargo flight from Brussels Airport (EBBR) to Leipzig/Halle Airport (EDDP), lost a part during climb. The part, a rear latch access door from the Rolls-Royce RB211-535C thrust reverser (Part Number LJ71687), was found in April 2016 in a private garden in Engis, Belgium, located approximately 6 km from the end of runway 23L of Liège Airport (EBLG). The part measured 57 cm by 21 cm. Aircraft records showed the part was missing on 4 November 2015 and had to be replaced.
Analysis
The part was sent to Rolls-Royce for detailed inspection. Examination revealed that the forward hinge assembly had separated at the butt hinge pivot point on the thrust reverser side, with the hinge pin completely missing. The rear hinge assembly had fractured due to complete fracture of the two butt hinge lugs. Deformation indicated the forward hinge separated first, then the door rotated downwards under aerodynamic loading, causing the rear lugs to fracture in overload. No evidence of propagated fracture was found. Some wear to pins and lugs was noted but not considered significant enough to have caused the pin to wear through. However, marks on the door cut-out adjacent to the missing hinge pin showed the pin had migrated forward. This migration was most likely due to a combination of in-service wear and insufficient pin retention, allowing the pin to disengage completely.
Conclusion
The release of the door assembly was due to separation of the forward hinge, which occurred as a result of axial migration of the hinge pin on the thrust reverser side of the hinge assembly. Migration was due to a combination of in-service wear and insufficient pin retention. Separation of the forward hinge allowed the door to dislodge, with aerodynamic loading causing the rear hinge lugs to fracture in overload. A contributing factor was that the condition check of the hinges of the rear latch access door was not required by the Aircraft Maintenance Program.
Safety Actions
Rolls-Royce introduced a Request for Manual Revision to add a specific wear check of the hinges into the existing Aircraft Maintenance Manual task, effective May 2017.