Incident
An aircraft cruising at Flight Level 310 experienced an uncontained failure of the No. 2 engine when the first stage turbine disc separated. The resulting turbine debris penetrated the fuselage structure, leading to cabin depressurization. The pilot executed an emergency descent and landed at Charleston, West Virginia, approximately 50 miles from the location of the event.
Investigation
Post-incident examination revealed severe rubbing and melting of the low pressure turbine interstage seal. Additionally, the drive flanges connecting the LP1 and LP2 turbine discs had separated. The findings indicated that the interstage seal had been in contact with adjacent components, leading to thermal damage and structural compromise.
Repair and Maintenance
Rolls-Royce repair scheme XRS 3505 outlines a procedure for repairing the interstage seals on the affected engine type. During the repair, the maintenance facility employed machining reference surfaces that differed from those specified in the repair scheme. Rolls-Royce subsequently amended XRS 3505 to improve its tolerance to rubbing or misassembly of the low pressure turbine seal.
Oxygen System Failure
All of the first class section and two cabin section passenger oxygen masks failed to deploy during the depressurization event. The cause of this failure was not specified in the investigation.