Incident Summary
A flight crew reported hearing a bang during cruise flight at flight level 350 (FL350) and subsequently noted a loss of power from engine number 3. The crew declared an emergency, diverted from their planned route, and landed without further incident.
Post-Landing Inspection
After the aircraft landed, inspection revealed that the number 3 engine was missing from the airframe. The engine was later located and examined. The examination showed that the compressor blades of the engine exhibited damage consistent with soft body foreign object damage (FOD).
Engineering Findings
Further investigation of the aircraft found that the forward lavatory external seal was missing its safety button. Additionally, the internal seal of the forward lavatory was improperly installed. These conditions allowed leakage when the aircraft was pressurized.
Additional Observations
On the fuselage, external skin aft of the forward lavatory service panel was stained with blue fluid. The source of the fluid was not specified, but it was noted as an observation.