Two passengers were killed and four injured when the left-engine hub disintegrated, sending debris into the cabin during take-off from Pensacola, Florida, on 6 July. The NTSB has recommended that the US Federal Aviation Administration require inspection of tie-rod holes in fan hubs which have accumulated more than 10,000 cycles. The checks would be conducted within 500 cycles of FAA approval of an "on-wing" eddy-current inspection method under development by Delta and P&W.
This interim check would be superseded by dye-penetrant and eddy-current inspections of tie-rod and stress-redistribution holes in all JT8D-200-series fan hubs by a fixed number of cycles, to be conducted when engines are removed for maintenance.
The NTSB says that the Delta fan-hub fractured because of a fatigue crack in a tie-rod hole, caused by "abusive machining", which created an area of ladder cracking and cold working. The hub failed at 13,835 cycles. Delta checked the hub at 12,693 cycles, but failed to detect the crack, which the NTSB believes was about 23mm long by then. The Board also urges the FAA to review procedures and training for non-destructive testing of engine rotating parts, and the process by which hubs with tie-rod holes showing signs of machining distress were in service.
Source: Flight International
