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Factual Information

Summary

History of the flight

Approximately 21 minutes after departure while the Boeing 767 was passing through flight level (FL) 285 on climb to FL310, a loud bang sound was heard from the right engine. Cabin crew and passengers reported a flash and sparks from the rear of the engine. The pilot reported an immediate drop in the right engine pressure ratio (EPR) and a rise in the exhaust gas temperature (EGT). A moderate vibration was felt through the airframe.

The crew actioned the engine surge/stall checklist but as the EGT continued to increase, the engine severe damage/separation checklist was actioned and the right engine was shut down. The engine fire bottles were not discharged.

The crew made a PAN call stating that the right engine had failed and requested a descent to FL240 and a return to Sydney. The pilot reduced speed to 240 kts in an attempt to reduce the vibration. However, the vibration reduced only during the final approach.

Engine inspection

An inspection of the right engine revealed that about one-quarter of the no. 28 fan blade had broken away, resulting in substantial damage to the inside of the nose cowl and to the majority of the fan blades. Abnormal displacement of fan blades (shingling) was evident on the mid-span shrouds of a number of blades surrounding the fractured blade.

The fan blade attrition lining was damaged around its entire circumference as a result of heavy fan blade rub. The forward fan case was distorted with five nose cowl attachment points damaged.

The nose cowl internal acoustic liners were damaged through to the outer skin in several locations with two punctures of the nose cowl outer skin. The nose cowl had shifted forward, creating a gap between the nose cowl and the forward fan case flange. Fan blade debris and the mid-span shroud root section of the fractured blade were found embedded in the nose cowl following removal of cowl access panels.

Fan blade maintenance

Operator maintenance records indicated that the right engine fan blades were inspected for leading edge cracks on 13 March 1999 (93 hours and 54 cycles prior to the incident). No indications of cracks were detected at that time. Routine inspections of the fan blade leading edges for cracks had been carried out on a monthly basis. A vibration survey test was carried out on 2 February 1999 after removal and inspection of two fan blades.

In the 9 months before the incident, 13 fan blades on the right engine were found to have incurred foreign object damage. These blades had been blend repaired and inspected for cracks. The fractured fan blade was not one of those blades.

The operator reported that fan blade leading edge restoration was carried out at a 5,000 cycle interval or at 3,000 cycles should an overhaul opportunity occur. Lubrication of the mid-span shroud to help prevent shroud lockup was not required while the engine was fitted to an aircraft (on-wing). The fan blades were overhauled 6,689 hours / 3,889 cycles before this incident.

 
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