What happened
On July 28, 2004, a Boeing 767-300ER, registration 5Y-QQQ, operated by East African Safari Air, experienced an engine fire shortly after departing from Rome Fiumicino Airport (FCO). The aircraft was performing flight HSA 1458, en route from Milan Malpensa to Zanzibar, carrying 165 passengers and 10 crew members.
During the initial climb, approximately 11 minutes after takeoff, the crew observed vibrations and a drop in engine oil pressure on the left engine. This was followed by an engine fire warning in the cockpit. The pilot promptly executed the required procedures to extinguish the fire and returned the aircraft to Fiumicino. The aircraft landed safely, and there were no fatalities or injuries.
Prior to the flight, during the taxi phase, the crew had noted intermittent instrument fluctuations and a momentary drop in oil pressure, which had been reported to maintenance. Although subsequent ground tests by technicians did not reveal any immediate defects, the aircraft was cleared for departure.
The investigation
The ANSV investigation focused on determining the immediate cause of the fire through a detailed examination of the engine wreckage and flight data. Investigators analyzed the Flight Data Recorder (FDR), which showed that engine parameters began to deviate during the flight.
Laboratory tests and the disassembly of the engine revealed that the failure originated within the high-pressure turbine (HPT) section. The investigation also reviewed maintenance records, noting that the aircraft had undergone recent scheduled inspections, including a borescope inspection in May 2004, which had not detected any defects in the component in question.
Findings
- The fire was triggered by the failure of the 1st stage HPT inner rotating air seal (P/N 50L664).
- The failure of this seal created high temperature and pressure conditions within the No. 3 bearing compartment.
- This intense heat caused a flexible oil return line to detach from the lubrication system.
- The resulting leakage of high-temperature engine oil onto the engine casing ignited, causing the fire and damaging the lower cowling.
- Metallurgical analysis suggested the failure was likely due to fatigue, a phenomenon previously observed in other PW4000-series engines, though the exact trigger for the fatigue remained undetermined.
- Maintenance practices were found to be in compliance with all required intervals and procedures.