The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence. The report presented below was prepared essentially from information supplied to the Bureau.
REPORTED INFORMATION
Aircraft arrival
At 0836 Eastern Standard Time, on 9 July 2004, after completing a scheduled flight from Los Angeles, the Boeing 747-400 aircraft registered VH-OEI, landed on runway 16R at Sydney airport.
Following the selection of reverse thrust, the flight crew observed a number 2 engine fire warning message displayed on the aircraft's primary engine indication and crew alert system (EICAS) screen. Vacating the runway and stopping the aircraft on the taxiway, the flight crew conducted the non-normal checklist, discharging the number 2 engine fire extinguishers, but the fire warning message remained. The crew then requested the attendance of the airport rescue & firefighting (ARFF) service.
On arrival at the aircraft, the ARFF advised the crew that there were no signs of fire present on the engine. The crew were then cleared to taxi the aircraft to the terminal, where ground engineers examined the engine, again confirming that no fire was present. On receiving that information, a normal disembarkation of passengers and crew was carried out.
Although the fire warning message was still displayed on the EICAS screen, a detailed inspection of the number 2 engine confirmed that the engine had not been subjected to a fire or overheat event. Further troubleshooting revealed the failure of an electrical relay installed in the fire/overheat detection systems test circuit.
Failed relay
The failed relay was installed within the fire detection `test 2' circuit and was energised whenever the FIRE/OVHT test switch was depressed. Once energised, the contacts closed allowing power to be provided to the automatic fire/overheat logic test system (AFOLTS) printed circuit cards, initiating the fire/overhead detection system test.
The internal failure of the relay led to power being supplied to select circuits within the AFOLTS cards without depression of the test switch. That resulted in the number 2 engine fire message displayed on the EICAS screen.
Following the replacement of the relay, the fire/overheat detection system was tested with no further faults found and the aircraft was returned to service.