Fire protection systems involving a Saab SF-340B, VH-OLN, Sydney, New South Wales, on 13 June 1997

After departing Dubbo for Sydney, whilst climbing through 7,000 ft, the right engine fire warning illuminated momentarily with associated aural warnings, but ceased before any crew action could be taken. As the warning was assessed to be erroneous, the captain elected to continue to Sydney, where the aircraft landed without further incident.

Whilst subsequently holding on taxiway 'Golf', enroute to the eastern apron, the right engine fire warning again illuminated and remained on. The engine was shut down as a precaution and the engine fire phase one drills carried out. As the fire warning ceased, the fire detector fail caution light illuminated. The captain ordered a full shutdown, and aircraft evacuation. There were no injuries, and an inspection of the aircraft revealed no evidence of fire.

An engineering investigation revealed that the engine fire detector loop connections were contaminated with oil. The connectors were cleaned, and the fire detector unit changed. The system then tested normally, and the aircraft was released for service. However, during subsequent operations further erroneous fire detector failure and fire warnings occurred. Further investigation, including wiring insulation checks, found a chafed wire to the control unit, in the cabin above a passenger overhead locker. Insufficient security of the wire had allowed it to sag and rub against the locker hardware. The operator reported that a fleet inspection indicated this was an isolated problem and no further action was required.