Avionics system event involving a Boeing 767-338ER, VH-OGC, 456 km south of Guam Aerodrome, on 14 August 1997

During cruise at FL370 in IMC, all aircraft automatic navigational aids, autopilot, autothrottle, flight directors and the attitude director indicator mode annunciators, failed simultaneously. The crew were unable to regain the flight directors or re-engage an autopilot and the inputs to these systems were unavailable. The flight management computers continued to function, but the waypoints had to be sequenced manually, and the navigation log had to be manually upgraded for time and fuel calculations. There was no wind, time or temperature available, but groundspeed was displayed. Attempts to reinstate the automatic equipment by cycling the circuit breakers was unsuccessful. The aircraft was flown manually to Brisbane without further incident.

Ground investigation at Brisbane determined that both sensors in the total air temperature (TAT) probe had failed. The operator is investigating the failure in conjunction with the manufacturer.