ILS SYSTEM FAILURE On 29 July 2000, during a standard ILS approach to Faleolo at night, an Air New Zealand Boeing 767 with 165 passengers and 11 crew on board commenced a go-around after descending to an altitude of about 400 ft some 6 miles short of the runway. An exhaustive investigation revealed that the ILS was transmitting invalid guidance information, while cockpit glide path and localiser indications were normal. This paper reviews the incident and sets out the results of the ensuing investigations. At no stage during the first approach, go-around, and second approach were any "flags" or EICAS messages displayed. Nor was there any autopilot warning or flight mode fault indicated. This serious incident has provided a valuable insight into a hitherto little recognised weakness in ILS systems that will create an extreme hazard unless great care is taken to adhere to ICAO standards and guidance material during ILS operation, design, and maintenance.

MD11 has 2 Autopilots (AP) and Auto Flight System (AFS) provides automatic flying of ILS precision approaches for Cat III autoland operations.