On 16 December 2002, approximately 1735 UTC, an Airbus A330-330, operating as Philippine Airlines flight 110 (PAL110), struck power lines while executing a localizer-only Instrument Landing System (Instrument Landing System (ILS)) approach to runway 6L at A.B. Pat Won Guam International Airport, Agana, Guam (GUM). Instrument meteorological conditions prevailed during the approach. Following a ground proximity warning system (GPWS/TAWS) alert, the crew executed a missed approach and landed successfully after a second approach to the airport.
At the time of the incident, Guam Combined Center-Radar Approach Control (CERAP) was clearing aircraft for localizer-only ILS approaches to runway 6L. The GUM Automatic Surface Observation System (ASOS), ILS 6L glideslope, middle marker, and approach light system were all out of service because of typhoon damage, as was the Nimitz (UNZ) VHF Omnidirectional Radio Range (VOR).
As the aircraft was passing 3,600 ft, the captain set the autopilot to fly a 3.4° descent angle, 0.4° steeper than the standard glideslope. The latter, combined with the fact that the aircraft was 460 feet below the glideslope resulted in a descent path that ended 4.5 nm from the runway 6L touchdown point, in the area of Nimitz Hill. The airplane struck power lines at the hilltop. The crew then responded to a ground proximity warning system (GPWS) alert and began a climb, returning for another approach
The National Transportation Safety Board determines the probable cause(s) of this incident as follows:
The pilot's initiation of a premature descent that was both below the nominal glideslope and steeper than normal. Contributing to the incident was the air traffic controller's failure to respond to the MSAW warning and issue a safety alert as required by FAA order.
The following recommendation was made:
After the 1997 KAL accident, the Safety Board recommended that the FAA consider designating Guam International Airport as a special airport requiring special pilot qualifications. At this time, that recommendation is classified as "Open - Acceptable Action" by the Safety Board.