Paul Lewis/SINGAPORE
The investigation into the crash of a Korean Air (KAL) Boeing 747-300 in Guam which killed 227 people, has begun to focus on controlled flight into terrain (CFIT) as a possible cause.
US National Transportation Safety Board (NTSB) team leader George Black has stated to NBC TV that the crash "-does have all the hallmarks of a controlled flight into terrain." The aircraft hit the 200m (658ft)-high Nimitz Hill on a night approach to Guam International Airport in bad weather in the early hours of 6 August.
Approaches to runway 06L have recently been flown using the instrument landing system (ILS) localiser only, because the ILS glide-slope system (GSS) was withdrawn on 7 July for upgrading. In the absence of the GSS, the Nimitz VOR beacon with its distance-measuring equipment (DME) provides pilots with position data to monitor their descent progress. A NOTAM pilot information notice also advised that the airport's surveillance radar was not operating.
Approach procedures to runway 06L without GSS call for an aircraft to be at 1,440ft over the Nimitz VOR/DME, which is 6km (3.3nm) short of the threshold, then descend further to a minimum safe altitude of 560ft by the "middle marker", just 1km short of the runway. The runway is located 256ft above sea level.
KAL flight 801 hit Nimitz Hill, which is the site of the 6.7m-high Nimitz VOR/DME antenna. Initial readouts from the cockpit- voice recorder and flight-data recorder downloaded by the NTSB indicate that the pilot may have assumed that the Nimitz beacon was located on the airfield, explaining why the 747 was some 800ft below its prescribed altitude.
The Guam route is normally operated using an Airbus A300-600R, but one of KAL's twinjets was recently withdrawn from service following a minor accident. o
Additional reporting by David Learmount and Ramon Lopez
Source: Flight International
