Accidents
Crash into Nimitz Hill, Guam
Summary:
Controlled flight into terrain; the ground-based minimum safe altitude warning designed to alert air traffic controllers had been inhibited. 228 fatalities; 26 serious injuries.
Details:
On 6 August 1997, Korean Air Flight 801 crashed at Nimitz Hill, Guam. This is high terrain approximately 3 miles southwest of Guam International Airport, where the aircraft had been cleared to land. Of the 254 people on board, 228 were killed and 26 survived with serious injuries.
Probable causes of the accident were the captain’s failure to adequately brief and execute a non-precision approach and the first officer’s and flight engineer’s failure to effectively monitor and cross-check this approach. Contributing factors included fatigue and inadequate flight crew training.
Another contributing factor was the intentional inhibition by the Federal Aviation Administration (FAA) of the Minimum Safe Altitude Warning (MSAW) system at Guam, and the agency’s failure to adequately manage the system.
The MSAW system uses a terrain database. It is designed to alert a controller if an aircraft equipped with a Mode C transponder descends below, or is predicted to descend below, a predetermined safe altitude.
In 1990, the Guam terminal MSAW was installed to provide protection within a 55 nm radius. In 1993, a new software package was produced in which warnings were inhibited within a 54 nm radius; this left a 1 nm annular region within which warnings could be generated. The motivation behind the new configuration was to reduce false alarms. The software became operational in February 1995. A further software update became operational in April 1996. This also had the 54 nm inhibition.
This incident illustrates the importance of the continuity Data Property, with respect to the MSAW coverage, and the fidelity / representation Data Property, with respect to the terrain database used by the MSAW system.
Links
- https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0001.pdf
(accessed 29 November 2017).