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 by FAA technicians for installation at Guam. The new software was designed to inhibit MSAW alerts inside a 54-nm radius of the Guam ASR-8 site. Thus, the MSAW was only available (uninhibited) for a 1-mile radius (from 54 to 55 nm around the Guam ASR-8 site). According to FAA representatives, this change, designed as a temporary solution to reduce false, or "nuisance," warnings, was submitted by the Guam CERAP and approved by the FAA's Western Pacific Regional Office. The Safety Board requested documentation of the reasons for the changes, but the FAA was unable to explain the specific reason(s) for the change in the MSAW configuration. The FAA Technical Center in Atlantic City, New Jersey, modified the software and delivered it to Guam in January 1994, but the software did not become operational until February 1995. (The EARTS MSAW system at Guam only generates visual MSAW alerts, and these alerts were not inhibited at the time of the accident.)

The ARTS IIA system recorded no alerts for Korean Air flight 801 at any time. The EARTS MSAW alert records showed that a visual approach path warning was generated at 0142:20, about 6 seconds before the crash of flight 801, and continued until at least 0142:49.

At the Safety Board's public hearing, the FAA's Deputy Program Director of Air Traffic Operations testified that, in some circumstances, controller issuance of an MSAWbased safety alert could be a first-priority duty equal to separation of aircraft. FAA Technical Center management testified that MSAW is a safety-critical service.

An FAA quality assurance evaluation report, dated July 31, 1995, on the Guam CERAP facility stated that the MSAW system had been inhibited and that a NOTAM had been issued about the inhibited MSAW. An FAA representative stated that, because no "established policy" existed for MSAW operations at the time of the 1995 evaluation, the MSAW inhibition was noted only as an "informational" item in the evaluation team's report and, as a result, did not require corrective or follow-up action. The report also indicated that a new digital terrain map had been ordered and was scheduled for delivery in April 1995 but that the delivery date had been rescheduled for August 1995.