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 2.4.1.4 Summary of Captain's Performance on the Approach

As the approach progressed without encountering the visual conditions the captain had anticipated, the captain likely experienced increased stress because of his inadequate preparation for the nonprecision approach, which made the approach increasingly challenging. CVR and FDR data indicated that, shortly after the captain appeared to become preoccupied with the status of the glideslope, he allowed the airplane to descend prematurely below the required intermediate altitudes of the approach. Thus, the captain may have failed to track the airplane's position on the approach because he believed that he would regain visual conditions, the airplane was receiving a valid glideslope signal, and/or the airplane was closer to the airport than its actual position. Regardless of the reason for failing to track the airplane's position, the captain conducted the approach without properly cross-referencing the positional fixes defined by the VOR and DME with the airplane's altitude. Therefore, the Safety Board concludes that, as a result of his confusion and preoccupation with the status of the glideslope, failure to properly cross-check the airplane's position and altitude with the information on the approach chart, and continuing expectation of a visual approach, the captain lost awareness of flight 801's position on the ILS localizer-only approach to runway 6L at Guam International Airport and improperly descended below the intermediate approach altitudes of 2,000 and 1,440 feet, which was causal to the accident.

CVR evidence indicated that the flight crew seemed confused about, and did not react to, a series of audible ground proximity warning system (GPWS) alerts during the final approach. The first audible GPWS callout occurred about 0141:42, with the "one thousand [feet]" altitude call. A second GPWS callout of "five hundred [feet]" occurred about 0142:00 (when the airplane was descending through about 1,200 feet msl), to which the flight engineer responded in astonishment, "eh?" However, FDR data indicated that no change in the airplane's descent profile followed, and the CVR indicated that the flight engineer continued to complete the landing checklist. Similarly, no flight crew discussion followed the GPWS callout of "minimums" about 0142:14, and the first officer dismissed a GPWS "sink rate" alert 3 seconds later by stating "sink rate okay." About 0142:19, the flight engineer called "two hundred [feet]," followed immediately by the first officer saying "let's make a missed approach." The flight engineer immediately responded "not in sight," followed by the first officer repeating "not in sight missed approach." According to the CVR, a rapid succession of GPWS altitude callouts down to 20 feet followed, as the flight crew attempted to execute the missed approach.