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 FAA documents revealed that new MSAW software became operational in April 1996, but it contained the same 54-nm-radius inhibition as the February 1995 version. About 1 year after the installation of the new software, the FAA conducted another facility quality assurance evaluation of the Guam CERAP. The evaluation report, dated April 1997, did not note that the ARTS IIA MSAW system remained inhibited.

According to the FAA, the MSAW system at Guam was restored to full, uninhibited operation on August 23, 1997 (17 days after the flight 801 accident), after the monitoring software parameters were adjusted to reduce false alert incidents. The FAA indicated that, since that time, controllers had been experiencing about 18 nuisance alarms per day and that work was ongoing to reduce these alarms.

1.10.1.3 Air Traffic Control Tower

The Agana tower is responsible for operations within the surrounding Class D airspace, which is defined as the airspace within a 5-statute mile radius from the center of the Guam International Airport up to, but not including, 2,500 feet agl. The tower facility is located on the south-southwest side of the airport and is operational 24 hours a day. The controller positions are arranged in a semicircular pattern that face generally from the southwest to the northeast. The four operational positions are the controller-in-charge, local control, ground control, and flight data. All of the positions are typically worked by one controller as a combined function, but the positions may be separated depending on traffic conditions and staffing levels.

In August 1994, Barton ATC International, Inc., was awarded the contract to provide ATC services at the Agana tower. Barton was purchased by Serco Aviation Services, Inc., in January 1997. According to a Serco official, 6 controllers with an average of 15 years of experience worked at the tower at the time of the accident. Three of these staff members, including the Air Traffic Manager, had worked at the facility when it was operated by the U.S. Navy.

The Guam Air Traffic Manager said that the FAA evaluated the tower facility at Guam in October 1995 to determine whether a new tower should be constructed or the existing facility should be upgraded. The FAA also evaluated the Guam tower in September 1996, and the Air Traffic Manager learned that the facility would be upgraded with digital bright radar indicator tower equipment (D-BRITE) displays.

In February 1997, two D-BRITE systems were delivered to the Agana tower, and the radar displays were installed by the FAA in July 1997. The tower controller on duty at