interpreted the intensity of precipitation by the different levels of opaque (white) shading and his experience as a controller.
The CERAP controller stated that he did not advise the flight crew or the Agana tower controller that he had observed the precipitation on radar while flight 801 was on the approach course to the airport. The controller said that he had assumed that the flight crew was using cockpit radar because they had asked him twice for deviations around weather. The controller stated that the airplane's cockpit radar was more accurate and more precise than the radar he was using at the CERAP. The controller further stated that he did not observe (on radar) the airplane entering the precipitation.
FAA Order 7110.65, "Air Traffic Control," paragraph 2-6-4 (a) states that a controller is to "issue pertinent information on observed/reported weather or chaff39 areas. Provide radar navigational guidance and/or approved deviations around weather or chaff[1] when requested by the pilot...." Paragraph 2-6-4 (c) states that a controller is to "inform any tower for which you provide approach control services if you have any weather echoes on radar which might affect their operations." Further, paragraph 2-9-2 states that, in the event of "rapidly changing conditions," a new ATIS is to be recorded and that the information is to be issued by ATC.
The Agana tower controller stated that, although it was not raining at the airport when flight 801 was inbound, a rain shower was moving in from the northeast over the airport and down the runway to the southwest. The tower controller said that he did not know when the rain began at the airport because he was using binoculars to try to locate flight 801 on the approach. He estimated that the visibility was 7 miles and stated that no low clouds were visible.
1.7.3 Additional Weather Information
A certified Navy weather observer on Nimitz Hill, about ¾ mile northwest from the accident site, stated that the cloud ceiling about the time of the accident was approximately 700 to 800 feet above ground level (agl), or 1,300 to 1,400 feet msl, during a heavy rain shower. Also, he stated that visibility was about 200 to 300 meters and that the windspeed was not more than 10 knots. The NWS forecaster on duty at the time of the accident stated that no SIGMETs [Significant Meteorological Information] were valid for Guam and that the night was "pretty routine." The flight crew of Continental Air Micronesia flight 960, a Boeing 747 that landed at Guam about 30 minutes before the accident, stated that visibility was "excellent" from PAYEE intersection (located about 240 nm north of the NIMITZ VOR) and that scattered thunderstorms were occurring around the area. Further, the pilots indicated that their on-board radar depicted rain showers over the NIMITZ VOR but not over the airport. They also stated the visibility was "good" under 2,000 feet and that they maintained visual contact with the airport throughout the approach.
- ↑ Chaff is aluminum foil strips dropped by military aircraft as phony targets to confuse radars.
