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SR 111 Investigation Report

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2.10  Air Traffic Services Issues

Approximately 15 minutes after take-off, radio communication with the occurrence aircraft was lost. The communication interruption continued for approximately 13 minutes, during which time several attempts were made by air traffic controllers to communicate with the aircraft on the assigned VHF radio frequency. No anomalies were recorded on the FDR, and none were reported by the pilots. No communications anomalies were reported by other aircraft or agencies that were operating on the same VHF radio frequency. No explanation was given by the pilots and no follow-up questions were asked by air traffic services (ATS) to shed light on the reasons for the 13-minute communications gap.

During the flight, there were occasional deviations from standard radio phraseology by both the SR 111 pilots and various controllers; these deviations had no detrimental effect on the outcome of the flight.

The reaction by the controller to the pilots declaration of an emergency was consistent with the controller having treated the situation as an emergency from the beginning. All of the controllers involved had done so even though the pilots, by virtue of the Pan Pan radio communication, signalled only an urgency situation that required communications priority.

When the pilots declared the emergency, aside from indicating the need to land immediately, they did not convey a message that they required additional information or that any other action on the part of the controller was required. In the 20 seconds between when the pilots first declared the emergency and the last intelligible transmission from SR 111, the pilots did not express a requirement for specific additional ATS actions or services.

During the diversion to Halifax, the controller was working exclusively with SR 111 and had no responsibility for controlling any other aircraft. Part of his duty, as stipulated by standard operating procedures, was to coordinate with others in the area control centre to facilitate the arrival of SR 111. At 0124:53, when the pilots stated that they were starting a fuel dump and had to land immediately, the controller was partially occupied by coordination activities, and did not fully comprehend all of the radio transmission. Therefore, he did not offer further information, such as a vector toward the Halifax International Airport. When the aircraft's communication radios failed within seconds after that transmission, the failure prevented any further requests by the pilots, or offers from the controller, for vectors toward the airport.

Communications equipment is important in emergency situations and neither the controller nor the pilots could have known in advance that SR 111 communications equipment would stop operating. In any case, aircraft performance calculations show that because of the subsequent rapid deterioration of aircraft systems and escalation of the fire, the aircraft was not in a position from which a successful landing at the airport would have been possible.

At the time of the occurrence, Canadian air traffic controllers did not receive specific training on the general operating requirements of aircraft during abnormal or emergency procedures, or on special procedures such as fuel dumping. The controller had experience with military aircraft refuelling exercises, during which aircraft receiving fuel would turn off some electrical systems. Based on this background, he presumed that the lack of radio response to his fuel dump clearance, and the subsequent loss of transponder and Mode C altitude information, were the result of intentional electrical load-shedding procedures initiated by the pilots.

The actions of the controller did not affect the eventual outcome of the flight.

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Updated: 2003-03-27

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