Aviation Investigation Report A98H0003

1.9.5  Air Traffic Services Communication Regarding Fuel Dumping

Fuel dumping information for Nav Canada air traffic controllers is contained in Part 7 of the ATC MANOPS. Section 701, "Fuel Dumping," instructs controllers to obtain information about the track, the time frame for dumping, and the in-flight weather conditions. As well, controllers are advised to encourage an aircraft to dump fuel on a constant heading over unpopulated areas and clear of heavy traffic. Controllers are also advised to restrict the altitude to a minimum of 2 000 feet above the highest obstacle within 5 nm of the track, and arrange for a warning to be broadcast frequently on ATC frequencies during the period of the fuel dump.

Additional fuel dump information for controllers in the Moncton ACC is contained in the Moncton ACC Operations Manual, 07-98. Section 3.20 identifies the preferred fuel dumping area for the Halifax area and instructs controllers to advise the appropriate flight service station (FSS) or stations.

After verifying with the pilots that a turn to the south was operationally acceptable to the crew, the controller chose a planned location for the SR 111 fuel dump, which was over St. Margaret's Bay, at an altitude above 3 000 feet. This location complied with ATS guidelines and would position the aircraft for a turn onto the on-course for the back-course approach to Runway 06.

When SR 111 advised the controller of the requirement to fly manually without further elaboration, the controller assumed that manual flight was a Swissair procedure to be followed during fuel dumping. When the pilots did not acknowledge the controller's clearance to commence fuel dumping, and when immediately thereafter the aircraft's Mode C transponder stopped providing data to the ATS radar, the controller interpreted this cessation of information from SR 111 to be the result of an electrical load-shedding procedure that Swissair used during fuel dumping operations. This interpretation was based on the controller's experience with military aircraft refuelling exercises carried out over Nova Scotia during which military fighter aircraft receiving fuel typically turned off unnecessary electronics, including the transponder.

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