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Air transportation safety recommendation A00-15

Reassessment of Responses to Aviation Safety Recommendation A00-15

 Recommendation A00-15 in PDF [138 KB]

Installation and Operation of Automated Conflict Prediction and Alerting System


On 18 January 1999, Canadian Airlines International flight 987 (CDN 987), a Boeing 767, departed Toronto, Ontario, en route to Vancouver, British Columbia, at flight level (FL) 390. Air Canada Flight 118 (ACA 118), a Boeing 767, departed Calgary, Alberta, en route to Toronto at FL 370. Approximately 55 nautical miles (nm) west of the Langruth, Manitoba, VOR (very high frequency omni-directional radio range), ACA 118 requested and was cleared to climb to FL 410. The pilot of CDN 987, when approximately 35 nm west of the Langruth VOR, advised the controller that he was climbing out of FL 390 because of a traffic alert and collision avoidance system (TCAS) resolution advisory (RA) straight ahead. A loss of separation occurred when the 2 aircraft passed within 3 nm horizontally with less than 1000 feet of vertical spacing. The required separation is 5 nm horizontally or 2000 feet vertically.

The Board concluded its investigation and authorized the release of report A99H0001 on 13 June 2000.

Board Recommendation A00-15 (31 August 2000)

Risk-of-collision occurrences between large transport category aeroplanes operating in a radar environment continue to occur in Canadian airspace. There are several ground and airborne layers of defence to prevent midair collisions caused by human errors. The last available ground-based defence that could have prevented this occurrence, human redundancy, was absent because the sector was operated by only 1 controller and the supervisor was actively controlling at another position. The TCAS provided an airborne defence that alleviated this dangerous situation. However, reliance on a TCAS as the sole automated defence against human error leading to midair collisions does not provide protection for all Canadian passenger-carrying aircraft. There are no Canadian regulatory requirements for TCAS installation on domestic, passenger-carrying aeroplanes, and there are no requirements for TCAS on any cargo aeroplanes.

The TSB has investigated other similar loss of separation occurrences (A98H0002, A97H0007, and A99W0064, under investigation) that contain many of the same elements addressed in this report. In the most recent occurrence (A00H0002, under investigation), 2 Airbus A340 aeroplanes were at the same altitude on undetected collision courses over the Gulf of St. Lawrence when the pilot of 1 aeroplane received a TCAS advisory and alerted the controller. These occurrences raise concerns about the lack of adequate, ground-based, conflict prediction and alerting systems in Canada.

The Canadian Aviation Safety Board (CASB) identified the need to develop and install automated conflict prediction and alerting systems in the Canadian air traffic services system in its recommendation CASB 90-36. Although work has been ongoing over the years by Transport Canada (TC), and most recently by NAV CANADA, there are no definitive commitments to set an implementation date.

There are serious consequences to midair collisions between large transport-category aeroplanes. Additionally, there is a lack of sufficient ground-based defences to contain normal levels of human error, which may lead to losses of separation. Therefore, the Board recommends, for the consideration of both NAV CANADA and the Minister of Transport, that:

NAV CANADA commit, with a set date, to the installation and operation of an automated conflict prediction and alerting system at the nation's air traffic control facilities to reduce the risk of a midair collision.
Transportation Safety Recommendation A00-15

NAV CANADA's Response to A00-15 (16 October 2000)

In its reply, NAV CANADA did not commit to a date by which an automated conflict prediction and alerting system would be installed and operational. Instead, NAV CANADA noted that the conflict alert software inherited from TC in 1996 contained problems that were so severe that it could not be used in certain environments. Testing of improved conflict alerting software is currently underway and a partial operational test, in the high-level en route environment only, will take place in the Toronto Area Control Centre by 31 March 2001.

Transport Canada's Response to A00-15 (21 November 2000)

In its response, TC noted NAV CANADA's intention to test a conflict alert system in the Toronto Area Control Centre by 31 March 2001. TC made no indication that they concurred with the recommendation, noting only that they would monitor the testing and then assess the necessity of a regulatory approach to address the Board's recommendation. In addition, TC noted that a Notice of Proposed Amendment (NPA) had been presented to the Canadian Aviation Regulations Advisory Council (CARAC) Technical Committee in June 2000 to require the installation of airborne collision avoidance systems (ACAS) in certain aircraft by 01 January 2003.

Board Assessment of NAV CANADA's Response to A00-15 (21 March 2001)

NAV CANADA's response indicates acceptance of the requirement for an operational conflict alerting tool for controllers in certain environments only, and it does not commit to a date by which such a system will be operational in the nation's air traffic control facilities. It does, however, indicate a date by which operational testing will commence in a high-level en route environment.

The NAV CANADA response is therefore considered to be Satisfactory in Part.

Board Assessment of Transport Canada's Response to A00-15 (21 March 2001)

The TC response indicates that staff will monitor the progress of the testing and assess the necessity of a regulatory approach to address the intent of the recommendation.

The TC response is considered to have Satisfactory Intent.

Board Reassessment of A00-15 (09 June 2004)

NAV CANADA advises that the operational conflict alerting tool is now operational in much of Canada's airspace which is served by radar coverage, but is not and likely cannot be instituted in certain low-level and terminal airspaces. However, NAV CANADA's activity since the publication of the recommendation should materially reduce the risk associated with the safety deficiency.

The action response is therefore considered to remain Satisfactory in Part.

Next TSB action

Further action is unwarranted.

This deficiency file is assigned a Closed status.