Multiple issues contributed to AC Halifax incident: TSB
In its investigation report (A15H0002) released today, the Transportation Safety Board of Canada (TSB) found that approach procedures, poor visibility and airfield lighting led to the 2015 collision with terrain of Air Canada Flight 624 at the Halifax/Stanfield International Airport in N.S.
On March 29, 2015, an Air Canada Airbus A320 was operating as Flight 624 from Toronto to Halifax with 133 passengers and five crew members on board. At approximately 00:30 local time, while conducting a non-precision localizer approach to Runway 05 during a snowstorm, the aircraft severed power lines and then struck the snow-covered ground approximately 740 feet before the runway threshold. The aircraft continued airborne through the localizer antenna, and struck the ground twice more before sliding along the runway and coming to rest about 1900 feet beyond the runway threshold. The aircraft was evacuated using the inflatable slides. Twenty-five people sustained injuries and were taken to hospital. The aircraft was destroyed.
The investigation found that the flight crew had set the autopilot to fly the appropriate constant descent flight path angle. Because company procedures did not require the flight crew to monitor the aircraft’s altitude and distance to the runway, the crew did not notice that wind variations had caused the aircraft’s flight path to move further back from the selected flight path.
Although requested by the flight crew during the approach, the runway lights were not adjusted to their maximum setting. At the time, the tower controller was preoccupied with snowplows on the runway and nearby aircraft on the taxiway. When the aircraft reached the minimum descent altitude for the approach, the flight crew saw some lights, which they interpreted as sufficient visual cues to continue the approach below the minimum descent altitude, expecting the lights to become more visible as they got closer to the airport. It was only in the last few seconds of the flight, after the pilots disengaged the autopilot to land manually, that they then realized that the aircraft was too low and too far back. Although they initiated a go-around immediately, the aircraft struck terrain short of the runway.
Following the occurrence, Air Canada and the Halifax International Airport Authority took safety actions to address the deficiencies identified in this investigation. Air Canada provided its pilots with more specific guidance on required visual references for landing approaches, made explicit warnings on the limitations of the autopilot and vertical navigation using the Airbus Flight Path Angle mode, and now requires instrument monitoring during all approaches when below the minimum descent altitude. For its part, the Halifax International Airport Authority upgraded the approach lighting for Runway 05, reviewed its emergency response plan and made upgrades to emergency assets, including backup power. NAV CANADA published a satellite-based approach on Runway 05 that provides lateral and vertical guidance to suitably-equipped aircraft.
The investigation highlights several factors as to risk, regarding passenger safety. It is important that passengers pay attention to the pre-flight safety briefings, review the safety features card and wear clothing that is appropriate to the season. During an evacuation, passengers must also leave any carry-on items behind to avoid creating delays. This accident also reinforces the need to address the outstanding TSB recommendation (A15-02) to require child restraint systems for infants and young children, to provide an equivalent level of safety to adults aboard commercial aircraft.