News conference for the release of Aviation Investigation Report A15H0002: Opening remarks
Chair, Transportation Safety Board of Canada
Investigator-in-Charge, Transportation Safety Board of Canada
Halifax, Nova Scotia, 18 May 2017
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Just past midnight on March 29, 2015, an Airbus A320 operating as Air Canada Flight 624 struck terrain 740 feet, or 225 metres, short of the runway while landing at the Halifax Stanfield International Airport during a snowstorm. There were 133 passengers and 5 crew on board. Twenty-five people were taken to hospital, with injuries ranging from minor to serious.
Accidents are almost never caused by just one factor, organization, or person, and this one was no different. Today the Transportation Safety Board of Canada will explain how a combination of factors all played a role, including: poor weather, airfield lighting, and Air Canada's practice of not requiring pilots to monitor the flight path during a key phase of flight. We will also explain what happened after the accident, and why passengers, some dressed in shorts and sandals, waited on the runway in a snowstorm.
Before we get to all of that, however, I'll turn things over to the investigator in charge, Mr. Doug McEwen, to walk you through the critical sequence of events.
Thank you, Kathy.
The sequence of events that night starts well before the final approach to the Halifax Airport. In fact, throughout the flight from Toronto the crew had been discussing the weather and what that would mean for the landing, especially since one of the two runways was closed for snow removal. Visibility was the big concern. Half a mile was the minimum requirement, and weather reports indicated that this was not always available.
At 15 minutes past midnight, while the aircraft was in a holding pattern near Halifax airport, the tower controller advised that visibility had improved to half a mile. The crew decided to continue their approach.
The runway available to them, Runway 05, was equipped with a "localizer"— a radio beam that gives the aircraft lateral guidance, to line it up with the centre of the runway. But what a localizer does not provide is vertical guidance; that is up to the flight crew, who must refer to their instruments to make sure they are at the correct height relative to their distance from the runway.
As Flight 624 approached Halifax airport, the tower controller was asked to turn the runway lights to their maximum setting. The controller, however, was preoccupied with the snowplows and a nearby aircraft on the taxiway, and never did adjust the lights.
The crew then set the autopilot to fly at the appropriate constant descent flight path angle.
In keeping with Air Canada's Standard Operating Procedures, they were not required to, and did not, monitor the vertical component of their approach. So when wind variations caused the actual flight path to diverge from the selected flight path, they did not notice they had moved away from where they needed to be.
One of the critical height parameters on approach is something known as the "minimum descent altitude." The aircraft must not go below this unless the crew has specific visual references such as the approach or runway lights.
When the aircraft reached the minimum descent altitude, just over a mile from the runway threshold, the crew could see some approach lights, which they interpreted as sufficient to proceed. They continued 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 that the pilots disengaged the autopilot to land manually. Almost immediately, they realized they had flown too low too soon, leaving them short of the runway. They initiated an overshoot, raising the nose and advancing the thrust to begin what's known as a "go-around," but the aircraft struck the terrain, bounced twice, and skidded forward, before coming to rest further down the runway.
Onscreen, you will see a brief animation showing the planned flight path, the aircraft's actual flight path, and how far they diverged—as well as an inset view giving a sense of the poor visibility.
During the subsequent evacuation, some passengers exited with their carry-on luggage, creating a risk that could have impeded progress, especially to those who were injured. After the evacuation, it was almost an hour before all passengers were transported to an indoor facility. Part of this delay was due to the severe weather conditions, and the failure of backup power systems after the aircraft severed commercial power lines near the runway, disrupting the airport's radio operations network. But we also identified issues with the airline's and the airport's emergency response plans, and specifically with respect to making arrangements for the timely transportation of all occupants.
As we've outlined, this accident resulted from a combination of factors. Change any one of them and Flight 624 might have landed without incident.
To reduce the risk of such an accident happening again, a number of safety actions have already been taken.
Air Canada pilots have been given more specific guidance to describe the visual references required to continue an approach, along with an explicit warning about the limitations of the autopilot and vertical navigation using the Flight Path Angle mode. The company's Flight Operations Manual has also been changed, placing greater emphasis on instrument monitoring during all approaches below the minimum descent altitude. Halifax airport has upgraded the approach lighting system on Runway 05, and Air Canada has recommended similar lighting upgrades at other airports nationwide.
The Halifax International Airport Authority has also taken steps to review, revise and update its emergency response plan and upgrade its emergency assets, including backup power.
This accident also reinforces the need for more action to address two outstanding TSB recommendations, both aimed at Transport Canada, including:
- the development of age- and size-appropriate child-restraint systems for infants and young children, to provide an equivalent level of safety to adults; and
- the requirement for independent power supplies for cockpit voice recorders, so that potentially valuable information continues to be available to investigators, even after an accident.
In Canada, airline accidents involving large jet aircraft are rare. But we hope that all airline passengers will take heed of the following—the importance of paying attention to pre-flight safety briefings, reviewing the safety-features card, and wearing clothing onboard that is appropriate to the season. You never know when you might have to evacuate. And should there be an emergency evacuation, leave carry-on items behind as directed by the cabin crew. It's simply not worth risking your life or the lives of others around you.
This accident was very serious, and the outcome could have been far worse. It should also be a lesson that all parties involved—Transport Canada, airports, airlines, flight crews, and yes, even passengers—must do their part to make sure every flight is as safe as it can be.
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