t took just 2 1/2 minutes for a combination of human and technical mistakes to turn a passenger and supply flight into a remote Arctic community from routine to calamitous.
A Transportation Safety Board report into the crash of First Air Flight 6560 blames an undetected autopilot change, a faulty compass reading and disagreement between the pilots about whether to abort the landing.
“This accident was the product of a complex series of events, all of them lining up together,” lead investigator Brian MacDonald said Tuesday as the report was released. “But what ultimately tied all these things together was that as the flight progressed each pilot developed a different understanding of the situation and they were unable to reconcile that difference.”
The crash at the Resolute airport Aug. 20, 2011, killed eight passengers and four crew members. Three passengers miraculously survived.
In cool, technical language the board’s report provides a second-by-second breakdown of what probably happened in the cockpit as the pilots crashed the Boeing 737 into a hillside more than a kilometre from the runway.
Problems began because on-board compasses were incorrectly adjusted by 17 degrees. That error was compounded when the captain turned into the final approach and unwittingly changed the operational mode of the plane’s autopilot. Busy with the landing checklist, in weather obscured by cloud, mist and light rain, neither he nor the co-pilot picked up the change.
“This incongruency would have negatively affected the pilots’ situational awareness and increased their workload as they attempted to understand and resolve this ambiguity,” the report says.
Within seconds after that final turn, co-pilot David Hare realized the plane was off course and repeatedly told the pilot, reminding him about the large hill to the right of the runway. Pilot Blair Rutherford replied that the autopilot was working fine.
Puzzled as to why the plane’s navigational instruments weren’t lining up with ground-based systems, Hare asked if they’d done something wrong. Five seconds later, he suggested they pull up and go around for another approach.
Rutherford, fully focused on landing the plane and on figuring out why his instruments were giving confusing readings, refused.
“It is likely that the captain did not fully comprehend information that indicated that his original plan was no longer viable,” says the report.
Less than 10 seconds after first suggesting they pull up, Hare asked again, pointing out that the plane wasn’t configured for a landing so close to the landing strip. The report suggests Rutherford is likely to have understood the remark as a request to prepared the plane for landing.
Cockpit communication had broken down.
“The captain’s mental model was likely that the approach and landing could be salvaged, and the (co-pilot’s) mental model was almost certainly that there was significant risk to the safety of flight and that a go-around was required. These divergent mental models compromised the pilots’ ability to communicate and work together.”
Four seconds after his second request to pull up, Hare asked Rutherford to bank to the left. Their navigational confusion was evident when Hare confused the shoreline of a small lake with the seashore.
Just under a minute after that, Hare said: “Blair, I don’t like this.” Almost immediately after, the plane’s ground position systems began to sound alarms. About 160 seconds after making the final turn, Rutherford tried to pull up and go around.
“There was insufficient altitude and time to execute the manoeuvre and avoid collision with terrain.”
The plane smashed into the hill and broke into three main pieces. Debris was strewn around the tundra.
Resolute residents and soldiers from a military exercise that happened to be underway nearby rushed to the scene to try to pull survivors from the flaming wreckage.
Within minutes, rescue crews and fire trucks were dispatched. Coast Guard and military helicopters arrived on the scene. Those not rescuing survivors or recovering casualties worked frantically to douse a fire from a fuel leak.
Military medical teams and equipment that had arrived shortly before the crash were pressed into service. The injured were stabilized in a field hospital and flown to Iqaluit.