The safety board released a report Wednesday examining the October 2011 crash, in which a Beechcraft King Air operated by Northern Thunderbird Air and carrying two pilots and seven passengers crashed while attempting to make an emergency landing.
A long chain of events contributed to the crash, including maintenance crews' failure to properly secure an engine oil cap, modifications to the plane's engines and propellers, and the pilots' decision to adjust the power on only one engine as the plane approached the runway, the report says.
But investigators concluded the pilots would likely have survived the crash if arcing wires, powered by the plane's battery, hadn't fuelled a fire in the cockpit. The pilots were alive when they were pulled from the aircraft, but they later died of burn-related injuries.
"It's clear that their injuries and their deaths were caused by the fire. The physical injuries they endured were likely survivable," Bill Yearwood of the Transportation Safety Board told a news conference on Wednesday a stone's throw from the crash site in Richmond, B.C.
"Electrical arcing is (a risk) that we believe can be addressed and is addressed in the automotive industry. Transport Canada agrees with us. However, I can't say why they haven't acted."
The seven passengers were all seriously injured, and six of them have since filed a lawsuit against Northern Thunderbird Air, based in Prince George, B.C.
The Transportation Safety Board released a report in 2006 that examined post-crash fires and made a number of recommendations to either prevent or reduce the severity of such fires. The report reviewed 521 crashes; of those, there were 128 crashes in which fire or smoke were linked to death or serious injury.
The report's recommendations included the development and installation of technology that would disconnect a plane's battery upon impact. The board has repeated its recommendations numerous times in the years since.
However, Transport Canada has allowed those recommendations to languish, while the risks to planes and passengers remains "significant," according to the safety board.
Transport Canada's failure to implement the board's recommendations "is difficult when you're talking to the lost one's loved ones to explain that," said Yearwood.
"We have to push and, as you can see in this report, the board is taking a further stand. That's the only force we have."
A summary posted to the Transportation Safety Board's website chronicles the federal government's repeated "unsatisfactory" responses to the board's recommendations, which also included a list of other design changes intended to reduce post-crash fires.
In 2006, Transport Canada indicated it was "not in a position to commit necessary resources" to study the feasibility of upgrading aircraft to address the board's recommendations. Transport Canada said it couldn't consider such changes because the technology wasn't available.
In February 2010, Transport Canada provided a follow-up response that raised concerns about the "immense resource effort" it would take to address the board's recommendations. Transport Canada said there were other safety issues that were considered a higher priority.
Transport Canada declined to make anyone available for an interview to discuss the safety board's latest report Wednesday.
Instead, the department provided a brief statement that said it would be reviewing the report but otherwise said very little about the safety board's recommendations related to post-crash fires.
"To reduce the number of post-impact fires and increase survivability of passengers, (Transport Canada) and other regulators continue to work towards developing improved standards," the statement said.
"In this particular case, part of the challenge is finding solutions that would apply to a wide range of aircraft."
In the statement, Transport Canada ignored specific questions about why the department has not taken steps to address the board's recommendations.
The King Air plane left Vancouver's airport on Oct. 27, 2011, but roughly 15 minutes into the flight, the crew noticed oil was leaking from one engine. Passengers also spotted the leak out of the window.
The leak wasn't severe enough to affect the plane's engines, the safety board concluded, but the pilots decided to return to Vancouver as a precaution.
While approaching the runway, the plane's speed dropped below the pilots' intended target. That prompted the crew to increase the power to one of the engines, leaving the leaking engine idle.
The pilots quickly reduced the power, allowing the aircraft to level out, but by then it was too late.
"He was recovering the aircraft, but ran out of time and altitude," said Yearwood.
Yearwood said the pilots were likely operating under the mistaken belief that increasing the power in only one engine would not affect their control of the plane.
The aircraft's minimum speed guidelines were calculated based on its original configuration, but the engines and propellers had been upgraded. The guidelines also assumed the propellers would be "feathered," which adjusts their angle to eliminate drag, but in this case the propellers were not feathered.
As for the oil leak, while it did not directly cause the crash, Yearwood noted the model of plane had a history of loose engine caps.
Beechcraft issued bulletins in 1995 and again in 2010 recommending changes to the oil cap to prevent a leak if the cap wasn't secured correctly, but those upgrades were not completed on the plane.
Northern Thunderbird Air general manager Mike Harris said the company was still in the process of making the recommended changes to its fleet at the time of the crash, but hadn't completed the work on all of its planes.
Now, all of the company's planes have been upgraded, said Harris.
"There was no direness to the service bulletin; it was just something that was going to be implemented over time," Harris said in an interview.
Harris said his company would be examining the safety board's report to determine whether any other changes could improve the safety of its passengers and crew.
He said there are no devices available that could be installed to address battery arcing after a crash.
Harris said Northern Thunderbird — a company with a fleet of eight planes and more than 50 employees — is still affected by the crash.
"We're a close-knit group, for sure," said Harris.
"Something like this is just extremely difficult for everybody in the operation. It's an ongoing, difficult thing."
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