Forensic expert, Prof. Doug Perovic, talks about the crash of flight PS752 with THE STAR

OTTAWA — Canada wants in on Iran’s investigation into the plane crash that killed so many from this country. Prime Minister Justin Trudeau has made that clear.

But questions remain about what Canadian officials will be able to do to ensure there is the “thorough and credible” probe Trudeau has called for, even though Iran has invited Canada’s Transportation Safety Board (TSB) to visit the crash site.

What does a “thorough and credible” investigation look like? And will Canada actually get the investigation it wants into the crash that killed 57 of its citizens?

Anatomy of a proper crash investigation

Doug Perovic, a University of Toronto professor who teaches forensic engineering, said one of the first steps in any proper probe is to check the plane’s black boxes — the cockpit voice recorder and flight data recorder. Often they can tell you a lot, he said, including what the pilots were saying and which warnings or technical problems they may have been dealing with.

But in the instance of a missile strike, which Canada, the U.S. and other countries consider likely, the recorders may not tell the whole story.

“In a catastrophic explosion, they’re only going to be good up to the point where data stops being recorded,” Perovic said.

Beyond that, investigators should turn to the “field of debris” — the bits and pieces of the plane scattered about the crash site, Perovic said. By examining pieces of the fuselage, wings and engines, investigators can start to “differentiate between a missile strike, a bomb on board, a drone strike, just a mechanical engine failure.”

David McNair, a former TSB investigator and military pilot, said all pieces of the plane should be carefully collected and photographed before being they are brought to a new location — such as a large hangar — to reconstruct the shape of the plane.

“Quite often you build a full-scale replica cage, and you start attaching those pieces to it to see the breakup pattern and if there’s any damage pattern,” he said.

“That’s a long, laborious process” that could take “months and months,” he said.

Perovic added that, at this stage, the investigation should be working to detect explosion patterns, test any residues to determine the chemistry of an explosion, and determining whether any blast came from outside or inside the plane.

Will Canada get the investigation it wants?

Like it or not, Canada will have to rely on Iran to answer that question, since Canada can only participate to the extent that Iran allows it to, aviation experts explain.

As of Friday night, no Canadian personnel had arrived in Iran even while the government pushes to obtain entry visas for a team of 10 consular employees and two TSB officials, Foreign Affairs Minister François-Philippe Champagne said.

“It starts with the visas, because until and unless we can have our people physically on the ground at the site, at the meetings, we are obviously not in a position to have all the influence we want,” he said.

“Time is of the essence. Every hour matters.”

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