Rescue workers search the scene where an Ukrainian plane crashed in Shahedshahr, southwest of the capital Tehran, Iran, Wednesday, Jan. 8, 2020. A Ukrainian airplane carrying 176 people crashed on Wednesday shortly after takeoff from Tehran’s main airport, killing all onboard. (AP Photo/Ebrahim Noroozi)

Rescue workers search the scene where an Ukrainian plane crashed in Shahedshahr, southwest of the capital Tehran, Iran, Wednesday, Jan. 8, 2020. A Ukrainian airplane carrying 176 people crashed on Wednesday shortly after takeoff from Tehran’s main airport, killing all onboard. (AP Photo/Ebrahim Noroozi)

How a missile might have shot a plane down in Iran, and what a probe will look for

At least 63 Canadians and 75 more people heading across to Canada were aboard the plane.

Commercial airline pilots flying out of Tehran’s airport know a simple rule, says Ross Aimer, a former United Airlines captain who has flown there.

You don’t turn right, because that takes you towards the Alborz mountain range. The Ukraine International Airlines flight that went down shortly after take-off Wednesday turned right.

That turn, among other evidence, suggests the crew knew something had gone horribly wrong. The crash that followed killed everyone on board, including at least 63 Canadians and 75 more people who were heading to this country. And now multiple western authorities, including Prime Minister Justin Trudeau, say they believe a surface-to-air missile was the cause.

How does a surface-to-air missile system work?

Most systems are automated and radar-based. The radar sends out a signal and gets a return off something flying. A computer system processes what it has pinged — taking into account things like speed, direction of travel and elevation, among other factors — and then someone on the ground reviews the results to see if the object is a fighter jet, a commercial airliner or something else.

READ MORE: At least 14 people from B.C. among victims in fatal Iran plane crash

“It’s not a precise match and depending on the system, there’s greater or lesser degrees of actual interpretation of the information. So you get something that’s not always 100 per cent accurate,” says defence analyst David Perry of the Canadian Global Affairs Institute.

Perry says the weapons systems the Iranians use are a mix of current Russian technology and some equipment that is far older.

How would a surface-to-air missile system fire at a commercial airplane?

These surface-to-air missile, or SAM, systems typically have three states: “Weapons tight,” meaning a crew fires when it’s confirmed the target is hostile; ”weapons hold,” which limits firing to self-defence or on a specific order; and “weapons free,” which, as the name suggests, allows firing without restriction.

A local crew, in error, could have set the system to “free” status. It could have automatically locked on to the Ukrainian plane when the airliner entered the missile system’s surveillance zone and fired, said retired Canadian lieutenant-general D. Michael Day.

What would the pilots of the plane have seen or heard?

Aimer, the former pilot, said some planes have warnings that alert pilots to a missile threat, and some planes — such as Air Force One or those flown by Israeli airline El Al — would have countermeasures designed to help the plan evade a missile strike. But most civilian airliners don’t have warning indicators, nor is such a threat something most commercial pilots train for.

“There’s nothing really… any pilot can do to evade an incoming surface-to-air missile. You just get hit and you’re done,” said Aimer, now CEO of California-based Aero Consulting Experts.

Is that what happened here?

The Iranian air defences would likely be linked to the civil aviation system, meaning weapons crews would have likely known a plane had just taken off from the airport, said James Fergusson, deputy director of the Centre for Defence and Security Studies at the University of Manitoba.

Day said Iran would have likely had its own civilian planes flying around the area as well, particularly so close to Tehran’s airport.

But Day said if Prime Minister Justin Trudeau was willing to suggest the cause was an Iranian missile, the intelligence had to be airtight and unequivocal.

“In probability, this means that there is some type of electronic evidence that the Iranian air-defence system identified, acquired and engaged the plane,” he said.

Richard Aboulafia, an aviation analyst with Teal Group in the Washington, D.C., area, said an unconstrained or over-active air-defence system seems like one of the likeliest causes for the crash because “planes just don’t do this.”

“Uncontained turbine failures,” when an engine breaks up while rotating and parts punch out of the casing, are not unheard-of. One caused the death of a passenger on a Southwest Airlines Boeing 737-700 in 2018. But such an event wouldn’t have resulted in the wreckage seen in pictures and video from the crash site, he said.

“Technical problems don’t look like this. It blew up,” he said in an interview Wednesday.

“Uncontained turbine failures don’t blow up. Yes, bad things happen, things come shooting out the back, it can rupture wires and control lines and do terrible things. But just blow up? No.”

Iran has denied a missile was the cause of the crash. Its civil aviation authority on Thursday called the theory “scientifically impossible.”

What kind of evidence would investigators look for to confirm the cause?

The first step would be to look at the wreckage of the plane and the remains of the deceased passengers and crew for residue from a missile strike, kerosene residue if fuel tanks caught fire, and shrapnel to see if pieces come from a missile or an engine, Aimer said. He said investigators would also pry information from the plane’s flight data and voice recorders.

Iran leads the investigation under rules set out by the International Civil Aviation Organization, as the country where the crash happened.

Iran might give the recorders to another country, possibly France or Canada, that has the expertise to do the work, though not the United States because of ongoing tensions.

Canada’s Transportation Safety Board said in a statement Thursday that it had accepted Iran’s invitation to be part of the crash probe, and investigators are making arrangements to visit the site.

Aimer said the crash site and its evidence appear to have been contaminated by wreckage moved without being properly catalogued for its location in the debris field, putting investigators at a disadvantage.

This report by The Canadian Press was first published Jan. 9, 2020.

— with files from Christopher Reynolds

Lee Berthiaume and Jordan Press, The Canadian Press

Like us on Facebook and follow us on Twitter.

Flight 752 crash in Iran

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Sidney Pier was one of two sites in Sidney as the Netflix series Maid shot in Sidney in late 2020. The show starring Margaret Qualley was one of 38 productions shooting in Greater Victoria. (Bob Orchard/Submitted)
Head of Greater Victoria film commission warns of lost economic opportunity

Kathleen Gilbert said without full funding, region will not be able to attract productions

A senior official with Victoria International Airport says the airport is still researching COVID-19 testing regimes but predicts testing and screening will remain part of the aviation industry even after vaccines have rolled out. (Black Press Media file photo)
Victoria International Airport researching COVID-19 testing options

Senior official predicts ‘screening and testing will be around long after the vaccination rollout’

Construction in Oak Bay is nearly all focused on rebuilding new single-family homes and without secondary suites. (Black Press Media File Photo)
Oak Bay nears regulation of secondary suites

Preliminary report hints there’s no preferred option

Sidney Jon Blair said he would have died if a van and car had collided at the intersection of corner of Resthaven Drive and Brethour Avenue in early December. (Wolf Depner/News Staff)
Sidney senior urges motorists to slow down on Resthaven Drive

Jon Blair said community must become more pedestrian-friendly

Bob Joseph, author of 21 Things You May Not Know About the Indian Act, will be available for a Q&A through the Vancouver Island Regional Library Jan. 28. (Courtesy of Vancouver Island Regional Library)
Q&A on the Indian Act with Bob Joseph open to Greater Victoria residents

Bob Joseph is the author of 21 Things You May Not Know About the Indian Act

A scene from “Canada and the Gulf War: In their own words,” a video by The Memory Project, a program of Historica Canada, is shown in this undated illustration. THE CANADIAN PRESS/HO - Historica Canada
New video marks Canada’s contributions to first Gulf War on 30th anniversary

Veterans Affairs Canada says around 4,500 Canadian military personnel served during the war

Williams Lake physician Dr. Ivan Scrooby and medical graduate student Vionarica Gusti hold up the COSMIC Bubble Helmet. Both are part of the non-profit organization COSMIC Medical which has come together to develop devices for treating patients with COVID-19. (Monica Lamb-Yorski photo - Williams Lake Tribune)
Group of B.C. doctors, engineers developing ‘bubble helmet’ for COVID-19 patients

The helmet could support several patients at once, says the group

(Black Press Media file photo)
From arts to environment, nominate your West Shore hero

Nominations for the Goldstream Gazette’s Local Hero awards are open to Jan. 15

A 17-year-old snowmobiler used his backcountry survival sense in preparation to spend the night on the mountain near 100 Mile House Saturday, Jan. 16, 2021 after getting lost. (South Cariboo Search and Rescue Facebook photo)
Teen praised for backcountry survival skills after getting lost in B.C.’s Cariboo mountains

“This young man did everything right after things went wrong.”

Conservative Leader Erin O’Toole holds a press conference on Parliament Hill, in Ottawa on December 10, 2020. THE CANADIAN PRESS/Sean Kilpatrick
No place for ‘far right’ in Conservative Party, Erin O’Toole says

O’Toole condemned the Capitol attack as ‘horrifying’ and sought to distance himself and the Tories from Trumpism

A passer by walks in High Park, in Toronto, Thursday, Jan. 14, 2021. This workweek will kick off with what’s fabled to be the most depressing day of the year, during one of the darkest eras in recent history. THE CANADIAN PRESS/Chris Young
‘Blue Monday’ getting you down? Exercise may be the cure, say experts

Many jurisdictions are tightening restrictions to curb soaring COVID-19 case counts

A health-care worker prepares a dose of the Pfizer-BioNTech COVID-19 vaccine at a UHN COVID-19 vaccine clinic in Toronto on Thursday, January 7, 2021. THE CANADIAN PRESS/Nathan Denette
COVID-19: Provinces work on revised plans as Pfizer-BioNTech shipments to slow down

Anita Anand said she understands and shares Canadians’ concerns about the drug company’s decision

Tourists take photographs outside the British Columbia Legislature in Victoria, B.C., on Friday August 26, 2011. A coalition of British Columbia tourism industry groups is urging the provincial government to not pursue plans to ban domestic travel to fight the spread of COVID-19. THE CANADIAN PRESS/Darryl Dyck
B.C. travel ban will harm struggling tourism sector, says industry coalition

B.C. government would have to show evidence a travel ban is necessary

(Phil McLachlan - Capital News)
‘Targeted’ shooting in Coquitlam leaves woman in hospital

The woman suffered non-life threatening injuries in what police believe to be a targeted shooting Saturday morning

Most Read