An initial report from Iranian authorities said an engine fire caused pilots to lose control of a Ukrainian International Airlines (UIA) Boeing (BA) 737-800 NG jetliner that crashed shortly after takeoff Wednesday morning from Tehran’s International Khomeini Airport, killing all 176 people on board.
The quick attribution to an engine-related cause for the crash raises questions about the reliability of Iran’s report. Ukraine’s embassy in Iran also published an initial statement Wednesday attributing the crash to an engine failure, then later withdrew its account.
“I'm surprised that they can be that definitive that quickly,” MIT professor of aeronautics, R. John Hansman, told Yahoo Finance. “Normally, you need to inspect the physical data, the wreckage, the flight data recorder data, and things like that to have information as to what happened.”
Regional tensions between Iran and the United States following Iran’s launch of more than a dozen retaliatory missiles on U.S. air bases in Iraq added to speculation concerning the downed plane. Boeing’s NG series is the immediate predecessor to its troubled 737 Max that has been grounded worldwide since March, due to two fatal crashes.
During a news briefing Wednesday in Kyiv, where the plane had been headed, Ukraine’s Prime Minister Oleksiy Honcharuk reportedly said, “Any versions before the official conclusion is just manipulation.”
“If there was a surface-to-air heat-seeking missile, it would tend to go into the engine, because it goes after the hottest thing it sees and the engine is the hottest thing,” Hansman said.
Hansman said there could have been a mechanical problem in the engine, such as an “uncontained engine failure,” like the one sustained on the same engine model on a Boeing 737-700 during a June 2018 Southwest Airlines flight from New York to Dallas when a structural problem inside the engine caused one of its components to dislodge, killing one passenger, and damaging the engine as well as other parts of the aircraft.
Another Southwest flight powered by the engine model experienced a similar failure in August 2016, though no one on board was injured.
‘Definitely one of the most reliable engines’
The engine in question, CFM56-7B, was manufactured by CFM International, a joint venture between General Electric (GE) and France’s Safran SA (SAFRF). At the time of the crash, the model, which is installed on all Boeing NG aircraft — 700, 800 and 900 models — had collectively flown 425 million total engine flight hours in revenue service. The engine first began revenue service in 1997, and despite prior failures, is regarded as highly reliable and safe. Each engine is equipped with two self-contained fire extinguishers.
“It is definitely one of the most reliable engines, and one of the engines which is most commonly found in large commercial aircraft. It is one of the largest and most popular turbo fan engines where the fan is generating most of the thrust,” Swetaprovo Chaudhuri, associate professor of the Institute for Aerospace Studies at University of Toronto, told Yahoo Finance. “But at the same time, there have been incidents with this engine, which is not uncommon given its time [in service].”
Hansman said one reason the engine involved in the 2018 Southwest Airlines flight may have been more susceptible to failure is its age.
“It was a relatively old engine, so it had gone through a lot of cycles,” he said. Inspection requirements for the engine were made more rigorous after the fatal accident.
According to UIA, its Boeing 737-800 NG aircraft involved in the crash was three years old, and had been delivered directly to the airline from Boeing. The airline said in a press release that the plane underwent scheduled maintenance on Monday.
“We are deeply saddened by the loss of Ukraine International Airlines Flight 752,” a spokesperson for CFM said in a statement emailed to Yahoo Finance. “We extend heartfelt sympathies to the families and loved ones of those on board.” The company said at the time it had no further information concerning the crash.
Yahoo Finance reached out to Boeing to inquire about the cause of the crash and did not receive a response. In a press release the company said, “This is a tragic event and our heartfelt thoughts are with the crew, passengers, and their families. We are in contact with our airline customer and stand by them in this difficult time. We are ready to assist in any way needed.”
On Wednesday afternoon The Guardian reported that Iranian officials plan to withhold from Boeing the aircraft’s black box that holds information from the flight’s data recorder. Traditionally, aircraft manufacturers are invited to participate in determining the cause of a crash, Chaudhuri said.
Asked whether determining the cause of the crash would have been possible within several hours of the accident, Chaudhuri said, “I don't think it is really possible to assert something without seeing the data at hand, without really seeing whether the fire extinguisher system was deployed, whether there was a fuel spillage, whether the sensors on both engines detected a flame, whether there is a high temperature rise inside the engine.”
Hansman said accident investigators will be able to rule in or rule out a missile strike. He added that the most stressful time for aircraft engines is during takeoff, which is also the point at which they are most vulnerable to failure.
“The damage that you would get if a missile hitting the engine would be different that if a component broke off into the engine,” he said, noting that the first line of business for accident responders would be to search for survivors and not to inspect engine damage. “That’s why I'm a little skeptical of their fast declaration of what the causes were, because there just hasn’t been time to go look at it. Data from the flight data recorder will tell you information about the rotation rates of the engines, and the temperatures and pressures.” Until there is evidence to support the cause, Hansman said, no conclusions should be drawn.
Officials in Ukraine and Iran differed on the nationality of the passengers who died in the crash, but both agreed that the majority of passengers who died were Iranian and Canadian.
Alexis Keenan is a reporter for Yahoo Finance. Follow her on Twitter @alexiskweed.