Investigators have begun sorting through the wreckage of Thursday’s plane crash in India, the nation’s deadliest in three decades. It could take months before a definitive explanation emerges, but videos of the accident and other evidence have begun to offer clues about what may have brought down the Air India flight, killing more than 260 people.
Here are some questions that investigators hope to answer in days and weeks ahead, according to aviation safety experts.
Were the wing flaps and slats properly extended?
Thursday’s crash occurred moments after the plane departed the airport in Ahmedabad, India. A short, blurry video showed what appeared to be the start of a routine takeoff, aviation safety experts said. But soon after leaving the ground, the plane, a Boeing 787 Dreamliner, began to descend before crashing and exploding.
At its most basic, the crash reflected a failure to meet the fundamental requirements of flight. To fly, a plane needs to generate enough lift to overcome gravity and enough thrust to overcome the air’s resistance, known as drag. The flight on Thursday seemed to fail on both accounts.
“There appeared to be an issue with the thrust and there appeared to be an issue with the lift,” said Anthony Brickhouse, an aviation safety consultant. “And we unfortunately saw what the result was.”
When an airplane takes off, flaps at the rear of the wing and slats at the front are typically extended to provide more surface area to create more lift as the plane gains speed.
“Just given the fact that this was a takeoff accident, begs the question regarding the settings of the wing slats and flaps, which is critical for taking off in a big jet that’s fully loaded with fuel,” said Jeff Guzzetti, a former accident investigator for the Federal Aviation Administration and National Transportation Safety Board.
It was not clear whether those flaps and slats were properly extended. If they weren’t, experts said, investigators will want to know why. Did the pilots choose not to extend them or fail to do so? Was there some kind of mechanical failure that prevented the pilots from extending those parts? Even if the slats and flaps were extended, it would be difficult to know if they were appropriately deployed because they can be configured differently for different situations. It’s also possible that they were extended but retracted too soon.
“The video is just too grainy, but that is something that’s clearly recorded in the flight data recorder,” said Mr. Guzzetti. “So hopefully, the recorders will tell the tale.”
Why was the landing gear down?
The video shows that the landing gear remained extended throughout the plane’s ascent and descent, which experts described as unusual. Landing gear creates drag, so retracting it is typically one of the first actions a plane’s pilots take after the plane is off the ground.
But experts said the pilots may not have retracted the gear for a number of reasons. A mechanical problem may have prevented the pilots from lifting the landing gear, for example. Or the pilots may have been preoccupied with another, more pressing problem.
“The airplane will climb fine leaving the gear down,” said Shawn Pruchnicki, a former accident investigator at the Air Line Pilots Association and an assistant professor of aviation safety at Ohio State University. If something else had gone wrong in the plane, the pilots may have focused on addressing that first, he said: “You have bells and alarms going off — there’s all kinds of stuff happening.”
Were there engine problems?
Engines provide thrust and investigators will want to know if they failed for any reason. An engine breakdown sometimes comes with telltale signs — smoke, fire, a flash — but experts said none of those are clearly apparent in the blurry videos of the crash.
One video shows what appears to be a dust cloud shortly after the plane leaves the ground. That could have been caused by an engine or it could have been caused by the wingtips disturbing the air, experts said.
Planes are designed to fly with just one engine, a situation that commercial airline pilots train for “excessively,” Mr. Pruchnicki said, adding that he believed the 787 Dreamliner probably didn’t experience a single engine failure, but both engines could have malfunctioned.
If that were the case, it would have happened at the “absolute worst time,” said Mr. Pruchnicki. A double engine failure occurring shortly after takeoff, when the plane was only several hundred feet off the ground, would have left the pilots without sufficient time to respond to the emergency.
“You can’t manage a double engine failure that close to the ground,” he said, recalling the 2009 “Miracle on the Hudson,” when a US Airways jetliner landed in the Hudson River after the aircraft lost power in both engines after striking a flock of birds. “These guys were in a residential area, a business area. They had no place to go either. There was no field to set it down gently. So, unfortunately, they ended up in buildings.”
A failure of both engines could have many causes: a bird or drone strike, inadvertent fuel shut-off, issues with automated thrust management. There is no evidence that these problems played a role in Thursday’s crash.
“There’s easily a hundred different explanations of possibilities,” Mr. Pruchnicki said. Analyzing the flight data recorder and inspecting the engine itself would provide an “unbelievably forensic” look at what happened, he added.
What was happening in the flight deck?
Investigators will also probably be sharply focused on what unfolded in the flight deck, or cockpit, before the crash.
There were two pilots on the Air India flight, which is typical in commercial aviation, with one pilot in charge of flying and the other providing support, monitoring the plane’s various systems. Were those duties split appropriately? What were the pilots saying to one another? And did they perform their jobs adequately?
Planes are also equipped with various warning systems to alert pilots of problems. Investigators will want to know if those warning systems worked as intended.
“Did they get the warning that they were supposed to receive or were they misconfigured? If they didn’t get a warning, then why? If they did, what did the crew do when they heard it?” said Mr. Guzzetti.
What other sources of evidence are there?
Investigators will also be on the hunt for more evidence.
Typically, they scour and analyze wreckage for clues and collect testimony from witnesses, such as airport personnel who may have seen the crash. They will also look for additional videos.
But their most important task will be recovering the wealth of technical information and audio recordings contained in the plane’s black boxes: a flight data recorder and a cockpit voice recorder, both of which have been recovered.
“Once they have that information, it will help focus the investigation into specific areas,” said John Cox, a former airline pilot and chief executive of Safety Operating Systems, a consulting firm. “So right now, it’s about gathering of documentation and evidence and keeping an open mind.”
