A flight from Asia that crashed at the San Francisco Airport could have stemmed from the crew misreading the approach, said a top official with the agency investigating the crash.
Four seconds before the crash, the cockpit crew was alerted that a stall was about to happen. Seconds later, a member of the crew called for a go-around–or an increase in power and height so the plane could abort the landing and try again after looping around.
But by that time it was too late. The plane crashed less than two seconds after the call.
The Asiana Airlines Flight 214 crashed on July 7, with 307 people on board. Two are confirmed dead and 182 others were taken to area hospitals.
The initial speed that the plane approached the runway with was also “significantly below” 137 knots, which is the target speed for approaching the runway, said Deborah Hersman, chairwoman of the National Transportation Safety Board. The NTSB has several teams studying different aspects of the crash, including the flight data recorder and the cockpit voice recorder.
At the same time, Hersman cautioned that her update is preliminary and that “we will not reach a determination of probable cause in the first few days that we’re on an accident scene.”
“We have a lot more work to do,” she told reporters in an afternoon press conference, including validating the raw data from the recorders.
The pilots were alerted that they were approaching a stall four seconds prior to the crash. A stick-shaker, or a yoke that the pilots are holding, started vibrating and shaking, said Hersman. One and a half seconds before the crash, a member of the crew called for the go-around, according to the cockpit voice recorder, which records communication between the crew.
Go-arounds, also known as aborted landings and missed approaches, can happen in several situations, including being too far down the runway to stop safely, and not being aligned right according to Bruce Landsberg of the Aircraft Owners and Pilots Association. However, “as the accident scenarios prove,” many pilots don’t know how to conduct go-around correctly, he writes in a post on the association’s website.
It’s unclear why the go-around didn’t happen in this case, but there may not have been enough time to increase the speed. There was a call from a crew member to increase speed about seven seconds prior to impact, and the throttles were advanced a few seconds prior to impact. “The engines appear to respond normally,” said Hersman.
One investigative team hopes to interview the crew within the next few days; that team, the operations group, will also look at, among other things, the geography of the airport, the cockpit instruments, the information the crew has to make decisions, and the crews’ experience.
The human performance investigator, meanwhile, will test the crew members for drug or alcohol use; look at the members’ 72 hours leading up to the crash; and examine factors such as fatigue, sleep disorders, and any medication use. The investigator will look at how the crew worked together and followed procedures as well.
Earlier in the day, the glide scope, which alerts pilots that the landing approach is not correct, was said to have been off, but according to Hersman that may not have been a factor in the crash.
Investigative teams will also interview plane passengers, document the extensive debris field and seating positions of the injured passengers, and look at the safety belts.