WASHINGTON — NTSB investigators say the flight clew aboard an Asiana Airlines flight that crashed at San Francisco International Airport last July were to blame.
The crash on July 6, 2013 killed three and left more than 180 injured.
“…the flight crew over-relied on automated systems that they did not fully understand. As a result, they flew the aircraft too low and too slow and collided with the seawall at the end of the runway,” said Christopher Hart, acting chairman of the NTSB.
The report also answers the basic question about the accident itself:
Why did this airplane crash while executing a visual approach on a clear day?
The Boeing 777 is one of the most sophisticated and automated aircraft in service. Automation has unquestionably made aviation safer and more efficient. But the more complex automation becomes, the more challenging it is to ensure that the pilots adequately understand it.
In this instance, the flight crew over-relied on automated systems that they did not fully understand. As a result, they flew the aircraft too low and too slow and collided with the seawall at the end of the runway.
More than 15 years ago, Professor James Reason wrote, “In their efforts to compensate for the unreliability of human performance, the designers of automated control systems have unwittingly created opportunities for new error types that can be even more serious than those they were seeking to avoid.”
Not surprisingly, Asiana Airlines, the pilots union, and Boeing, which manufacturer the Boeing 777 involved in the crash, have starkly different opinions of what role the pilots played in the crash, and the role of automation.
“The airplane and all airplane systems were functioning as expected prior to impact and did not contribute to the accident,” Boeing said in a March submission to the safety board. The accident was caused by the pilots’ failure to monitor and control the plane’s airspeed and direction, and could have been avoided if they had initiated a timely go-around.
Asiana, meanwhile, blamed Boeing and the pilots. The pilots, just three months before the accident, had received “specific instruction” about the possibility the airspeed protection would be disabled in a certain mode, Asiana said.
The airline assigned blame to the pilots for not ensuring “a minimum safe airspeed,” and Boeing for creating autopilot system that led to an “unexpected disabling” of speed protections.
The warning system, the airline says, also did not give the pilots enough time to recover.
The Asiana Pilots Union blamed crew training, saying they were not trained that a combination of autopilot and auto-throttle modes would not prevent the plane from going too slow.
“In this case, a key piece of information was not provided as part of the normal training program at Asiana,” the union said.
Boeing said it was without fault.
“All airplane systems were functioning as expected prior to impact and did not contribute to the accident,” it told the safety board.
Asked why the “hold” mode did not protect against dangerous drop-offs in speed, Boeing told the board, “To do this would violate (Boeing’s) design philosophy: the pilot is the final authority for the operation of the airplane.”
“If the auto-throttle automatically (switched mode to prevent an aerodynamic stall), it would be overriding the crew’s selection,” Boeing said.
Fly the plane manually
If pilots are confused by the technology, there is a simple solution: fly the plane manually, Boeing said.
“This accident would have been avoided had the flight crew followed procedures and initiated a timely go-around,” Boeing told the safety board.
What no one contests is that by the time the plane’s captain recognized the plane was traveling too slow, it was too late.
At 11 seconds before impact, the plane’s low airspeed alert was triggered.
Eight seconds before impact, one of the pilots pushed the throttles forward. But it takes engines seven to eight seconds to spool-up from idle to full power.
The plane slammed into the seawall, ripping off the landing gear, the tail and both engines. The spun 330 degrees in a shower of sparks and debris.
Of the 307 people on board, three died. Almost 200 were injured.