Asiana crash: five clues to help understand what happened

Investigators expect to spend weeks or months determining what caused Asiana Airlines Flight 214 to crash-land at the San Francisco airport Saturday, killing two of the 307 passengers and crew members aboard.

The National Transportation Safety Board and South Korean investigators are interviewing the flight’s pilots and crew this week. Two South Korean investigators are also scheduled to arrive in Washington Tuesday to examine the plane's black box.

As the probe continues, here are five key factors known so far that may have contributed to the crash landing:

1. The plane was approaching the landing too low and too slowly.

Flight 214 was on a straight, 17-mile approach to the San Francisco International Airport on Saturday, according to NTSB Chairman Deborah Hersman, when it quickly lost too much speed and height to make a safe landing.

Data show that the plane’s autopilot was turned off 82 seconds before the crash, when the plane was about 1,600 feet in the air, Ms. Hersman said Monday. At 34 seconds before the crash, the plane was at 500 feet and its speed dropped below the level required for a safe landing.

Seven seconds before collision, the cockpit recorder captured a call from somebody in the cockpit to increase the plane’s speed, Hersman said, and three seconds later, the control yoke started vibrating to warn of the potential to stall. At 1.5 seconds before the impact, a crew member issued a call to abort the landing, but it was too late to regain speed and height. The tail of the plane appears to have clipped the sea wall there, sending the plane slamming into the runway, where it skidded about 2,000 feet before catching fire.

In the last three seconds, the plane was traveling at least 37 miles per hour below the minimum recommended approach speed of 137 knots (about 158 miles per hour). 

2.  The control pilot and supervising pilot were new to their positions.

The pilot at the controls during the attempted landing, Lee Gang-guk, had logged only 43 hours at the controls of a Boeing 777, the aircraft he was flying Saturday. Mr. Lee had more than 10,000 hours of experience on other planes, including the Boeing 747, according to an Asiana Airlines spokeswoman, but was making his first landing at San Francisco with the larger 777 model.

The pilot serving as a training supervisor for Lee was also in a new position. Although the supervisor, Lee Jeong-min, had landed 33 times at the San Francisco airport in a Boeing 777, he had become a training supervisor in June, and Saturday’s flight was his maiden flight as a Boeing 777 supervisor, an Asiana official told The Wall Street Journal Saturday.

Asiana president Yoon Young-doo defended the experience of the supervising pilot at a news conference in Seoul, South Korea, Tuesday.

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