Pilots tried to abort SFO landing

Information taken from the cockpit voice recorder of Asiana Flight 214 shows the first sign of any trouble was seven seconds before impact, when the crew tried to accelerate. A stall warning sounded four seconds before the crash.

The crew then tried to abort the landing and carry out a "go around" maneuver just 1.5 seconds before hitting the runway. Deborah Hersman, chair of the National Transportation Safety Board, said the Boeing 777 plane was traveling much slower than the intended target speed.

"There was a call to go around from one of the crew at 1.5 seconds prior to impact," Hersman told reporters at a news conference in San Francisco on Sunday.

The call out is "communication between the crew that they want to go around, that means they want to not land but apply power and go around and try to land again," she said.

"During the approach, the data indicate that the throttles were at idle and air speed was slowed below the target air speed of 137 knots," Hersman said.

"Airspeed was significantly below the target airspeed," she added.

Two teenage girls from China were killed in Saturday's crash, while at least 182 were injured. The flight had been carrying 307 people, including 16 crew members.

The flight data recorder has been taken to Washington, DC, for examination, and investigators intend to talk to the pilots, crew and passengers.

Investigators are also looking into whether the shutdown of a key navigational aid at the airport played any role. The glide slope, which is based on the ground and helps pilots stay on course while landing, had been shut down since last month.

Hersman refused to say whether pilot error contributed to the incident and said all scenarios were being considered.

"Everything is on the table. It is too early to rule anything out," she said.

Clues emerge

Video footage showed the jet on its belly surrounded by firefighters with debris scattered along its landing path. The top of the 777's rear fuselage was burned away. One engine appeared to have broken off.

Images suggested that the aircraft struck a rocky area at the water's edge, short of the runway. The 777's tail was ripped off. San Francisco's airport is one of several in the United States which border bodies of water, and therefore have walls to prevent planes from landing in the water if they overrun a runway.

Mike Barr, an aviation expert from the University of Southern California, told the news agency AP that it's possible the plane's landing gear or tail hit the sea wall, an occurrence that would effectively cause it to slam into the runway.

Barr said witness reports of the plane's engines revving up before the crash were consistent with a pilot realizing at the last minute that the plane was too low, boosting power to increase altitude.

jr/ccp (AP, dpa, AFP)