A decision by the Asiana Airlines pilots moments after the 6 July crash delayed the evacuation of the passenger cabin for about 90sec, says US National Transportation Safety Board (NTSB) chairman Deborah Hersman.
The lead flight attendant entered the cockpit after it came to a stop off Runway 28 Left at San Francisco International airport and asked the flight crew what she should do.
"The flight crew told the flight attendant not to initiate an evacuation," Hersman says.
Instead, the lead flight attendant announced to the passengers to remain seated. In the economy class cabin, however, another flight attendant could see a fire on the No. 2 engine, tucked next to the fuselage around Row 10 of the passenger cabin. He sent another flight attendant to the front to explain to the flight crew that the passengers needed to evacuate, Hersman says.
Videos reviewed by the NTSB show that the passenger doors were not opened and the slides deployed until 90sec after the Boeing 777-200ER with 307 passengers and crew came to a stop.
The reasons for the delayed evacuation order will be scruintised as part fo the NTSB investigation, Hersman says. She noted that the US Federal Aviation Administration requires all aircraft to prove they can be fully evacuated within the time consumed by the 90sec delay caused by the flight crew's inaction.
At the same time, Hersman emphsised that the pilots lacked critical pieces of information in the moments immediately after the crash in which two people died.
"They don't have a good sense of what's going on behind them," Hersman says. "Hindsight is 20:20."
The delayed evacuation caused a scary moment inside the cabin. Two of the emergency escape slides deployed within the cabin after the crash. One of the slides trapped a flight attendant from escaping, even as flames began entering the cabin through window in the fuselage sidewall. Other crew members and firefighters battled the fire while the relief first officer used a utility knife to free the trapped flight attendnant.
The investigation is still focused several critical unanswered questions about the moments just before the crash.
The NTSB still doesn't know why there was apparent confusion in the flight deck about the status of the autothrottles. The 777 crashed after clipped the seawall at the Runway 28L threshold because the aircraft came down too low and was late too correct.
Hersman also says the pilot flying, Lee Gang Guk, reported to investigators during a 4h debriefing that he was "temporarily" blinded by a flash of light from the ground as the aircraft passed through 500ft. The apparent distraction added to the challenge of making simultaneous vertical and lateral corrections at the last minute, while all three flight crew members appeared to lose track of the 777's falling airspeed.