A clearer picture is emerging of what happened in the seconds leading up to the crash of Asiana Airlines Flight 214 at the San Francisco Airport Saturday.
On Sunday afternoon, National Transportation Safety Board (NTSB) Chairman Deborah Hersman presented details of those final seconds based on information from the two “black boxes” – the flight data recorder and the cockpit voice recorder – which had been flown back to Washington overnight, guarded by air marshals and then examined by NTSB experts.
Here are the most relevant details as presented and described by Ms. Hersman:
Flight 214 was approaching Runway 28 Left with its landing gear down and wing flaps set at 30 degrees. The approach speed – the “target speed” or speed to which the aircraft was to slow – was 137 knots. There was no cockpit discussion of any concerns or anomalies.
At 7 seconds before impact, someone in the cockpit called for an increase in speed.
At 4 seconds before impact, the sound of the “stick shaker” can be heard. This is a device which gives both an aural and physical alert to the pilot that the aircraft is approaching stall speed – too slow to maintain lift and keep flying normally. In commercial aircraft, the “stick” is actually a yoke used by the pilot to adjust wing roll and nose pitch.
“The speed was significantly below 137 knots, and I’m not talking about a few knots,” Hersman said at a briefing Sunday afternoon, noting also that the throttles had been pulled back to idle as the aircraft slowed below the target speed.
At 1.5 seconds before impact, someone in the cockpit called for a “go around” – which means adding power, waving off the approach to landing, and climbing back up to an altitude necessary to fly around for another attempt to land.
The throttles were advanced and the engines responded as they should. But by then it was too late. The Boeing 777’s low altitude and sink rate were such that its tail clipped the seawall off the end of the runway, and the aircraft skidded several hundred yards to a stop as one engine and parts of the wings came off.
Asked if all of this indicated pilot error – particularly since the weather was good and there had been no reported mechanical problems – Hersman declined to answer directly, citing the need to validate the information on the recorders.
“Everything is on the table right now,” she said. “We won’t speculate; we’re just telling you what we know to be true.”
The NTSB team headed by Hersman expects to be on the scene in San Francisco for at least a week, or however long it takes to complete the initial on-scene investigation.
Among other things, investigators want to interview the four pilots onboard and the cabin crew as well as passengers. Regarding the flight crew, investigators will be looking at how well they worked together and followed established procedures as well as such issues as cockpit configuration and issues that could affect crew performance, especially on a flight lasting more than 10 hours – fatigue, use of medications, sleep disorders, or drug and alcohol use.
Visibility was 10 miles at the time, and there was a slight wind (7 knots) from the left. No wind shears or other potentially adverse conditions had been reported.
It was noted that aircraft landing on Runway 28 Left were operating VFR (using Visual Flight Rules), which means that the electronic glide path was not in service and it was up to the pilot to fly the approach to landing visually and manually.
In this case, the Federal Aviation Administration (FAA) had issued a worldwide “notice to airmen” (NOTAM) that the glide path on that runway would not be operating from June 1 to August 22 while construction to improve the runway was underway.
As Hersman and airline pilots point out, this was not an unusual circumstance.
The NTSB has asked anyone with still photos or video of the crash to contact the agency through its web site.
Most such investigations take 12-18 months to complete, but Hersman pointed out that the NTSB can issue safety recommendations based on an ongoing investigation at any time.
There were 307 people aboard Flight 214, 291 passengers and 16 crew members. The flight had originated in Shanghai and stopped in Seoul before flying on to San Francisco.
Two people aboard the plane died (both Chinese teen-age girls). Of the 182 injured people taken to hospitals, at least 49 were in critical condition late Saturday. The remaining 133 had minor to moderate injuries, while many of the other passengers or crew members had more minor injuries that didn't require extra treatment, according to the Associated Press. Thirty of the passengers were children.
"I think when we look at this accident we're very thankful that we didn't have more fatalities and serious injuries and we have so many survivors," NTSB Chairman Hersman said on CNN's "State of the Union" Sunday. "Really, very very good news as far as survivable accidents, which many accidents are."
The robustness of the 777 aircraft allowed many passengers to walk away from a catastrophic crash landing, other experts point out – including such safety features as multiple redundant systems, stronger seats, and the use of nontoxic materials in construction. Also, the Federal Aviation Administration now requires new aircraft models to be equipped and staffed to allow all passengers to exit within 90 seconds.
South Korean officials said the plane's passengers included 141 Chinese, 77 South Koreans, 61 Americans, three Canadians, three from India, one Japanese, one Vietnamese, and one from France, while the nationalities of the remaining three haven't been confirmed.