- Witnesses describe hearing a "boom" as the flight from Seoul landed short
- Tilmon: "Pilot did not have enough power available to correct the rate of descent"
- A British Airways Boeing 777 landed short at London Heathrow in 2008 due to ice in fuel
- Curtis: Information from crew about moments before landing will be critical
With all passengers and crew aboard Asiana Airlines Flight 214 from Seoul now accounted for, air crash investigators are beginning the painstaking search for clues as to why the incident, which killed at least two people, happened.
While the sequence of events that led to accident remains unclear, witnesses described hearing a "boom" as the Boeing 777 appeared to come in short, touching down heavily on the runway close to the water's edge at San Francisco International Airport before it disappeared in a cloud of smoke. Parts of the aircraft, including its tail section and engines, snapped off as it spun off the tarmac on its belly.
"For whatever reason, the pilot did not have enough power available to correct the rate of descent that brought him into contact with the ground before he wanted to be there," Jim Tilmon, an aviation expert and former airline pilot, told CNN.
"There are a number of other considerations that may or may not have been made clear: One of them has to do with the fact that at least on one other occasion -- with a [Boeing] 777 in London -- they were on approach to land and they also ended up landing short. It's my understanding that it was all because of a fuel situation. For one reason or another, the throttles were moving but the engines were not increasing their thrust. Therefore they landed short of the runway and short of the power they needed to continue with a safe landing."
British Airways Flight 38 from Beijing landed short of the runway at London's Heathrow airport in January 2008 after losing critical power as it prepared to touch down. Fortunately, the pilot was able to partially control the impact, allowing everyone on board to escape serious injury. Investigators believe the incident was caused by ice in the fuel system of the Boeing 777. Their report suggested the aircraft passed through unusually cold air over Siberia as it traveled from the Chinese capital.
"Mechanical things can be present in these airplanes that will make it impossible for the crew to do the things that they know how to do," Tilmon added.
Todd Curtis, a former Boeing aviation safety engineer, agreed Flight 214's touch down point was far shorter than intended. "It should never even have been close to hitting the seawall at the edge of the runway like that," he said.
Curtis said the pilot rather than the computer would have been in control at this point.
"Typically the pilot would be hand-flying the plane right at the final approach. This was a relatively good-weather day. They didn't have to have a full auto-land system in place -- even when you have a lot of automated systems right before touch down, you're going to have the pilots under positive control of the aircraft," he said.
"As for why it hit the runway the way it did, or how fast it was, it depends in the weight of the aircraft and other factors. But this is something that has to be discovered through the cockpit voice recorder and the digital flight data recorder.
"How fast this aircraft was going, both horizontally along the ground and its vertical speed, that may be the critical factor that made it land so short.
"The initial impact was strong enough to cause both horizontal stabilizers and the vertical fin to come off the aircraft. This was major, major structural damage, which made it very difficult to control the aircraft."
Flight data recorders recovered from crash
Curtis said investigators would be keen to speak to the crew as soon as possible. "Of course we have all sorts of information from the 'black boxes' but the state of mind of the pilots -- why they made the decisions they did prior to landing -- is something that would be very important to know.
"Also, from outward appearances, until the very end of the flight it looks as though things on the flight were normal. One question I would like to ask those pilots is: 'was there anything going on in the minutes or hours leading up to the landing where you were taken off your usual schedule, where you doing things not on the checklist, where you are not following procedures? Was there anything out of place or out of the ordinary?'"