SAN FRANCISCO - A navigation system that helps pilots make safe descents was turned off at San Francisco airport on Saturday when a South Korean airliner crashed and burned after undershooting the runway, officials said.
The system, called Glide Path, is meant to help planes land in bad weather. It was clear and sunny, with light winds, when Asiana Flight 214 from Seoul, South Korea crashed just before noon, killing two passengers and injuring more than 100.
Aircraft safety experts said Glide Path was far from essential for routine landings, and it was not unusual for airports to take such landing systems off line for maintenance or other reasons.
But pilots have grown to rely on the decades-old technology, which is designed specifically to prevent runway misses, so investigators are likely to look closely at the issue.
"The pilots would have had to rely solely on visual cues to fly the proper glide path to the runway, and not have had available to them the electronic information that they typically have even in good weather at most major airports," said Captain Chesley "Sully" Sullenberger, the former US Airways pilot who gained fame with a successful crash landing on the Hudson River in 2009.
"What that means is that then the automatic warnings that would occur in the cockpit when you deviate below the desired electronic path wouldn't have been available either. So we don't know yet if that's a factor in this particular situation, but that's certainly something they'll be looking at," he told the local CBS News affiliate.
Glide Path is a computerized system based at an airport that calculates a plane's path of descent and sends it to pilots in real time.
San Francisco International has turned off the system for nearly the entire summer on the runway where the Asiana flight crashed, according to a notice from the airport on the Federal Aviation Administration's Web site. It showed the system out of service June 1-August 22 on runway 28 Left.
Kevin Hiatt, chief executive of the Flight Safety Foundation and a former Delta pilot, said it was common for airports to take instrument landing systems offline for maintenance on clear days. Pilots use several other instruments and visual cues to land in clear conditions, Hiatt said.
"All of those are more than adequate to fly an aircraft down for a successful landing on the runway," he said.
Sullenberger said the San Francisco runway safety area had been increased to avoid short landings.
Airport spokesman Doug Yakel told reporters there had been construction on the runway recently, but not on Saturday.
"Given that we had clear visibility today, we were operating under what's called visual flight rules," when good weather allows a pilot to see well to operate the plane, he added. He did not take further questions on the instrument landing technology.
Former Inspector General of the US Department of Transportation Mary Schiavo said pilots had become increasingly dependent on instruments for flying. But she added that modern planes had plenty of systems for landing safely, down to a pilot watching the lights on the runway.
Air crash in San Francisco causes confusion, frayed nerves
By Laila Kearney and Ronnie Cohen
SAN FRANCISCO - Bystanders watching an Asiana Boeing 777 flight make a seemingly routine approach to a San Francisco runway were stunned to see it come in fast and hit the ground hard on Saturday, while on board, passengers'survival instincts took over.
The crash at San Francisco International Airport left two people dead, while more than 180 people were transported to area hospitals, including many with serious injuries.
Vedpal Singh, a native of India, was on board the flight along with his wife and son when the aircraft struck the landing strip hard.
"Your instincts take over. You don't know what's going on,"said Singh, who had his arm in a sling as he walked through the airport's international terminal and told reporters he had suffered a fractured collar bone.
"I'm very, very thankful to God," he said.
Singh lives in South Korea and had taken the flight for a vacation to California. He said that his son was fine but he had not yet been reunited with his wife.
Elliott Stone, a passenger on board the plane, told CNN that he thought the aircraft approached the airport "a little high"and made a sharp descent.
"All of a sudden, boom, the back end just hit and flies up into the air and everyone's head goes up the ceiling," Stone told CNN.
Greg Claxton, 39, of Sarasota, Florida, was among those who witnessed the crash from a shuttle bus traveling from his hotel to the airport.
"I saw a plane coming in really fast, really hard," Claxton said. "It appeared to land, spin and then fire. I instantly was praying for those people on board." Claxton added that he ran off the shuttle. Others on board were crying at the sight of the crash.
After the crash, some reflected on how the disaster could have been worse. "It is incredible and very lucky that we have so many survivors," San Francisco Mayor Ed Lee told reporters.
Passengers who remained at the airport and family members who rushed to join them dealt with their frayed nerves. Some collected themselves at the airport's "Reflection Room," where workers from the Salvation Army were on hand to offer comfort to those involved in the crash.
"They are in shock, they're telling their stories," said Salvation Army Major Wayne Frodenberg, a disaster services coordinator for the organisation. "It's quiet, people are sort of decompressing." The Salvation Army was providing shoes to some passengers who lost their footwear in the crash, he said.
Most on board the Asiana Airlines flight 214 that crashed were Chinese, South Korean or American, and the two dead were reported to be Chinese citizens.
Among the scores of passengers injured in the crash and taken to hospitals, some suffered serious wounds such as internal bleeding and spinal fractures, said Dr. David Spain, chief of trauma medicine at Stanford Hospital, where about 45 patients from the crash went to its emergency room.