Two navigation systems used to help pilots land were not operating Saturday at San Francisco International Airport, possibly contributing to the Asiana crash that killed two passengers.
Officials disabled electronic and visual systems while the airport’s main landing strip is undergoing a reconfiguration to give pilot’s more breathing space from the bay, pilot Kirk Koenig, 46, told the Daily News
“The landing threshold — sort of where you're aiming for — it's going to be moved back” as part of the reconstruction, said Koenig, a pilot with 30 years of experience.
“So they had to turn off the electronic glideslope and they had to disable the light guidance system.”
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The systems provide information on a plane’s altitude and distance from the ground.
Both systems, known by their acronyms ILS — for Instrument Landing System — and VASI — for Visual Approach Slope Indicator — are dependent on the airport, rather than the aircraft.
“You’re tired after a 12-hour flight, so it’s nice having all these extra things telling you, ‘Hey, I’m exactly where I need to be,’” Koenig said.
JED JACOBSOHN/REUTERS
The airline’s main runway will be reconfigured to change the spot that pilots are aiming for.
If both are disabled, a pilot must rely on a computer in the airplane that provides similar information on the plane’s descent, said Koenig, president of Expert Aviation Consulting.
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He said the systems, which provide critical information even on a day when the weather is ideal, had been turned off at SFO in the last two weeks.
The lack of those tools would likely be a focus of investigators as they try to determine what caused the plane to descend at a 35-degree angle tail-first. When it crashed, the plane’s wing came off and half of its roof was left charred and sliced open, injuring 182 of the 307 people aboard.
Many reports speculated the plane had landed short of the runway, which is at sea level, surrounded by San Francisco Bay.
A pair of sources at the airport reinforced that scenario.
"Boulders from the sea wall (were) knocked 150 yards down the runway," one source told the Daily News.
A separate source said some of the boulders along the sea wall had been split in half from the impact of the Boeing 777.