A report by US air safety investigators has catalogued how close to disaster an Air Canada Airbus A320 came after it lined up to land on a busy taxiway at San Francisco International Airport.
A National Transportation Safety Board preliminary report released Wednesday shows the plane dipped even lower than originally thought after the crew of Flight ACA759 aborted their July 7 landing over the airport’s taxiway C.
The NTSB report shows the pilots pushed forward the engine thrust levers when the aircraft was 85 feet above the ground and about the time it was over the first of four planes on the taxiway. But it dipped down to 59 ft (18m), barely above the 56ft (17m) height of a Boeing 787 tail, before it started to climb.
“Flight data recorder data indicate the airplane was over the taxiway at this time,’’ the report said. “About 2.5 seconds after advancing the thrust levers, the minimum altitude recorded on the FDR was 59 feet above ground level.”
One of the San Francisco’s parallel runways, 28L, was closed on the night of the incident and had its lights turned off with a 20.5ft-wide flashing closure marker at the threshold.
Normal runway and approach lighting was turned on for the operating Runway, 28R, and lighting on the parallel taxiway was also on default settings.
Occupying the taxiway were four planes: a United Airlines Boeing 787, a Philippines Airlines Airbus A340, another United 787 and a United 737.
“Both pilots said, in post-incident interviews, they believed the lighted runway on their left was 28L and that they were lined up for 28R,’’ the report said. “They also stated that they did not recall seeing aircraft on taxiway C but that something did not look right to them.”
The captain was flying the aircraft and had 20,000 flight hours, including almost 4800 in command of an A320.
The aircraft was lined up to land on the taxiway for the final three nautical miles (5.5kms) of the approach but about 0.7 miles from the threshold the crew contacted air traffic control. They mentioned seeing lights on the runway and requested confirmation of the clearance to land.
The aircraft had disappeared from the local air traffic controller’s airport surface surveillance display because it was too far to the right and it would not be visible for about 12 seconds.
It was during this time, and when the plane was about 0.3 miles from the runway, that the controller confirmed it was cleared to land on runway 28R.
About a second later, the flight crew of the United 787 at the head of queue asked: “Where’s this guy going.?’’ and then “He’s on the taxiway’’. A second plane in the queue also turned on its landing lights.
The aircraft reappeared on the controller’s display at this time and about six seconds later he directed ACA759 go around.
However, the Air Canada crew had already advanced the thrust levers and the aircraft had started to climb at this point.
The NTSB’s preliminary report did not include an analysis of the incident but experts have said it could have been one of the biggest disasters in aviation history.
The NTSB has formed working groups to investigate air traffic control, flight crew operations, human factors and the flight data recorder.
