The Air Canada A320 that almost landed on a crowded taxiway at San Francisco International Airport on 7 July 2017 was only 59 feet above the ground at its lowest point and that occurred between two of the four aircraft on the taxiway. This is one of the details the
FAA NTSB released today as part of its initial investigation into the Air Canada flight 759 incident. The Air Canada A320 passed over a United 787 and Philippines Air A340 while still descending; it then passed over another United 787 and a United 737 as it climbed, after instructed by ATC to go around.
The timeline established by the
FAA NTSB includes a number of interesting data points, any one of which likely should’ve caused the pilots to abort the landing. Ultimately they successfully did but a certain amount of luck appears to be involved in avoiding the disaster this time around.
From three miles out (just over a minute of flight time) the plane was lined up to land on the taxiway, not the runway. The incident was not a last minute shift in positioning.
The pilot reported seeing lights on the assigned runway and asked to reconfirm clearance to land. At that time the aircraft was still lined up for the taxiway and, according to
FAA NTSB reports, not on the Airport Surface Detection Equipment Model X (ASDE-X)/Airport Surface Surveillance Capability (ASSC) radar screen. This is one of the systems ATC uses to track aircraft location when very close to the ground, places where traditional RADAR is less useful.
As ACA759 approached SFO, at 2355:52 PDT, the airplane flew too far right of course to be observed by the local controller’s ASDE-X/ASSC and was not visible on the ASDE-X/ASSC display for about 12 seconds.
At 2355:56 PDT, when ACA759 was about 0.3 mile from the landing threshold, the local controller confirmed and recleared ACA759 to land on runway 28R.
The controller did not have the plane visible on the surface radar screen and still cleared the landing, even after the pilot expressed some concern. That seems to me an unusual set of circumstances and probably worth further consideration during the rest of the investigation.
By the time the ATC controller issued the “Go Around” command the plane was already climbing. The pilots applied thrust after passing over UA 1, the first 787, around 85 feet above the taxiway. Roughly 2.5 seconds later the plane began to climb, having reached a minimum altitude of 59 feet over the taxiway, positioned between the A340 and the second 787 lined up for departure. The top of the A340 tail sits 59 feet above the ground; the 787 is about 3.5 feet shorter.
I held off on commenting for the most part because the altitude and positional data was mostly unclear in initial reports. The minimum altitude varied wildly and it was unclear just how close the A320 got to a catastrophe. Now we know, both from the data and the photos, that it was an incredibly close call. And, while the pilots certainly bear responsibility for lining up incorrectly, it also appears they did finally figure out they screwed up before ATC did. That’s a nice save.
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