The near crash of Air Canada flight 759

August 20, 2019 3:35 PM

On the 7th of July 2017, Air Canada flight 759 lined up to land on the taxiway instead of the runway at San Francisco International Airport, in the process coming just seconds away from causing what might have been one of the worst aviation disasters in history.
posted by Chrysostom (32 comments total)

Glad I read this AFTER I just spent the last day taking three flights across 6 time zones.
posted by thecjm at 3:57 PM on August 20, 2019 [5 favorites]

I think this has a much better perspective than a medium.com article. I always check pprune for aviation type stuff (oh, it's EU focused for most stuff)
posted by baegucb at 4:05 PM on August 20, 2019 [5 favorites]

Jesus, the article is pretty dry but the CCTV footage of them just missing two planes on the ground is fucking terrifying.
posted by The Tensor at 4:13 PM on August 20, 2019 [24 favorites]

Lack of sleep is a big--and growing--problem with a LOT of people. Airline pilots, truckers, any number of others that operate heavy and potentially life-threatening machines and vehicles.
posted by zardoz at 4:19 PM on August 20, 2019 [10 favorites]

What I like best about this story is it highlights how important the humans in the cockpit still are to flying. The instruments knew for sure they were in the wrong spot but no airplane cockpit (or pilot) would let the instruments override the pilots. That may be for the best. But every once in awhile a pilot makes a mistake and it can be very serious.

I've almost made this specific mistake (landing on a taxiway instead of a runway) myself. It's remarkably difficult to visually identify features from the air. And once your brain makes the wrong assumption it's really hard to shake yourself of that. It's like seeing the "wrong" side of an optical illusion.
posted by Nelson at 4:22 PM on August 20, 2019 [27 favorites]

Many years ago I was flying home from Venice, severely jetlagged and sleep-deprived since I don't sleep well on planes. Out the windows I saw the lights of the neighborhoods and the connecting arteries as islands and bridges; I was vividly hallucinating Venice.

Now a pilot has experience and training, but at the same time only a mere biological brain and all the weird sensory issues that arise therefrom. It's not hard at all to imagine mistaking the taxiway for the expected second runway, despite the protective measures that had been taken. Indeed, an earlier landing almost made the same mistake (fortunately not compounded by failing to key in the ILS frequency).

What I like about this is that it does not focus on the failures of the pilots--they were experienced and well-trained--but rather on the systemic issues that misled them. And better, that the focus has been on correcting these issues to prevent them from happening again. It's this iterative process of evaluation and systems-improvement that has resulted in an international airline system that is remarkably, and increasingly, safe.

There is "blame" to be assigned: a system that required (Canadian) pilots to operate outside their biological limits, crucial information embedded among the mundane, errors in aircraft control staffing, and, despite efforts to avoid it, misleading visual cues. It appears that efforts to correct the problems are focussed on these things rather than citing pilot error. Good.

I also note that, although by the narrowest of margins, the experience, training and professionalism of the pilots (including the ones on the ground) did in fact avoid a disaster.

What I'm saying is that, however harrowing, this is a success story. It shows a system that works very well but also acknowledges that it is not and never will be perfect, and continually strives improve its procedures based on what it learns along the way. Healthcare practitioners are now adopting checklist procedures developed in the aviation industry to improve outcomes. In my own experience as a software engineer, the adoption of retrospectives and continual evaluation and improvement of processes has made a huge difference in productivity, predictability and quality.
posted by sjswitzer at 4:29 PM on August 20, 2019 [21 favorites]

The instruments knew for sure they were in the wrong spot but no airplane cockpit (or pilot) would let the instruments override the pilots.

And the 737 Max crashes are actually a pretty good illustration of why aircraft systems are usually designed this way.
posted by tobascodagama at 4:49 PM on August 20, 2019 [3 favorites]

A good read on a scary thing, and yeah, on preview, what sjswitzer said, aviation disasters and near misses are incredibly dangerous, so the system that controls them takes it very, very seriously.
One thing I do sometimes when it feels like everything is completely off the rails is to listen to ATC radio recordings of both routine and emergency situations, because even in the worst, hardest of situations, the sheer professionalism and dedication they have always shows in their voices.
As an example, the audio from this very incident, along with a flight sim rough demonstration of how it happened.
posted by neonrev at 4:50 PM on August 20, 2019 [6 favorites]

Well that's going in the same file as the SEC postmortem on the Knight Capital flash crash.

That file is named "things to hit managers with when they're not making use of all available risk mitigation measures."
posted by PMdixon at 5:07 PM on August 20, 2019 [6 favorites]

I always check pprune for aviation type stuff

Heh, I'm enjoying reading through it for the forum-ish progress of the discussion and digging in on details, so thanks for the link. But I can't help but twitch at the second comment in that thread being a classic "well, in fact, this is all overblown nonsense, it obviously wasn't a big deal" dismissal from Random Forum Dude.
posted by cortex at 5:15 PM on August 20, 2019 [17 favorites]

But I can't help but twitch at the second comment in that thread being a classic "well, in fact, this is all overblown nonsense, it obviously wasn't a big deal" dismissal from Random Forum Dude.

Wow there are uh quite a lot of comments insisting that thing people were providing documentation of in other cases is impossible.
posted by PMdixon at 5:22 PM on August 20, 2019 [3 favorites]

Lack of sleep is a big--and growing--problem with a LOT of people. Airline pilots, truckers, any number of others that operate heavy and potentially life-threatening machines and vehicles.

Yabut to change that you’d have to value human lives above value to shareholders
posted by ricochet biscuit at 6:27 PM on August 20, 2019 [6 favorites]

Fair point ricochet, but in aviation perception of safety (and, therefore ultimately, safety) is crucial to the bottom line. In long haul trucking not so much.

At the same time, while we should be skeptical--especially now--of the efficacy and motives of regulatory agencies, they have actually done a pretty good job across the board to increase transportation safety. I'm as cynical as the next guy but on the whole they have been pretty effective and we should put our efforts into keeping them that way. They are under dire threat today.
posted by sjswitzer at 6:57 PM on August 20, 2019 [6 favorites]

While the engines spooled up, the A320 dropped to a low point of about 65 feet, coming a hair’s breadth from clipping the 55-foot-tall vertical stabilizer of Philippine Airlines flight 115.

I...I...I... 10 feet
posted by nikaspark at 7:06 PM on August 20, 2019 [10 favorites]

This reminded me irresistibly of another (but fictitious) landing on the wrong runway as told in the story of The Shepherd [previously, previouslier]. Includes expectation bias.
posted by heatherlogan at 7:08 PM on August 20, 2019 [1 favorite]

It was also a nearly full moon that night, which probably would have decreased the visual differences between the runway and the taxiway, by brightening everything up.
posted by mantecol at 8:21 PM on August 20, 2019

It says the passengers were unaware and gosh I hope so but I'm not sure how you could be unaware of a plane 10 feet away from you.
posted by bleep at 9:36 PM on August 20, 2019

If anyone's looking for it, the official NTSB report is here [PDF]. (You know, in case the Medium article wasn't dry enough for you.)
posted by Syllepsis at 9:45 PM on August 20, 2019 [2 favorites]

The plane on the ground is directly underneath you which you can't see from the passenger cabin.
posted by Mitheral at 9:46 PM on August 20, 2019 [5 favorites]

The ppl in the plane above would have seen. And also I didn't specify the ppl in the plane below because I imagine there would have been a sudden ominous shadow and a huge noise.
posted by bleep at 10:09 PM on August 20, 2019

The people in the plane above would have felt and seen the plane itself going in for what was clearly a landing and then hastily pulling up. But they'd have seen it out of side-facing windows with not a very good pitch downward; I agree with Mitheral, it feels really really likely they wouldn't have gotten a view of the planes they nearly collided with.

So they probably knew something weird happened, but didn't know what, and then the plane circled and they landed and they went on with their day. From what the Medium piece describes, even the pilots of 759 didn't really comprehend in the moment how close a call they'd had; I don't know why they would have passed any sliver of that on to the passengers vs. just saying "welp, folks we've been instructed by air traffic control to circle around for another approach, so it'll be a few more minutes here and then we'll have you on the ground".
posted by cortex at 10:23 PM on August 20, 2019 [4 favorites]

Audio of the ATC comms during the exciting part.
posted by ctmf at 11:27 PM on August 20, 2019 [2 favorites]

whoops, missed neonrev's much more dramatic version above
posted by ctmf at 11:33 PM on August 20, 2019

A few years ago (before this incident occurred), I was looking at the airport diagram for SEA. I noticed the comment on the right about taxiway T not to be confused for a landing surface. So, being the problem solver that I am, I questioned why the markings/lighting for a taxiway are the same as a runway. Pilots: why aren't taxiways marked and illuminated in such a way that, on a standard approach, they would appear as snaking or zigzagged lines? Maybe some kind of dazzle pattern? Anything that breaks up long, parallel lines to communicate information seems like it would be a win. As for the tower, with the technology that we have, why are there still "oblique viewing angles"? Given the quality of the video in the article, why isn't it possible to place cameras on the centerline in or just past the overruns?

I just got an entry-level job in aviation and even before any real training, some of the stuff I have already learned is just wow. That's probably why this fires me up so much; even moreso than as a regular passenger.
posted by bonje at 11:46 PM on August 20, 2019 [1 favorite]

At the risk of being a fanboy, Admiral Cloudberg has been documenting historical airplane disasters, near-misses, and close-calls on Reddit and Imgur for years. His most fascinating work is on lesser-known air disasters like the Mount Salak Sukhoi Superjet crash and TAROM Flight 371 . Most of the archives are on Imgur, which is admittedly not the best way to read articles like this, but at least there's plenty of GIFs and images.

I have a fascination with air disasters mainly because they are so rare. When one happens, it's the result of many things going wrong at once (usually) and the typical thoroughness of crash investigators means every story gets a satisfying conclusion with corrective action.

Admiral Cloudberg has his own subreddit with archives to over a hundred similar articles here: /r/AdmiralCloudberg
posted by Enkidude at 12:12 AM on August 21, 2019 [14 favorites]

why aren't taxiways marked and illuminated in such a way that, on a standard approach, they would appear as snaking or zigzagged lines? Maybe some kind of dazzle pattern? Anything that breaks up long, parallel lines to communicate information seems like it would be a win. As for the tower, with the technology that we have, why are there still "oblique viewing angles"? Given the quality of the video in the article, why isn't it possible to place cameras on the centerline in or just past the overruns?

Taxiways are designed differently than runways. Check out the Pilot's Handbook of Aeronautical Knowledge, section 14-5. Runways are outlined in white, with white dashed centerline markings and white numbers. Runway lights are green and red (edge) or white and red (centerline). Taxiways are outlined in yellow, with a single yellow centerline. Taxiway lights are blue (edge) and green (centerline).

In daylight conditions, you can generally easily see the runway end indications - giant numbers and the "piano keys" which denote the beginning of the touchdown zone. At night, there are a number of visual aids to help you identify the end of the runway - flashing Runway End Indicator Lights (REIL), high intensity runway edge lighting, and the "rabbit" (a series of strobes lined up with the runway that pulse in sequence to lead you in to the runway).

In my experience, generally, what you see while landing at night is darkness all around except for a long box outlined in green and red - that's the runway. If it's a bigger airport, you'll get REILs and other lights. What you might see that would confuse you is the flashing landing lights from another airplane pointed straight at you on the taxiway - I would totally believe that could trick someone into thinking the runway is offset from where it really is. Making zigzag patterns on taxiways would be useless because you can't see them. I think confusing patterns on the taxiway would do nothing except increase the number of ground incursions as pilots taxi in to the grass.

Cameras for tower control is actually gaining traction for a number of reasons (mostly economical). They're not being used to augment tower visibility, though - airports (low saturation airports especially) are starting to use remote towers that control multiple fields at once. The control tower is replaced with, essentially, a pole with a bunch of cameras on it; the feeds are sent to a remote operations center which recreates the look and feel of a real control tower. There are some safety benefits (you can do some interesting things with data overlays), but for the most part it's so you can take three or four towered airports that may only get a couple planes an hour in traffic and combine them in to one facility to save money on staffing.
posted by backseatpilot at 5:44 AM on August 21, 2019 [10 favorites]

Yeah the passengers knew something, going from so close to touchdown to a go around is loud and startling. The engines just roar and it's so much more noticeable than on a usual take off because then you hear the roar from the start, while you're speeding along the ground. And in my experience (of going around, not nearly landing on a bunch of planes!) the crew are too busy to say anything to the cabin until after the landing.

Regular flyers might've known something was odd with the view but I agree they wouldn't have seen the planes. Jesus though, the poor pilots in the ones lined up. I wouldn't want to have to depart for a longhaul flight at that point, I'd want a strong drink.

Ten feet!
posted by kitten magic at 6:16 AM on August 21, 2019 [5 favorites]

> Glad I read this AFTER I just spent the last day taking three flights across 6 time zones.

Many, many things had to go wrong for this to almost happen, but you can get killed by a car because some idiot did *one* thing wrong. Variations on this theme are what I tell myself every time I get nervous about flying, which personally I find a lot less frightening than driving on the 401. Which isn't to say this article wasn't terrifying.
posted by The Card Cheat at 7:10 AM on August 21, 2019 [4 favorites]

I wouldn't want to have to depart for a longhaul flight at that point, I'd want a strong drink.

"Avoidance apron"
posted by thelonius at 10:37 AM on August 21, 2019 [1 favorite]

A few months before this near-disaster took place, I was a passenger on a Singapore Airlines flight from San Francisco, probably the same one that is mentioned in the article. It is eerie and fascinating to realize how differently everything could have turned out. (Side note, it was a really fun trip: I circumnavigated the world going west, from Washington, DC -> San Francisco -> Singapore -> Dubai -> DC. I lost a day to the international date line that I may never get back!)
posted by wicked_sassy at 10:43 AM on August 21, 2019

You gained it back when you crossed the midnight line.
posted by The Tensor at 11:13 AM on August 21, 2019 [1 favorite]

Watch out for langoliers.
posted by Chrysostom at 2:50 PM on August 21, 2019 [5 favorites]