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NTSB Issues Investigative Update on San Francisco Airport Near Miss

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Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#31

Post by ssambros »

phire wrote: post #24
Flammy wrote: post #2

Previous discussion on this topic: https://news.ycombinator.com/item?id=14741605 This literally could have been one of the worst accidents in American aviation history had the pilots of the landing airplane failed to react in time. There were 4 fully loaded and fueled passenger jets directly ahead of them.

And they cut it extremely fine. The final NTSB report will probably calculate this, but I'm guessing if they had waited another second or two before shoving those throttles forwards they would have hit a plane (or three). Whats even more scary, is I get the impression that the pilots only shoved the throttles forwards because the tower told them to abort.

If you listen to the recording the pilot suspected something was not right, that's why he asked for confirmation that the runway is clear. Most likely he already anticipated a high probability of a go-around.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#32

Post by dakrisht »

abritinthebay wrote: post #26
viraptor wrote: post #20

I've seen people mentioning this could be a big disaster, but I'm curious exactly what the effects could be. Specifically, ignoring the wheels for the moment, would the hull of the landing plane slide off on contact at all, or would the planes just get squashed? I have no intuition about friction / stiffness of materials at that scale. (I'm also assuming the planes were at least a little bit offset to the side) With…

It wouldn’t have been just the wheels. They’d have flattened onto each other in a big squash that blew fuel everywhere. It would have probably continued due to momentum as a fireball towards the 3 other fully loaded planes. Basically it could have been a 5 fully loaded plane bowling alley of flaming metal at 150mph

This. Sure. But pure speculation. The forward momentum of that airplane could have clipped a tail and taken it off while pulling up and max thrust. He was wayyyy below minimum decision height (called out and set before landing, usually a few hundred feet).

OTOH, he could have very well collided with the other Airbus on the taxiway rapidly halting his forward momentum and exploding into a fireball subsequently taking out everything for half a mile ahead.

What's alarming her is the distance of the Air Canada jet to the ground, less the tail of the Airbus = this guy was FEET AWAY from clipping that jet.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#33

Post by drfuchs »

phire wrote: post #24
Flammy wrote: post #2

Previous discussion on this topic: https://news.ycombinator.com/item?id=14741605 This literally could have been one of the worst accidents in American aviation history had the pilots of the landing airplane failed to react in time. There were 4 fully loaded and fueled passenger jets directly ahead of them.

And they cut it extremely fine. The final NTSB report will probably calculate this, but I'm guessing if they had waited another second or two before shoving those throttles forwards they would have hit a plane (or three). Whats even more scary, is I get the impression that the pilots only shoved the throttles forwards because the tower told them to abort.

No, they started pulling up just before hearing from the tower; click on the link at the bottom of the referenced page: "The full investigative update and other information about the incident are available online at: https://go.usa.gov/xRPFk​ " for more detail, including:

o At 2356:04 PDT, ACA759 reappeared on the local controller’s ASDE-X/ASSC display as it passed over the first airplane positioned on taxiway C.

o About 2.5 seconds after advancing the thrust levers, the minimum altitude recorded on the FDR was 59 ft agl.

o At 2356:10 PDT, the local controller directed ACA759 to go around. The airplane had already begun to climb at this point (see figure 4).

This means that if they hadn't acted until they heard from the tower, it would have almost certainly been a disaster.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#34

Post by mosheroperandi »

notatoad wrote: post #23
modeless wrote: post #3

Before I couldn't imagine how anyone could make this mistake, but now I see it. The pilots were familiar with SFO and knew that there were two runways, but didn't realize the left hand runway lights were turned off, so they had an off-by-one error when choosing the runway.

i'm not a pilot and have no idea what it looks like when landing a plane at night, so i really shouldn't be commenting here, but: the report says the one operational runway had 2400 ft of approach lighting that was functional. The disabled runway had no approach lighting, and presumably the taxiway didn't have any approach lighting because nobody should be approaching a taxiway. So yes, they were just "off by one", b…

Yeah, but once you decide that the leftmost runway you see (with the dark void on its left) is the left runway, then obviously the parallel strip of lights to the right of it is the right runway. Sure, the lights look odd, and your gut's giving off this feeling, but you see, that's the left runway, and I don't see the right runway anywhere else, so this must be the...

They probably got stuck in several cycles of that before the contrary evidence was overwhelming enough to break them out of their off-by-one mental model.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#35

Post by mseebach »

notatoad wrote: post #23
modeless wrote: post #3

Before I couldn't imagine how anyone could make this mistake, but now I see it. The pilots were familiar with SFO and knew that there were two runways, but didn't realize the left hand runway lights were turned off, so they had an off-by-one error when choosing the runway.

i'm not a pilot and have no idea what it looks like when landing a plane at night, so i really shouldn't be commenting here, but: the report says the one operational runway had 2400 ft of approach lighting that was functional. The disabled runway had no approach lighting, and presumably the taxiway didn't have any approach lighting because nobody should be approaching a taxiway. So yes, they were just "off by one", b…

Well, they were off by one in adjusting the length of their internal model of the dataset (two runways) with the currently active model (one) and thus suffered a buffer overflow.

Anyway, score one (more) for the robots, who would have picked up the correct ILS localizer.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#36

Post by kpil »

matt_wulfeck wrote: post #28
greenhouse_gas wrote: post #22

What I don't understand (and I'm being honest here) is that between GPSs, computers, and HUDs, how do these errors still happen? I mean that if your GPS sees you're aiming at the wrong runway, why can't it alert the pilot (and/or tower) that it's going to miss.

I'm wondering the same thing. Why don't planes land themselves at this point?

The main reason is that computers aren't very smart although I know that even some developers think that.

Actually they can autoland but not everywhere and then you still need to tell them where, basically tune them in on the right glide path. Then you really need to be prepared to take over any second, which is a dangerous position on its own. (Just like all self driving cars right now.)

It's still possible to select the wrong ILS beacon or entering the wrong speed or whatever, and something can still show up in front of the plane.

It's just better in low visibility where you otherwise manually have to follow the ILS 'needles'.

Didn't a plane crash there killing some chinese schoolgirls just because the pilots forgot to set the correct speed. Either it was set too low or they set it but did not activate it. And then the monitoring pilot forgot to monitor the speed since the autopilot never fails...

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#37

Post by silvertonia »

notatoad wrote: post #23
modeless wrote: post #3

Before I couldn't imagine how anyone could make this mistake, but now I see it. The pilots were familiar with SFO and knew that there were two runways, but didn't realize the left hand runway lights were turned off, so they had an off-by-one error when choosing the runway.

i'm not a pilot and have no idea what it looks like when landing a plane at night, so i really shouldn't be commenting here, but: the report says the one operational runway had 2400 ft of approach lighting that was functional. The disabled runway had no approach lighting, and presumably the taxiway didn't have any approach lighting because nobody should be approaching a taxiway. So yes, they were just "off by one", b…

28L was dark apart from the X, and the taxiway was lit (albeit with taxi Lane instead of runway lights). Expecting two lit lanes and approaching the one on the right, they certainly saw something "off" but this wasn't a case of pilots choosing to avoid the only lit lane.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#38

Post by stordoff »

viraptor wrote: post #20

I've seen people mentioning this could be a big disaster, but I'm curious exactly what the effects could be. Specifically, ignoring the wheels for the moment, would the hull of the landing plane slide off on contact at all, or would the planes just get squashed? I have no intuition about friction / stiffness of materials at that scale. (I'm also assuming the planes were at least a little bit offset to the side) With…

We're discussing a matter of 10s of feet between the near-collision we saw, clipping the tail of one plane, or hitting the plane behind at landing speed, so I imagine the set of "what could have happened" is rather large.

That said, I suspect the following three crashes give _some_ indication of what might have happened:

USAir 1493 - 737 collides with a turbo-prop on landing; the smaller plane is essentially crushed by the 737

Asiana 214 - Landing gear and tail clip seawall on approach

Tenerife disaster - 747 strikes the side of a second 747 a few seconds after leaving the ground on takeoff; engines, lower fuselage and main landing gear struck the plane. 583 fatalities.

https://en.wikipedia.org/wiki/USAir_Flight_1493 / https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214 / https://en.wikipedia.org/wiki/Tenerife_airport_disaster

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#39

Post by mosheroperandi »

mirimir wrote: post #5
modeless wrote: post #3

Before I couldn't imagine how anyone could make this mistake, but now I see it. The pilots were familiar with SFO and knew that there were two runways, but didn't realize the left hand runway lights were turned off, so they had an off-by-one error when choosing the runway.

That is quite plausible. They somehow didn't register the "X" on 28R. Edit: Sorry, I meant 28L. Just dyslexic, I guess.

You wouldn't be the first person to confuse R for L.

Re: NTSB Issues Investigative Update on San Francisco Airport Near Miss

#40

Post by Animats »

DavidSJ wrote: post #16
johnm1019 wrote: post #14

Earlier quoted context omitted.

Something doesn't add up then, the listed elevation for SFO is 13.1 ft MSL. http://www.airnav.com/airport/KSFO UPDATE: tolerances around GL are 20 ft https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=&SID=&r=PART&n=...

Also, they might not have been directly above the A340 at lowest altitude.

They were very close. See [1]. They were over the centerline of taxiway C, and 85 feet AGL crossing taxiway W. Minimum altitude was 2.5 secs later. There were three planes ahead, an A-340, a B-787 (also 55 feet high at the tail), and some UAL jet of about the same size.

A few feet lower and there would have been a collision.

[1] https://ntsb.gov/investigations/Pages/DCA17IA148.aspx

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