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I am just a passenger, but this looks very over-blown. A pilot aligned with the taxiway, that's bad. But no pilot would ever land on a runway (or taxiway) with

I am just a passenger, but this looks very over-blown. A pilot aligned with the taxiway, that's bad. But no pilot would ever land on a runway (or taxiway) with 3 planes on it. Just search the Aviation Herald for "runway incursion". And indeed, he spotted them, communicated, went around. Aviation safety margins are so wide that this does not qualify as a near-miss.

meowface 9y ago
Right, I'm confused by this. Surely the pilot would notice at least one of the planes he'd be inevitably crashing into well before he started to land?
- ddeck 9y ago
  >Surely the pilot would notice at least one of the planes he'd be inevitably crashing into well before he started to land In theory yes, but the risk is that the plane you crash into is not yet on the taxiway or that poor visibility or tunneled focus prevents you from noticing it. You don't need to be moving quickly to have a significant accident. The deadliest aviation accident in history (583 fatalities) resulted when two planes collided on a taxiway (edit: actually on the runway) in dense fog [1]. Edit: as correctly pointed out below, the actual collision took place on the runway at significant speed. [1] https://en.wikipedia.org/wiki/Tenerife_airport_disaster https://en.wikipedia.org/wiki/Tenerife_airport_disaster
  - Pinckney 9y ago
    You're mistaken. The KLM plane took off when it was not cleared, and they collided at 260km/h.
    - cyberferret 9y ago
      That was just one of seven distinct mistakes that lead to the crash. The PanAm pilot missed his turnoff, the controllers were busy watching a football match and missed the radio cues that could have alerted them to the fact there was an impending problem etc. etc.
  - kgwgk 9y ago
    It's interesting that it happened 40 years ago. Risks might be decreasing if we didn't see a larger one yet.
- notatoad 9y ago
  >Surely the pilot would notice at least one of the planes he'd be inevitably crashing into well before he started to land? Which seems to be what happened here - the pilot aligned with the taxiway, noticed he was in the wrong spot, and the tower told him to try again.
- cyberferret 9y ago
  At night, and if he was fatigued or on instruments for a long time before that, the disorientation could have easily lead to such an error. LOTS of planes accidentally line up on the taxiway if visibility is reduced and cockpit workload is high. Heck, aircraft have even taken off on non active runways at the most advanced airport in the world with disastrous results at night. [0] Inclement weather on approach at the end of a long flight can also lead to crew pressing home while under confusion, as in the case of the Korean airlines accident that landed short. [1] More recently, at SFO too, the Asiana B777 crash was something that should have been almost impossible in a modern jetlines, but over reliance on automation and lazy piloting lead to that disaster. [0] - https://www.youtube.com/watch?v=iHekCU9CYvI https://www.youtube.com/watch?v=iHekCU9CYvI [1] - https://www.youtube.com/watch?v=II4dwx00v28 https://www.youtube.com/watch?v=II4dwx00v28
milesf 9y ago
Seems that it was the ATC and another pilot who spotted it.
rdtsc 9y ago
This isn't quite a regular "runway incursion". That term is usually reserved for a taxiing aircraft (or maybe a service vehicle) which didn't stop in time at the threshold and went a bit beyond it. This is more like runway "confusion". A term I made up, not sure if there is such an official name for it.
- FiloSottile 9y ago
  Right, I meant that if pilots sort-of-routinely spot runway incursions, they surely won't land on 3 wide-body jets sitting there. This is why you want human pilots, instead of computers, not the opposite. A human can apply common sense and decide not to land on three planes after all even if it looks like a cleared runway.
  - cyberferret 9y ago
    > This is why you want human pilots, instead of computers I actually believe the opposite is true. Systems like ACARS have managed to avoid the prevalence of air to air incidents that used to be almost an epidemic in the 60's and 70's. Autolanding technology has brought planes home safely where a pilot would have had to go around and find an alternate aerodrome.
    - tjohns 9y ago
      Are you sure you're not thinking of TCAS? (ACARS is used for delivering clearances and other routine operational/maintenance messages. Basically text messaging for airplanes.)
      - cyberferret 9y ago
        Sorry yes (Duh!) TCAS, not ACARS! Thanks for the correction. I haven't flown in a LONG while now, and sometimes the acronyms get muddled in my brain. :)
MaxfordAndSons 9y ago
Ehh, the fact that he was cleared to land and the taxing aircraft could tell he was over the taxiway means it was probably less than 1 minute from landing. That's a pretty close call imo.
csours 9y ago
> Aviation safety margins are so wide that this does not qualify as a near-miss. I think you have this kind of backwards here. If you were going in for an amputation, and they only prepped the wrong leg, would that not be a near miss? Rare incidents are hard to reason about and measure because they are so rare; but there are things that lead up to rare events - like being on approach to the wrong runway, that are less rare, and so they are easy to measure. After you have plans and procedures to stop the actual rare disasters, reducing near misses is the most effective way to stop disasters. > But no pilot would ever land on a runway (or taxiway) with 3 planes on it. https://en.wikipedia.org/wiki/Tenerife_airport_disaster https://en.wikipedia.org/wiki/Tenerife_airport_disaster
- FiloSottile 9y ago
  > After you have plans and procedures to stop the actual rare disasters, reducing near misses is the most effective way to stop disasters. Oh, full +1. This is a bad incident that should result in an investigation and maybe safety recommendations. My point is that aviation has been at it for so long, that a "bad incident" is very far removed from what the common interpretation of "near miss could have triggered greatest disaster" (#1 on HN) would suggest to a random observer. (And I think the author knew it, and went for clickbait.)
  - mnm1 9y ago
    Maybe, the author went for the clickbait, but only 584 people have to die for this to be the worst airline disaster in history. With potentially five planes involved, if he had crashed, I think that'd be highly likely in this situation.
- will_hughes 9y ago
  More recently: https://www.youtube.com/watch?v=Cj192PZ_riE https://www.youtube.com/watch?v=Cj192PZ_riE
- dx034 9y ago
  Tenerife was very different. Here, the aircraft were at the beginning of the runway and clearly visible. In Tenerife, aircraft were at different part of the runway and couldn't see each other until it was too late. That's not comparable. We know from the recording that the pilot saw planes on the taxiway and asked the tower about it. He would've never landed there after the tower confirmed that the runway should be empty.
ChuckMcM 9y ago
I expect you are correct, but I also note that it has happened before. One could have said this just before the Asiana flight flew into the ground as well. "What pilot would miss the fact that they were way too low?" Or just before Harrison Ford flew over a plane on the Taxiway and then landed on that taxiway. Fundamentally it takes several things to fail all at once for an air disaster to actually transpire, but it does happen.
- omegant 9y ago
  The Asiana problem is that some asian pilots are encouraged NOT to fly manually ever. There is a pprune forum post of an american instructor explaining how a visual circuit flown in manual was the worst "emergency" he could set in a simulator. Up to the point that he failed one of the chef pilots in Asiana and they wanted to fire him. This seems to be a cultural thing, they ace the theory (really know all the manuals by heart), but are not allowed to think outside the box at all. This airmiss is important, but could only happen flying in manual and visual conditions. It's hard to ignore the sigthing of other planes in that conditions, even if you are confused about which strip you are aligned with. In my opinion it's much more dangerous taxing in a complex airport with fog. There is a real problem of runway incursions, that could be solved with better systems. I'll try to find the pprune post.
hyperbovine 9y ago
> But no pilot would ever land on a runway (or taxiway) with 3 planes on it. Just like no pilot would ever crash into the seawall short of 28L in broad daylight with unlimited visibility. In that case the pilots knew what was about to happen seconds before impact and they were powerless to stop it. I could easily see the same thing happening here. Airplanes are big cumbersome objects with a ton of inertia.
- kobeya 9y ago
  When did that happen?
  - rl3 9y ago
    https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214 https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214
  - TacticalMalice 9y ago
    2013, see https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214 https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214
  - deleted 9y ago
    [deleted]
  - chinathrow 9y ago
    https://www.aeroinside.com/item/2761/asiana-b772-at-san-francisco-on-jul-6th-2013-touched-down-short-of-the-runway-broke-up-and-burst-into-flames https://www.aeroinside.com/item/2761/asiana-b772-at-san-fran...
  - deleted 9y ago
    [deleted]
- WalterBright 9y ago
  Inertia wasn't the problem for that accident. It takes several seconds for the engines to spool up, and they didn't have any seconds to spare.
exDM69 9y ago
Assuming the liveatc audio in the article has not been edited, it sounds like there's about 10 seconds between ATC giving go around and the United pilot saying they flew right over. With instructions given to Air Canada in between so it might have been seconds earlier. Based on that, it was seconds away from a collision. It seems like a near miss when considering aviation safety margins.
- CaliforniaKarl 9y ago
  What's missing is, when (relative to radio traffic) did the pilot begin the go-around maneuver. Did they begin doing so before being told to go around, or did they only start to do so after?
  - exDM69 9y ago
    If the pilot initiates a go around they need to announce it to the ATC. It is usually a drastic full power pull up that will certainly disrupt nearby air traffic. So the pilot probably did not start the go around before being told so.
    - CaliforniaKarl 9y ago
      Sorry, I have to partially disagree. The FAA is pretty clear on this: The priorities (in order) are Aviate, Navigate, and Communicate[1]. The pilot is ultimately the person responsible for the safe operation of the aircraft. That will occasionally mean performing a maneuver before telling anyone. In response to this, procedures are designed so that pilots can safely abort an approach without posing a danger to themselves (i.e. running into terrain) or other aircraft. For example, let's look at the LDA PRM runway 28 Right approach [2] into SFO, which the pilot may have been flying. If you have to abort the approach prior to the DARNE waypoint, you make a climbing right turn to heading 030 and 3000 feet, then you proceed directly to the Oakland VOR, and then you hold as published. When Approach clears you for this approach, the controller is also clearing you to fly the missed approach, if needed. If you have to go missed-approach after DARNE, the instructions are similar, but are documented in [3] instead of in [2]. But note the "unless otherwise instructed by ATC". In this case (see [4]), Tower placed the pilot onto runway heading, likely with a climb to avoid the hills. Approach would then have taken over, and brought the pilot back around. [1]: https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=40 https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=... [2]: http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF [3]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF [4]: https://flightaware.com/live/flight/ACA759/history/20170708/0055Z/CYYZ/KSFO https://flightaware.com/live/flight/ACA759/history/20170708/...
lisper 9y ago
I'm a private pilot who has flown into SFO once, and flies over SFO on a regular basis (I'm based at Palo Alto airport). This is not being overblown. If you listen to the audio tape, the tower orders the go-around at the 33 second mark, and United 1 reports that "Air Canada flew directly over us" 16 seconds later. That is a breathtakingly close call. Safety margins are wide when pilots don't screw up. But this one did. Royally.
- dotancohen 9y ago
  > Safety margins are wide when pilots don't screw up. But this one did. Royally. And the safety margin was wide enough to absorb that screw up. This is _why_ we have wide safety margins. So that one screw up doesn't absorb all of it. People will always screw up, and policy accounts for that fact.
  - lisper 9y ago
    > And the safety margin was wide enough to absorb that screw up. Barely.
  - wfunction 9y ago
    Can you tell me what the second safety margin that kicked in here and saved them was? Seems to me that it was another pilot noticing them and asking "Where's this guy goin'?" which is not something I'd consider to be a safety margin kicking in... it sounds like sheer dumb luck, where the last margin had already failed.
    - CaliforniaKarl 9y ago
      Unfortunately we don't have enough information here to know for sure. For example, the approach controller may have noticed that a plane they recently handed off to Tower was not yet lined up. The controller would then call up to Tower to make Tower aware of the issue. Or, Tower may have a screen showing them a radar view of the approach, similar to Approach's screen. They may have noticed it there. But, the nature of aviation radio is such that you use one frequency to transmit and receive. That means you can't speak over anyone else; you have to wait for them to stop talking before you can start. And if you mess up, there's no easy way for you to know (except when someone else on frequency says "blocked").
kobeya 9y ago
What if the airport was fogged out and the Air Canada pilot was doing a instrument landing?
- CaliforniaKarl 9y ago
  Then this specific type of incident would likely not have happened. The pilot here was flying visually (which I expect either means a visual approach, or else the LDA PRM Runway 28 Right approach). If the airport was fogged out, the pilot would be on an ILS or RNAV (area navigation) approach. The former uses ground-based signals to provide precise lateral and vertical navigation; the latter uses either GPS or multiple ground-based aids to accomplish the same thing. The downside to ILS, RNAV, etc., is that you can't fit planes as close together while still being safe. That's why you get delays when major airports have reduced visibility: The flight scheduled are "tuned" for maximum planes per runway per minute, which is only possible when skies are clear and winds are (relatively) calm, so that you can use visual approaches.
rl3 9y ago
https://en.wikipedia.org/wiki/USAir_Flight_1493 https://en.wikipedia.org/wiki/USAir_Flight_1493 Though air traffic was not heavy at Los Angeles airport, the local controller was distracted as Flight 1493 was on final approach by a series of abnormalities, including an aircraft that inadvertently switched off the tower frequency and a misplaced flight progress strip, which resulted in the SkyWest flight being told to taxi into takeoff position while the USAir flight was landing on the same runway without the Metroliner ever being given a takeoff clearance. Upon landing, the 737 collided with the twin-engine turboprop, continued down the runway with the turboprop crushed beneath it, exited the runway, and caught fire. All 12 people aboard the smaller plane were killed, as well as an eventual total of 23 out of the 89 passengers on the Boeing.

meowface 9y ago

Right, I'm confused by this. Surely the pilot would notice at least one of the planes he'd be inevitably crashing into well before he started to land?

ddeck 9y ago
>Surely the pilot would notice at least one of the planes he'd be inevitably crashing into well before he started to land In theory yes, but the risk is that the plane you crash into is not yet on the taxiway or that poor visibility or tunneled focus prevents you from noticing it. You don't need to be moving quickly to have a significant accident. The deadliest aviation accident in history (583 fatalities) resulted when two planes collided on a taxiway (edit: actually on the runway) in dense fog [1]. Edit: as correctly pointed out below, the actual collision took place on the runway at significant speed. [1] https://en.wikipedia.org/wiki/Tenerife_airport_disaster https://en.wikipedia.org/wiki/Tenerife_airport_disaster
- Pinckney 9y ago
  You're mistaken. The KLM plane took off when it was not cleared, and they collided at 260km/h.
  - cyberferret 9y ago
    That was just one of seven distinct mistakes that lead to the crash. The PanAm pilot missed his turnoff, the controllers were busy watching a football match and missed the radio cues that could have alerted them to the fact there was an impending problem etc. etc.
- kgwgk 9y ago
  It's interesting that it happened 40 years ago. Risks might be decreasing if we didn't see a larger one yet.
notatoad 9y ago
>Surely the pilot would notice at least one of the planes he'd be inevitably crashing into well before he started to land? Which seems to be what happened here - the pilot aligned with the taxiway, noticed he was in the wrong spot, and the tower told him to try again.
cyberferret 9y ago
At night, and if he was fatigued or on instruments for a long time before that, the disorientation could have easily lead to such an error. LOTS of planes accidentally line up on the taxiway if visibility is reduced and cockpit workload is high. Heck, aircraft have even taken off on non active runways at the most advanced airport in the world with disastrous results at night. [0] Inclement weather on approach at the end of a long flight can also lead to crew pressing home while under confusion, as in the case of the Korean airlines accident that landed short. [1] More recently, at SFO too, the Asiana B777 crash was something that should have been almost impossible in a modern jetlines, but over reliance on automation and lazy piloting lead to that disaster. [0] - https://www.youtube.com/watch?v=iHekCU9CYvI https://www.youtube.com/watch?v=iHekCU9CYvI [1] - https://www.youtube.com/watch?v=II4dwx00v28 https://www.youtube.com/watch?v=II4dwx00v28

milesf 9y ago

Seems that it was the ATC and another pilot who spotted it.

rdtsc 9y ago

This isn't quite a regular "runway incursion". That term is usually reserved for a taxiing aircraft (or maybe a service vehicle) which didn't stop in time at the threshold and went a bit beyond it. This is more like runway "confusion". A term I made up, not sure if there is such an official name for it.

FiloSottile 9y ago
Right, I meant that if pilots sort-of-routinely spot runway incursions, they surely won't land on 3 wide-body jets sitting there. This is why you want human pilots, instead of computers, not the opposite. A human can apply common sense and decide not to land on three planes after all even if it looks like a cleared runway.
- cyberferret 9y ago
  > This is why you want human pilots, instead of computers I actually believe the opposite is true. Systems like ACARS have managed to avoid the prevalence of air to air incidents that used to be almost an epidemic in the 60's and 70's. Autolanding technology has brought planes home safely where a pilot would have had to go around and find an alternate aerodrome.
  - tjohns 9y ago
    Are you sure you're not thinking of TCAS? (ACARS is used for delivering clearances and other routine operational/maintenance messages. Basically text messaging for airplanes.)
    - cyberferret 9y ago
      Sorry yes (Duh!) TCAS, not ACARS! Thanks for the correction. I haven't flown in a LONG while now, and sometimes the acronyms get muddled in my brain. :)

MaxfordAndSons 9y ago

Ehh, the fact that he was cleared to land and the taxing aircraft could tell he was over the taxiway means it was probably less than 1 minute from landing. That's a pretty close call imo.

csours 9y ago

> Aviation safety margins are so wide that this does not qualify as a near-miss. I think you have this kind of backwards here. If you were going in for an amputation, and they only prepped the wrong leg, would that not be a near miss? Rare incidents are hard to reason about and measure because they are so rare; but there are things that lead up to rare events - like being on approach to the wrong runway, that are less rare, and so they are easy to measure. After you have plans and procedures to stop the actual rare disasters, reducing near misses is the most effective way to stop disasters. > But no pilot would ever land on a runway (or taxiway) with 3 planes on it. https://en.wikipedia.org/wiki/Tenerife_airport_disaster https://en.wikipedia.org/wiki/Tenerife_airport_disaster

FiloSottile 9y ago
> After you have plans and procedures to stop the actual rare disasters, reducing near misses is the most effective way to stop disasters. Oh, full +1. This is a bad incident that should result in an investigation and maybe safety recommendations. My point is that aviation has been at it for so long, that a "bad incident" is very far removed from what the common interpretation of "near miss could have triggered greatest disaster" (#1 on HN) would suggest to a random observer. (And I think the author knew it, and went for clickbait.)
- mnm1 9y ago
  Maybe, the author went for the clickbait, but only 584 people have to die for this to be the worst airline disaster in history. With potentially five planes involved, if he had crashed, I think that'd be highly likely in this situation.
will_hughes 9y ago
More recently: https://www.youtube.com/watch?v=Cj192PZ_riE https://www.youtube.com/watch?v=Cj192PZ_riE
dx034 9y ago
Tenerife was very different. Here, the aircraft were at the beginning of the runway and clearly visible. In Tenerife, aircraft were at different part of the runway and couldn't see each other until it was too late. That's not comparable. We know from the recording that the pilot saw planes on the taxiway and asked the tower about it. He would've never landed there after the tower confirmed that the runway should be empty.

ChuckMcM 9y ago

I expect you are correct, but I also note that it has happened before. One could have said this just before the Asiana flight flew into the ground as well. "What pilot would miss the fact that they were way too low?" Or just before Harrison Ford flew over a plane on the Taxiway and then landed on that taxiway. Fundamentally it takes several things to fail all at once for an air disaster to actually transpire, but it does happen.

omegant 9y ago
The Asiana problem is that some asian pilots are encouraged NOT to fly manually ever. There is a pprune forum post of an american instructor explaining how a visual circuit flown in manual was the worst "emergency" he could set in a simulator. Up to the point that he failed one of the chef pilots in Asiana and they wanted to fire him. This seems to be a cultural thing, they ace the theory (really know all the manuals by heart), but are not allowed to think outside the box at all. This airmiss is important, but could only happen flying in manual and visual conditions. It's hard to ignore the sigthing of other planes in that conditions, even if you are confused about which strip you are aligned with. In my opinion it's much more dangerous taxing in a complex airport with fog. There is a real problem of runway incursions, that could be solved with better systems. I'll try to find the pprune post.

hyperbovine 9y ago

> But no pilot would ever land on a runway (or taxiway) with 3 planes on it. Just like no pilot would ever crash into the seawall short of 28L in broad daylight with unlimited visibility. In that case the pilots knew what was about to happen seconds before impact and they were powerless to stop it. I could easily see the same thing happening here. Airplanes are big cumbersome objects with a ton of inertia.

kobeya 9y ago
When did that happen?
- rl3 9y ago
  https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214 https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214
- TacticalMalice 9y ago
  2013, see https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214 https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214
- deleted 9y ago
  [deleted]
- chinathrow 9y ago
  https://www.aeroinside.com/item/2761/asiana-b772-at-san-francisco-on-jul-6th-2013-touched-down-short-of-the-runway-broke-up-and-burst-into-flames https://www.aeroinside.com/item/2761/asiana-b772-at-san-fran...
- deleted 9y ago
  [deleted]
WalterBright 9y ago
Inertia wasn't the problem for that accident. It takes several seconds for the engines to spool up, and they didn't have any seconds to spare.

exDM69 9y ago

Assuming the liveatc audio in the article has not been edited, it sounds like there's about 10 seconds between ATC giving go around and the United pilot saying they flew right over. With instructions given to Air Canada in between so it might have been seconds earlier. Based on that, it was seconds away from a collision. It seems like a near miss when considering aviation safety margins.

CaliforniaKarl 9y ago
What's missing is, when (relative to radio traffic) did the pilot begin the go-around maneuver. Did they begin doing so before being told to go around, or did they only start to do so after?
- exDM69 9y ago
  If the pilot initiates a go around they need to announce it to the ATC. It is usually a drastic full power pull up that will certainly disrupt nearby air traffic. So the pilot probably did not start the go around before being told so.
  - CaliforniaKarl 9y ago
    Sorry, I have to partially disagree. The FAA is pretty clear on this: The priorities (in order) are Aviate, Navigate, and Communicate[1]. The pilot is ultimately the person responsible for the safe operation of the aircraft. That will occasionally mean performing a maneuver before telling anyone. In response to this, procedures are designed so that pilots can safely abort an approach without posing a danger to themselves (i.e. running into terrain) or other aircraft. For example, let's look at the LDA PRM runway 28 Right approach [2] into SFO, which the pilot may have been flying. If you have to abort the approach prior to the DARNE waypoint, you make a climbing right turn to heading 030 and 3000 feet, then you proceed directly to the Oakland VOR, and then you hold as published. When Approach clears you for this approach, the controller is also clearing you to fly the missed approach, if needed. If you have to go missed-approach after DARNE, the instructions are similar, but are documented in [3] instead of in [2]. But note the "unless otherwise instructed by ATC". In this case (see [4]), Tower placed the pilot onto runway heading, likely with a climb to avoid the hills. Approach would then have taken over, and brought the pilot back around. [1]: https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=40 https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=... [2]: http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF [3]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF [4]: https://flightaware.com/live/flight/ACA759/history/20170708/0055Z/CYYZ/KSFO https://flightaware.com/live/flight/ACA759/history/20170708/...

lisper 9y ago

I'm a private pilot who has flown into SFO once, and flies over SFO on a regular basis (I'm based at Palo Alto airport). This is not being overblown. If you listen to the audio tape, the tower orders the go-around at the 33 second mark, and United 1 reports that "Air Canada flew directly over us" 16 seconds later. That is a breathtakingly close call. Safety margins are wide when pilots don't screw up. But this one did. Royally.

dotancohen 9y ago
> Safety margins are wide when pilots don't screw up. But this one did. Royally. And the safety margin was wide enough to absorb that screw up. This is _why_ we have wide safety margins. So that one screw up doesn't absorb all of it. People will always screw up, and policy accounts for that fact.
- lisper 9y ago
  > And the safety margin was wide enough to absorb that screw up. Barely.
- wfunction 9y ago
  Can you tell me what the second safety margin that kicked in here and saved them was? Seems to me that it was another pilot noticing them and asking "Where's this guy goin'?" which is not something I'd consider to be a safety margin kicking in... it sounds like sheer dumb luck, where the last margin had already failed.
  - CaliforniaKarl 9y ago
    Unfortunately we don't have enough information here to know for sure. For example, the approach controller may have noticed that a plane they recently handed off to Tower was not yet lined up. The controller would then call up to Tower to make Tower aware of the issue. Or, Tower may have a screen showing them a radar view of the approach, similar to Approach's screen. They may have noticed it there. But, the nature of aviation radio is such that you use one frequency to transmit and receive. That means you can't speak over anyone else; you have to wait for them to stop talking before you can start. And if you mess up, there's no easy way for you to know (except when someone else on frequency says "blocked").

kobeya 9y ago

What if the airport was fogged out and the Air Canada pilot was doing a instrument landing?

CaliforniaKarl 9y ago
Then this specific type of incident would likely not have happened. The pilot here was flying visually (which I expect either means a visual approach, or else the LDA PRM Runway 28 Right approach). If the airport was fogged out, the pilot would be on an ILS or RNAV (area navigation) approach. The former uses ground-based signals to provide precise lateral and vertical navigation; the latter uses either GPS or multiple ground-based aids to accomplish the same thing. The downside to ILS, RNAV, etc., is that you can't fit planes as close together while still being safe. That's why you get delays when major airports have reduced visibility: The flight scheduled are "tuned" for maximum planes per runway per minute, which is only possible when skies are clear and winds are (relatively) calm, so that you can use visual approaches.

rl3 9y ago

https://en.wikipedia.org/wiki/USAir_Flight_1493 https://en.wikipedia.org/wiki/USAir_Flight_1493 Though air traffic was not heavy at Los Angeles airport, the local controller was distracted as Flight 1493 was on final approach by a series of abnormalities, including an aircraft that inadvertently switched off the tower frequency and a misplaced flight progress strip, which resulted in the SkyWest flight being told to taxi into takeoff position while the USAir flight was landing on the same runway without the Metroliner ever being given a takeoff clearance. Upon landing, the 737 collided with the twin-engine turboprop, continued down the runway with the turboprop crushed beneath it, exited the runway, and caught fire. All 12 people aboard the smaller plane were killed, as well as an eventual total of 23 out of the 89 passengers on the Boeing.