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I'm not a pilot, or real-world ATC, but I was one a _virtual_ air traffic controller, on VATSIM[1]. I was a member of the virtual Indianapolis ARTCC[2], and ha

I'm not a pilot, or real-world ATC, but I was one a _virtual_ air traffic controller, on VATSIM[1]. I was a member of the virtual Indianapolis ARTCC[2], and have worked positions from Dispatch up to & including Center. Listening to the LiveATC clip, the important bit is the phrase "visual 28 right", meaning the Air Canada pilot had been assigned a visual approach to runway 28 Right. The clip sounds like it's from Tower, so you're not hearing the point where the pilot was assigned that approach (that would've happened with Approach). A visual approach is pretty simple: The controller sets you on a heading & altitude. Then, the controller confirms that you have the runway/field in sight, as well as any other air traffic that may potentially pose a conflict. Once the pilot verbally confirms those things are in sight ("traffic in sight" / "field in sight"), the approach controller will clear the pilot for the "visual runway XXX approach", also issuing appropriate warnings regarding wake turbulence. Once the visual approach has been cleared, and the pilot has acknowledged, it is now the pilot's responsibility to navigate the plane to the runway, while keeping the plane clear of the traffic that has been pointed out to them. If the pilot were assigned an ILS, LOC (localizer), LDA (localizer-type directional aid), or RNAV (area navigation) approach, that approach would have included a lateral component, which would have ensured that the plane was lined up with the runway, and not the taxiway. So, why do a visual approach, when you have so many other options? Mainly because it allows more planes to be put into the same space. If a plane is on a different approach, or is enroute, or is being vectored by the controller ("turn right heading 350"), the controller is responsible for maintaining proper lateral (3 or 5 miles) and vertical (500, 1000, or 2000 feet) separation from other traffic. But traffic cleared on a visual approach does not have that restriction. Visual approaches are an important part of maintaining the high flow rates that Class B airports (SFO, ORD, etc.) want. This comment's gotten pretty long, so I'll post another one with another possibility as to what may have happened! I'll leave you with the FlightAware radar trail, where (if you zoom in on SFO) you can see the go-around taking place. [1]: https://www.vatsim.net https://www.vatsim.net [2]: http://zidartcc.org http://zidartcc.org [3]: https://flightaware.com/live/flight/ACA759/history/20170708/0055Z/CYYZ/KSFO https://flightaware.com/live/flight/ACA759/history/20170708/...

CaliforniaKarl 9y ago
So, I should clarify something: A visual approach is pretty simple from the controller's point of view; it's more work for the pilot. But, the pilot is always the one in command of the plane: If the pilot is unwilling to accept a particular approach, they just need to say so. It may lead to delays, but controllers will accommodate. I originally said that the pilot had been assigned a visual approach to runway 28 Right. Looking at the charts for SFO[1], and the FlightAware trace[2], I have an alternative: The pilot may have been flying the LDA PRM runway 28 Right approach[3]. (You should open up [3] to look at while reading the rest of this comment.) As has been mentioned, SFO is a bit weird: The two main runways are close enough together that it's not possible for you to have normal simultaneous approaches. For example, have a look at the diagram for Cincinnati/Northern Kentucky International (CVG)[7], another Class B field. Now, compare that to SFO[8]. At CVG, the parallel runways are far-enough apart that simultaneous approaches are possible, but with SFO, that's not possible. So, the FAA came up with the PRM (perimeter) approach. Essentially, the plane approaching runway 28 Left is on an ILS approach. The plane on approach to Runway 28 Right is on an approach that is kindof like an ILS approach, but the plane isn't heading towards the runway, the plane is heading to a point to the right of the runway. Notice on [3], the point labelled "CFFKC". That's a fix (a point in lateral space), marking the point that you're being guided to. Note how the fix doesn't line up with the runway; that's why this approach is an "LDA (Localizer-type Directional Aid) with Glideslope" approach. As per the detailed instructions (in [4], and point 4 in [6]), pilots on the LDA PRM runway 28 Right approach switch to a visual approach after the DARNE waypoint (3.4 nautical miles from the runway end). For most of the approach, they are monitoring a second frequency, which is only used if planes get too close together. But, once you pass DARNE, you no longer need to listen on that frequency. And although tower might have a radar view of surrounding traffic, it's not their primary tool (their eyes are). If the Air Canada pilot was flying the LDA PRM RWY 28R approach, I think the final sidestep (from the LDA to the runway) may have been missed, or not completely executed, causing the pilot to line up with what he thought was the runway, but what was actually the taxiway. [1]: http://www.airnav.com/airport/KSFO http://www.airnav.com/airport/KSFO [2]: https://flightaware.com/live/flight/ACA759/history/20170708/0055Z/CYYZ/KSFO https://flightaware.com/live/flight/ACA759/history/20170708/... [3]: http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF [4]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF [5]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C.PDF [6]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C2.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C2.PDF [7]: http://155.178.201.160/d-tpp/1707/00655AD.PDF http://155.178.201.160/d-tpp/1707/00655AD.PDF [8]: http://155.178.201.160/d-tpp/1707/00375AD.PDF http://155.178.201.160/d-tpp/1707/00375AD.PDF

CaliforniaKarl 9y ago

So, I should clarify something: A visual approach is pretty simple from the controller's point of view; it's more work for the pilot. But, the pilot is always the one in command of the plane: If the pilot is unwilling to accept a particular approach, they just need to say so. It may lead to delays, but controllers will accommodate. I originally said that the pilot had been assigned a visual approach to runway 28 Right. Looking at the charts for SFO[1], and the FlightAware trace[2], I have an alternative: The pilot may have been flying the LDA PRM runway 28 Right approach[3]. (You should open up [3] to look at while reading the rest of this comment.) As has been mentioned, SFO is a bit weird: The two main runways are close enough together that it's not possible for you to have normal simultaneous approaches. For example, have a look at the diagram for Cincinnati/Northern Kentucky International (CVG)[7], another Class B field. Now, compare that to SFO[8]. At CVG, the parallel runways are far-enough apart that simultaneous approaches are possible, but with SFO, that's not possible. So, the FAA came up with the PRM (perimeter) approach. Essentially, the plane approaching runway 28 Left is on an ILS approach. The plane on approach to Runway 28 Right is on an approach that is kindof like an ILS approach, but the plane isn't heading towards the runway, the plane is heading to a point to the right of the runway. Notice on [3], the point labelled "CFFKC". That's a fix (a point in lateral space), marking the point that you're being guided to. Note how the fix doesn't line up with the runway; that's why this approach is an "LDA (Localizer-type Directional Aid) with Glideslope" approach. As per the detailed instructions (in [4], and point 4 in [6]), pilots on the LDA PRM runway 28 Right approach switch to a visual approach after the DARNE waypoint (3.4 nautical miles from the runway end). For most of the approach, they are monitoring a second frequency, which is only used if planes get too close together. But, once you pass DARNE, you no longer need to listen on that frequency. And although tower might have a radar view of surrounding traffic, it's not their primary tool (their eyes are). If the Air Canada pilot was flying the LDA PRM RWY 28R approach, I think the final sidestep (from the LDA to the runway) may have been missed, or not completely executed, causing the pilot to line up with what he thought was the runway, but what was actually the taxiway. [1]: http://www.airnav.com/airport/KSFO http://www.airnav.com/airport/KSFO [2]: https://flightaware.com/live/flight/ACA759/history/20170708/0055Z/CYYZ/KSFO https://flightaware.com/live/flight/ACA759/history/20170708/... [3]: http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF http://155.178.201.160/d-tpp/1707/00375LDAPRM28R.PDF [4]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP.PDF [5]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C.PDF [6]: http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C2.PDF http://155.178.201.160/d-tpp/1707/00375PRMAAUP_C2.PDF [7]: http://155.178.201.160/d-tpp/1707/00655AD.PDF http://155.178.201.160/d-tpp/1707/00655AD.PDF [8]: http://155.178.201.160/d-tpp/1707/00375AD.PDF http://155.178.201.160/d-tpp/1707/00375AD.PDF