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Comment by isomorphic | Hacker News Reader

I don't think GPS is accurate enough for that sort of thing, you'd need ground radar, working with onboard computers that understand which runway you're cleared for, etc. (I'm not a pilot, I'm speculating.)

If you read the Guardian article from planetjones' comment:

https://www.theguardian.com/business/2017/aug/03/air-canada-...

Quoting:

The investigators said that as the Air Canada jet approached the taxiway just before midnight after a flight from Toronto, it was so far off course that it did not appear on a radar system used to prevent runway collisions.

The next paragraph states they are working on improving that.

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It's called ILS, Instrument Landing System, and it's been around for literally 80 years.

> The first landing of a scheduled U.S. passenger airliner using ILS was on January 26, 1938, when a Pennsylvania Central Airlines Boeing 247D flew from Washington, D.C., to Pittsburgh, Pennsylvania, and landed in a snowstorm using only the Instrument Landing System

https://en.wikipedia.org/wiki/Instrument_landing_system

Presumably they must have done a visual approach or something, because their ILS would have been outright incapable of directing them down the taxiway, as it's for obvious reasons not equipped for ILS approaches.

ILS is separate from the radar system mentioned by parent. ILS uses directional radio signals from each end of the runway to provide a glideslope and lateral guidance, not radar.

The signals are transmitted from the ground and used for guidance by the aircraft. No part of ILS could alert ATC to anything since the ground stations are only transmitters.

Yes, I know. But it's analogous to the GPS system the parents are discussing.

Trouble there is that, at least to the best of my knowledge, ILS glide slope and localizer are generally only surfaced in the cockpit as a pair of bugs vertically and horizontally peripheral to the artificial horizon indicator. If you're already having a helmet fire, these are likely easy to overlook, and there's no horn or anything. (But as has been pointed out here by several other commenters before now - if you're already having a helmet fire, another horn may not do any good.)

I don't think there's any indication that these pilots were under any kind of undue stress when they lined up their approach? If at any point during the several minutes of their final approach they'd looked even once at their ILS they'd have seen that they were way off.

Final approach is the most stressful two or three minutes of an otherwise unexceptional flight; there's a great deal to do, and very little time in which to do it, during a period in which the aircraft's proximity to the ground, and low available energy, make it very easy for what would otherwise be a minor mishap to instantly place everyone aboard in imminent danger of death.

I don't suppose I would call such stress "undue", since every commercial flight ideally ends with a landing. But the probability of helmet fire is directly proportional to the degree of cockpit stress, and the ILS alignment indicators are very easy to overlook. I suspect the user interface could be improved, but I'm not nearly familiar enough with the subject domain to imagine how.

Agreed. Just to be clear, I'm not suggesting that we gang up and witchhunt the pilots for not checking the ILS, my agenda was simply to point out that the technology does indeed exist.

They were sitting there because of a bomb threat at another airport and that was the only storage space. Did you read the article?

It's irrelevant why they were there, it's a taxi way, it's fine, indeed expected, for planes to hang out there. The important bit was why the AC tried to land there and the crew confirming their approach on ILS would have prevented that.

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