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Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

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Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#81

Post by captain_perl »

throwaway5250 wrote: post #55
sokoloff wrote: post #25

Earlier quoted context omitted.

Harms night vision adaptation of other pilots. My SOP is beacon (red, top and bottom) on with aircraft battery bus on, strobes on only when on an open runway, landing lights on when cleared for takeoff (or lined-up and waiting in position for takeoff). That seems to be a fairly common SOP for aircraft with separate control of beacon vs strobe. It communicates a small amount of additional information, but more relevan…

I guess that sounds good, though it might sound less good after a mass casualty collision. Wonder if we couldn't have "ground strobes" visible only to viewers looking downward at a significant angle.

No, because when there's fog, the strobe gets reflected within the cloud everywhere. This is SFO after all.

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#82

Post by abaillargeon »

ryandrake wrote: post #60
abaillargeon wrote: post #24

I've been anticipating the release of this report this since I heard about the incident. I work on an avionics product that's designed to prevent this exact scenario. We use the aircraft's position along with a database of runways and taxiways to determine if the aircraft is approaching the runway the pilot intends. If we determine the aircraft is landing, we issue a visual and aural alert to the pilot ("TAXIWAY LAND…

Curious: what inputs feed your system? Presumably at least localizer and GPS, but anything else? What accuracy / confidence interval do you require in order to make a call?

We actually don't use the localizer to check for an incorrect runway or taxiway landing because the pilot can choose to do so and we don't want to issue nuisance alerts. Runways don't move often and we've found that a GPS and two databases (runways and airport ground features) are sufficient to determine if the pilot is approaching a runway or not.

We use inputs like GPS position, ground track, ground speed, altitude, and a phase-of-flight state machine that's determined for individual aircraft. This allows us to tailor the criteria for determining if the aircraft is landing for different aircraft. For some, we use throttle and landing gear position and others we use speed and altitude above the landing airport.

As for accuracy, we have minimum levels of GPS figure of merit where there's enough certainty to issue alerts. I don't remember the number off the top of my head, but in the US WAAS has made GPS quite accurate.

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#83

Post by userbinator »

lolc wrote: post #36
cmurf wrote: post #5

I'm not operationally familiar with SFO. But based on experience at other airports, a taxiway at night can be a sea of black at even 100' above the ground. I would probably see airplane navigation lights at some point, but would I bet my life on it? No. So this incident has to be taken seriously. However, I'm still not clear from this reporting how the crew mistook blue taxiway lighting for white runway lighting. Thi…

Human consciousness tries to form a coherent model that integrates current sensory perception with knowledge. During an approach at night, scarce sensory input is interpolated to form a full model by the brain. The report uses the term "expectation bias" for this phenomenon. This drive for coherence runs below consciousness and we only notice when the coherence falls apart: When our sensory input cannot be reconciled…

This process can easily lead to nominally weird things like blue lights being percieved as white.

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

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#84

Post by abaillargeon »

outworlder wrote: post #47
abaillargeon wrote: post #24

I've been anticipating the release of this report this since I heard about the incident. I work on an avionics product that's designed to prevent this exact scenario. We use the aircraft's position along with a database of runways and taxiways to determine if the aircraft is approaching the runway the pilot intends. If we determine the aircraft is landing, we issue a visual and aural alert to the pilot ("TAXIWAY LAND…

What is the chance of false positives (or negatives) due to out of date databases?

We do get some nuisance alerts from time to time, and part of my job is to investigate them and determine the cause. I did investigate one recently, however, where the cause was a runway that was "one-way". Most runways have two ends and the pilot/ATC determines which one to take off. EDDF (Frankfurt) RWY18 is only used for takeoffs and was causing nuisance alerts due to the way we search for the runway in front of the aircraft.

There's another runway (I don't remember where) where the direction in our database does not match what satellite imagery shows. I don't work in the database group but I was told that this can only be fixed by asking the airport manager to re-survey the runway. Short of that, we can't fix it even if we know it's wrong.

However, It's quite rare for them to be due to a database that's out of date -- most of the time it's due to an incorrect determination that the aircraft is taking off or landing.

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#85

Post by djrogers »

TylerE wrote: post #41
peterwwillis wrote: post #38

Earlier quoted context omitted.

what happens when the camera lens gets a smudge?

I'd assume like cameras used at sporting events the lens would be covered by a clear plastic film on a roll, which can be moved to get a clean section. A bit like those toilet seat covers in airports, ironically.

> covered by a clear plastic film on a roll, which can be moved to get a clean section. A bit like those toilet seat covers

What? Is that really a thing? Toilet seat covers on a roll? How would that even work?

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#86

Post by abaillargeon »

sandworm101 wrote: post #70
abaillargeon wrote: post #24

I've been anticipating the release of this report this since I heard about the incident. I work on an avionics product that's designed to prevent this exact scenario. We use the aircraft's position along with a database of runways and taxiways to determine if the aircraft is approaching the runway the pilot intends. If we determine the aircraft is landing, we issue a visual and aural alert to the pilot ("TAXIWAY LAND…

How do you account for winds and pressure differences, both of which will modify an approach. A plane may look like it is landing short, or to the left/right, when in fact the pilot is anticipating a change in wind as they drop in altitude.

Good question. We've run into similar issues while developing a related feature that helps pilots perform a stable approach. Sometimes pilots were performing a circling approach to a different runway, and a naive approach to determining lateral deviations would have caused a nuisance alert.

For this particular system, the alerting threshold is only met when we've determined that the aircraft is "landing". As I mentioned in another comment, I'm vague about this point because it depends on the way the aircraft manufacturer has configured this state machine. Sometimes we use throttle position, altitude, speed above Vref, gear position, height above threshold, etc. You're correct that conditions can slightly modify an approach, but we're confident that we can nail down "we're landing" closely enough to mostly eliminate nuisance alerts.

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#87

Post by fanzhang »

geofft wrote: post #54
sokoloff wrote: post #32

Earlier quoted context omitted.

It's a loop recorder. When that aircraft was certified, only a 30 minute loop was required. If that aircraft was newly certified, it would now require a 2 hour loop.

Can they not sync the recording elsewhere once they land and every passenger has a high-bandwidth internet connection the second the wheels are on the ground? (Is it too hard to certify that a system that connects to the internet is safe?)

I think it's a matter of privacy rather than capability. The airlines unions don't want their conversations to be easily accessible.

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#88

Post by abaillargeon »

Waterluvian wrote: post #73

Speaking with a fair level of ignorance, how hard would it be for some onboard computer to be freaking out that a landing attempt is being made way off course of a known runway? Going to guess this is one of those things where, yes, we have all the requisite technology, but practical implementation is the hard part.

I get excited seeing stories about aviation on HN because it's something I work on every day. I've written a few comments above but I'm developer on the system you described (and more) being used in aircraft today.

With a GPS and onboard databases of runways and taxiways, we can determine if a pilot is attempting to take off or land on a taxiway. The key is preventing nuisance alerts when the pilot is just flying around and happens to be aligned with a runway. The "11 secret herbs and spices" depend on the aircraft but are usually speed and configuration (ie landing gear) based. Approaches are fairly predictable and we can use that to sequence through a state machine that tells us the pilot intends to land.

Here's a video of the system on a G1000 (meant for smaller planes) skip to 0:45ish https://www.youtube.com/watch?v=V2bswm0w4cY

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#89

Post by jandrese »

zackbloom wrote: post #72
augustz wrote: post #45

Earlier quoted context omitted.

Just for SFO you have 84 NOTAMs. !SFO 06/079 SFO OBST RIG (ASN 2017-AWP-3368-NRA) 373740N1222224W (0.5NM NE SFO) 41FT (34FT AGL) FLAGGED AND LGTD 1806201400-1811010100 This is a flagged and lighted obstruction half a mile way that is 34 feet above ground level. Now put in a full route and takeoff airport and maybe if you have had some stops during the day. The NOTAM seems a bit long. Then if are overseas and have to…

This was 100% my read as well. NOTAMs are terribly formatted and have no priority distinction between ones which are essentially useless, and ones with meaningful consequences.

Had a project once where we were trying to parse NOTAMs so we could program a GPS with a warning indicator if you were about to fly into a restricted airspace.

Turns out that people type what they want and the parser ended up needing to be almost a full AI. The exclusion zone around DC is a nightmare to parse for example.

Re: Abstract of the NTSB Report on Air Canada flight 759's taxiway overflight at SFO [pdf]

#90

Post by Waterluvian »

abaillargeon wrote: post #88
Waterluvian wrote: post #73

Speaking with a fair level of ignorance, how hard would it be for some onboard computer to be freaking out that a landing attempt is being made way off course of a known runway? Going to guess this is one of those things where, yes, we have all the requisite technology, but practical implementation is the hard part.

I get excited seeing stories about aviation on HN because it's something I work on every day. I've written a few comments above but I'm developer on the system you described (and more) being used in aircraft today. With a GPS and onboard databases of runways and taxiways, we can determine if a pilot is attempting to take off or land on a taxiway. The key is preventing nuisance alerts when the pilot is just flying aro…

Thank you for sharing. Really cool to see just how much real-time GIS there is in aviation these days.
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