[abaillargeon]

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 LANDING" or "NOT A RUNWAY").

[sandworm101]

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.

[abaillargeon]

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.

[oh_sigh]

What's your market? Light aircraft? airliners?

[abaillargeon]

Our market right now is general aviation and business jets. I believe our biggest customer is the Cessna Citation Longitude (max takeoff ~40,000lbs). I noticed the NTSB abstract had some recommendations for inclusion and certification of a system on a broader range of aircraft. Larger aircraft are required to have similar safety-related systems such as terrain, reactive windshear, etc so this could be the next step.

[outworlder]

What is the chance of false positives (or negatives) due to out of date databases?

[abaillargeon]

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.

[ryandrake]

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?

[abaillargeon]

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.