How does this happen? Shouldn’t the pilots see the approaching aircraft on radar (and assuming 3nm visibility) also see the approaching aircraft. This feels like a situation where a lot of things went wrong with multiple crews.
TCAS exists and can provide collision warnings and some degree of information on where other aircraft are using secondary radar data, but it's very much a last line of defense.
Both planes are expected to see each other, and they're also expected to hear each other on the radio.
Would an A320 not have a similar system? Likewise, both pilots physically moved their heads to scan both directions of the runway for hazards. I’m just confused why the big boys wouldn’t be more sophisticated than this.
Yes, it's called TCAS / TCAS II (mentioned). Or portable systems called PCAS for the smallest planes.
Alerts are generally disabled on the ground, and .. there's a lot of technical factors that limit its usefulness in this scenario.
> Likewise, both pilots physically moved their heads to scan both directions of the runway for hazards. I’m just confused why the big boys wouldn’t be more sophisticated than this.
A careful, visual scan is essential. But when you have oncoming fast aircraft, convergence rates are fast. They were 8-9nm apart, at night, when the A320 started its takeoff roll.
There's basically 3 defenses against this scenario at an untowered airport:
- Weakest: hopefully both aircraft pick the same runway direction. There's a "calm wind" runway for this reason. But when winds are 0 and not quite calm, do they agree?
- Stronger, but problematic-- unicom: aircraft are supposed to announce their intents and listen on a common frequency. If someone has the wrong frequency tuned, that won't work.
- Strongest: visual avoidance. That happened late here, and triggered an overreaction in this case.
Lots of GA aircraft have TCAS-like systems, where they listen to secondary radar responses from other transponders. So, when airliners or ATC interrogates planes, these other planes hear the responses. And, of course, ADS-B makes all of this easier and more precise.
But in any case, TCAS is not designed to prevent a runway conflict. It doesn't know about flight intentions: that the Airbus is going to be climbing a bunch soon.
EDIT Just read it was an uncontrolled airport as i posted this, so i guess ATC is out of the picture.
An interesting tidbit from wikipedia: "Straight-in approaches are discouraged at non-towered airports in the United States"
Additionally, there are guidelines for how to enter the airspace of an uncontrolled airport to reduce congestion and the chance of a collision. There are a few exceptions, one of them being an approach during poor weather, which appears to have been the case in the incident mentioned here. In those situations, the approach controller usually coordinates arriving and departing aircraft to use appropriate runways. I'm not sure why that didn't happen in this case, but I haven't gone and looked for the ATC archives.
[1] https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...