[Part 1 of 2]
ETA:[The conversation has moved on a bit while I was responding to Tripler’s first mention of TCAS. Oh well. So some of this is redundant to Richard’s fine words. None of this should be taken as quibbling with what he’s said. Oh well.]
TCAS was designed in the 1970s and first delivered in the mid-1980s. Pretty much trailing edge tech now, at least for big guys. It’s always been kinda expensive to put on small aircraft.
Although the design incorporates the idea that one airplane in the mix (e.g. the small guy) may be oblivious to the encounter and the other one (e.g.the big guy), does all the maneuvering to avoid the other’s predicted trajectory. So even though small guys aren’t TCAS-equipped, they gain safety from collision with TCAS-equipped big guys and those big guys gain safety vs. them as well
Bottom line: it’s not new but it works and works well. Over the years substantially everyone I know in the biz has had close calls that were made much less close by TCAS. At the same time we’ve all also had our share of nuisance alerts as well. Hard to say how many actual mid-airs it’s prevented, but I’d wager it’s more than zero.
ADS in all it’s various sub-flavors (-B-in, -B-out, -C, CPDLC, etc) is the current / next big thing. Some early parts of it have been flying (as FANS) for 15-20 years now in oceanic airspace. But widespread adoption in the US, EU, & the more inhabited parts of the rest of the world is happening in 2018 & up. Just this summer it’s essentially universal on US & EU jet aircraft, although it’s far from universally available on the ground side.
As Richard_Pearse says, Australia was leading the rest of the world by years on this. Their civil aviation authority and users were really the big beta tester on the whole thing.
Ultimately, ADS is a digital communications channel. What gets sent over the channel determines what it can be used for.
The promise of ADS is that ATC can shut down their expensive & maintenance intensive radars while everyone’s on-board nav system will just broadcast their position, altitude, speed, near-term intentions etc. for anyone and everyone to listen to.
So ATC can watch all the traffic with simple cheap low-maintenance radio receivers that receive all those transmissions, each airplane can listen for, display, and eventually maneuver to avoid, nearby traffic etc. The ATC receivers can even be on satellites so finally we will have traffic surveillance over the open ocean. Which will greatly increase airspace capacity in busy airspace (pre-COVID that is) like the North Atlantic or air routes between North America & China. That will also eliminate mystery disappearing ghost-jets like Malaysia 370.
Everybody wins.
Unfortunately, just like the global Internet, the groundwork was laid before anyone thought of the possibility of bad actors. A lot of effort has gone into retrofitting something approaching security into the system. Color me skeptical.