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Comment by hinkley | Hacker News Reader

Sounds like the FAA altitude problem all over again.

As altimeters got more accurate, the odds that you were flying at exactly 28000 feet went up. If an air traffic controller fucks up and puts two planes at 28000ft, they can now collide because they're ±10ft instead of ±200ft. That was the RCA of that mid-air collision over Brazil a while back.

The more you try to control a thing the more problems you can have. A parking lot for stealth ships is... I don't want to say dumb but confusing for sure.

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That's why we've implemented SLOP https://en.wikipedia.org/wiki/Strategic_lateral_offset_proce...

Thank you, pretty interesting

> That was the RCA of that mid-air collision over Brazil a while back.

Yeah the article made me think about that incident too, described here in detail:

https://www.vanityfair.com/culture/2009/01/air_crash200901

It's a great read.

> The more you try to control a thing the more problems you can have. A parking lot for stealth ships is... I don't want to say dumb but confusing for sure.

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

These days there are special collision avoidance systems on big commercial planes:

TCAS II provides the pilot with specific instructions on how to avoid the conflict with traffic. These instructions are known as a “Resolution Advisory” (RA) and may instruct the pilot to descend, climb, or adjust vertical speed. TCAS II systems are also able to communicate with each other to ensure that the RA provided to each aircraft maximizes separation.

From https://nbaa.org/aircraft-operations/communications-navigati...

My understanding is these automated instructions override those from ATC

I believe TCAS is built off of ADS-B which is terribly insecure https://youtu.be/CXv1j3GbgLk

TCAS isn't built off of ADS-B (it existed long before ADS-B was ever conceived), but it's the same basic idea (mode c / mode s transponders) and probably has the same theoretical security vulnerabilities.

There's a pilot at the controls so that the technology doesn't have to be perfectly secure.

If you want to walk around broadcasting fake ADS-B or Mode C signals, someone will probably find you in hours, and the only effect it will have is maybe reducing the throughput of the busiest airports if the weather happens to be particularly marginal that day.

TCAS does not work if your transponder (or theirs) is off, which is how that collision in Brazil happened.

https://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Fl...

The Legacy's pilot footrest places the end of your shoes dangerously close to the transponder standby button.

https://www.bangaloreaviation.com/wp-content/uploads/2014/04...

The footrest is below the white screen with the navigational chart on it. The radio and transponder panel is the black screen to the right of that, with the yellow and green text on it. The 0512 is your transponder code (squawk); the button to the left of that and down one row turns it off.

This resulted in the Legacy losing its TCAS ability, and the 737 it collided with being unable to see the Legacy.

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