Bucky wrote:
I'm not a pilot, just your typical passenger. I don't fly United often,
so I just discovered that they put the ATC on the inflight audio. I was
totally fascinated and want to learn some more. Is there a website that
has some basic ATC protocols? Not some huge reference manual, just the
common phrases that you hear over a commercial flight's radio.

You might find it to be in the reference manual category, but the AIM
(Aeronautical Information Manual) really isn't too hard to read, especially if
you are a motivated learner, and you can get it free on the internet:
http://www.faa.gov/ATPubs/


A few questions I had while listening:

- What happens if 2 people try to talk at the same time? Do you hear
both voices or neither? How do they avoid talking over each other?

If two people try to talk at the same time, you just hear a squeal, neither
party's message gets through, and then both try again, hopefully not at the same
time. This is just simple low-tech stuff.


- It seems that there is no authentication/security, the parties just
identify themselves. Have there been cases of troublemakers making
false impersonations?

Yes, there have been cases, but they are rare.


- They ask pilots their speed, altitude, and heading a lot. Can't the
transponder send that information?

They ask a lot? Doesn't seem so to me. The transponder (typically) sends an
identification code and altitude. The ATC computer can derive the speed and
track over the ground, which differ slightly from the airspeed and heading.


- Do any other airlines put ATC on the inflight audio?

I don't think so.