Matt Barrow wrote:
I thought P-P-P was equivalent to "MAYDAY", which (I thought??) is an
abbreviation for declaring an emergency.

I would put it this way: Both are emergencies, but P-P-P means it's
not a critical situation yet. You're crossing the Atlantic and start
losing a little fuel, that might be a P-P-P alert. The fuel leak grows
to the point that you know you can't make it, that's definitely a
Mayday.

P-P-P is probably rarely used by GA pilots. But airline pilots do use
it to alert ATC as to just how serious _they_ think the situation is.
Perhaps this is because a full airliner emergency might have a larger
affect on airport or airspace operations. (GA planes can safely land
in a small grass field if they lose power... jetliners can't.)

For example, remember Swiss Air 111 that caught fire and then crashed
off Newfoundland before they could land? (Basically because they
followed the book and circled dumping fuel... so as not to be over
landing weight... but the time wasted doing that killed them all.)

Anyway, their calls went something like the following, going from what
they thought was "just" an urgent situation, then to life or death:

10:14PM - "Swissair 111 heavy is declaring Pan Pan Pan. We have smoke
in the cockpit. Request deviate immediate right turn to a convenient
place. I guess Boston..."

10:24PM - "We are declaring an Emergency. We have to land immediately."

10:30PM - crashes into the sea

Best,
Kev