I know I'm comparing apples with oranges here, but for those who turn 121.5 off below 10,000', it might be instructional to remember that the Iranian A300 was climbing through 14,000' out of Bandr Abass when the US Navy missile hit it. The USS Vincennes radio operator had been calling them for some time before that, but they didn't have the frequency selected.
It's not well known, but only a year or so after that terrible incident, the USN went within seconds of shooting down a Gulf Air A320 in very similar circumstances. The crew of the 320 that was approaching the US ship had a squark code of something like 7235 and neither pilot was listening out on 121.5. When the US Navy ship made its first call, another Gulf Air A320 at the same level and on a parallel course about 20 NM away and with a squark code of 7325 replied and made the turn away as demanded by the US ship. When the blip on the radar continued heading straight at the ship despite the pilot saying he had turned away, I understand that things got rather exciting in the ship's fire control centre.
It was only when the pilot of the 320 who had answered realised that he was over land and couldn't be the target the USN ship was tracking that he was able to convince the Americans he wasn't part of some ruse to attack them.
I understand the US ship got to within 30 seconds of launching a missile.
Meanwhile, the crew of the 'offending' A320 flew on oblivious.
I know this scenario isn't likely over London, but it might give some an idea why some people like to have 121.5 selected at all times.
Last edited by Andu; 22nd May 2006 at 05:53.