Hi Guys,
In response to the first post..
>Ive been meaning to go to the site where the MIRSI beacon is located but i just not had time
You'll never find it, it's not a beacon!
In simplistic terms - it's a point in space created for the fmc's to navigate to, and to hold around. Normally 5 mile tracks, inbound course 064 degrees, right hand turns (as I recall from the last time I had to hold there!!). The basic situation is this, London send us (say over Birmingham) to Manchester, who will clear us to MIRSI and before we get sent to there we swap to Radar, if we get no clearance to proceed, we go into the hold at MIRSI - it's automatic, no clearance - into the hold you go. After MIRSI it's onto Director and then to tower as we intercept the localiser and start the descent on the ILS. Busy(!)
>As i was watching the aircraft going round the track it became evident that no aircraft ever gets the track exactly right,
Correct, some fmc's have the inbound course 065 degrees, but the book (egcc arrival plates) specify 064 degrees. Also, as it's an fmc route, the accuracy is all down to the IRS's (for the airline I fly for, 0.24 mile accuracy). Other airlines have GPS updating of the fmc's and it's down to 0.1 mile accuracy.
> if this wasnt good enough another dash came along, but it entered at about 15-20,000ft, it took around 10-15min to get to the usual 6,000ft, which was equally great to watch.
You should try being in the hold - great fun looking down and seeing other aircraft turning. Also bear in mind all this is visible on the TCAS system, white diamonds with their relative height readings everywhere!
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