I can't remember seeing the magenta line until much later when diagnosing the problem in the cruise. The FMS position was about 9W of us, which i guess is in the order of 270 miles at UK latitudes (Dumped the theory after passing the exams
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and there was no radio position, the system was looking for beacons on the south west coast of Ireland.
As far as the runway coordinates it worked fine the next time with the same aircraft, so it must have been yours truly. I'm just confused as to why if it thought we were somewhere near Shannon why did it try to turn me towards the south west, when the initial points of the sid were in London.
The system has no GPS input on our aircraft, which leads me to a seperate thought and question. Does EGPWS use a GPS position to provide information and if so is it possible to feed this input to FMS? It's purely a theoretical question, not worried about the legislation, cost etc, it's just an urban myth running around the fleet at the moment.