BOAC,
I am sorry, but I have must given you the wrong impression. I am a pilot and flight instructor. The questions above arose during a class of a colleague of mine. I have posted the problem here since it does involve us pilots and ATC.
ATC creep,
thanks for your thorough post. It's good to read from a controller's point of view.
As bookworm stated, if we do happen to fly a non-precision approach and we do not have a radio altimeter, then the temperature can be a problem for us.
And that exactly was the initial question. It is great to read all these posts. Thank you!
Regards,
TG.