quite large variations exist
I accept having a single QNH setting might be a way of getting every one on the same QNH.....while enroute but conflict still exists once the Aerodrome QNH is used.
As we do not have such a concept as Regional QNH....limit ourselves to a Standard QNH once we go to Flight Levels....we do not have a problem.
When then does the UK insist upon a different system than we do?
If safety is the issue....which system is better and to what degree?
If there is scant difference in safety....which system is easier to use?
Now I do recall having fun teasing you folks about Altimeter Settings during a Missed Approach combined with a change in the Handling Pilot... and all that....so there must be something to the fact the UK system is far more complicated than it need be. Why else would there have been that mock BA Memo on the subject?
So I repeat the question.....how big a difference can there be between two Airport QNH settings within a hundred mile radius and does it present a real hazard to safe flight?
Come on PN....educate us on the dangers of doing away with the Regional QNH system....as the USA has done by never adopting such a concept.