Re: Regional Pressures
"more accurate, more relevant pressure setting"... of course QNH is more accurate, but "relevant"... only in certain circumstances? If you departed from the Isles of Scilly for, say, White Waltham, transitting below 3000ft what pressure setting would you use... QNH, which would be OK for about the first 20-30 miles but become increasingly less accurate as you progressed along your route. RPS has a built in safety factor, and is available in advance (so you could even obtain pressures for your entire trip before departure)
It also means that in airspace populated by several airfields everyone using RPS is flying on the same setting... believe me QNH can differ by a couple of millibars over quite a short horizontal distance. As for Chilli's reply to my earlier post about using both QFE and QNH... and him being told he had to use QFE. Use of this datum is still mandated by HQ STC, but it is to be made available for "in cockpit use", so he only had to ask... Currently, a few UK military airfields are happy to accept QNH based procedures, and procedures are currently being drawn up that should increase the scope for QNH Ops elsewhere.
I also couldn't agree more that the RAF is a minority airspace user, considered colectively. But would suggest that perhaps on an operator to operator basis they are as large if not larger than any other single user in the UK... their procedures are based on experience formulated with a high regard for Air Safety. Switching to QNH is regularly considered as an option, but has so far been ruled out (except for one, frankly badly managed, excursion in the 80s)... but shouldn't be discounted in the future.