Originally Posted by
chevvron
Link doesn't work for me but I'm not using Windows.
10 years ago was about the time the CAA designated QNH as the 'official' pressure setting.
This was the original post of that thread:
I am convinced that GA altimeter setting procedures in the UK are far too complicated. Do we really need Regional Settings? Do we really need QFE? The VFR pilot flying in Class G airspace has to reset his or her altimeter several times. Two problems arise: firstly, there is always a chance of setting an incorrect subscale setting every time it is adjusted and secondly, distraction during resetting can draw the pilot’s attention away from other vital tasks, such as lookout and navigational monitoring.
A simpler procedure would be to set local QNH for the whole flight, resetting only if the QNH changes. Rarely does barometric pressure change rapidly, so even if the subscale was not reset at all during the flight the resulting altimeter error would be unlikely to exceed 100 feet or so. Is this significant for VFR flight?
Two further advantages of 'local QNH' flight are improving terrain awareness (which QFE degrades) and reducing the potential for violation of controlled airspace, which in the lower levels usually has a base expressed as an altitude. For student pilots doing circuit work, patterns flown with QNH set would not be difficult to learn. When they came to land away from base, adding field elevation to pattern heights to determine pattern altitude would be part of their pre-flight preparations and could be recorded on the nav log. If a MATZ controller specifies a QFE-based penetration height it is easy to convert this to a QNH-based altitude, rounding up or down to the nearest 100ft.
Finally, it should be noted that commercial airliners around the world fly local QNH below transition altitude and 1013 above it. If it works for the big boys and girls, why not for GA traffic too?