Originally Posted by chevvron
I would personally suggest that if flying in class G below TA and NOT talking to ATC, you use RPS; if talking to ATC you use the observed QNH they give you.(But be warned some tower only ATC units plus FISO units with no qualified met observer may only be able to issue QFE!)
Chevvron, although use of RPS helps to guarantee (a bit extra) terrain clearance during cruise or descent, in a decreasing barometric pressure weather system, the use of it during a climb is likely to lead a pilot to bust into controlled airspace above. The airspace over the Pennines to the east of Manchester is a good example of where this might happen. From that point of view, it is better (for the security of one's pilot licence) to use the local QNH when climbing.