Thanks all for your answers to the 'Q' question. I seem to remember the term from my fluid dynamics ...
Speaking as a relatively baby pilot, it seems much more sensible to read your height relative to the aerodrome on T/O and Ldg. After all, you don't particularly care about anything else in this scenario. If you're low-flying, the RPS is useful, and if you want flight levels, set SPS. A case of horses for courses, is it not? I suppose QNH might come in handy if flying a Catalina ...
