Originally Posted by
Johnm
Approaching GWC you enter cloud so adjust to the correct quadrantal for heading and call Solent "GABCD Request zone transit and traffic service" They'll ask for details and you give them including flight rules IFR.
In real life (not withstanding ToadPole's technically correct comment), a typical IMC OCAS flight in the South of England (as described) is heavily influenced by the overhead controlled airspace and hence has limited flexibility to comply with quadrantal altitudes (QAs). It is a system that makes sense in the absence of wide swathes of controlled airspace (i.e. post WWII Britain), and makes very little sense in Wales and Scotland (where the land pokes up into the Flight Levels, so you have to keep your other altimeter on QNH or RPS to know where the ground is relative to you.
On the hypothetical flight, from the departure to around GWC you are under the London TMA (TA 6000 ft so no QAs required below this for IFR ) and the Class A starts at between 2500 and 4500. Around GWC you are no longer under the TMA (so 'shall' adopt QAs (although the boundary of the TMA in respect of where the TA changes is not that clear looking at L620 coming out of MID with a floor of 4500, but doesn't appear to be fully contained in the TMA, but maybe it is ??). You then go for about 10 miles on 1013 (if following the rules you can only be at FL040 or FL045 depending on route, and from a practical perspective would not be able to level off at the correct QA on the way home) before entering Solent's airspace (TA 6000 ft again so back to QNH) and then leave on the other side going through Yeovilton's AIAA - which is in class G, not under a TMA so should have a TA of 3000ft, but seems to have its upper bound specified as an altitude of 6000ft rather than FL060.
Is it any wonder the whole area is often treated as 'below the TA' by pilots