Hi there,
Many thanks for your replies here.
I think the problem is probably more straightforward than it first appears, but is actually based on an exam question in the 'PPL Confuser'.
I hope I'm not breaching any copyright issues, but the Q is as follows:
"After turning at Wolf Rock (lighthouse between The Scillies and Land's End), you accept a FIS from Culdrose LARS advising the controller that you plan to over-fly the St Mawgan MATZ at 4000ft. Your altitude west of the MATZ should be based on:
A - the St Mawgan QFE
B - the lower of the Scillies RPS and the Wessex RPS
C - the ST Mawgan QNH
D - the Scillies RPS"
The answer is given as D, with the following supporting comment:
"To the west of the St Mawgan MATZ, you should have your altimeter sub-scale set to the current Scillies RPS. Over-flight at 4000ft will position you above the MATZ, but as the Scillies/Wessex ASR boundary bisects the MATZ, so the Wessex RPS would have to be entered into your altimetr sub-scale as you cross the ASR boundary. (Note: If the controller at St Mawgan is very busy controlling other traffic in the St Mawgan area, Culdrose may ask you to free call St Mawgan to advise the controller there of your intentions. For the purpose of safe separation, you may be asked to use the St Mawgan QNH for transit over the St Mawgan MATZ)".
The reason I originally queried this is that I've seen other 'sources' suggest that the St Mawgan QFE should be set on the altimeter (ie answer A above), even though the flight takes you over/outside the vertical limit (3000ft) of the MATZ.
Getting this wrong could be the difference between passing and failing the Nav exam, and that's before consideration given to 'real flight' issues. . . .
Hope this clarifies.
HW