The bottom line is it isn't just for getting in and out below minimums.
> It is a required clearance before you will even be allowed into your > destination if it lies within a class D or E CTR.
From what you posted, UK SVFR sounded like the same thing we have in North America -- a way to land or depart in MVFR, not a special way to get into controlled airspace when otherwise forbidden. I didn't see anything in the posting suggesting that you needed SVFR to enter class D or E airspace in good VMC, but I don't know all the underlying assumptions and background that a UK pilot would bring to it, so I could be missing something obvious. It's worth noting that ICAO classes D and E are the lightest types of controlled airspace: here's how I understand the ICAO airspace designations (the UK may have some variations):
Class A: - IFR clearance required - VFR not allowed - ATC separation applied to all traffic - North America uses this only for traffic between FL180 (or higher in the arctic) and FL600
Class B: - IFR and VFR clearance required - ATC separation applied to all traffic - the U.S. uses this for busy airports like KSFO; Canada uses it for all controlled airspace between 12,500 ft and FL180, but never for airports.
Class C: - IFR and VFR clearance required - ATC separation applied to all IFR traffic, and between IFR and VFR, but not between VFR and VFR - traffic advisories to VFR traffic when able - Canada uses this for large airports; the U.S. uses it for medium-sized ones
Class D: - IFR clearance required - VFR radio contact with ATC required - ATC separation applied to IFR traffic only - traffic advisories to VFR traffic when able - Canada uses this for terminal area control zones; Canada and the U.S. both use it for small, towered airports
Class E: - IFR clearance required - VFR does not require a clearance or radio contact, unless otherwise noted on the charts - ATC separation applied to IFR traffic only - traffic advisories to VFR traffic may be available on request - North America uses this for low-level airways, many untowered airports, control-zone extensions, etc. (but in Canada it all becomes class B at 12,500 ft).
Class F: - unknown: the U.S. does not use it, and Canada uses it in a non-standard way (for restricted or advisory airspace)
Class G: - no clearance required for IFR or VFR - no separation applied to IFR or VFR traffic
So from my, probably flawed reading of the excerpt you posted, SVFR is simply a way to get under weather minima, but it is available only at smaller airports with class D or E airspace. It certainly couldn't get you inside Heathrow's airspace, if that is, in fact, class A as aeroplanner.com claims (we never use class A for airport control zones in North America).
<aside>
The separation rules for each class matter a lot to controllers -- if two planes get too close when separation is required, the controllers get a deal, and they lose their jobs after some small number [three or so]. So if two VFR aircraft get too close in class B, they have a deal; if two VFR aircraft get too close in class C, they do not, since they do not have to apply separation to VFR aircraft in class C. Understanding this can help a lot when dealing with ATC. European rules might be a bit different, again.
</aside>
I'll be interested to learn more about how the UK airspace system works. Eventually, we'll have to have all of this knowledge programmed into our AI controllers in FlightGear.
All the best,
David
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