Ergo, airspace above F245 should be either F or G, otherwise it's 'upside down'.
Howabout et al,
Herein lies a problem of giving classes of airspace "letter" names.
As a matter of fact, when I started serious flying in Europe, Qantas used to flog around in 707's at FL250 or below, in all the worst of the weather, turbulence, icing etc, because the "FIRs" were "controlled", the UIRs, FL250 to FL600 were only "advisory airspace" --- close to F, as India used to operate F.
And they were largely NDB to NDB below FL250, only the "upper airways" were VOR to VOR. QF 707s at M0.81, mixing it with the Viscounts, Electras, Vanguards etc. made for some interesting ATC problems, not to mention the huge waste of fuel. However, BOAC, which came from a country that wasn't so totally anal about "controlled airspace", tootled along in the clear at somewhere between FL350 and FL410.
Then, as jet traffic increased, ICAO/FAA decided that VFR was not a good idea above FL XXX (sometimes FL200, usually FL250) and that was adopted widely, with military aircraft exempt.
As the years rolled on, and we got to "Alphabet Soup" airspace, high level airspace became A, NOT because risk levels required A, but because it was the only class that prohibited VFR.
Dick is right about inverted airspace, I have already referred to this at some length previously, and I am not going to repeat it. Suffice to say that the principle has been re-confirmed, again and again, by every consultant ever hired by AsA and CASA.
What some/all of you should dig up is the extensive C v. E analysis done by Airservices for the mid levels. Very interesting, and accurate. Then the results were ignored.
Follow that by the same organization's analysis for the NAS 2b windback. In my opinion and many others the "risk assessment" was a disgrace, (after 12 months of successful operation) including assumptions that ALL pilots will make a mistake with ATC instructions between 1 in 2 and 1in 1 times ----- how many of you actually routinely even make a mistake in any interaction with ATC 50% of the time, let alone 100% of the time (OK!, I'll make an exception for several on this thread, who probably could get it wrong 50% of the time, but they are insignificant, statistically speaking, of course) --- but that nonsense is what was fed into the model.
But never mind, compared to the pilot error rate, we are saved by the world's most perfect human beings, ASA ATC staff, with an error rate of 1E6, only one error per million actions, compared to dopey pilots (assumed) 50% to 100%.
In my opinion, such figures used made the risk analysis for the 2b windback a travesty of proper risk analysis. and published external analysis,
including that paid for by CASA, agrees with me.
A at high level does not disprove the validity of E over D etc. Nor does using C where E is all that is required by analysis, produce "safer" results, because the collision risk (if E is the analysis result) in E is already so low, that C does not/cannot lower the risk, because it is already close to "vanishingly small", the statistical equivalent of zero (See ASNZ 4360).
Maybe is is time to re-institute the "Alwyn Awards", last awarded in the late 1990s.
Tootle pip!!