Yep, because Bomber Command, Coastal Command OTUs etc etc were all still using 87 octane fuel. Barbi forgot to mention all those medium/heavy bombers flying boats et al which consumed rather a lot of 87 octane fuel. Fact is the RAF were confident enough in their reserves of 100 octane that orders were issued in early August that all commands could convert to using 100 octane - it took about a month but use of 100 octane began to increase in September, while 87 octane declined.

I read it a bit different. "Issue of this fuel to certain units in the Bomber Command will, however, take precedence over the units equipped with the above mentioned types of aeroplanes." There is a clear constraint on "certain" units in Bomber Command but no constraint on units with Hurricane, Spitfire and Defiant. ;)

Pretty much sums it up. We won't find a exact date, the change was made a soon as possible.

The "approved stations" are given in the referenced letter No. F.C. 15447/76/E.Q.2:
http://www.wwiiaircraftperformance.o...0oct-issue.jpg
http://www.wwiiaircraftperformance.o...0oct-issue.jpg

It was also shown here:
http://forum.1cpublishing.eu/showpos...&postcount=121
http://forum.1cpublishing.eu/showpos...&postcount=125
http://forum.1cpublishing.eu/showpos...&postcount=133
http://forum.1cpublishing.eu/showpos...&postcount=135

that the "certain units" of Bomber Command had received 100 octane fuel until May 1940. And then the Fighter stations started to receive 100 octane fuel, which pretty much agrees with the reported use of 100 octane fuel in several fighter squadrons starting from May 1940.

"These are, or will be operational Stations although they have no Hurricanes or Spitfires at the moment. In the near future these stations will have Merlin engine aircraft that will require 100 octane fuel." 9 December 1939

Not might require, not maybe require but will require 100 octane fuel. Clear recognition that as early as December 1939 Merlin engine aircraft such as the Hurricane and Spitfire required 100 octane fuel, and that bases operating Merlin powered aircraft needed stocks of the fuel.

[QUOTE=41Sqn_Banks;399463]I read it a bit different. "Issue of this fuel to certain units in the Bomber Command will, however, take precedence over the units equipped with the above mentioned types of aeroplanes." There is a clear constraint on "certain" units in Bomber Command but no constraint on units with Hurricane, Spitfire and Defiant. ;)

Only if you simply forget about the preceeding sentence - ""serving the fighter stations concerned". Its a quite clear constraint, repeated again in the April - May docs, posted previously.

The paper reads to me as a request, not an approval.

It was also shown here:
http://forum.1cpublishing.eu/showpos...&postcount=121
http://forum.1cpublishing.eu/showpos...&postcount=125
http://forum.1cpublishing.eu/showpos...&postcount=133
http://forum.1cpublishing.eu/showpos...&postcount=135

The 'certain' restristion was not limited to Bomber Command. Subsequent papers keep speaking of 'certain' concerned etc. fighter stations the same as 'certain' concerned bomber stations.

I did not forgot, I just do not care to give any weight to your childish speculations and outright nonsense, Minnie. :D

Moreover:

16 Fighter and 2 Bomber Squadrons by September 1940

"The change-over would start towards the end of the present year and ACAS would select the particular squadrons which would operate on the new fuel."

"fighter stations concerned" could also mean all fighter stations with Hurricane, Spitfire and Defiant. But I agree with you that this is not clear and one can be read in both ways.

Yes, that's right, however, its interesting to note that stations were supplied with 100 octane fuel and squadrons were consuming 100 octane back in 1937 and 1938. The following document lists six stations and three squadrons that received 100 octane fuel during 1937 - 1938. 90 Squadron flying Blenheims, 98 Squadron flying Hawker Hinds, and 201 squadron flying Saro Londons were using 100 octane fuel during trials in 1937 and 1938. Also worthy of note is the listing of Hucknall, which is where Rolls-Royce had their Experimental Flight Test Establishment.

http://www.wwiiaircraftperformance.o...0oct-37-38.jpg

We also know that the following units were supplied with 100 octane during 1938.

Duxford: No. 19 in Spitfire I, No. 66 in Gloster Gauntlet II
Debden: No. 85 & No. 87 in Hawker Hurricane
Northholt: No. 111 in Hawker Hurricane
Digby: No. 46 in Gaunlet II & No. 73 in Hurricane

http://www.wwiiaircraftperformance.o...oct-6dec38.jpg


It bears repeating that the use of 100 octane fuel for Hurricanes and Spitfires was approved by 24 September 1938.

http://www.wwiiaircraftperformance.o...t-approval.jpg

Theoretically it could, but then again, since all fighter stations had either Hurricane, Spitfire and Defiant anyway - what purpose would that serve..?

Secondly, about the two letters from December 1939. If we assume that the 24 Stations (if I counted right) listed there are indeed the ones that were said to be selected by ACAS in the March 1939 paper by the end of the year, that leaves a bit of problem, because there were about 60-odd fighter stations operated by Fighter Command in the Battle of Britain...

Which leaves if these were the ones effected, or 'concerned' it leaves about half of fighter command operating on 100 octane. A curious coincidence is that there are only combat reports indicating 100 octane supply for about half the Squadrons that participated in the Battle.

That leaves with a very well supportable case that half of Fighter Command was operating on 100 octane, and the other half on 87 octane.

Its not an easy case and I am thankful that as opposed to Fighter Command's case of 100 octane use, the Jagdwaffe's use of 100 octane fuel (naturally denied by lane, glider and minnie :D ) is so much more clearly documented and we know the very exact units, and the number of planes effected. Makes so much less room for arguements. ;)

Good work. My original post also noted that in September, 16 squadrons was a significant portion of Fighter Commands combat power.

The points to think about:

It was not until sometime in September the RAF had 16 fighter squadrons using 100 Octane. That could be the 1st of September or the 30th of September that 16 squadrons were operational. We don't know the exact date. I point this out because during the 100/150 grade debacle, knowing the exact dates revealed the fuel was used for several weeks before being withdrawn in the 2nd TAF. During that time, many squadrons converted back to 100/130 grade on their own because of the unreliability of the engine when using 100/150 grade. As a pilot myself, I have an aversion to flying with anything that will stop that propeller from turning, too. I like it when it works and don't like dying.

Second point is the logistical planning of the RAF in many ways was much better than the Luftwaffe. I would be willing to bet the RAF did not wait and suddenly stand up those 16 squadrons at once. Instead, at the completion of operational trials, the units were stood up on 100 octane as soon as the field built up the required reserve, the aircraft converted, and the logistical support in place to maintain combat operations.

This would make for a gradient curve and by sometime in September a full 16 squadrons were using the fuel. A word of caution, this is just my opinion and stated to participate or add fuel to any "make my gameshape better" butchering of history.

Unfortunately, we don't have the facts to fill in the gaps in our knowledge on that part so the very presence and actual slope is just more guesswork.

Given time, the facts will be revealed. Five years ago, I know very little about the development details or extent of operational use of either GM-1 or Alkohol-Einspritzung on the FW-190. We just knew we wanted our aircraft to be as authentic a restoration as possible. After several years of ploughing archives the gaps in our knowledge have narrowed considerably and the picture is much clearer.

The same will happen with the introduction of 100 Octane. I highly doubt it will be solved here and now. The answer is probably collecting dust in the files of an archive somewhere.