[NZtyphoon]

Originally Posted by Crumpp

It is a fact the manual was reprinted in January 1942 and it is a fact the fuel changeover to "All Operational Units" is important enough to be added to Paragraph 1, Operating Limitations.

The 100 Octane fuel changeover is important enough to make it into every Operating Notes, Paragraph 1, Operating limitations when it occurred.

For example, the Hurricane II Operating Notes dated September 1943 clearly list 100 Octane as the ONLY fuel to be used:



It will note in paragraph 1 the fuel options when 100 Octane becomes common and it will note when all operational units will use the fuel, and when it is the only choice.

It is the operational documentation and not logistical!!

Now, it might not be the exact month because there is some lag time and technical orders will cover that short time period.

you will not see technical orders that are applicable to operational units that do not make it into the new edition.

It is really simple. We have a 1939 edition and we have a June 1940 edition with no changes to paragraph 1, Operating Limitations. That fact tells you 100 Octane was not in common use. It was in use but it was not the most common operational fuel in the RAF at that time.

In between that time we have a technical order to AP1590 which is the engine series and not the airframe series. It makes a difference in aviation and there are plenty of engines that modifications are not approved in specific airframes. There will be an order approving that engine modification for the specific airframe.

For example:





http://www.autofuelstc.com/autofuels...Mogas_FAQ.html

I don't know the specific explaination in the case of 100 Octane as too why the large lag time between the engine approval and the airframe operating limitations but I do know that is a flag to anyone knowledgeable in airplane maintenance for claims of widespread general use.

I would get the editions to the Operating Notes and throw away any squadron logs that do not specifically state "100 Octane Fuel in use".

You will have good factual picture on the timeline for the fuels operational use if you do that.

FACT: The RAF issued amendment slips with the Pilot's Notes before reprinting the notes with the amendments included - just because the June 1940 Pilot's Notes do not have the required amendments does not mean the RAF wasn't using 100 octane fuel - it simply means the Pilot's Notes continued with the convention of noting limitations for the fuel for which the Merlin II/III series was designed; to wit 87 Octane. Even in January 1942 Pilot's Notes stated 100 Octane for Operational Units 87 for "Other units".

you will not see technical orders that are applicable to operational units that do not make it into the new edition.

Wrong - as long as the engine was originally designed and rated for 87 Octane fuel the Pilot's Notes did not incorporate anything else until 1943. Any amendments to the engine's ratings continued to be issued as supplementary slips. The Hurricane notes of 1943 say 100 Octane because the Merlin XX was designed to use 100 octane.

The Pilot's Notes General 2nd ed printed in April 1943 dropped the convention because most engines which were originally designed to use 87 octane fuel were well out of frontline service.