Inaccurate performance data for BOB fighters in COD comparing to RL data

[Crumpp]

Let’s look at some of the facts being supplied.

First we have this document:



Estimates...estimates for consumption and estimates future stocks two months ahead of 29 Oct 1939.

Estimates = best educated guess. An estimate is not a fact. While interesting, it means nothing for establishing the extent of use of 100 grade. It does establish the fact in October 1940 the United Kingdom had just over half the 800,000tons of 100 Octane in strategic reserve they initially required. There was a shortage of 100 Octane fuel.

We have evidence that some 100 Octane was used as early as 16 February 1940. This squadron log definitively states the aircraft are converted and using the fuel.



It is a fact; this unit was using 100 grade. However, that does not mean the RAF had adopted the fuel or it was in widespread use.

A technical order for conversion of the aircraft had not even been published at that time. It is highly unlikely that the RAF was in the process of widespread conversion to 100 Octane without disseminating the technical knowledge to convert the airplanes in the force.

Technical Order dated March 1940:



The technical order tells us the major work required to convert an engine by replacing the cylinder heads, in some cases piston rings, and altering the fuel metering system. It also gives us the plan to make the conversions. Airplanes were to be converted when their service inspections where due. In order to make this conversion, there must be an adequate supply of the new cylinder heads and parts in the inventory to replace the old ones. Somebody has to make the parts required and distribute them.

These squadron log entries prove that the conversion was taking place. It does not show that they were using 100 octane fuel. The only fact it shows is that the planes were converted according to the plan laid out in the technical order.





Looking at this document, we know for a fact nobody in the United Kingdom was using any sizable quantity of 100 Octane fuel before June of 1940.



That would make sense given the other facts we have at hand.

1. There was no technical order or instructions to convert until March 1940.
2. Conversion required major work and a supply of cylinder heads to be in the manufactured and distributed to the inventory.
3. Conversion was done on the periodical major inspection schedule of the aircraft when it was down for service anyway.
4. None of the POH's list +12lbs as authorized before June 1940. If it was the major fuel, those instructions would eclipse the instructions for 87 Octane.
5. There were no stocks in any quantity of 100 Octane fuel at any airfields prior to June 1940.
6. 100 Octane fuel does not become the major fuel on hand at any airfields until October 1940.
7. In October of 1940, the United Kingdom as just half the Strategic Reserve required of 800,000 tons. In other words, there is a shortage of 100 Octane fuel in the United Kingdom.

Even after June 1940, 100 Octane does not come anywhere close to eclipsing 87 Octane use. It represents on 27% of the fuel on the airfields during July thru August.

In September, 100 Octane represents 37% of the fuel on hand at the airfields. In October the increase is significant with 47% of the total fuel at the airfields being 100 Octane. The other 53% in October is still 87 Octane.

That concludes the facts at hand. All of this points to the biggest fact of all, we don't know for sure at this point.

Lastly lets address why I believe the 16 squadrons over simplistic calculations.

Now the 16 squadrons is found in two sources. First Morgen and Shacklady list RAF Fighter Command as having 16 squadrons for Fighter Command and 2 Squadrons for Bomber Command by September of 1940. The Trimpell Oil Company also confirms this plan. They list 19 squadrons and 384 Spitfires using the fuel by 31 July 1940. If we count squadrons listed in both sources:

16 squadrons in Fighter Command + 2 Squadrons in Bomber Command + 1 PRU unit in Coastal Command = 19 Squadrons.

16 Spitfire squadrons in Fighter Command = 352 A/C at the establishment of 22 A/C per squadron enacted in July 1940.

That leaves 32 Aircraft for Coastal Commands PRU unit.

Both sources seem to agree and their conclusions are close enough on the 16 squadrons. Those conclusions are backed by the Aircraft Operating Instructions and the airfield stocks as listed in the United Kingdom’s Table II - Consumption report and Strategic Reserve situation.

That 16 squadrons using 100 Octane fuel during the Battle of Britain puts the reserve to consumption ratio at a much more believable rate and the accounts for the inventory lag of replacing cylinder heads. In short, from a logistical standpoint, it is much more credible and is agrees with the evidence found in the aircraft operating instructions.

Now several second hand sources make the statement that 100 Octane was the predominate fuel for Fighter Command during the Battle of Britain. This is true depending on the dates you choose to end the battle. On 15 September, I would say it was unlikely that 100 Octane was the predominate fuel. However by December 1940 it did become the predominate fuel and by the German date for the end of the battle, May 1941 when the bombers were transferred to the east, 100% of the RAF was using 100 Octane fuel.