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

[winny]

Originally Posted by TheGrunch

As Kurfurst noted in the thread on ww2aircraft.net, that particular "Spitfire and Hurricane units" is an unnecessary alteration made by Mike Williams and it actually says "the Units concerned".
However I think the first quote you posted gets us *most of the way* toward saying that 100 octane was available at all operational units, i.e. "issue will be made as soon as the fuel is available in bulk at the distribution depots serving the Fighter Stations concerned".

I don't really know enough about it! But I do know that there was a conversion involved to the Merlin and that if the fuel was at a certain airfield then some of the aircraft must therefore have been converted (or were in the process of being converted). It wasn't a complicted procedure.

Stocks were ample (given total usage for the battle of 55,000 tons).
so I think it's pretty safe to assume 100 octane to be in use by most if not all RAF frontline fighter sqns by June '40

[TheGrunch]

Haha, don't forget winny, this isn't about what's logical, this is about satisfying Lufwhiners...totally different matter.

[DC338]

On October 29, just before the end of the Battle of Britain, 423,400 tons of 100 octane fuel was in stock in the UK. The War Cabinet recorded that 100 octane stocks stood at 202,000 tons on 31 December 1939 and that 100 octane stocks had risen to 499,000 tons one year later on 31 December 1940. The Air Ministry recorded that 58,000 tons of 100 octane were issued during the Battle of Britain. The War Cabinet recorded that 100 octane consumption within the UK for the whole of 1940 amounted to 130,000 tons, an average of 2,500 tons per week. Consumption of 100 octane during the Battle of Britain averaged 10,000 tons per month for the months of July and August rising to 14,000 tons in September followed by 17,000 tons during October. Total consumption of 100 octane fuel during the Battle of Britain therefore was on the order of 50,000 tons.

So lets look at the figures again.

50,000 tons of 100 octane used is the equivalent of 185,750 hurricane sorties in which all fuel was used.


I think there is no doubt from the above figure that 100 was available and more importantly was actually consumed by the fighters of RAF. If you don't agree then how do you account for the consumption.

[winny]

Originally Posted by TheGrunch

Haha, don't forget winny, this isn't about what's logical, this is about satisfying Lufwhiners...totally different matter.

Ahhh, I see. I that case the whole of the RAF was on 100 octane simply because all the aircraft were so pretty and curvey..

[TheGrunch]

@DC338: That's enough for four full fuel tanks a day for 60 12-aircraft squadrons over 60 days. And as we know, Fighter Command didn't usually send up aircraft in squadron strength.

Not true winny, they were on 100 octane because it was green, and people didn't understand what "being green" meant back then.

[Kurfürst]

Originally Posted by DC338

50,000 tons of 100 octane used is the equivalent of 185,750 hurricane sorties in which all fuel was used.

Not accounting for non-operational flights (I've just checked the link given for old RAF records, one of the ORB's, iirc for 56 Sqn states that 159 non-operational - ie. training, setup - flying hours were accumlated by the Squadron in the first week of August 1940 alone.

This roughly translates to 25-30 tons of avgas, for a single fighter Squadron, for a week, or about 100-120 tons per month if the first week of August was typical. How many Fighter Squadrons were there, 60 or so..? Works out at roughly 6-7000 tons per month for the entire comand. And at this point not a single operational sortie was flown yet..

It does not take into account bombers that consumed many times that of a fighter on a single sortie, or non operational flight. Its a good educated guess that a single bomber Squadron would consume about 5 times as much avgas than a fighter Squadron - and we know some Blenheim Squadrons were involved. How much fuel that would be, say 500 tons of avgas per month per Bomber Squadron? With just two Blenheim Squadrons we are at 1000 tons for non-operational flights. So we are 7-8000 tons with the two Blenheim Squadrons a month.

It does not account for requirements for engine manufacturers to test run engines etc. IIRC in 1944 the British aviation industry required some 2000 tons of 150 grade avgas per month for testing, run-in purposes. Engines have to run-in, and so do newly produced aircraft.. let's assume they needed the same amount in 1940m too. Engines have to be run in before they are safe for full power - the Germans iirc prescribed 15 hours for DB 605AM running time before full ratings could be used and there wouldn't be too much wear or risk of failure. Lets assume 15 hours for the RAF in 1940, which received about 500 new fighters a month, and probably twice the number of engines, at low-power consumption of 25 gallons/hour. That's 15x1000x25=ca. 1700 tons per month.. pretty close.

Hmm. We have 10 000 tons of 100 octane per month, assuming 60 Fighter Squadrons and 2 Blenheim Squadrons are using 100 octane and flying regular non-operational missions, and that the manufacturers also run-in their engines and planes properly instead of placing a 'Hope you get lucky' sticker on them upon delivery.

But at this point, not a single flight was made against the Luftwaffe using 100 octane fuel.

Trouble is, according to the consumption figures, for example in August 1940 an avarage of 10 000 tons of 100 octane was consumed for all the above purposes AND operational flights. There's simply not enough high octane fuel for all that for all Squadrons, hence why about 2/3s-3/4 of the consumption is 87 octane.

Of course the figures above are just a rough guess, but then again simply dividing fuel/hurri tank capacity is even rougher..

[winny]

This isn't a rough guess.

Wood and Dempster wrote in their book "The Narrow Margin":

As it turned out, aviation spirit was to prove no worry for the R.A.F. By July 11th, 1940, the day after the Battle of Britain opened, stocks of 100 octane petrol used in the Merlin engine stood at 343,000 tons. On October 10th, twenty-one days before the battle closed, and after 22,000 tons had been issued, stocks had risen to 424,000 tons. With other grades of aviation spirit total stock available on October 10th, 1940, was 666,000 tons. Oil reserves were 34,000 tons

[TheGrunch]

Sounds like that's an extreme case to me Kurf. I've looked at a few of them, but so far:

• 32 Squadron flew 60 and-a-half non-operational hours in the first week of August 1940, all of which were transfers to and from their forward base.
• 43 Squadron flew approximately 10 non-operational hours in the first week of August 1940, namely one transfer of six aircraft and their return and another transfer of seven aircraft, and three night practise flights.
• 54 Squadron flew approximately 106 non-operational hours of a huge variety of kinds (beware that one page of the ORB appears twice in a search for some reason).

There's no data for 56 Squadron in 1940 so I'm not sure which one you looked at. Anyway, won't be posting for a while, I hear the human body needs sleep.

[DC338]

Why would they use 100 octane fuel to run in a engine? If it was as scarce as you would have us believe surely they would have used 87oct for non operational purposes.

[madrebel]

because there was a conversion process that wasn't exactly trivial. further engine testing would be done at the levels the engine was expected to run at. you wouldn't test an engien you planned to run on 100 octance with 87 octance.

etc.