The use of 100 Octane Fuel in the RAF pt 2

[NZTyphoon]

More information: The Battle of Britain by T.C.G. James shows 51,364 sorties, day night from July 10 through Sept 30; some of the most intensive combat took place between these dates.

51,364 divided by 13 weeks = 4,280 sorties = 611 sorties daily average: well within my rough calculations. How good does 25% of Fighter Command aircraft using 100 octane fuel look now?

 

[Juha]

In principle the answer should be in already published books. I'd not be surprised if there are some official or semi-official histories on RAF supply and maintenance organizations and on British fuel policies during WWII. One possible source for the answer is that mentioned in Gavin Bailey's already mentioned article in note 13, namely D.J. Payton-Smith, Oil. Study of War-Time Policy and Administration (London 1971).

But as NZTyphoon's rough calculations shows all FC combat sorties flown during the BoB could have easily covered with 100oct used during that time and still a great deal left for training at fighter sqns, transfer flights, test flights and engine testing.

After 30. Sept things seems to have cool down a bit, From Hooton's Eagle in Flames, Table 2, FC flew Sep 23-29 4,825 defensive sorties, it had flew more per week only twice after 1st July, but Sep 30 – Oct 6 it made only 1,782 defensive sorties.

Juha

 

[NZTyphoon]

Continuing; because the fuel capacities of the three main Fighter Command fighters varied it would be worth revising the mathmatics:
B P Defiant =: 97 gallons
Hurricane = : 90
Spitfire = : 85
Total = 272 divide by 3 = 90.7 gallons

315 gallons per ton of 100 octane divided by 90.7 = 3.47
10,000 tons = 34,700 Combined Fighter fuel loads
14,000 tons = 48,450 CFl
17,000 tons = 58,990 CFl

41,000 tons =142,140 sorties divide by 22 weeks = 6,461 divide by 7 days = 923 CFl per day

Other variables: Some Blenheim Bomber units also used 100 octane.
Presuming Spitfire PR unit also used 100 octane.

One possible source for the answer is that mentioned in Gavin Bailey's already mentioned article in note 13, namely D.J. Payton-Smith, Oil. Study of War-Time Policy and Administration (London 1971).

Yep, this is my source for the fuel weight; the book is full of excellent details on 100 octane aviation fuel.

After 30. Sept things seems to have cool down a bit, From Hooton's Eagle in Flames, Table 2, FC flew Sep 23-29 4,825 defensive sorties, it had flew more per week only twice after 1st July, but Sep 30 – Oct 6 it made only 1,782 defensive sorties.

So, 4,825 divide by 7 = 689 sorties per day
1,782 divide by 7 = 255 (rounded up)

 

[Mike Williams]

Hi Juha:

The Royal Air Force – History Section on-line is rather straightforward about the whole business.

 

[Juha]

Hello Mike
Yes, You, I and others have already given many books and authorative net sources which mentioned as a fact that FC had converted to 100 oct before the BoB began, but that have not satisfied all participants of these discussions, so I only gave some hits from where the doubters may look more detailed info.

And thanks a lot for those numerous documents you have published here and on your own sites.

Very much appreciated!

Juha

 

[Kurfürst]

Continuing; because the fuel capacities of the three main Fighter Command fighters varied it would be worth revising the mathmatics:
B P Defiant =: 97 gallons
Hurricane = : 90
Spitfire = : 85
Total = 272 divide by 3 = 90.7 gallons

315 gallons per ton of 100 octane divided by 90.7 = 3.47
10,000 tons = 34,700 Combined Fighter fuel loads
14,000 tons = 48,450 CFl
17,000 tons = 58,990 CFl

41,000 tons =142,140 sorties divide by 22 weeks = 6,461 divide by 7 days = 923 CFl per day

Other variables: Some Blenheim Bomber units also used 100 octane.
Presuming Spitfire PR unit also used 100 octane.

Interesting calculation, but it does not address non-operational flights (training, excercises, transfers etc.) by combat units.

To give some idea of the extent of non-operational flying, the German Luftwaffe in the four months of the Daylight phase of BoB (July-October) wrote off 404 aircraft on operations, but without enemy interference, and further 280 aircraft outside operations (training, familiarisation, transfer etc.); 349 aircraft were damaged on operations, but not due to Enemy Action, while 301 aircraft were damaged during non-operational sorties.


In other words, some 40% of the write offs and some 46% of the varying degree of damage occured during flights which were not directly related to the battle.

Assuming aircraft were wrecked by pilots in a similiar rate during operations and outside the scope of operations during training and practice, it would also point to that operational flying time, ie. combat sorties accounted for only about 50-60% of the total flying time.

The calculations by NZTyphoon only take account the actual combat sorties, but ignore the training flights during which the more seasoned pilots initiated fresh replacements into combat flying, and integrated them into the unit. Given that according to the documentation presented so far, stations either had 87 octane fuel or 100 octane fuel, but not both, this kind of non-operational flying has to be factored into consumption.

Bombers, like the Blenheim would of course consume far greater amount of fuel than single engined fighters. The tankage for the Bristol Blenheim, one type we know to have been marked for 100 octane fuel use, had an internal tankage of 278 gallons, a bit more than 3 1/4 times that of a single engined fighter.

Further of interest is the Spitfire I pilot notes - it seems to specify to seperate boost limits, one when the aircraft is using 87 octane fuel, and a seperate one when the aircraft is fueled with 100 octane fuel.

 

[Glider]

If you are going down this route Kurfurst the first thing we need to know is how many is 25%. How many aircraft do you think managed to burn through 10,000 tons of fuel a month.

Before I address the question of the Pilots Notes can you tell me when they were prepared?

But before then, can we ask when you are going to reply to some of the questions being asked of yourself.

 

[Kurfürst]

If you are going down this route Kurfurst the first thing we need to know is how many is 25%.

One in four, twenty five in hundred, about 125 in 500.

How many aircraft do you think managed to burn through 10,000 tons of fuel a month.

Well, that is a more practical question. In late 1944, the Allied High Command noted that the monthly requirement of 150 grade fuel for 25 Sqnds of Sptifire IX, 5 Sqns of Spitfire XVI and 5 Sqns of Spitfire XIVs was 15,000 tons - presumably this included the requirements for non-operational flying.

The rest is a simple. If 35 Spitfire Squadrons are said to require 15 000 tons, then 2/3s of this, 10 000 tons, should be sufficient for 24 Squadrons.

But to show what interesting results can be arrived at with a bit of calculation, lets examine the same calculation method for the Luftwaffe.

In August, 1940, the Luftwaffe aviation gasoline consumption, was appx. 100 000 (one hundred thousend) tons.

Each Bf 109E took on 400 liters of fuel, or 296 kg (make it 300 kg, or 0.3 tons).

Thus, in August 1940, the Luftwaffe had sufficient fuel for over 330 000 Bf 109E sorties. Very impressive, but of course this ignores the requirements of bomber units, training flights, transfer flights, requirements of the engine industry for testing engines, test flights, non-operational flights, fuel lost in accidents and fuel lost due to enemy bombing (Manston anyone..?) et cetera.

Before I address the question of the Pilots Notes can you tell me when they were prepared?

Please see the Spitfire II pilots notes from July 1940, showing similiar limitations when 87 octane fuel is used (a PDF version can be found at Zeno's Warbirds website).

But before then, can we ask when you are going to reply to some of the questions being asked of yourself.

I can only answer specific questions.Unfortunately, I will be absent for the rest of week due to a trip to Steyrmark.

I believe you are already aware what the Australian papers say.

 

[Hop]

In late 1944, the Allied High Command noted that the monthly requirement of 150 grade fuel for 25 Sqnds of Sptifire IX, 5 Sqns of Spitfire XVI and 5 Sqns of Spitfire XIVs was 15,000 tons - presumably this included the requirements for non-operational flying.

No, they didn't. The requirements for 2nd TAF AF were 15,000 tons. That included not just the Spitfire squadrons you mention, but also 20+ (iirc) Typhoon squadrons, along with Mosquito and Tempest squadrons.

The rest is a simple. If 35 Spitfire Squadrons are said to require 15 000 tons, then 2/3s of this, 10 000 tons, should be sufficient for 24 Squadrons.

Apart from the fact 15,000 tons was also for the Typhoon, Tempest, Mosquito etc squadrons, your figures are flawed in that drop tanks were commonly used in 1944, and not available in 1940. Maximum fuel for a 1940 Spitfire was 85 gallons, in 1944 it was 175 (or more) gallons for the Spitfire IX and over200 for the Spitfire XIV.

 

[Juha]

And on Kurfürst August 40 calculations
and RAF also burned much 87 oct, BC, CC and TC were still using 87 oct, and how big were fuel loads of Sunderland, Hudson and Whitley for ex? So Kurfürst is simply comparing apples and oranges.
BTW, have you info on how much Bf 109 units used fuel in August 40? that would be more relevant on FC comsumption.
Juha

 

[Juha]

Just to show how futile it is to compare consumption of a whole airforce to consumption of a fighter component of an air force. Normal fuel load of FW 200C-3 Condor, it is the earliest subtype on which I have info, was 8060litre, that is more than 20 times of the normal fuel load of Bf 109E. Also how the sorties divide between fighters and other types are usually different in attacking force than in defending force, for ex LW flew many night bombing missions during the BoB, and they were purely bomber missions.

Juha

 

[Glider]

Sticking to the 1940 BOB the sums seem to be

10,000 tons equals 34,700 flights assuming that all the flights use up all the fuel.

Kurfurst believes that the RAF only had 150 fighters using the fuel.

So each fighter flew of average 231 flights a month, around 8 flights a day. So each fighter flew for 16 hours a day, simple really. All you have to do is ignore any maintanence, night time, combat repairs, bad weather. Don't know why I didn't think of it mysef.

Now for some specific questions
1) Have you any book that supports your version
2) Have you any official reports that support your version
3) Have you the Australian Paper that neither you or I have ever seen (selected quotes are not close)
4) Have you any action reports that support your story

Re the Pilots Notes we have an interesting situation. I also have a copy of the Spit II Pilots notes dated July 1940 and they only mention 100 Octane. Its odd as I would expect the Pilots notes for around May 1941 to mention both fuels as by that time they were being passed to training units that didn't have 100 Octane.

 

[NZTyphoon]

Kurfurst says

The calculations by NZTyphoon only take account the actual combat sorties, but ignore the training flights during which the more seasoned pilots initiated fresh replacements into combat flying, and integrated them into the unit. Given that according to the documentation presented so far, stations either had 87 octane fuel or 100 octane fuel, but not both, this kind of non-operational flying has to be factored into consumption.

Kurfurst knows full well I said:

87 Octane: Mike William's table also shows that consumption of 87 octane was far higher than 100. This is easily accounted for because there were aircraft and second-line operations still using 87 octane fuel: heavy bombers, Coastal Command aircraft, Army Co-operation Command, aircraft deliveries, training etc.

If Kurfurst is right and only 25% of stations were supplied with 100 octane then the consumption rate would read more like:

June-Aug = 2,500 tons
Sept = 3,500 tons
Oct = 4,250

So where was the rest of the fuel consumed? Carrier pigeons, perhaps?

Further of interest is the Spitfire I pilot notes - it seems to specify to seperate boost limits, one when the aircraft is using 87 octane fuel, and a seperate one when the aircraft is fueled with 100 octane fuel.

A clear indication that aircraft engaged in secondary duties (including training) were still able to use 87 octane fuel, which is yet another reason for 87 octane consumption being greater. This would include factory test flights etc.

So far Kurfurst has not explained why 75% of Fighter Command aircraft were still using 87 octane fuel when the consumption rate of 100 octane still more than covers the average sortie rate, ie:

41,000 tons =142,140 sorties divide by 22 weeks = 6,461 divide by 7 days = 923 CFl per day

when we know that James shows 51, 364 defensive sorties day and night between 10 July and 30 September;

51,364 divided by 13 weeks = 4,280 sorties = 611 sorties daily average: well within my rough calculations.

Hooton:

Eagle in Flames, Table 2, FC flew Sep 23-29 4,825 defensive sorties, it had flew more per week only twice after 1st July, but Sep 30 – Oct 6 it made only 1,782 defensive sorties.
So, 4,825 divide by 7 = 689 sorties per day
1,782 divide by 7 = 255 (rounded up)

More than enough to allow for training flights with squadrons.

Bombers, like the Blenheim would of course consume far greater amount of fuel than single engined fighters. The tankage for the Bristol Blenheim, one type we know to have been marked for 100 octane fuel use, had an internal tankage of 278 gallons, a bit more than 3 1/4 times that of a single engined fighter.

According to Warner The Bristol Blenheim: A Complete History: Amazon.co.uk: Graham Warner: Books
Blenheim units were using 87 octane fuel in their inner fuel tanks and 100 octane in their outer fuel tanks during this time, leading to some potentially nasty complications for the pilot. Pages 98 to 101

Well, that is a more practical question. In late 1944, the Allied High Command noted that the monthly requirement of 150 grade fuel for 25 Sqnds of Sptifire IX, 5 Sqns of Spitfire XVI and 5 Sqns of Spitfire XIVs was 15,000 tons - presumably this included the requirements for non-operational flying.

More powerful engines? Larger fuel capacity? Use of Drop tanks? Perhaps these have something to do with a need for more fuel than in 1940...

 

[Glider]

Can I suggest that people come up with specific questions for Kurfurst as he has said that he will awnser them? Keep them as short as possible to give him a chance.

 

[Shortround6]

It is quite possiable that training flights, if conducted from airfields out of the general combat zone, could have been done with 87 octane fuel. After all each use of the extra boost (higher than 6lb) that the 100 octane fuel allowed was supposed to be noted in the aircraft log book and maintence schedules modified accordingly.

I would also note that the fule consumption of the BoB Spitfire might be just a bit less than the fuel consumption of a late war Spitfire. After all, just how much fuel is needed for about 1000hp if the pilot doesn't use the extra boost vrs the fuel consumption of the later 2 stage engines? According to the Manuals for the MK II and the MK ( t the Zeno's sight the later model Spit might use anywhere from just a few gallons an hour more to over 30 gallons and hour mor depending on throttle setting.
This is for missions of the same duration, as has been notted in other posts the fact that many late war missions used drop ranks seriously alters the comparison.

 

[Glider]

Re the Pilots Notes we have an interesting situation. I also have a copy of the Spit II Pilots notes dated July 1940 and they only mention 100 Octane. Its odd as I would expect the Pilots notes for around May 1941 to mention both fuels as by that time they were being passed to training units that didn't have 100 Octane.

I have been looking at the two different copies of the Pilots Notes and the one on Zenos warbirds site as quoted by Kurfurst cannot be for June 1940. I say this as in section 35 page 9 on the firing controls it gives a description of the controls for the IIA which had 8 x LMG and the IIB with 2 x 20mm and 4 x LMG. In June 1940 the IIB wasn't even a glimmer on the horizon.
The original one only mentions the LMG and doesn't refer to it as a IIA only a II which again is correct.

Its only fair to add that Zeno's is dated June 1940 so no blame can be given to Kurfurst for his confusion.

 

[Milosh]

In August, 1940, the Luftwaffe aviation gasoline consumption, was appx. 100 000 (one hundred thousend) tons.

Where is the primary source proof for this 100,000 tons of consumption?

 

[Glider]

One in four, twenty five in hundred, about 125 in 500.

Specific Question
Are you saying that the RAF had 18 squadrons of fighters on 100 Octane or about 125 fighters which equates to about 6 squadrons.
Or of course the 34 squadrons for which we have combat reports for could have shared them out, four each!!!

 

[NZTyphoon]

I have been looking at the two different copies of the Pilots Notes and the one on Zenos warbirds site as quoted by Kurfurst cannot be for June 1940. I say this as in section 35 page 9 on the firing controls it gives a description of the controls for the IIA which had 8 x LMG and the IIB with 2 x 20mm and 4 x LMG. In June 1940 the IIB wasn't even a glimmer on the horizon.
The original one only mentions the LMG and doesn't refer to it as a IIA only a II which again is correct.

Its only fair to add that Zeno's is dated June 1940 so no blame can be given to Kurfurst for his confusion.

Some pilot's notes I have were updated using Amendment Lists which were "...issued as necessary and will be gummed for affixing to the inside back cover of these notes." These were like postit notes and covered amendments which were to be made to the pilot's notes - the pilot pasted them into the book where needed. For example I have a copy of the PN for the Corsair I - IV: on one page (17 PART II HANDLING INSTRUCTIONS)
which has A.L.4 Part II pasted just below the main heading. A.L.4 reads "Note. - On aircraft KD868 and subsequent, oxygen should be used at all times during flight."

I don't know whether these were in use in 1941 but it is possible that the notes used by Zenos had not had any amendment lists added. It is also possible that earlier issues of the Spitfire II notes were not amended or updated until the notes were reprinted.

 

[Glider]

Some pilot's notes I have were updated using Amendment Lists which were "...issued as necessary and will be gummed for affixing to the inside back cover of these notes." These were like postit notes and covered amendments which were to be made to the pilot's notes - the pilot pasted them into the book where needed. For example I have a copy of the PN for the Corsair I - IV: on one page (17 PART II HANDLING INSTRUCTIONS)
which has A.L.4 Part II pasted just below the main heading. A.L.4 reads "Note. - On aircraft KD868 and subsequent, oxygen should be used at all times during flight."

I don't know whether these were in use in 1941 but it is possible that the notes used by Zenos had not had any amendment lists added. It is also possible that earlier issues of the Spitfire II notes were not amended or updated until the notes were reprinted.

That is also the case for my Hunters notes which have gummed in updates with the changes logged at the start but that isn't the case for these examples. The layout and in some cases level of detail are totally different.