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

[335th_GRAthos]

I am sorry to jump into this discussion (I would prefer to burn in my burning Bf109 with a properly exploding central fuel tank than post in this thread, LOL) but I there is something that raised my curiocity:

I am looking at the numbers for the first year of war (Sep.'39 - Aug.'40)
Did anybody notice that the line Total for first year numbers make no sense?


Just wonder what the reason may be for this discrepancy.

~S~

[lane]

Originally Posted by 335th_GRAthos

I am looking at the numbers for the first year of war (Sep.'39 - Aug.'40)
Did anybody notice that the line Total for first year numbers make no sense?

Actually, the figures do add up and do make sense. The figures given are Monthly Average Consumption in thousands of tons.

For the 1st Year of War Sept.-Nov.'39, 16 is given as the monthly average, in thousands of tons, for that 3 months period.
With that understanding (16x3) + (14x3) + (23x3) + (10x3) + (26x3) = 267

[NZtyphoon]

Originally Posted by Crumpp

There is nothing in that technical bulletin that reads engines produced before March 1940 will have the modification.

Once again, if it was the standard fuel in service, the Operating Instructions would reflect that.

They would not continue to publish 87 Octane Operating limits with scant references to the ability to use 100 Octane. They would publish the 100 Octane limits and the 87 Octane would be a foot note or a supplemental instruction.

Where is the 100 Octane fuel at the airfields in March??

Read AP1509B again, properly it says:

"Newer engines will already have Mod.No.Merlin/136 embodied" it means what it says - new engines on the production lines - engines being built before the issue of this document - were already being fitted with the modifications. Older engines were also being modified.

Ever heard of wartime emergency modifications Eugene? - that means that normal, peacetime practices of leisurely annual maintenance are suspended in favour of ensuring that the latest modifications are embodied as quickly as possible in as many frontline units as possible.

A prime example:Starting on June 22 1940, in co-operation with de Havilland, the RAF mounted a crash program to ensure all of its frontline Merlin engine fighters were fitted with Constant Speed propellers

"Minutes of a meeting held on June 22nd with the Senior Technical Officer of Fighter Command relate that de Havillands would start the conversion at twelve Spitfire stations on Tuesday, June 25th (less than a week after the first test flight) and could provide twelve men capable of supervising a
station apiece; that the firm estimated that each squadron would take ten days to convert, and that all Spitfire squadrons could be completed by July 20th. The same minutes recorded that de Havillands had put in hand the production of 500 conversion sets, without contract cover, and that these would be coming out at the rate of 20 sets daily from June 24th, two days later. Supermarines were to be supplied with 20 sets per week from June 25th for aircraft coming off the production line; this would mean that two-thirds of the Spitfire production from that day onward would be "constant-speed...."

The conversion called for this constant-speed unit; a small shaft drive to connect it to the engine; four external engine oil pipes; a complete cockpit control with conduit, and detail parts. The airscrews did not have to be changed, having been designed for constant-speeding, but each had to be dismantled to move the index pins so as to give full pitch range....As Rolls-Royce could not, consistent with other heavy demands, produce the quill shafts for driving the c.s. units, or the engine oil pipes, the data were given to de Havillands and the facilities of the Gipsy engine factory were pressed into service to make over 1,000 sets of these parts. Everybody in the D.H. organisation who could contribute anything was transferred to this job....
The working times of the D.H. engineers during the ensuing weeks averaged about 105 to 110 hours (15 to 16 hours a day), with instances of 130 and up to 150 hours (19 to 21½ hours out of the 24). At some squadrons as many as four and five Spitfires were converted and test-flown in a day....
An entry dated Friday, August 2nd, records that by then, 44 days after the test flight of the first converted Spitfire, the production of conversion sets for all existing Spitfires (more than 800 sets, fulfilling the schedule of 20 a day) was complete, and they had therefore started producing for the Supermarine assembly line; De Havillands then had 400 Hurricane conversion sets in hand and expected to convert a total of 700, after which constant speed airscrews would be embodied in the new aircraft." (Before you dismiss this as "propaganda" this information is reproduced, almost word for word, in Morgan and Shacklady)

Wartime emergency: de Havilland worked overtime to manufacture, distribute and fit the CS conversion without a formal contract. In 44 days more than 800 propellers had been modified. Nothing like a wartime emergency to spur things along. And just to be clear, the same can apply to Merlins.

[Crumpp]

It doesn't mention +12 boost, it mentions that a unspecific higher boost than +6 1/4 can be used for take-off by operating the boost-control cut-out.

Let's see this unspecific boost!

The June 1940 Operating Instructions make no mention whatsoever for a higher boost at take off.

Read AP1509B again, properly it says:

It is being read properly. That is backed up by the logs.

Notice the engine is modified during Service Inspection:

engines being built before the issue of this document

LMAO!! It specifics which method of compliance will be used in production. It does not say a single thing about engines produced in the past!!

[Crumpp]

A prime example:Starting on June 22 1940, in co-operation with de Havilland, the RAF mounted a crash program to ensure all of its frontline Merlin engine fighters were fitted with Constant Speed propellers

Not a prime example, a very atypical example and heroic effort on the part of DeHavilland.

I am sure you would love to think this was normal.

a small shaft drive to connect it to the engine; four external engine oil pipes; a complete cockpit control with conduit, and detail parts.

Is extremely easy when compared to the technical level of producing a cylinder head.

[41Sqn_Banks]

Originally Posted by Crumpp

Let's see this unspecific boost!

As said, there is no fixed boost value specified. The possible boost value had to be determined individually before the take-off. I will dig out the pages ASAP.

The June 1940 Operating Instructions make no mention whatsoever for a higher boost at take off.

It does:

http://forum.1cpublishing.eu/attachm...1&d=1332111649
http://forum.1cpublishing.eu/attachm...3&d=1332111666

Well, as long as you are not doing a "long period take-off" ...

[NZtyphoon]

Originally Posted by Crumpp

Let's see this unspecific boost!

The June 1940 Operating Instructions make no mention whatsoever for a higher boost at take off.




It is being read properly. That is backed up by the logs.

Notice the engine is modified during Service Inspection:





LMAO!! It specifics which method of compliance will be used in production. It does not say a single thing about engines produced in the past!!

If you can't read properly that's your problem; the form says absolutely nothing about what type of inspection K9878 is undergoing, and the final sentence says END change to 100 Octane, referring to the fact that the entire unit has gone over to 100 Octane by 16 March 1940, PRE dating AP1590B which is dated 20 March 1940 and confirming what AP1590 says, that Merlin engines were already being modified.

[Crumpp]

If you can't read properly that's your problem;

I can read very well. The entry complies with the technical instructions found in A.P. 1590B/J.2W. It does not mean they are using 100 Octane fuel.

Once again, where is in any significant quantity of the fuel at the airfields in March 1940? Answer is there is no fuel in any significant quantity. Your own documentation shows that. Problem is you gamers are so bent on finding what you need that you do not see any other outcome.

Once again, if 100 Octane fuel is not listed as the primary Operating Instructions even in June 1940.

For example Operational Notes for Pilots on Merlin II and III. 2nd Edition January 1939.

I have the June 1940 version. All previous instructions are included in the later version AND any technical orders are incorporated. That is a fact.

If the later version of the Operating Instructions does not include it, you can bet the earlier did not.

That looks like somebodies photo-shop work.

[Crumpp]

Yes, just as the Total for 1st Yr. = 267 refers to 100 Octane and Other Grades.

Baloney.

Total is just that...TOTAL for the year.

In 1938 they had 100 Octane in quantity?? No they did not.

I don't think it has anything to do with the columns above it. Can you prove it does not?

[Crumpp]

Well, as long as you are not doing a "long period take-off" ...

It is not at take off. The +12lbs is allowable up to 1st Gear FTH.

Even in June 1940, 100 Octane has not eclipsed 87 Octane as the predominate fuel. The Pilots Operating Instructions would have published with the latest data. This is reflected in Table II as no significant quantities of 100 Octane exist at the airfields.

If the technical instructions were published in March then that gives them 4 months until the update is published.

The Operating Notes still list 6 1/2lbs as the 5 minute all out emergency setting for the engine as the most common configuration.

The limiting operational conditions does not make any mention at all of 100 Octane.

Frankly, it is very difficult to follow this discussion ...

For me it is easier to understand articles that have reviewed the literature and where I can draw conclusions:


Palucka, Tim. The Wizard of Octane. American Heritage of Invention & Technology, 20. 3 (Winter 2005): 36-45.
Resume: IF, AS THE DUKE OF WELLINGTON IS SUPPOSED TO HAVE SAID, the Battle of Waterloo was won on the playing fields of Eton, then one can assert with equal justice that the Battle of Britain was won at the Stevens Hotel, in Chicago, on November 18, 1938. It was there, at the annual meeting of the American Petroleum Institute, that Arthur E. Pew, vice president and head of research of the Sun Oil Company, described his company's extraordinary new catalytic refining process. Using it, he said, Sun was turning what was normally considered a waste product into gasoline-and not just ordinary gasoline, but a highoctane product that could fuel the era's most advanced airplanes. That process would make a crucial difference in mid-1940, when the Royal Air Force started filling its Spitfires and Hurricanes with 100-octane gasoline imported from the United States instead of the 87 octane it had formerly used. Luftwaffe pilots couldn't believe they were facing the same planes they had fought successfully over France a few months before. The planes were the same, but the fuel wasn't. In his 1943 book The Amazing Petroleum Industry, V. A. Kalichevsky of the Socony-Vacuum Oil Company explained what high-octane gasoline meant to Britain: "It is an established fact that a difference of only 13 points in octane number made possible the defeat of the Luftwaffe by the R.A.F. in the fall of 1940. This difference, slight as it seems, is sufficient to give a plane the vital `edge' in altitude, rate of climb and maneuverability that spells the difference between defeat and victory."

Bailey, Gavin. The Narrow Margin of Criticality: The Question of the Supply of 100-Octane Fuel in the Battle of Britain. English Historical Review; Apr2008, Vol. 123 Issue 501, p395-411, 17p, 3 Charts
Resume: The article focuses on the supply of 100-octane fuel during the battle of Great Britain. Aviation historians have advanced the supply of 100-octane aviation fuel as critical American contribution to the battle. A study of the contemporary Air Ministry records in the Public Record Office shows that this assertion can be challenged. The challenge can be made on the grounds of the aircraft performance benefit involved, as showed by contemporary Royal Air Force (RAF) testing, and on the national origin attributed to 100-octane fuel supplies. The records reveal that contrary to the assertion of aviation history, the supply of 100-octane fuel to RAF in time for use in the battle must be attributed to pre-war British planning and investment on the rearmament period of the late nineteen-thirties.

My only conclusion is that only in this forum I read the statement that 100-octane did not have a role in the Battle of Britain (statement supported by the devs? ) ... and not supported in a peer-reviewed article...

The answer to the question of the extent of 100 Octane all depends on when you place the dates of the Battle of Britain. September 15th 1940 as an end date is a post war and has nothing to do with Fighter Command's actions in context.

The RAF official history takes the battle out to the end of October 1940 when German Daylight raids ceased. Other histories end the battle in December 1940:

On 9th September 1940, No 92 Squadron, with Geoffrey Wellum now operational, was moved back to 11 Group, to Biggin Hill, one of the most famous Fighter Stations, and to the Sector that experienced the most ferocious fighting during the Battle of Britain. Although they were entering the fray towards the end of the Battle, by December 1940, No 92 Squadron would claim 127 enemy aircraft destroyed.

http://www.raf.mod.uk/bbmf/theaircra...eoffwellum.cfm

The German's end the battle in May 1941 when their bombers where transferred to the east and offensive operations against England were called off.