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

[NZtyphoon]

Originally Posted by KG26_Alpha

Probably because they never had the good fortune to make a combat report.

The ridiculous arguments are valid of course, as everyone has thier opinion of how it should be in CoD.

Actually not a "ridiculous argument" because detonation would have been a serious possibility had pilots tried to use +12 lbs override boost with 87 Octane, which did not have the anti-knock properties of 100 Octane. The engine might not have failed right away but it would certainly have been damaged and the pilot given a boot up the backside by the mechanics.

This is one of the absurdities of Crumpp's argument that somehow most of the Merlins used in frontline fighters during the Battle of Britain were restricted to using 87 Octane fuel - Hugh Dowding would not have been complaining to all Groups, Stations and Squadrons about pilots overusing +12 lbs boost, he would have been reminding pilots to never use +12 lbs boost under any circumstances, unless they belonged to the select few units permitted to use 100 Octane and +12 lbs boost.

[Seadog]

Originally Posted by Skoshi Tiger

Could that be that when the pilots 'pulled the plug' the boost was still at a level before detonation occurs.

One of the pilot stories (show in this thread) before did mention black smoke comming from the exhaust and the plane vibrating a lot. Sound like he was pushing it a bit too far. But none of the others mentioned it.

Prior to the 12lb mod/100 octane, if you pulled the boost override you would get 18lb boost up to about 5000ft, 16 lb boost to about 7500ft, 12 lb boost to about 11000ft and 7lb boost at ~17500ft. 7lb was the maximum permissible with 87 octane so the altitude range that it would be beneficial is very restricted; below that altitude power would be reduced because detonation would occur, engine would no longer run smoothly and the engine would quickly fail altogther. The only way that the boost override would be beneficial would be if it had a mod to restrict the additional boost to ~7lb, but of course this would only result in a very modest power increase, and this mod was never done.

AFAIK, the 109E was limited to 7lb boost as well (1.4 ATA) when using 87 octane.

[TomcatViP]

That's a poor argument.

The DB of the 109 had far more cylinder volume than the Merlin.

RR did ran the Boost horse simply because that was the way they had to go against the DB. Latter in the war they might also hve understood the huge advantage they had in therm materials of quality.

My old 2L Swedish SAAB engine had as much power than an average 5+L US V8 without supercharger .... But a 2+bar boost level.

I hope you will understand that way

The boost level in German plane is more linked to the lack of Nickel in their engine material. They had to build thicker internal surface and build bigger eng in order to run their eng at a lower temperature.

This has nothing to do with a comparison with the Merlin.

Interestingly, if we do compare the application of aviation engine in tanks, we might show that reciprocally, the bigger German eng where more reliable in that application. But honestly this is pure speculation.

[KG26_Alpha]

Originally Posted by NZtyphoon

Actually not a "ridiculous argument"

It was with reference to Klems post

I said they were valid.

[camber]

Originally Posted by Seadog

Prior to the 12lb mod/100 octane, if you pulled the boost override you would get 18lb boost up to about 5000ft, 16 lb boost to about 7500ft, 12 lb boost to about 11000ft and 7lb boost at ~17500ft. 7lb was the maximum permissible with 87 octane so the altitude range that it would be beneficial is very restricted; below that altitude power would be reduced because detonation would occur, engine would no longer run smoothly and the engine would quickly fail altogther. The only way that the boost override would be beneficial would be if it had a mod to restrict the additional boost to ~7lb, but of course this would only result in a very modest power increase, and this mod was never done.

AFAIK, the 109E was limited to 7lb boost as well (1.4 ATA) when using 87 octane.

Exactly right as I understand it Seadog. Although I would add one proviso...the boosts you mention are at maximum throttle. There would be nothing to stop a pilot pulling the boost override and adjusting his throttle handle (which is now directly linked to the actual throttle valve) to get a desired boost. So the pilot could possibly get some more performance, say by adjusting to +7psi where before he was stuck on +61/4 psi. Boost is no longer controlled, so if he dived to a lower altitude the boost will rise on it's own and possibly damage the engine. No wonder it was not an approved way of getting combat power on 87 octane...the gain was probably modest, the risk of misuse large. Whether or not it was used unofficially is open to conjecture.

Good point about the 109E, 1.45 ata is about +6.6psi boost. So I disagree Tomcat, it appears on 87 octane both the DB601 and Merlin were restricted by the maximum usable boost avoiding fuel predetonation..not by engine design paramaters or materials.

I am still intrigued by the engine test bed report apparently stating figures of 12500 feet, ~10.5psi boost and 1300bhp. But whether these are calculated figures, an engine tested with 100 octane, whether intake pressure was actually set to 12500 ft equivalent etc. does not appear to be available. Interesting to know what would happen if in a 87 octane Spit pre BCCO mod if you pulled the cutout and progressively raised boost above 6 1/4 psi. At what boost points would:
1) predetonation be detected
2) bhp start to decrease with increased boost (due to predetonation)
3) Significant loss of engine life occur
4) High risk of rapid engine failure.

[41Sqn_Banks]

Originally Posted by Crumpp

Where does it clearly say that?

"it is emphasized that the high boost for emergency may only be employed with 100 octane fuel"

It does not, the General Operating Notes clearly say he can use it.

http://forum.1cpublishing.eu/attachm...8&d=1337207418

"Clearly say ..." we obviously have a different understanding what clearly means.

That's what I call clearly:
January 1939: http://forum.1cpublishing.eu/attachm...0&d=1334682385
"100 octane must be used"

March 1940: http://www.spitfireperformance.com/ap1590b.jpg
"100 octane must be used"

April 1940: http://www.wwiiaircraftperformance.o...erlin3-pg6.jpg
"100 octane ... must be used"

November 1940: http://forum.1cpublishing.eu/attachm...5&d=1337196053
"only be employed with 100 octane fuel"

June 1941: http://forum.1cpublishing.eu/attachm...0&d=1334727256
http://forum.1cpublishing.eu/attachm...1&d=1334727263
"only of 100 octane fuel is in the tanks"

[NZtyphoon]

Originally Posted by Kurfürst

Well let's see now the reality.

Tanker losses to all causes, I have gathered a total of 78(!!) tankers were sunk by mine, U-boot (typically), aircraft and raiders, between September 1939 and November 1940. About 90% of them were British, though there are a couple of Swedish, Dutch, French etc. tankers

I have them by name, date, cause of loss, route, cargo, tonnage and so on. For example indeed one tanker that went through Halifax, Inverdagle (9456 tons) was sunk by mines laid by the submarine U 34, with 12 500 tons of avgas - about a month worth consumption of 100 octane, though I am not sure what grade it actually carried - on the 16 January 1940....

Alltogether 558,260 GRT of tankers went to Davy Jones locker, by the end of November 1940, along with 385,957 tons of oil product. Half of that, ca. 243 000 GRT worth of tankers were sunk by the end May 1940.

Fuel oil was the greatest loss, 116 000 tons of it went down with tankers (luckily, no green peace back then). Avgas seems quite untypical as a load, but in the end it didn't really matter, because if a tanker sunk with diesel oil, or even empty, the next one had to haul about its cargo again.

Tanker losses were serious, unfortunately.

33rd Weekly Report Oil Position 23 April 1940 showing out of 242 Norwegian tankers 119 had been bought under Allied control, with 18 heading to Allied ports and the other 93 in neutral ports, or heading into neutral ports, the 119 brought under Allied control more than making up for the total tanker loss for the entire war period September 1939 to November 1940:

Originally Posted by Kurfürst

So disprove the statement of Pips. Since you misrepresent his position, I put it forward to you in its originality:

This is from a researcher, researching another subject (Dutch East Indies Fuel levels prior to the Japanese Invasion) at the Australian War Memorial Archives, from a document, copied to the Australian Military Commission in England in February 1941, by Roll Royce to Lord Beaverbrook outlining past, current and proposed changes to the Merlin; and factors that affect it's performance. It was a collection of lose-leaf typed pages, included as an addendum in a report titled Fuel Supplies to The British Empire And It's Commonwealth; Outlook, Ramifications and Projections For The Prosecution Of The War.

The reason why it is included amongst AWM papers is because the Australian Government at that time was protesting vigoriously about the continued supply of lower grade 87 octane fuel when it too wanted 100 octane for the RAAF. McFarland, Pugh, Hart, Perret, Lumsden and even Churchill have all quoted parts from the report.

The first bulk shipment of 100 octane fuel had arrived in Britain in June 1939 from the Esso refinery in Aruba. This and subsequent tanker shipments from Aruba, Curacao and the USA were stockpiled while the RAF continued to operate on 87 octane petrol. Having secured what were considered reasonably sufficient quantities of 100 octane, Fighter Command began converting its engines to this standard in March 1940, allowing boost (manifold) pressures to be raised without the risk of detonation in the cylinders. This initial increase in maximum boost from 6 lb to 9 lb delivered a useful power growth of around 130hp at the rated altitude.

By the time of the invasion of the Low Countries by Germany in May 1940 the RAF had converted approximately 25 % of it's total fighter force to 100 octane fuel use. The subsequent escalation in air activity and demands placed upon Fighter Command over the next two months put great strain on both the 100 octane fuel stockpiles and aircraft modified to use the fuel. Against the backdrop of total war the RAF found that it's reserves of 100 octane fuel was well below the level considered necessary for widespread use, for any sustained length of time.

Two actions were immediately undertaken by the British War Cabinet in May to resolve the looming crisis. Firstly 87 octane fuel was deemed the primary fuel source to be used until further supplies could be discovered and delivered in sufficient quantities to allow the Merlin conversions to again take place. Those existing fighters already so converted (approximately 125) would continue to use what supplies of 100 octane were available, but all other fighters that had not been modified to continue with the use of 87 octane (of which there was more than adequate supply). The second action was for the British Government to contract the Shell Oil Refining Company to assist the British-controlled Iraqi Petroleum Company at Kirkuk to produce 100 octane fuel. This arrangement proved quite successful as production was quickly converted to 100 octane fuel.

The first Middle East shipment of 100 octane fuel arrived in Portsmouth on 12th August, with a further two deliveries in September and four in October. Although too late to allow widespread conversion for the use of the fuel the deliveries did ensure that from this point on Britain would not be lacking in 100 octane fuel levels. With the newfound supply RAF Fighter Command again embarked upon a Merlin II and III conversion to 100 octane use from late September, finally achieving 100% conversion of it's fighter force by the end of November in 1940.

"The subsequent escalation in air activity and demands placed upon Fighter Command over the next two months put great strain on both the 100 octane fuel stockpiles and aircraft modified to use the fuel"

1st Monthly Oil Position Report July 1940 ( Dated 6 August 1940)



Table from 1st Monthly Oil Report July 1940: Consumption: Read in conjunction with attachment 1:


Table from 1st Monthly Report July 1940; Stocks dropped by 15,000 tons April-May then increased by 12,000 tons to June:


Table from 33rd Weekly Oil Position Report 23 April 1940 showing 100 Octane fuel being stockpiled in the UK and overseas; "West of Suez" - France springs to mind.




Oil Position 5th Monthly Report November 1940:

[Crumpp]

Could that be that when the pilots 'pulled the plug' the boost was still at a level before detonation occurs.

Absolutely. They could have easily "pulled the plug" to achieve any boost they desired once the override was on.

"The subsequent escalation in air activity and demands placed upon Fighter Command over the next two months put great strain on both the 100 octane fuel stockpiles and aircraft modified to use the fuel"

Why don't they just say "all aircraft" instead of specifying just modified ones? All aircraft should be modified, right??

Table from 33rd Weekly Oil Position Report 23 April 1940 showing 100 Octane fuel being stockpiled overseas "West of Suez" - France springs to mind.

What is the asterisk note and the bottom about? Can you show the whole document?

The last time you started talking about stockpiles in France, it was in reference to a report projecting fuel stocks for future war.

Now your saying West of the Suez means France? Heck, it could mean Cleveland Ohio or maybe Hornchurch, too?

Considering that they were shipping troops to begin the Desert War I would imagine that is a future projection of their needs for aviation fuel. The first British troops went on the offensive on 11 June 1940 in North Africa.

[Crumpp]

"Clearly say ..." we obviously have a different understanding what clearly means.

It is right there, you highlighted it. The RAE opened the can of worms and gave their pilots license to violate the airworthiness of the aircraft:

Camber says:
There would be nothing to stop a pilot pulling the boost override and adjusting his throttle handle

Exactly. We also see two things the give insight into the state of mind of Fighter Command.

1. First from the fuel committee meetings the confusion on exactly what must be done to modify the engine. I don't know if you have taken Organizational Behavior in college but if there is confusion at the top of any organization, there is even more confusion at the bottom of it. Even with a clear vision at the top, it is a process to get that vision communicated and enacted at the bottom. The larger the organization, the longer the lag time and more difficult the process.

Secondly, we see Dowding's memo warning the pilots about the dangers of overboosting. You can bet Dowding did not sit around wondering what to do that day and just decided to fill his time writing a memo about overboosting destroying engines. "Squeaky wheel gets the grease", that memo came about because his maintenance and logistics people complained if it does not change there could be consequences that effect their ability to keep his planes flying.

That memo was printed because they felt was a problem with pilots "pulling the plug" before they properly balanced the risk.

[NZtyphoon]

Originally Posted by Crumpp

Why don't they just say "all aircraft" instead of specifying just modified ones? All aircraft should be modified, right??

This is one of the amazing inconsistencies about the Pips memo - according to this

By the time of the invasion of the Low Countries by Germany in May 1940 the RAF had converted approximately 25 % of it's total fighter force to 100 octane fuel use. The subsequent escalation in air activity and demands placed upon Fighter Command over the next two months put great strain on both the 100 octane fuel stockpiles and aircraft modified to use the fuel.

a mere 25% of the fighter force - supposedly 125 fighters - caused such a high strain on 100 octane fuel supplies that all further conversions were stopped and the RAF ordered that 87 Octane fuel be the primary fuel.

Question is if 125 fighters can put a huge strain on reserves of 263,000 tons of 100 Octane fuel (as of 18 April - see Table 33rd Weekly Oil Report) , what kind of a strain are the other 475 fighters, plus all the other aircraft using 87 Octane going to put on the reserves of 327,000 tons of "Other grades" of fuel? This hasn't to my knowledge been commented on before, but it is patently ridiculous to state that 125 fighters put any kind of a strain on 263,000 tons of 100 Octane: then, on top of that, to insist the RAF decided to put even greater strain on the "Other Grades" stockpile beggers belief.

Originally Posted by Crumpp

What is the asterisk note and the bottom about? Can you show the whole document?

Take a look at the extreme RH side of table i (b) Weeks' supplys showing how long it was estimated the current stocks would last based on average consumption, and assuming no more supplies were shipped in.

This is the rest of the document:

Originally Posted by Crumpp

The last time you started talking about stockpiles in France, it was in reference to a report projecting fuel stocks for future war.

Nonsense, the documents showed quite clearly how much fuel was already in France (attached) and other papers in the series showed the projected requirements.

Originally Posted by Crumpp

Now your saying West of the Suez means France? Heck, it could mean Cleveland Ohio or maybe Hornchurch, too?

Yeah right, use a bit of common sense because in April 1940 the Italians had yet to declare war, so the Mediterranean and Africa were not war theatres, nor were there any aircraft using 100 octane fuel based in those areas and, contrary to your unproven speculation, fighters based in France were using 100 octane fuel, while some Hurricanes had been active in Norway. Not forgetting the Blenheim IVs of 2 Group and the BEF.

Originally Posted by Crumpp

Considering that they were shipping troops to begin the Desert War I would imagine that is a future projection of their needs for aviation fuel. The first British troops went on the offensive on 11 June 1940 in North Africa.

This is just pure speculation on your part - there is absolutely nothing in the paper talking about "future needs, projections" or any other such language.