The use of 100 Octane Fuel in the RAF pt 2

[FLYBOYJ]

I believe that was covered in Mike Williams post #48

I missed it - thanks!

 

[Colin1]

QUESTION:
When 100 octane was used, what was done to the aircraft besides placing a 100 octane sticker by the fuel nozzle?

As it's a piston-engined aircraft
I would imagine manual advance of the ignition timing to take advantage of the higher octane number
I can't think of a reason why it would be different to pre-engine management automobiles
I've no idea if strobes etc existed in those days

 

[Mike Williams]

QUESTION:
When 100 octane was used, what was done to the aircraft besides placing a 100 octane sticker by the fuel nozzle?

As it's a piston-engined aircraft
I would imagine manual advance of the ignition timing to take advantage of the higher octane number
I can't think of a reason why it would be different to pre-engine management automobiles
I've no idea if strobes etc existed in those days

Hello FLYBOYJ and Colin: Please refer to these documents for details of the modifications necessary to convert from 87 to 100 octane.

 

[Shortround6]

As it's a piston-engined aircraft
I would imagine manual advance of the ignition timing to take advantage of the higher octane number
I can't think of a reason why it would be different to pre-engine management automobiles
I've no idea if strobes etc existed in those days

Many WW II aircraft engines used FIXED ignition timing. While it may be possiable to adjust the igniton timing once it was set it didn't move with the engine runnig unlike most automobiles.
Some engines did use an ingition retarder for starting but once the engine was running the ignition timing stayed in the same place regardless of throttle setting or rpm.

 

[FLYBOYJ]

As it's a piston-engined aircraft
I would imagine manual advance of the ignition timing to take advantage of the higher octane number
I can't think of a reason why it would be different to pre-engine management automobiles
I've no idea if strobes etc existed in those days

Read below....

Many WW II aircraft engines used FIXED ignition timing. While it may be possiable to adjust the igniton timing once it was set it didn't move with the engine runnig unlike most automobiles.
Some engines did use an ingition retarder for starting but once the engine was running the ignition timing stayed in the same place regardless of throttle setting or rpm.

Shortround6 hit it on the head. In today's world an impulse coupling in the magneto would retard the spark for starting and then advance as engine RPM increased.

Somthing to think about - The document that Mike posted mentioned Mod 136 to Merlins that would have the described field mods (64, 77) embodied. It seems mod 64, 77 154 were the documents used to field modify the noted aircraft for 100 octaine. It would be interesting to find out when Merlins were rolling out of the factory with Mod 136 embodied. It would seem that all engines installed on Merlin powered aircraft would have to have mod 154 completed during installation. This would include engines at the factory as well as new or overhauled engines in the field. I know in today's world that when an engine is overhauled all mods are done to that engine prior to return to service and I would assume this would be the same case for the RAF in 1940.

 

[claidemore]

March 1940 they started the field modifications on the Merlin II and III. Pilots notes from April 1940 state "the automatic boost control has been modified".

Variable speed props were installed in the field by Dehavilland techs, and all subsequent planes left the factory with them. I believe the same would have been done with the mods for 100 octane. Wouldn't make sense to keep manufacturing and installing engines set up for 87 octane, and having them continually converted in the field after issue to squadron. I don't think it's a stretch to assume that every 'new' plane issued during the Battle would have been 100 octane ready.

 

[FLYBOYJ]

March 1940 they started the field modifications on the Merlin II and III. Pilots notes from April 1940 state "the automatic boost control has been modified".

Variable speed props were installed in the field by Dehavilland techs, and all subsequent planes left the factory with them. I believe the same would have been done with the mods for 100 octane. Wouldn't make sense to keep manufacturing and installing engines set up for 87 octane, and having them continually converted in the field after issue to squadron. I don't think it's a stretch to assume that every 'new' plane issued during the Battle would have been 100 octane ready.

All good points Claid although somtimes deliverey schedule may dictate where and when a mod was to be completed, but again I believe that these mods were more than likely done prior to delivery.

 

[Mike Williams]

...that looks like 31 different squadrons to me.

Hi claidemore:

Here are three more:

Jeffrey Quill, 65 Squadron, 12 August 1940: "I pressed my boost cut-out and felt the surge of power as the boost went suddenly up and black smoke poured from my exhausts."
Jeffrey Quill, Spitfire, A Test Pilot's Story, (Crecy Publishing Limited, Manchester, 1998), pg. 185.

P/O K B McGlashan, 245 Squadron, 28 May 1940: "We'd boost an extra four pounds, from eight to twelve…"
S/L Kenneth Butterworth McGlashan with Owen Zupp, Down to Earth, (Grubb Street, London, 2007), pg 29.

P/O T D Welsh, 264 Squadron (Defiant), 29 May 1940: "I pulled the boost cut out and my motor picked up."

 

[merlin]

And another (though it may have already have been quote) - from Tim Vigors autobiography - 'Life's too short to cry': - p.137

Driving through London we saw little traffic. Petrol rationing had, by this time, really started to bite. It had not affected us pilots too badly as, quite illegally, we used to top up the tanks of our cars from the petrol bowsers used for refuelling aircraft. As long as this was done reasonably discreetly the authorities kindly turned a blind eye. What effect 100 octane fuel was having on the pistons and cylinders of my Ford 8 remained to be seen. so far EGO (part of the car's no plate) was still going like a bomb. in fact the diet seemed to suit her.

And there's the gladiator squadron in Norway - and that was before the Battle of France let alone the Battle of Britain - that was sent 100 fuel but they couldn't use it, they wanted 87 octane!!

 

[Mike Williams]

The use of 100 octane fuel was approved for Spitfire Squadrons by 24 September 1938. No. 19 Squadron had received the first Spitfire into service on 4 August 1938 and was equipped with a full complement of sixteen Spitfires by December 1938.

In December 1938 Fighter Command noted that Duxford, Debden, Northholt and Digby had received 100 octane fuel. Nos. 19 66 Squadrons were at Duxford in Spitfires. These were the only units equipped with Spitfires in December 1938. Nos. 85 87 Squadrons were based at Debden and were equipped with Hurricanes. No. 29 squadron, equipped with Demons Blenheims, was also based at Debden at this time. No. 111 Squadron was based at Northholt with Hurricanes. Nos. 46 and 73 Squadrons were at Digby; 46 with Gauntlet IIs and 73 with Hurricanes.

Thanks to Gavin Bailey and Neil Stirling for their assistance.

 

[Kurfürst]

The use of 100 octane fuel was approved for Spitfire Squadrons by 24 September 1938. No. 19 Squadron had received the first Spitfire into service on 4 August 1938 and was equipped with a full complement of sixteen Spitfires by December 1938.

In December 1938 Fighter Command noted that Duxford, Debden, Northholt and Digby had received 100 octane fuel. Nos. 19 66 Squadrons were at Duxford in Spitfires. These were the only units equipped with Spitfires in December 1938. Nos. 85 87 Squadrons were based at Debden and were equipped with Hurricanes. No. 29 squadron, equipped with Demons Blenheims, was also based at Debden at this time. No. 111 Squadron was based at Northholt with Hurricanes. Nos. 46 and 73 Squadrons were at Digby; 46 with Gauntlet IIs and 73 with Hurricanes.

Thanks to Gavin Bailey and Neil Stirling for their assistance.

Also of interest is the page from the same set of documents, which sheds some context of these two papers detailing the shipments to stations involved in these early trials.

 

[Kurfürst]

More

 

[Kurfürst]

Proposals for securing adequate supplies of 100 octane fuel to meet war requirements

Annex I.
December 1938.

 

[Colin1]

Proposals for securing adequate supplies of 100 octane fuel to meet war requirements

Annex I.
December 1938.

Pulled the comment

 

[Kurfürst]

Proposals for securing adequate supplies of 100 octane fuel to meet war requirements

Annex II.
December 1938.

 

[Kurfürst]

Proposals for securing adequate supplies of 100 octane fuel to meet war requirements

Appendix I.
December 1938.

 

[fibus]

I would be proud of such research.

 

[Glider]

Its certainly interesting that in 1938 the UK was making preparations to equip 2,500 aircraft with 100 Octane Fuel.

 

[NZTyphoon]

Pardon for a newbie butting in but I have been reading this discussion, and others on the same subject with some interest. From what I can gather from the primary documentary evidence contributed by Glider, Mike Williams and others 100 Octane fuel was being used by RAF fighters from at least 1940, correct? It seems to me from the evidence supplied that the argument is conclusive; the RAF used this fuel as a matter of course throughout the battles of France and Britain.

So what is Kurfürst's big deal? In support of his argument that RAF fighters were not using the fuel in large quantities in 1940 he supplies documentary evidence from 1938, well before the war started, when the British could not guarentee supplies from the USA, and 1942, which simply confirms that the RAF consumed 400,000 gallons of the fuel in 1941. I don't see 1940 being mentioned anywhere in the document on Beaverbrook's memo .

Much more intriguing is the document marked "Consumption of 100 Octane Fuel in No.s 90, 98 201 Squadrons" which shows that the RAF was experimenting with the fuel in 1937. According to The Royal Air Force - History Section 90 Sqn was equipped with Blenheims, which means that the Bristol Mercury was capable of using 100 octane fuel, The Royal Air Force - History Section 98 Sqn with Battles, meaning the Merlin I could use 100 octane in 1937, and RAF - 201 Squadron 201 Sqn used Supermarine Southamptons, using the Napier Lion. Three different types of aircraft and three different types of engine all able to use 100 octane fuel in 1937. This proves that the Air Ministry was well up with the new development in aviation fuel. Note too that the long range Wellesleys which broke distance records in 1937 used 100 octane fuel - Bristol Pegasus.

In the balance of the information submitted by Kurfürst there is no evidence whatsoever that the RAF lacked supplies of 100 octane fuel in 1940. The word "Proposals" indicates these are planning documents which are based on a "worst case" contingency ie;as of 1938 Britain could expect no help from other countries in the event of war, therefore the projected supplies of aviation fuel were based on this assumption. The document confirms that Britain recognised how essential 100 octane fuel would be and was planning to refine the fuel in the West Indies - there is nothing startling or new about the Air Ministry making such plans in 1938. Nor did the Air Ministry have a crystal ball which told them that the USA would continue to supply 100 octane fuel in 1940. Primary documents from 1940 beat primary documents from 1938 or 1942. Or am I just being obtuse? 8)

 

[Kurfürst]

So what is Kurfürst's big deal? In support of his argument that RAF fighters were not using the fuel in large quantities in 1940...

Problem is nobody made such an arguement. Glider etc. state that each and every RAF Figther Station was was supplied with 100 octane fuel, and each and every RAF fighter Squadron was running on 100 octane fuel during the Battle of Britain. As others have noted, there is no conclusive evidence for this (yet) in the documentation so far found. As opposed to this, reasearch and some of the documentation (including research in the Australian archieves, papers the 18 May Meeting, and fuel consumption data) points to that 100 octane fuel was issued to some stations, while others relied on 87 octane fuel. It is yet to be determined what was the ratio between these stations. Whether the RAF used 100 octane fuel or whether the engines were capable of using it was never a question, and nobody questioned this here AFAIK.

Generally using higher octane fuel in an engine originally for lower octane fuel, say 87 which was the standard in the 1930s, was no particular problem as it would appear. For example, the Germans were using their own 96/115 octane fuel 'C-3' during the Battle of Britain even with Ju 88 bomber units, even those the Jumo 211 engines of these bombers were probably not gaining any extra output with it.

Glider's post and documents he posted cover the period up to May 1940, and it makes clear that some specific bomber Stations were issued with this fuel, as well as Mike's collection of Pilot combat reports show that several RAF Squadrons were using the fuel in France and later over Britain in the summer of 1940. The question is of course complicated by the fact that the Squadrons were rotated amongst fifty-odd stations during the Battle. I will address this later.