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

[NZtyphoon]

Originally Posted by Crumpp

Really guy?

You clearly had no idea of what the boost cut out is for so I explained...

Originally Posted by Crumpp

The aircraft is only approved for 87 Octane fuel.

So? For ages you have been swearing black and blue that because the Pilot's Notes stipulated certain engine limitations and certain types of fuels those were the limits observed no matter what, in spite of it being explained to you several times, very carefully, that supplementary slips were issued to the pilots with the Pilot's Notes revising such information when it was relevant.

Now, on the basis of this one test certificate you are saying what? That the engine limitations were not observed? I haven't noticed any pilot's notes stipulating 10.55 lbs boost maximum using 87 octane fuel, so I guess you want to withdraw all of your previous comments regarding the legal limits etc set by the pilot's notes?

You now want to claim that when pilots refer to pulling the plug it meant they went to 10.55 lbs boost on 87 octane fuel, right? Then present some documentary evidence showing that pilots were authorised to use 10.55 lbs boost on 87 Octane.

Then explain why Dowding found it necessary on 1 August 1940 to send a memo to All Groups, ALL Fighter Stations and ALL fighter squadrons stating that +12 lbs boost was only to be used in emergencies? Why not state +10.55 lbs boost, and send a separate memo to the supposedly small number of squadrons authorised to use 100 octane fuel?

http://www.spitfireperformance.com/dowding.pdf

Note he also uses the expression "Pulling the Plug" referring specifically to +12 lbs boost.

[Crumpp]

Now, on the basis of this one test certificate you are saying what?

I will explain this ONE time and then I will probably ignore you as I don't think you have much to add. It is according to the training manual and fits with everything I have already told you about Operating Notes.

The 1937 RAF Training Manual explains the use of boost cut out. In 1937, 100 Octane was not an issue.

The certificate limitations appear to back up the use of the system.

That is completely independent of 100 Octane.

It means most of the reports you claim prove the use of 100 Octane fuel really have nothing to do with it at all.

[Crumpp]

Then explain why Dowding found it necessary on 1 August 1940 to send a memo to All Groups, ALL Fighter Stations and ALL fighter squadrons stating that +12 lbs boost

Well one day, all those units will be equipped with 100 Octane. It is not proof that all of the operational units were using it. Why put the word out on something like the information in that memo piecemeal?

What is proof that that 100% of the operational units were NOT using is the Notes on a Merlin Engine found in the Operating Notes.

That is a fact.

[Crumpp]

the damage being done is generally not instantainous and will not result in immediate loss of the engin

Sometimes it will and sometimes it will not.....

It all depends and it is just as likely to end your trip that flight as the next if the motor is damaged.

[Crumpp]

You now want to claim that when pilots refer to pulling the plug it meant they went to 10.55 lbs boost on 87 octane fuel, right?

I am not claiming anything outside of known facts, NzTyphoon. I will leave the speculation to you.

The known facts are that system was in place before 100 Octane fuel was around as evidenced in the 1937 RAF training manual.

The Operating Notes will specify the authorized fuel for the aircraft. The type Operating Notes clearly state that "ALL Operational Units - 100 Octane" after the fuel is adopted for all operational units.

We don't see that in any of the Operating Notes during the BoB. Only the Spitfire Mk II carried the 100 Octane specification. The rest require replacing the heads and in some cases, rings as well as the required modifications to the fuel metering system. This work was performed at Service Inspection intervals. Do you know what that means?

[Seadog]

Originally Posted by Crumpp

The rest require replacing the heads and in some cases, rings as well as the required modifications to the fuel metering system. This work was performed at Service Inspection intervals. Do you know what that means?

The March 20 1940 memo clearly states that new built aircraft already had the internal engine mods:

http://www.wwiiaircraftperformance.org/ap1590b.jpg

Given the production numbers for Hurricanes/Spitfires and RAF operational and combat losses prior to the start of the BofB, it is extremely doubtful that any unmodded aircraft were still in front line service. Production during March, April, May and June, and July, of 1940 would have amounted to approximately 1500 Hurricane/Spitfire aircraft, or greater then RAF FC's front line strength at the start of the BofB.

The memo clearly establishes that all RAF FC Hurricanes/Spitfires were modded for Hundred octane fuel and 12lb boost prior to the start of the BofB.

[41Sqn_Banks]

Originally Posted by Crumpp

The known facts are that system was in place before 100 Octane fuel was around as evidenced in the 1937 RAF training manual.

So please tell us what there is written ... or at least tell us which chapter and paragraph.

This is from the Air Publication 129 Royal Air Force Flying Training Manual Part I - Landplanes; Revised June, 1940 (Reprint April 1941 incorporating A.L. No. 1), A.L. No. 2 from May 1941 is slipped in.

Chap. VII
Boost control

53. ... Some boost controls are provided with an emergency cut-out, which over-rides the automatic boost control. This must only be used in emergency and not, in any circumstances, for ordinary flying, because, even if the correct boost is not exceeded, the mixture enrichment is also put out of action and, as has been previously explained, high boost is only allowed with rich mixture, and without it may cause serious damage.

[Skoshi Tiger]

Originally Posted by Crumpp

Sometimes it will and sometimes it will not.....

It all depends and it is just as likely to end your trip that flight as the next if the motor is damaged.

I doubt it would be just as likely. If you read the memorandum point one and two,

"A recent increase in the number of engine failures, due to the failure of bearings, is an inication that some pilots are over-stepping the engine limitations laid down in the Pilot's handbook.

2. The use of the automatic boot cut out control enables the pilot to get an emergency boost of +12lbs per sq in. from the engine for 5 minutes when circumstances demand it. Some Pilots "pull the plug" with little excuse on every occasion."

The wording of this memo suggest that the practice of exceeding the limits was quite widespread. Now if it was as you suggest a 50-50 chance of engine failure when the limits were exceeded then the culprits responsible for abusing their engines would be quickly identified and I expect grounded. The practice of exceeding the limits would only become common place if the pilots thought they could get away with it. Maybe thats why they put the wire seal on the boost control to make it obvious to the maintenance staff that it had been used. Then the pilot would have had to justify their use of boost after the mission.

As long as they didn't overheat their engines and the correct fuel was used the boost control still limits the boost available to stop destructive pre-ignition and detonation as a cause of engine damage. (ie if you run the 12lb boost on 87 octane fuel you could get servere and possibly imediate damage from detonation, but not with 100 octane fuel.) So what was left was damage caused by accellerated wear on the engine that was "liable to manifest themselves on some subsequent occasion"


http://www.spitfireperformance.com/dowding.pdf

[NZtyphoon]

Originally Posted by Skoshi Tiger

I doubt it would be just as likely. If you read the memorandum point one and two,

"A recent increase in the number of engine failures, due to the failure of bearings, is an inication that some pilots are over-stepping the engine limitations laid down in the Pilot's handbook.

2. The use of the automatic boot cut out control enables the pilot to get an emergency boost of +12lbs per sq in. from the engine for 5 minutes when circumstances demand it. Some Pilots "pull the plug" with little excuse on every occasion."

The wording of this memo suggest that the practice of exceeding the limits was quite widespread. Now if it was as you suggest a 50-50 chance of engine failure when the limits were exceeded then the culprits responsible for abusing their engines would be quickly identified and I expect grounded. The practice of exceeding the limits would only become common place if the pilots thought they could get away with it. Maybe thats why they put the wire seal on the boost control to make it obvious to the maintenance staff that it had been used. Then the pilot would have had to justify their use of boost after the mission.

As long as they didn't overheat their engines and the correct fuel was used the boost control still limits the boost available to stop destructive pre-ignition and detonation as a cause of engine damage. (ie if you run the 12lb boost on 87 octane fuel you could get servere and possibly imediate damage from detonation, but not with 100 octane fuel.) So what was left was damage caused by accellerated wear on the engine that was "liable to manifest themselves on some subsequent occasion"


http://www.spitfireperformance.com/dowding.pdf

Also note section 6

It is in the best interest of pilots...to acquaint the maintenance personnel with the facts so that oil filters may be inspected at the first convenient opportunity to investigate whether damage to the bearings has resulted.

So using +12 lbs boost did not inevitably damage the engine, but it was better for all concerned that the pilot let the ground crew know that he had gone through the gate - should the pilot neglect to mention that +12 lbs boost was used as Skoshi has mentioned, they could check to see if the throttle wire had been broken.

All frontline RAF aircraft were given a daily inspection whenever possible and this would be when any such issues were found and, if need be, notified in the aircraft's engine log.

BTW Some might remember this thread? http://forum.1cpublishing.eu/showthread.php?t=20117 £74.50 for a copy of the Mk I Pilot's Notes from Kew? v $15.9 from http://www.flight-manuals.com/ap1565a-vol1.html Apart from these there don't seem to be many original Spitfire I Pilot's Notes available.

Also note the Defiant used 100 octane and +12 lbs boost - the attachment is dated 24 5 (or 6?) 40 lower LH side

[NZtyphoon]

Originally Posted by Crumpp

Well one day, all those units will be equipped with 100 Octane. It is not proof that all of the operational units were using it. Why put the word out on something like the information in that memo piecemeal?

That is a fact.

Absolute nonsense! The memo says nothing about "In Future, once 100 Octane fuel becomes available..." it was written in the present tense stating unambiguously that too many pilots were using +12 lbs boost for situations other than emergency.

Originally Posted by Crumpp

Why put the word out on something like the information in that memo piecemeal?

Pure speculation on your part.