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

[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

[Glider]

Originally Posted by Crumpp

Right, so it appears you can throw out all those combat reports that do not specify +12lbs or 100 Octane.

Like this one:

http://www.wwiiaircraftperformance.o...on-1july40.pdf

For all you know 145 sqd is one of your 16 squadrons you claim were using the 100 octane. After all, action in that area is right in the front line and by your standards most likely to have the fuel.

Unles of course you can prove that they were not using the fuel which reminds me, to do that you need to prove which 16 squadrons or stations were using the fuel.

Any update?

I admit to not holding my breath

[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

Right, so it appears you can throw out all those combat reports that do not specify +12lbs or 100 Octane.

Like this one:

http://www.wwiiaircraftperformance.o...on-1july40.pdf

Wrong: this is simply your arbitrary "ruling" made on the basis of one document. Fact is Dowding used the phrase "pull the plug" in his 1 August memo, recognising that this phrase (and others such as "squeezed the tit") was pilot jargon for "used emergency boost" or +12 lbs boost - you have already tried to rule out all such pilot's reports based on some other such arbitrary concept, so if you don't like them being used, too bad.

Unless, that is, you can find a memo or other such document stating, for example, that, until further notice, 87 Octane fuel will be used by the majority of the RAF's frontline fighters.

Either that or find a list of units authorised to use 100 octane fuel, and/or an explanation of the logistical processes used by the RAF to ensure a limited supply of 100 octane directed at selected units or stations.

[Al Schlageter]

Originally Posted by Glider

For all you know 145 sqd is one of your 16 squadrons you claim were using the 100 octane. After all, action in that area is right in the front line and by your standards most likely to have the fuel.

Unles of course you can prove that they were not using the fuel which reminds me, to do that you need to prove which 16 squadrons or stations were using the fuel.

Any update?

I admit to not holding my breath

At the time 145 was based at Tangmere. Also based there were 43, 601 and the FIU. The FIU flew Blenheims so 100 fuel must have been available. It should also be noted that Tangmere was one of those stations listed in the Dec 7 1939 document http://www.wwiiaircraftperformance.o...0oct-issue.jpg

It shouldn't be that hard to identify those 16 squadrons should it Glider? So why the evasiveness in identifying these 16 squadrons by a certain party?

[lane]

Originally Posted by 41Sqn_Banks

I hope you guys are aware that the line "Emergency 5 mins.max." is related to "95°C" oil inlet temperature?



This test certificate has a better layout: http://www.spitfireperformance.com/k...ertificate.jpg

The power curve is a simplified form of this graph: http://forum.1cpublishing.eu/attachm...1&d=1337143252
and most certainly only contains calculated values which were derived from certain reference values or were applied shorty under controlled conditions to determine the engine power.

Good post 41Sqn_Banks,

I concur that "Emergency 5 mins.max." on the Inspection and Test Certificates is related to "95°C" oil inlet temperature.

Unfortunately I haven't seen a power curve for the Merlin III similar to the one you posted for another type. My understanding is that the power curve figures shown on the Inspection and Test Certificates were obtained through bench testing. In the case of N.3171 the engine Inspection and Test Certificate is dated 9-6-39 whilst N.3171's first flight occured on 10-11-39. The A.&.A.E.E. report on N.3171 notes:

"The engine installed in the aeroplane develops slightly less power under test bed conditions than that in K.9793, the aeroplane fitted with the 2-pitch airscrew. This could have the effect of reducing the top level speed by about 2 m.p.h. "

One can see that the power figures were not pulled from a chart given the differing powers obtained:

K.9703 Inspection and Test Certificate
N.3171 Inspection and Test Certificate

[Crumpp]

I doubt it would be just as likely.

Ok, your opinion is noted. What do you want me to do? Agree with you when I know it is not the case?

Overstress an engine and it might fail then and might fail later. The point being, it will fail and its life is significantly shortenend.

That memo is telling the pilots of the RAF that reality. Overstress the motor and it will fail. There is a good reason why it was a requirement to log the use and have the motor inspected to ensure some reasonable life was left in it.

[Crumpp]

I hope you guys are aware that the line "Emergency 5 mins.max." is related to "95°C" oil inlet temperature?

I know that banks.

The 1937 RAF training manual amends the RAF old definitions for engine ratings.

The only difference is the 1937 RAF Training Manual list's the system for take off purposes.

Chap II
75. Supercharged engines fitted with automatic boost control embodying an override for the take-off at maximum permissible boost, may have a separate control for for the override, or use the mixture control with a gate, or have a gate on the throttle for the same purpose. This override is invariably inter-connected with a mixture enrichening device on the carburetor, to suppress detonation.

[Crumpp]

One can see that the power figures were not pulled from a chart given the differing powers obtained:

There you go, they are testing the engines on a bench at boost over-ride on 87 Octane.

Everything in aviation related to the airworthiness is tightly controlled and must be specified. The Air Ministry documents the standards and conditions they expect their pilots to use down to the point of defining the standards they expect if a pilot violates the airworthiness standards in an life threatening emergency.

The RAF instructs its pilots to balance and evaluate risk before taking the risk of moving outside of the airworthiness instructions. From 1937 on, they are able to use boost override.

Without the specific mention of using +12, an anecdote that makes any reference to boost override, pulling the tit, boost cut out, or anything other term related to the system is irrelevant to the use of 100 Octane.