Spit IIa is now so much more inferior to the 109

[Kwiatek]

Originally Posted by 41Sqn_Banks

I don't know if you had a look at the merlin em files so far. I've looked at them a year ago, so maybe this has changed, but at that time the Merlin III and XII were very identical. The nominal rpm was 2600 RPM for both. I assume that normal rpm is the value that can be maintained without critical overheat.
My impression is that the Merlin XII - as we have it know - is modeled more like a Merlin III running 100 octane (with +8? instead of +12 emergency boost).

Hmm i didnt look at emd file for CLod yet. But if it is true like you said so there is obviously error in engine data which probably casue problem with Merlin XII power limiation in game.

Luckly i checked today spitfireperformacne site and i found interesting data for Merlin III at 87 octan fuel which i didnt see before:



So for Merlin III at 87 octan fuel we have:

max take off - +6 1/4 at 2850 RPM
climbing - +6 1/4 at 2600 RPM
All-out level flight - +6 1/4 at 3000 RPM

With 100 Octan fuel modification Merlin III power settings was rised to:



So with Merlin III at 100 Octan we have:

take off - +6 1/4 at 3000 RPM
1/2 hr climbing - +6 1/4 at 2850 RPM ( below 20 000 ft) and at 3000 RPM (above 20 000 ft)
all-out level flight - +6 1/4 at 3000 RPM ( 5 minutes)
emergency power - +12 lbs at 3000 RPM ( 5 minutes)


Of course for Merlin XII nomial RPM should be 2850 not 2600 the same like with Merlin III at 100 Octan fuel.

[41Sqn_Banks]

Originally Posted by Kwiatek

So for Merlin III at 87 octan fuel we have:

max take off - +6 1/4 at 2850 RPM

...

So with Merlin III at 100 Octan we have:

take off - +6 1/4 at 3000 RPM

It's interesting to note that publications from 1938 and 1939 give maximum take-off engine speed of 2850 rpm for both Merlin II and III. Publications from 1940 give 2850 for Merlin II and 3000 rpm for Merlin III. The increase is not associated with the use of 100 octane fuel.

[Kwiatek]

Originally Posted by 41Sqn_Banks

It's interesting to note that publications from 1938 and 1939 give maximum take-off engine speed of 2850 rpm for both Merlin II and III. Publications from 1940 give 2850 for Merlin II and 3000 rpm for Merlin III. The increase is not associated with the use of 100 octane fuel.

Hmm interesting have you some documents with such Merlin power settings? I miss really manual ( pilot notes) for Spitfite MK1 and Hurricane MK1

[Crumpp]

from 1938 and 1939 give maximum take-off engine speed of 2850 rpm for both Merlin II and III

It also shows maximum boost at emergency power at 12,500ft as +10.55lbs at 3000 rpm for the Merlin III when you use boost override or pull the tit on 87 Octane.

Absolutely NOTHING to do with the use of 100 Octane fuel.

[Kwiatek]

Originally Posted by Crumpp

It also shows maximum boost at emergency power at 12,500ft as +10.55lbs at 3000 rpm for the Merlin III when you use boost override or pull the tit on 87 Octane.

Absolutely NOTHING to do with the use of 100 Octane fuel.

Yep it is also interesting

[Crumpp]

Yep it is also interesting

I thought something like this might be discovered when I saw the 1937 instructions for boost cut out in the RAF Training Manual......

[41Sqn_Banks]

Actually this is not the emergency power rating, these are the results from the power test to determine to performance of the engine.
As +12 boost has a FTH of 10,000 feet this is the power achieved with throttle valve fully open.

[Crumpp]

As +12 boost has a FTH of 10,000 feet this is the power achieved with throttle valve fully open.

Two possibilities.....

If our FTH is at 10,000 feet and our boost is 12lbs then by 12,500 it will be reduced and 10.55lbs is certainly in the ballpark.

OR

12,500 ft was the FTH at 10.55lbs on 87 Octane.

It warrants more investigation.

Actually this is not the emergency power rating

That is exactly what it says and the 1937 RAF Training Manual talks about boost cut out and emergency ratings on RAF aircraft under the general definitions. It revises the old definitions of "Normal rpm" and Maximum Permissible rpm".

[Ernst]

Originally Posted by Kwiatek

Yep it is also interesting

Are the SPITFIRE FMs at UP 3.0 RC4 yours?

[Crumpp]

The power figures on the engine Inspection and Test Certificate come from "test bed conditions", either at RR, RAE or the dynamometer at AAEE, i.e. the engine wasn't even mounted in an airframe and the engine surely wasn't running at 12,500 feet without an airframe.

Sure it was running at 12,500 feet on an altitude test stand.