# Spitfire MKV and Merlin45 in 1941



## Kwiatek (Apr 11, 2009)

H!

I making some realism mod for IL1946 and need info about performance of Spitfire MK V with Merlin 45.

I have problem with Merlin 45 and boost which was used early in 1941. 

Most Spitfire MKV RAF test in 1941 was made using only + 9 lbs so performance of these plane was derated.

Spitfire Mk VB W.3134 Report

Some charts show that Spitfire MK V with Merlin 45 could get +12 lbs emergency power or even +16 lbs.













So how its really look? RAF didnt test Spitfre MKV initialy with emergency power? Or +12 lbs ( or +16 lbs) was initialy not allowed Merlin 45?

Any help?


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## HoHun (Apr 11, 2009)

Hi Kwiatek,

>So how its really look? RAF didnt test Spitfre MKV initialy with emergency power? Or +12 lbs ( or +16 lbs) was initialy not allowed Merlin 45?

It's pretty certain that the +16 lbs/sqin rating resulted from technical changes implemented in about August 1942 and communicated to the squadrons by an Air Ministry memorandum, reproduced in Price' "Spitfire - The Complete Fighting History".

It's not entirely certain if the Spitfire V was initally cleared for +12 lbs/sqin, or if it started into service with +9 lbs/sqin only. I tend towards the latter opinion.

I think there was an in-depth discussion of this topic already here on this board, but I can't seem to find it currently 

Regards,

Henning (HoHun)


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## Kwiatek (Apr 11, 2009)

Thx HoHun for quick replay. So i think i got still a problem 

Difference between 9 lbs ans 12 lbs is very noticable at low to medium alt so it make big difference between Spit MK V and 109 F performance comparison.

Maby there is someone who can resolve it?


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## HoHun (Apr 11, 2009)

Hi Kwiatek,

Here is the old thread: http://www.ww2aircraft.net/forum/engines/merlin-40-series-performance-curves-16568.html

Regards,

Henning (HoHun)


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## claidemore (Apr 11, 2009)

It gets confusing comparing climb, all out level, takeoff and combat power levels. In a later date Merlin 45 the numbers would be 12 lbs takeoff, 9 lbs climb, 16 lbs combat (5 min.)

I always understood the numbers as being 9 lbs for *takeoff*, with 12 lbs emergency *combat *power (for 1941),,,,and 12 lbs *takeoff*, with 16 lbs emergency *combat *power (for 1942). 

They also used different boost levels at different rpms, for example, the Merlin XII used 12 lbs boost at 2270 rpm for takeoff (3 min), but 9 lbs boost at 3000 rpm for max combat (5 min).


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