Early Spitfire V with 12 lbs boost?

Discussion in 'Technical Requests' started by Achi, Feb 20, 2010.

  1. Achi

    Achi Member

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    From early Spitfires MK V i only have the performance-datas with the 9 lbs boost.Was this the highest avaiable powersetting?Regards,Achi.
     
  2. Glider

    Glider Well-Known Member

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    This might be of interest
     

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  3. Vincenzo

    Vincenzo Active Member

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    the document it's not for early spit V, it's for late is upgraded until feb '44
     
  4. Hop

    Hop Member

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    The only definite information I have seen either way is a document from the Ministry of Aircraft Production, dated 3 January 1942, which discuss the requirements for 100 octane fuel. It says the Merlin 45 was "introduced" with 12 lbs boost, now being upgraded to 16 lbs (or 15, can't remember exactly).

    It's worth noting that the July 1940 Spitfire II manual gives the maximum level flight engine rating as 9 lbs, with 12 lbs only available for take off, but the manual also tells pilots to pull the automatic boost cut out control if they need extra power in an emergency. The ABC cutout allowed 12 lbs boost.

    The A&AEE test of the Spitfire II was conducted in June or July 1940. They tested the Spitfire II at 9 lbs against the Spitfire I at 6.25 lbs, even though Spitfire Is were already using 12 lbs in combat.
     
  5. Achi

    Achi Member

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    Thank you all. In my opinion there is somethimg with this in the blur.regards,Detlev.
     
  6. Colin1

    Colin1 Active Member

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    What does that mean?
     
  7. Achi

    Achi Member

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    that means that in my opinion there is something unclear.The Spitfire II was clear for 12 boost,its successor Spitfire V in 1941 only for 9(from my sources).Regards,Detlev.
     
  8. Vincenzo

    Vincenzo Active Member

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    #8 Vincenzo, Mar 7, 2010
    Last edited: Mar 7, 2010
    the original boost for Spit II was 9 lbs.

    and the engine was different so if need some tiem for up the boost, starting late end late
     
  9. Achi

    Achi Member

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    Hello Viencenzo_On the site "ww2spitfireperformance" one can see that "by the battle of britain all operational squadrons had changed over to 100 octane fuel and the engine limits had been increased to +12 lbs./sq.in.3000 rpm with 1/2 hour climb limit increased to 2850-3000 rpm."Maybe this dont referes to the new Spitfire II.The engine was different, thats my opinion ,too.But what do you mean with "time up for the boost"?
     
  10. Glider

    Glider Well-Known Member

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    Spit II in the BOB did have 100 octane fuel but the boost was limited to 9lb apart from on take off where 12 ib was available
     
  11. Hop

    Hop Member

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    This is from the instruction clearing the Spitfire I and Hurricane I for 12 lbs boost:

    [​IMG]

    Mike William's site WWII Aircraft Performance has the full document, plus dozens of combat reports mentioning the use of 12 lbs boost.

    If you read the Spitfire II manual, you will see the instructions on using the boost control cut-out that enabled 12 lbs boost:

    [​IMG]

    That's from the June 1940 Spitfire II manual.

    I've never seen any evidence that the Spitfire V couldn't use 12 lbs boost in combat from the start. I've seen one piece of evidence it could.
     
  12. bada

    bada Member

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    I think the question was about th MkV with M45 and not about the MkII with M12.

    It's like comparing apples and oranges.:rolleyes:

    till now never seen a MKV manual from 1941, only from 43 and from44, till then, only speculations can be done, but what is sure is the 9boost and 12 (only) at take-off untill 1000feet.
     
  13. Hop

    Hop Member

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    Bada, what makes you sure 12 lbs was only used for takeoff?
     
  14. Vincenzo

    Vincenzo Active Member

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    On spitfireperformance the early test of V go with 9 boost
     
  15. Kurfürst

    Kurfürst Banned

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    Regarding the question of boost limitations and clearances for the Merlin 45 series.

    Merlin XLV / 45 power curve. Note that the highest rating shown is +9 lbs, while Merlin III etc. is shown with a limit of + 12. So obviously the early rating was +9 lbs boost.

    Also keep in mind that the Merlin 45 was a simplified deriviative of the two-speed Merlin XXs, operating at much higher supercharger pressures, which is probably the reason why it had lower ratings than the single-speed Merlin II/IIIs.

    [​IMG]

    2, Later on, the engine was cleared for +12 lbs. When this occured is not entirely clear. I think that towards the end of 1941 would be a good guess.

    2, Merlin 45 etc. clearance for + 16 lbs boost, July 1942. (probably via Neil Stirling.)

    [​IMG]

    M-series Merlins were cleared for +18 with a cropped supercharger, but this is something different, as it only allowed power increase up to marginal low altitude bands, and performance fell off quickly with altitude below that of "normal" Mark Vs with +9/+12/+16.
     
  16. Hop

    Hop Member

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    Vincenzo, look at the early test of the Spitfire II: Spitfire Mk IIA Performance Testing

    That was carried out in June or July 1940. Note that not only did they test the Spitfire II at 9 lbs, they compared it against the Spitfire I at 6.25 lbs, even though the Spitfire I was already running 12 lbs in combat.
     
  17. Vincenzo

    Vincenzo Active Member

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    first in the test i told the spit V it's tested, it's not add for compare with other. 2nd in your link the spitfire I was not tested in that but previous, 19th march '40 and the 12 lbs was cleared in 20th march
     
  18. Achi

    Achi Member

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    Thank you all for reply!Regards,Detlev
     
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