Spit Mk1 Boost?

[Seadog]

Performance data for Spitfire Mk1 with 12 and 16lb boost:

[TomcatViP]

*Fake (or very highly suspicious) !

pls refer to my earlier post if ever needed regarding power increase Vs speed

[IvanK]

The 12Lb Boost lines and +16Lbs are computed projections of performance I believe. 12lbs we know was available on the MKI. 16Lbs was not available/used in the MKI. I think the first operational use of +16Lbs was on the Spit MKV with Merlin 45

[Seadog]

Originally Posted by TomcatViP

*Fake (or very highly suspicious) !

pls refer to my earlier post if ever needed regarding power increase Vs speed

Originally Posted by IvanK

The 12Lb Boost lines and +16Lbs are computed projections of performance I believe. 12lbs we know was available on the MKI. 16Lbs was not available/used in the MKI. I think the first operational use of +16Lbs was on the Spit MKV with Merlin 45

Here's actual flight data from the Hurricane using 6 and 12lb boost:



Note how closely the performance increases match the previous data for the Spitfire I at 6 and 12lb boost.

I haven't read of the Spitfire I/II using 16lb in combat, but they must have run the Merlin III at 16lb boost to certify it for the Sea Hurricane, and those tests are just as easy to do in a Spitfire with a Merlin III.

[lane]

The following passage from Wing Commander Royce Wilkinson's book is interesting and germane to the discussion.

[Blackdog_kt]

Wow, nine aircraft in ten days?

Probably these guys flew quite a lot during those days, let's take a guess and say 3 to 5 sorties per day (depending on distances/time flown), this gives us nine "busted" engines for 30 to 50 sorties total for these 10 days.

Now, divide the amount of engines used up by the sorties and you get a per-sortie engine failure rate of 18% to 30% for going above the limits. In other words, almost one in five to one in three sorties results in a busted engine, not exactly a trivial risk.

Pretty interesting reference there to get a feel of how easy it was to break an engine under operational conditions, thanks for linking it.

[lane]

Originally Posted by Blackdog_kt

Pretty interesting reference there to get a feel of how easy it was to break an engine under operational conditions, thanks for linking it.

Sure, no problem. 18 lbs., 3200 rpm clearly exceeded approved limits and as mentioned was hard on the engines. +12 lb., 3000 rpm on the other hand was approved and could be used operationally in emergencies without damage to the engine.

[Al Schlageter]

It does say Boscome (Aeroplane and Armament Experimental Establishment), so I would say it was from testing done there.

The source for the graphic is on the graphic.
http://www.spitfireperformance.com/