Originally posted by Nashwan
We know the Merlin XII was authorised for 12 lbs boost because the manual says so.
Go to http://www.fourthfightergroup.com/eagles/spit2.html
and scroll down to the bottom. It clearly says combat limit 12 lbs.
Perhaps it's not such a silly stretch after all?
What`s the date of the manual?
I still don`t get what the MkII / Merlin XII has to do with the MkV/Merlin 45.
Kinda like saying just because the MkV was cleared to +16lbs in late 1942, then so was the MkIXs,too.
We know however at that time all MkIX were 'derated';) to +15lbs.
Another example, we know the DB 605D could run for Kampfleistung at 1.45ata, so can we say the DB 605A could run at 1.45ata kampfleistung as well, even though we have no reference to it?
You claimed that because there was no test at 12 lbs, it was not authorised.
We know it was, yet there are no tests.
Oh-oh, sorry I didn`t. I even pointed that one out. Get off that train. I simply say as there no indication of +12 lbs boost until 1942 AT ALL, it was probably not used initially on a new engine type, which is rather untested at the time.
Abscence of a 12 lbs rating on a particular test cannot be proof it was not allowed, even at that time. They may simply have tested at normal rated power, not wep. ie not used the "emergency" rating.
Expect of course if that test is explicitely about the maximum performance of the plane available to it at the moment. That is reached with maximum powers, u know.
Tell me, Nashwan, if you would like to know what is the
maximum speed and climb ability of a plane, on what would you test it, +9 or +12, hypothesizing both are cleared at the time...?
They tested it on +9 in all tests I have seen from `41, the first mentioning of +12 is from an mid-1942 AFDU test vs. the 190A.
Re XIV at +25
Are there? I've never seen them. I've seen documents saying it is not yet cleared, but will be in the future. If you've found anything new in the meantime, I'd be glad to see it.
Well then it appears you and Mike are the only partisans of a lost cause. I thought you have seen the light in the meantime, but it appears I was overly optimistic. Even Neil says +25lbs wasn`t cleared for the Griffon 65 series. From the doc I have seen on that, +21 is enough for 366mph at SL (in fact a bit worser than I expected and calculated).
Moreover, the Mk21 tested in mid-45 on Mike site uses the same engine as the MkXIV (the only difference being reduction gear), and the test say the relevant limitation of the engine is still +21lbs, provide 150 grade is available.
BTW, it also appears that +25lbs 'tests' on the Spit XIV were really a short run at a single altitude, with the rest of the curve calculated from it, as the engine had problems during the tests running on that boost.
We do know, for certain, that the abscence of the use of 12 lbs on the Spit II test doesn't mean the Spit II couldn't use 12 lbs, though.
Though it
points towards it wasn`t used at the same time as MkIs. Or just the test plane didn`t have the modifications for it, remember, the RAF did not fully convert to 100 grade fuel until November 1940.
What we have is a test report of a Spit II tested somewhere after May 1940, and an undated Spit II manual that could be anywhere between 1940 and 1945.
See the Bf 109 k4 climb chart at 1.8 ata. There is a line showing a revs switch at 8,000m, and the "time to climb" line, which is at climb and combat power, reflects that change above 8,000m.
I believe we had a big argument about that before you finally accepted it 
I'm not an engineer, so I don't know why rev increases were permitted during high altitude climbs, but it does seem to have had a valid reason on some 109s and Spits.
There`s a simply reason to that, the supercharger speed is directly linked to engine speed, and the 603G supercharger probably couldn`t keep up the 1.45ata boost for Kampfleistung above 8000 without increasing the speed by 200rpm to 2800. I doubt this would be speciality on the 109K only, unless it happened automatically (to which I didn`t find any reference) possible all the others could do the same trick to maintain their 1.3ata to higher altitudes by simply pushing the throttle forward.
Ie.
http://www.x-plane.org/users/isegrim/109/198_drehzahl.jpgNotice the DB reference and the date of the report BTW.
Note the test of AA878, where climbs were done at combat rating (16 lbs, 3000 rpm) and "Normal" rating, 9 lbs 2850 rpm.
http://www.fourthfightergroup.com/eagles/aa878.html
[/B]
Yep, in mid-42. We are speaking of mid41, combat ratings could have been easily raised during a year.
The Spit V manual I have says
Maximum climbing limit 2850 rpm +9 lbs [/B]
Hmm, and it`s date, early 1944 or 1943 I presume with increased ratings, supposed to prove
in 1941 it was already used ?
