109 elevator trim

[Kurfürst]

Originally Posted by Robo.

Ah, makes sense. I thought though that Merlin performed better than DB higher up due to higher full throttle height and supercharger designs of bothe engines. I might be wrong but it seems that above 16.500 feet, the Spitfire was faster than the 109 even with 87 octan fuel and also climb performance was slightly better. It was later Spitfire marks and Friedrichs where I've read accounts of Germans being some 2000ft higher and RAF unable to climb any further but I was not aware of any advantage of the Emil over early Spitfire marks. If you could point me out to some sources that would be great!

Depends. The Spitfire in the period of the BoB went on with just two Merlin engines, the III and XII. The latter IIRC was marginally better for lower altitudes and worse for higher altitudes.

On the German side its a bit more complicated - most books will tell you that they used 'DB 601' but in reality 109s/110s had a number of DB 601 variants installed during the Battle:

DB 601A-1 with old type supercharger - this had a rated altitude of just 4000m.
DB 601A-1 with improved type supercharger - this had a rated altitude increased to 4500m.
DB 601Aa - this had increased boost pressures, which meant it developed about 10% more power than the 601A-1 below rated altitude, operating at 1.35/1.45ata instead of 1.30/1.40 ata, but similiar altitude performance. I believe this is the variant we have modelled.
DB 601N - this one was fitted to 109s and 110s and used 100 octane fuel, and had both increased boost pressures, higher compression ratio and a more powerful supercharger with a rated altitude of 4800 m. Off all engines during BoB, British or German, this had the best altitude performance. The one fitted to the 109F had a better supercharger and a rated altitude of 5200 iirc.

In addition, during the Battle the Luftwaffe cleared increased RPMs for the DB 601 A and N-series engines, and this would increase altitude performance (the supercharger's rotation speed was linked to the engine speed, so increasing the engine speed also increased the supercharger performance)