[Charles Bavarois]

Hello Dan,

DB 605 AS or D engines with 1.98 ata boost are still a mystery.

Firstly I think that 1.9 ata was only used for testing at II/JG 11 to minimize engine troubles.

We know, that a DB 605 AS or D was able to run at both 1.8 or 1.98 boost and could easily change from one to the other. But we lack information on the amout of actual frontline use of 1.98 “superengines”. IMHO very few Bf 109 were runing on 1.98 and only during the very last weeks of the war.
The last hard evidence I have is a DB-document dated 24. Jan. 1945 remarking that “all four engines with 1.98 ata boost at Rechlin have been wrecked during tests. E-Stelle Rechlin has therefore not cleared the DB 605 DC. It was decided zu keep on runing the tests with Jagdgruppe 2/11 (which is II/JG 11) to get more information. Other fronline unit should not be run with 1.98 ata.” So at the end of January 1945 1.98 ata boost was not clear for the frontline-units.
Other documents from Luftwaffenführungsstab may be a hint that at least in March 1945 the problems were solved. A very few Jagdgrupen – all fighting in the West – were to be eqpipped with 1.98 boosted Messerschmitts. Among them were were JG 27 and JG 53 which would need the extra power for fighting against high-performance British and US-american fighters at moderat hights (remember: fighting the US-bombers and their escort with German piston-engined fighters had no priority any more).
What might be most important is gas. 1.98 ata could only be obtained with C3-gas and MW-50, 1.8 ata was available using plain C3 or B4 with MW-50. Germany had nearly exhausted its aviation-fuel in 1945. Producing C3 was much more elaborate than B4 and thus C3 was very limited. Even if all Bf 109 AS/D could be boosted to 1.98, there simply was not enough gas for all of them.
On the Ostfront the situation was even worse. The SU ground troops were driving staight into Germany and the Luftwaffe desperatly tried to counter with their Schlachtgruppen. Schlachtflieger flew a lot more than Jagdflieger. And they were equipped with Fw 190 which ran on C3 only. Thus what was left on C3 was needed at the SGs. What 1.98 ata a/c were transfered to the Ostfront in early 1945 may have to change to 1.8 quickly. I don’t think, that many Messerschmitts in the east were able to get C3 for runing 1.98 boost.

PS: Kutscha. Could you tellme, what “Umrüstnummer 63253” is?

Carl