1.98ata testing

[Kutscha]

Carl, I will quote from the link,

II. / JG 11 was ordered to do trials of 1.98ata by Umrüstnummer 63253 vom 16.1.1945. II / JG 11 performed the operational trials with 1.98ata and had reported in February 1945 that it had converted 11 of its G-14s, G-10s and K-4s to 1.98 ata (i.e. note that by this time also ASM engines of the G-14/AS had this 1.98ata rating, so basically all 109s with high altitude engines) and had not much trouble with it, with two engines failing in unrelated conditions in normal flight conditions, otherwise the spark plugs were also OK.

Thank you again for sharing your unbiased knowledge.

[Kurfürst]

Originally Posted by Charles Bavarois

It was II. Gruppe JG 11 you're talking about, which was at Wunstorf from October to 17th December 1944 for R&R. It was nearly completely refitted with new Bf 109 G-14 AS.

BTW: The test was with 1.9 ata, not with 1.98 ata.

in a Daimler-Benz document dated 10th Oct. 1944, filed after a meeting at the “Entwicklungskommission Flugzeuge und Flugmotoren” on 3rd and 4th of October they remarked:

“Es wird beschlossen, dass die Umstellung der zurzeit in Wunstorf befindlichen 70 Motoren DB 605 ASM durchgeführt wird, wobei der bei diesen Motoren mögliche maximale Ladedruck von ca. 1,9 eingestellt wird, der dann ca. 1900 PS Leistung ergibt“. Roughly translated like „We decide, that the changes (for higher boost) will be done with the 70 engines DB 605 ASM, currently at Wunstorf. The boost for this engines is to be set at around 1.9 ata maximum, which will make around 1.900 PS output.”

I think, this makes it quite clear, that the testing of higher boost on unit-level was with Bf 109 G-14 AS and not on K-4s. BTW: II./JG 11 got its K-4 only after 20th Dec. 1944, having mainly G-14 AS and 2 G-6 in early December.

Testing at the manufacturer continued of course: Daimler-Benz weekly report dated 28. Nov. 1944 lists a Bf 109 K-4 WNr. 330.103 with DB 605 D and a Bf 109 G-10, WNr. 490.128 with DB 605 D on
tests with MW 50 and 1.98 ata Aufladung.


Greeting
Carl

Hello Carl,

Thanks for this information, it was new to me about the early testing of the 1,98 ata boost in October November 1944. It fits in well with the 1 December 1944 DB 605DB/DC manual, which lists both 1,8 and 1,98ata for the DB / DC engine respectively.

It also confirms that the ASM and D series engine development was converging at this point, with the ASM becoming / was upgraded to ASB/ASC engines, i.e. roughly equivalent to the DB/DC but using the A-series engine as a basis. I presume they were a hybrid of A and D series engines, much like the G-10 being a hybrid of G airframes with K internal equipment.

Originally Posted by Dan History

Carl,

Let me thank you, as an interested reader of this discussion from its beginning, for sharing excellent information.

Do you happen to know whether Bf 109s with 1.9 or 1.98 ata boost were employed on the Eastern front? I assume that they were, at least in limited numbers, after the transfer of many units to the East in the middle of January 1945, but I have no primary source information about this.

Kind regards,

Dan

Originally Posted by 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.

Additional testing has been done on II/JG 11 in February 1945 indeed(at which point they were stationed at Strausberg, East of Berlin, so more or less Eastern Front) as has been noted in their February 1945 experience report (i.e. after the arguement with Petersen and Rechlin when it was decided to perform operational trials with 1,9 and 1,98ata at the II. Gruppe)

One particular note is that the Gruppe says that there was little tactical opportunity to use the special boost, since tactical conditions on the Eastern Front seldom required using high powers in the first place.

Originally Posted by Charles Bavarois

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).

Indeed there is a trail of documents, this one from 4 March 1945 (i.e. just prior to the Lw Führungstab order in mid-March on the boost increase for JG 27 and JG 53) notes that the problems were fixed.

http://forum.12oclockhigh.net/attach...1&d=1525080386

Add to that that a week later a new technical instruction (Reperatur Anweisung was issued for the DB 605DB/DC on 1st March 1945, that notes that some changes are required for the B-4 fueled DB, but none for the 1,98ata DC engines suggest that the main culprit was the declining production quality of B-4 fuel, but since C-3s quality's was not effected, no changes were required to the DC engine.

Originally Posted by Charles Bavarois

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.

This is not supported by any of the documents on the fuel supply situation. There is no indication of specific shortage of C-3 as opposed to B-4. In fact, the USSBS specifically mentions that the majority of the production was C-3 in the later war years.

C-3 production was not particularly elaborate, AFAIK it merely consisted of that B-4 was blended with approx. 20% iso-octanes, which was AFAIK the only difference between the two grades. Of iso-octanes, there were still relatively generous reserves - but no more forthcoming after the Auschwitz synthethic plant was overrun - with the Luftwaffe becoming increasingly 'creative' to solve the avgas issue for piston engine warplanes at this point it was even considered to run planes on pure isooctane as a last resort.

Avgas (i.e. base stock~) in general was indeed in short supply by 1945. Since base stock was in short supply, but isooctane was not, it would actually make sense to blend more C-3 since it contained 20% additives, meaning you could actually more usable avgas from the base fuel. As of end of Febuary 1945, the stocks of A3, B4, C3 avgas was cc 52 000 tons, while isooctane stocks amounted to cc 24 000 tons. Given that you needed to blend 20% iso-octane to get C-3, it follows that the isooctane stocks alone would have been sufficient to make 120 000 tons of C-3 - if there have been enough base stocks in the beginning!

It also worths mentioning that there were also trials with B-4 blending with 2% anilin and 0.16 TEL, which basically made B-4 equivalent of C-3. So it would appear that the differences between B-4 and C-3 become blurry by the end of the war, performance wise it appear that they have become similar fuels, but produced from different blending agents.

The following is the ANR's fuel delivery and stocks as of early 1945 via 'Air War Italy' by Ferdinando D'Amico / Gabriele Valentini / Nick Beale. It is notable that the ANR was operating mostly 109s and that C-3 shipments were dominant in 1945, to an air force that was probably not taking priority for fuel over German units.

http://forum.12oclockhigh.net/attach...1&d=1525080386

Similiarly, some fragments of the stocks of B4/C3/J2 stocks at the airfields under LWKdo West in April do not really indicate that C-3 would have been preciously scarce vs B-4. By this point the Germans were using the last fuel reserves anyway and decision was already made to stop almost all piston engine production and switch to jets almost entirely, since their J-2 jet fuel was far more available than normal avgas.

On April 22 1945 Luftwaffenkommando West reported the following fuel stocks on airfields in Bavaria:

B-4 = 350,000 liters
C-3 = 284,000 liters
J-2 = 1,897,000 liters

Originally Posted by Charles Bavarois

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.

Carl

Indeed it appears to be the case that Eastern Front units primarily relied on B-4. DB memo no 6730 specifically hints at this: 'Da der Einsatz im Osten vornemlich mit B 4 beflogen wird ist es notwendig die TAGL fur Spaeterstellen des Zuendung sofort herausgaben.'

Indeed Luftflotte 6 in mid-March reported the fuel allocation accordingly, and its noteworthy that Eastern Front 109s were relying chiefly on B4, with some notable exceptions like IV/JG 4 and II/JG 11 - I suppose this was also have to do with simplifying fuel logistics to a single C-3 fuel for units which had both 190As and 109s. BTW this would also make IV/JG 4 a strong candidate for 109s operating 1.98ata in the East (apart from II/JG11)

http://www.kurfurst.org/Operations/1...ftflotte6.html