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Old 12th September 2005, 14:54
Kurfürst Kurfürst is offline
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Documentation of 2000HP Bf 109s of 1945

Note : Both Bf 109 G-10 and K-4 used the same type(s) of engines, namely :

DB 605DM for 1800PS, at 1,75ata, and a rated altitude of 6,5km. fitted to early production planes. DM engine being a 605D-2 with MW injection.
DB 605 DB/DC. The latter could be converted into each other, 605DB running on 87 octane 'B-4' fuel for 1.8ata and 1800/1850 PS at SL, 1600PS at 6km, as opposed the DC`s maximal boost of 1.98ata with 96 octane 'C-3' fuel, for 2000 PS at SL and 1800 at 4.9km, both achieved with the built-in MW 50 injection.

The output of the DB/DC engines were the same above 6000m, under which the DC was more power, if at higher boost.

Summary of the clearance 1.98ata/2000 HP for the DB 605DC and the Bf 109G-10/K-4 story - so far :

Early troubles.

So far we seem to know DB cleared the 1.98ata rating somewhere before Jan 1945, and released it to the troops and Gen Galland, probably in december 1944 : the first known, being the third edition already, DB 605 DB/DC manual was issued on the 5th December 1944, and already noted 1.98ata.

Furthermore, referecences to 1.98ata were made in various docs from December 1944 :

The clearance of 1.98ata p*ssed some guys at Rechlin out, since several tests done with 1.98ata in early January - such as one that tested four different VDM airscrews - showed the engines failed at the rating, to which DB replied to that their previous test runs at 1.98ata were positive.

It was agreed in mid-January, 1945, to test the rating at 'Gruppe 2/11' before released to troops, along with 1.8 and 1.9ata ratings :

"Nach Lage der Dinge wird denn festgelegt, dass vorläufig die Erprobung des Ladedruckes 1,98 ata nur bei der Gruppe 2/11 durchgeführt werden darf, und dass im übrigen nur die bereits angelaufenen Erprobungen mit 1,9 ata zu Ende geführt werden dürfen bis die entsprechenden Motoren ausgefallen sind. Der Nachschub für diese Motoren darf dann nur mit Motoren mit Einstellung 1,8 ata Ladedruck erfolgen. Bei Nichtbeachtung dieses Befehls wird strenge Bestrafung angedroht. Die Genehemigung zur Einstellung 1,98 ata darf ausschliesslich nur durch die Abtlg. VI des Generalstabes erteilt werden.

Seitens der Herren das Chef-Ing. wird vorgeschlagen, evtl. auch einzelnen Aufklärer mit dem Ladedruck 1,98 ata auszurüsten. Eine Entscheidung hierüber ist jedoch nicht gafällt worden.

Zur thermischen Entlastung der mit 1,98 ata und 1,90 ata eingestellten Motoren wird festgelegt, dass auch diese das spätgestellte Zündprogramm erhalten. Somit werden also all Motoren, die mit der sogenannten Sondernotleistung geflogen werden, auf die späte Zündung umgestellt."

Translation :

"After the delays in the matter, it has been laid down, that testing of 1.98ata manifold pressure is foreseen to be proceeded with only with the Gruppe 2/11, otherwise only the already initiated tests in process with 1.9ata manifold pressure are to be completed, until the the said engines fail. The replacements for these engines should be with the 1.8ata setup only. Not following this order will result in severe punishment. Permission for adjusting for 1.98ata can only be given in cooperation with Department VI. of the General Staff.

On behalf of the Chief Engineer`s men it has been presented, that it may be possible to equip single fighter-recons to 1.98ata manifold presure. Decision has not been taken on this yet.

Delayed ignition is to be used with engines at 1.9ata and 1.98ata setups, as a result of the termal load that had been observed with them. Therefore all engines, that are flown with the abovementioned Sondernotleistungs, are to be set to delayed ignition."

See : Niderschrift Nr. 6730 Daimler-Benz AG, Sektor Entwicklung. 20.1.45

Butch2k says the 1.98ata clearance came in late February,
after the trials were successfull, but there was some delay, probably due to finding the correct spark plugs etc.

It is also known that a maintaince document was issued at that time, namely Reparatur-Anweisung 2. Nachtrag Nr. 191/345 from des Reichministers für Rüstung und Kriegproduktion, in 14 March 1945 which tells the details of converting the 1.8ata capabe 605DB into the 1.98ata capable DC version.

Moreover this document tells that "C-3 fuel is available for use in unreduced quality", as opposed to B-4:

"Sämtliche Änderungen sind durch die Forderung bedingt, für die leistungsgesteigerten Motoren auch B4 Kraftstoff minderer Qualität ohne Gefahr verwenden zu können. Da kraftstoff C3 in unverminderter Qualität zur Verfügung steht, werden Motoren 605 ASC und 605 DC, falls sie in dieser Ausführung aufgebaut werden, unverändert wie bisher abgegeben;"

... which makes claims about specific shortage of C-3 fuel, that was required for 1.98ata operation, doubtful, C-3 was appearantly not any more on short supply than any other fuel in 1945.

Furthermore, it is proven that C-3 was not some kind of ultra-rare fuel curiosity, but a major volume of aviation produced in Germany in the 2nd half of the war.

From the "TECHNICAL REPORT NO. 145-45, MANUFACTURE OF AVIATION GASOLINE IN GERMANY, 2. Supply and Composition of Aviation Gasolines, "prepeared by the U.S. Naval Mission to Germany after the surrender. The original can be found at the Fishcer-Tropsch archives :

"(B) Composition and Specifications

There were two (2) grades of aviation gasoline produced in volume in Germany one the B-4 or blue grade and the other the C-3 or green grade. Both grades were loaded with the equivalent of 4.35 cubic centimeters tetraethyl lead per gallon. The B-4 grade was simply a fraction of the gasoline product from coal and coal tar hydrogenation. It contained normally 10 to 15 percent volume aromatics, 45 percent volume naphthenes, and the remainder paraffins. The octane number was 89 by a measurement corresponding to the C.F.R. motor method. The C-3 grade was a mixture of 10 to 15 percent volume of synthetic isoparaffins (alkylates and isooctanes) and 85 percent of an aromatized base stock produced by hydroforming types of operation on coal and coal tar hydrogenation gasolines. The C-3 grade was permitted to contain not more than 45 percent volume aromatics. This aromatic limitation sometimes required that the base stock component include some diluents other than the aromatic fraction, which could then be balanced if necessary by the inclusion of slightly more isoparaffin. (The C-3 grade corresponded roughly to the U. S. grade 130 gasoline, although the octane number of C-3 was specified to be only 95 and its lean mixture performance was somewhat poorer.)

The components of the two grades were therefore simple and few in number. The isoparaffins were produced by standard, well known methods and there was nothing abnormal found in their compositions. The base stocks were fractionated to and points of 300 to 320 degrees Fahrenheit. No normal isopentane separation was carried out and the pentane and butane contents were adjusted simply for vapor pressure control. Small amounts of specially synthesized aromatic compounds were included from time to time but no regular large scale use of such materials was practiced. No aromatic olefines or other special additives were used.

Oxidation inhibitors were not used in the regular blended aviation gasolines. It will be seen that the components were in general of such nature that addition inhibition should not have been necessary. Lead depositions from fuels was an operating problem, however, but no inhibitors were used for its prevention. This lead instability was believed to be related to aromatic content and fear of lead deposits was a reason for the limitation of the aromatic contents of the two grades.

The relative volumes of production of the two grades cannot be accurately given, but in the last war years the major volume, perhaps two-thirds (2/3) of this total has the C-3 grade. Every effort was being made toward the end of the war to increase isoparaffin production so that C-3 volume could be increased for fighter plane use. The isoparaffin usage in that grade had already been cut to a minimum."

Some details of the actual supplies of C-3 fuel to the Bf 109 units in 1945 :

The following relates to the use of C-3 fuel by the Axis-Italian air force in the last stages of the war. I guess they were not preferred over genuie Luftwaffe units in being supplied with high octane fuel.

Via the Hungarian edition of :
Beale-D`Amico-Valentini : "Air War Italy, 1944-45: The Axis Air Forces from the Liberation of Rome to the Surrender"
Airlife Publishing, Ltd. (January, 1996) ISBN: 1853102520

Aircrafts on hand,the Order of Battle of the ANR (the Axis-allied northern italian airforce) during 22nd April 1945 :

Bf 109s
7 x G-6s
27 x G-14s
39 x G-10
3 x K-4s
2 x G-12 trainers

Futher 12 S.79 transports, I take these operated on B-4.

As seen, the most important engine was the DB 605D in the 109K and G-10, developing 1850 PS w. B-4 fuel and 2000 HP w. C-3 fuel.

The DB 605 A and AM engines of the G-6/G-14 could run on either fuel, but the output would remain the same.

The fuel stocks were as the following during the same period, during April 1945, and suggest that the primary fuel used by the Italian 109s was C-3.

It`s doubtful that the Italians would enjoy some kind of 'special treatment' and priority in being supplied with high quality fuel over the own Luftwaffe units.

Introduction of 1.98ata into service occured during March 1945 :

Orders issued to units to increase boost pressure to 1.98ata, according to a classified order dated 20th March 1945 from the LW high command (OKL, Lw.-Führüngstab, Nr. 937/45 gKdos.(op) 20.03.45) :
via :
Fritz X. Kober - Jakob Maria Mathmann : The Messerschmitt Bf 109 Vol.2. Schiffer Publishing, 1996.

"The development in the equipment status of day fighter units is based on the standard types laid down in the emergency program and anticipates :

for Bf 109 units : K-4

for FW 190 units : D-9, D-12 with changeover to Ta 152 H and C

The arrival of the Ta 152 and it`s assignment to FW 190 units will result in an improvement in the equipment status of these units.

Essentially Bf 109 development will conclude with the K-4 an will inevitably lead to the conversion of Bf 109 units - those not scheduled for disbandment - to TL (jet fighters). Homogeneity of the equipment is to be strived for, combination of similar types is temporary and to be accepted based on levels of production."

The proposed changes to units equipped with Bf 109 were as follows :

OKL, Lw.-Führüngstab, Nr. 937/45 gKdos.(op) 20.03.45

No. Unit Present type Convert to Notes
1. III./ JG 1 Bf 109 G-10 He 162 (April/May) -
2. II. / JG Bf 109 G-10 K-4 when deliveries permit -
3. III. / JG 3 Bf 109 K-4 no change -
4. III. / JG 4 Bf 109 K-4 no change -
5. IV. / JG 4 Bf 109 K-4 K-4 -
6. III. / JG 5 Bf 109 G-14 K-4 when deliveries permit -
7. IV. / JG 5 Bf 109 G-14 K-4 when deliveries permit -
8. III. / JG 6 Bf 109 G-14/AS K-4 when deliveries permit -
9. II. / JG 11 Bf 109 G-10 K-4 when deliveries permit -
10. I. / JG 27 Bf 109 K-4 no change boost increase to 1.98 ata
11. II. / JG 27 Bf 109 G-10 K-4 when deliveries permit -
12. III. / JG 27 Bf 109 G-10 no change boost increase to 1.98 ata
13. I. / JG 51 Bf 109 G-14 K-4 when deliveries permit -
14. III. / JG 51 Bf 109 G-14 K-4 when deliveries permit -
15. IV. / JG 51 Bf 109 G-14 K-4 when deliveries permit -
16. II. / JG 52 Bf 109 G-14/U4 K-4 when deliveries permit -
17. III. / JG 52 Bf 109 G-14 K-4 when deliveries permit -
18. II. / JG 53 Bf 109 K-4 no change -
19. III. / JG 53 Bf 109 K-4 no change boost increase to 1.98 ata
20. IV. / JG 53 Bf 109 K-4 no change boost increase to 1.98 ata

21. I. / JG 77 Bf 109 G-14/U4 K-4 when deliveries permit -
22. II. / JG 77 Bf 109 G-10 K-4 when deliveries permit -
23. III. / JG 77 Bf 109 G-10 K-4 when deliveries permit -
24. III. / JG 300 Bf 109 G-10/R6 via K-4 to Me 262 planned, deadline
25. IV. / JG 300 Bf 109 G-10/R6 via K-4 to Me 262 -
26. I. / KG(J) 6 Bf 109 G-10/R6 K-4/R6 when deliveries permit -
27. II. / KG(J) 6 Bf 109 K-4 K-4/R6 when deliveries permit -
30. I. / KG(J) 27 Bf 109 G-10/R6 K-4/R6 when deliveries permit -
31. I. / KG(J) 55 Bf 109 G-10/R6 - -
32. II. / KG(J) 55 Bf 109 K-4 - to industrial defense
33. Ist Italian FG Bf 109 G-10 K-4 when deliveries permit -
34. IInd Italian FG Bf 109 G-10 K-4 when deliveries permit -
35. IIIrd Italian FG Bf 109 G-10 K-4 when deliveries permit -

Fritz X. Kober - Jakob Maria Mathmann : The Messerschmitt Bf 109 Vol.2. Schiffer Publishing, 1996. English edition.

This order notes in relation of I./JG 27, III./JG 27, III./JG 53, IV./JG 53 to increase the maximum boost pressures to 1,98 ata manifold pressure. It is not known if and how many units had converted to 1,98ata before that order came, but it should be noted these units, in particular III./JG 27, III./JG 53 and IV./JG 53 were the major users of the Bf 109 K-4 in the Lufwaffe.

It is also known these were the Bf 109 units in 1945 that stayed in the West and continued to perform actions against the Western Allies, as opposed to the most of the Jagdwaffe that tied to slow the down the Red advance in the east.

The four Wings/Gruppes tasked to increase boost pressure to 1.98ata could still muster considerable strenght - and basically they were the only units remaining on the Western front in the last months.

Overview of unit strenghts for the units that used 1,98ata. As per 9th April 1945.
Source : Alfred Price : The Last year of the Luftwaffe

Unit - On hand - Servicable

I./JG 27 - 29 - 13
III./JG 27 - 19 - 15
III./JG 53 - 40 - 24
IV./JG 53 - 54 - 27
Total : 142 on hand, out of which 79 is servicable at the given date

Picture of Bf 109K Werknummer 334 210, taken in 1945 :

I seen veltro also posts in this boards, perhaps he can add more on Italian fuel shipments to the ANR.
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