Bf 109 G-6/U4

[Jochen Prien]

Gentlemen,

I wonder whether someone from the community can enlighten me with respect to the following question:

The Bf 109 G-6/U4 was a sub-series of the G-6 that was fitted with a 3 cm MK 108 as centrally mounted weapon instead of the regular 2 cm MG 151/20. It was built by WNF, the planned production figure for 1943 being 800 - or 810 according to another official source -, beginning in May 1943 with the delivery of the first two a/c. The actual production figure was considerably lower, in fact only 181 Bf 109 G-6/U4 being delivered until the end of 1943.

E-Stelle Tarnewitz was given the task to instal and assess the MK 108 in the Bf 109 G-6, beginning in June 1943. They handled two pre-series, the first of 27 a/c, the second of almost the same number of a/c. The first deliveries began in the second half of July, the 27 a/c of the first pre-sereis being delivered to front line units until August 22nd, 1943 with the second pre-series being completely delivered until October 23rd, 1943.

My question is: Were those pre-series a/c in fact the first Bf 109 G-6/U4 coming off the production line at WNF from May through to end of August that were originally delivered without their MK 108 to be completed at Tarnewitz, or were the a/c converted at Tarnewitz completely different a/c that had nothing to do with the series production of WNF ?

This also raises another question: The sharp drop in deliveries in November and December 1943 was at least in part due to the aerial bombing that the production plants of WNF were succumbed to in the fall of 1943 - has anbody got details as to how many Bf 109 G-6/U4 were lost to aerial attacks on WNF Wiener Neustadt prior to acceptance by the Luftwaffe ?

Any founded opinion - or preferably source - would be appreciated.

Thank you in advance and

Regards

Jochen Prien

[ArtieBob]

The Messerschmitt monthly reports for Jan-Aug 1943 are on microfilm Reel 2656 at the US National Air and Space Museum archives. These reports also give the production totals by sub-type for Nachbau Bf 109 production. Until recently, these reports were not indexed, so I do not believe they have been seen by too many. At the same location in the ADi (k) microfilm are a number of Tarnewitz files scattered through reels 153, 154, 155. Many of these files identify the test aircraft by either W.Nr. or Stammkennzeichen. Since the Bf 109 is not my primary area of study, I did not copy all of the material related to that type, but if I remember correctly, the Bf 109 tests with the Mk 108 were covered. Finally, I have a document, translated into English, originating from test pilot Beauvais. In it he mentions some difficulty flying the Mk. 108 equipped aircraft, because of the larger breech housing, which apparently restricted control movement.

Best regards,

ArtieBob

[Jochen Prien]

Thank you very much, ArtieBob. Would it be possible that you contacted me off line via email ?

Cheers

Jochen Prien

[red-star25]

In the weekly reports from Tarnewitz deal mostly with the problems
concerning the installation of the MK 108. Only 1 WNr is given (20734) in this reports. But it looks like, that the MK 108, which came from DWM Posen, were not installed into the a/c at WNF, as the reports mentioned problems about the guns delivered from Posen.

Regards

Dirk

[Jochen Prien]

Thank you very much Dirk. I have got copies of the weekly reports from Tarnewitz which unfortunately do not contain the neccessary information to answer my question.

Regards

Jochen

[George Hopp]

My dear Herr Prien,
Having enjoyed your superb books for many years, it is an honor to try to be of some small help to you in the matter of the 109G-6/U4.

I have a copy of the Tarnewitz report for 21.7.43 with the title "Einbau und Funktionsüberprüfung der MK 108 in den ersten 30 Flugzeugen Bf 109 G6/U4" (Installation and functional testing of the MK 108 in the first 30 Bf 109 G6/U4s). I had hoped to post the report, but some of the words are difficult to make out, so I will, in the interests of time, just give you the gist of the report: The task was originally to simply install the MK 108s in the a/c, and then to give them a short functional test.

The implementation of this simple plan would consist of the following: The a/c were accepted minus the weapons, which I assume meant only the MK 108, rather than also the MG 131s. The weapons came from the final production line at DWM-Posen. The associated units for remote firing of the weapon came from Rheinmetall-Borsig, Berlin-Tagel and its sub-contractors. Anticipated was a short firing of the weapon on the firing stand, then a short firing of the installed weapon on the ground, and finally a short firing of the installed weapon in the air. But, in the rush to make the MK 108 operational it had not undergone the complete testing as specified by GL/C-E6.

Results: The 9 MK 108s delivered at the end of May had so many problems on the firing stand that installing them in a/c was out of the question. In mid-June, 24 improved MK 108s were delivered. They worked well enough that one was installed in an a/c for testing. But, there were numerous problems with the installation that required extensive firing on the firing stand. The report then listed 8 major problems encountered. It also mentions that the training ammunition supplied by DWM had a different fuse cap than the Rheinemetall training ammunition with the result that 3 cannon were destroyed by the exploding cartridge casings.

In the end, everything was fixed up; and at the date of the report (21 Jul 43), of the original 30 a/c, 10 were still at Tarnewitz, and the others had been sent on to Schwerin or to Lärz.

So, according to the wording of the report, it would appear that the 30 a/c mentioned were, in fact, accepted by Tarnewitz as genuine production G6/U4s rather than any other modified a/c. The factory of origin of these a/c is never mentioned, nor were any a/c W.Nrs.

I hope this helps,
George Hopp

[Jochen Prien]

Dear Mr. Hopp,

thank you for your kind words and for the time you took to refer to the Tarnewitz report; it is obvious from your message, that my copies are incomplete because some of the facts and data you mentioned are lacking in my copies. Therefore your reply was certainly helpful.

I think that with what we have now we can with good reason assume that the a/c fitted with MK 108 at Tarnewitz - 1st and 2nd pre-series - were in fact the first Bf 109 G-6/U4 to roll off the assembly lines at WNF albeit minus their MK 108, and that it was at E-Stelle Tarnewitz, where these newly developed weapons were to be added to the aircraft. This is born out by the one WerkNr. that is mentioned in one of the weekly reports, which refers to a Bf 109 G-6 that was definitely built at WNF. Only after the more or less successful elimination of the many faults of the early MK 108 with the completion of the 2nd pre-series at Tarnewitz was it possible, to instal the weapons already on the assembly line at WNF and deliver the complete a/c as Bf 109 G-6/U4, which seems to have started with appr. the 60th a/c to be completed.

What would you call this - an educated guess ? Thanks everbody for their help and input so far. There remains the question of losses to aerial attack on the WNF plant.

Regards

Jochen Prien