Bf 109 H WNr.110073

[harrison987]

Thanks for the image...



Here is the problem though...

This was never implemented. Prototype only.

So, the H model would never have had this...

[pvanroy]

On a related note, I remember that over a decade ago, David Wadman announced that he had discovered two photographs of the 109 H operated by 5.(F)/123 in a German private collection, and had obtained rights to publish one of those images in an upcoming book of his (while negotiating the release of the second image). Nothing seems to have ever come of this. Does anyone here know more about this? It would be amazing to finally have some photographic evidence of this aircraft!

[Graham Boak]

The Guyancourt operation wasn't 1943.

Unlike the K, however, the Hs was based on G-5 airframes, so were pressurised already. It seems to me that it wouldn't have been a great task for a prototype to block off the rear of the cockpit opening to seal it and permit the fitting of a standard Erla canopy. I don't recall mention of the G having anything other than a standard canopy, perhaps this is wrong. I don't say that this was done, just that it seems to be well within the capability of the prototype workshop shop. Something of a bodge rather than proper production standards.

[pvanroy]

Just a couple of points:

1. No-one in this thread ever claimed that 110073 was definitely equipped with a pressurized Erla Haube. Piero suggested that it had received an Erla Haube at some point, to which I replied that if this was the case, it would be quite interesting, as this would need to have been a pressurized Erla Haube - which is not entirely inconceivable considering a pressurized Erla Haube was prototyped. That's all.

2. Of course, if the construction of the pressurized Erla Haube post-dates the May-July 1944 time frame (NOT 1943 as misquoted by harrison987) of the use of 110073 by 5.(F)/123, that machine obviously cannot have been equipped with it.

3. Modifying a regular unpressurized Erla Haube for cabin pressurization, as Graham Boak suggests, would not really be possible. The construction and materials of the regular Erla Haube are simply too flimsy to withstand the pressure differential. It would also have been difficult to accommodate the double canopy glazing required by the cold wall-type pressure cabin used by the G-5. The pressurized Erla Haube really required an almost entirely new design from an engineering point of view.

4. The date of 28 November 1944 as cited by Charles Bavarois for the letter to which the photographs of the the pressurized Erla Haube was attached poses an interesting question: what purpose did this work serve at that point, as by that time both pressurized versions of the K series and the H series had been long abandoned? Also, if these photos were part of a test report, the pressurized Erla Haube clearly must have existed before that date.

5. Harrison987's argument that "Even the Me109K never had it in 44/45" is a non-sequitur: the only K version produced in series was the K-4; in addition, there may have been two K-2 airframes, and one K-6 converted from a K-4. All these machines lacked cabin pressurization, so why would they be equipped with a pressurized Erla Haube? The G-5 was the last pressurized 109 produced in series, with the final machines being delivered by Erla in June 1944. So, after that date, there was simply no longer any requirement to produce pressurized canopies of any type for the 109 - and obviously no need at all to equip unpressurized aircraft (i.e. all K machines constructed) with a canopy set up for pressurization.

6. Years ago, George Hopp posted on LEMB a document entitled "Me 109H/ DB 628 Höhenjäger Kurzbeschreibung", dated 27 May 1943. You can download it here:

https://disk.yandex.com/i/F_uGWbCHbTW9GQ

Interestingly, in the description of the fuselage, it states "Normaler Me 109 G 5 Rumpf mit Druckkabine ohne GM 1 Anlage, jedoch mit folgenden Änderungen: ... ohne Panzerscheibe, Kopfpanzer, Rückenpanzer, Leichtmetallrückenpanzer..." So, if I understand this correctly, this aircraft (likely referring to the V49, possibly V50) had a pressure cabin, but lacked the head armor. In the regular three-piece pressurized canopy, the head armor doubled as a pressure bulkhead, and was an integral part of the central hinged portion of the canopy. Hence, removal of the head armor in the standard three-piece pressurized canopy would have resulted in the loss of cabin pressurization. Yet, this aircraft is described as pressurized.

In summary, I am not at all arguing that 110073 definitely had a pressurized Erla Haube - in fact, as I've clearly indicated in my earlier posts in reply to piero, I think it is quite likely that the machine had a standard three-piece pressure canopy during its entire existence. However, I do feel, that, on balance, the possibility that this experimental aircraft at some point might have received a pressurized Erla Haube cannot be entirely discounted. Hopefully, the photos mentioned by David Wadman al those years ago will one day show up!

Many thanks to Nick Beale and Charles Bavarois for providing the transcripts, and for further information regarding the pressurized Erla Haube!

[Graham Boak]

Thanks for the additional detail on the cabin pressurisation of the G-5. I'm a little surprised, therefore, that the G-5 canopy is not clearly distinguishable from the standard.

It would not surprise me to find that the V49 was not pressurised. Its role would be entirely to get engine hours up on the new engine, with the high altitude regime studied later. Presumably the head armour could easily be restored, although perhaps this depends upon just why they took it off in the first place?

It shouldn't have surprised anyone that the high-altitude engines require a larger cooler. Or is the timing just in advance of the appearance of AS/D engiines?

[pvanroy]

Originally Posted by Graham Boak

Thanks for the additional detail on the cabin pressurisation of the G-5. I'm a little surprised, therefore, that the G-5 canopy is not clearly distinguishable from the standard.

It would not surprise me to find that the V49 was not pressurised. Its role would be entirely to get engine hours up on the new engine, with the high altitude regime studied later. Presumably the head armour could easily be restored, although perhaps this depends upon just why they took it off in the first place?

It shouldn't have surprised anyone that the high-altitude engines require a larger cooler. Or is the timing just in advance of the appearance of AS/D engiines?

The reason that the pressurized and unpressurized three-piece G canopies are very similar is because of standardization: a new heavy steel canopy framing was designed for the G, to be used one both pressurized and unpressurized variants. In unpressurized variants, this heavy framing mounted single-layer transparencies, and the typical sloped head armor. In the pressurized variants, double transparencies were mounted in the same basic canopy frame, and a vertical combined pressure bulkhead/armor plate with small triangular transparencies and pressure valves was installed at the back of the central canopy part, forming the upper rear wall of the pressure cabin. Silica gel cartridges and pressure valves for the barrier were incorporated into the lower right corners of the outer transparencies. The canopy framing was not the only part that was standardized: the basic cockpit tub of unpressurized early G versions is also similar to that of pressurized variants, using the same pressure-sealed connections for cabling and connecting rods; these were dispensed with on later versions, when development and construction of pressurized 109 variants was discontinued.

It is indeed possible that the V49 (W.Nr. 16281, converted from G-3) lost its pressurization: only ten rather short flights are documented for this machine between 23 April 1943 and 14 May 1943, and the majority of them is concerned with evaluating the effects of the longer and heavier engine on stability around the axes and general handling (Vogt 2018). It is also known that the aircraft started flying without the first compressor stage of the DB 628 installed due to continued metallurgical problems with the bearings of this stage. The machine was then transferred to DB at Echterdingen, where the second compressor stage was finally installed and tested in flight on 18 August 1943. In total, there seems to be a record for at least six flights at DB between 21 June 1943 and 30 October 1943 (Mermet & Ehrengardt 2015). All these flights seem to have focused on general performance of the engine, lubrication and cooling systems (which proved insufficient). So, for this type of work, the aircraft indeed would not have needed pressurization. The machine was reportedly destroyed on 14 August 1944 in a raid on Echterdingen (Vogt 2018). One, or possibly two more Bf 109s were equipped with the DB 628 – this may have involved the V50 (W.Nr. 15338, converted from G-5/U2) of which very little is known, but Mermet & Ehrengardt (2015) report that W.Nr. 15708 (converted from G-5/U2) was also used as a DB 628 test bed prior to being converted into the V54 as a full H-prototype with extended wings. The only (partial) photograph I know of that shows a DB 628-engined Bf 109 undergoing maintenance shows it had the pressurized windscreen; however, the canopy is removed, and the rear part of the cockpit is outside the frame of the photograph, so it is impossible to know if it had a pressurized canopy or not.

And while indeed it seems fairly obvious that flying at high altitude would have required increased cooling capacity, the V54, which was tested with the DB 605 A and B, and a significant part of AS-engined machines were equipped with the standard smaller Fo 870 oil cooler, before switching over to the larger Fo 987 during G-14/AS production.

References:

Mermet, J.C. & Ehrengardt, C.J. (2015) Messerschmitt Bf 109. Caraktère Presse & Editions, Aix-en-Provence, France. 192 p.

Vogt, H.H. 2018. Messerschmitt Bf 109. Versuchs und Erprobungsträger und der Weg zur Serienproduktion. VDM Heinz Nickel, Zweibrücken, Germany. 496 p.

[pvanroy]

One more thing to add: a test report of the V54 (W.Nr 15708) by Beauvais, dated 22.12.43, states the following:

"... Das Seitenleitwerk ist für eine Serie nicht ausreichend. Jedoch kann man den Bau von 6 Aufklärern mit diesem Leitwerk verantworten..."

Further, Wendel's test report regarding his flights with the Guyancourt machine (W.Nr. 110073) on 5 and 6 April 1944 starts by saying:

"Am 5. und 6. April 1944 habe ich in Guyancourt die erste dort montierte Me 109 H eingeflogen..."

Both quotes indicate there were plans to convert more (up to six, apparently) airframes to H standard at Guyancourt. However, from the information provided by Nick Beale, it seems in the end only W.Nr. 110073 was actually converted.

[Graham Boak]

One point to catch up on: the B-17 was not at "mega-high" altitudes. The B-29 might have been... and there was an effort to convince the Germans that the B-29 was coming. There was, after all, no reason why they should expect anything else.

I read the Beauvais/Wendel quotes as evidence that there were intentions to build more H development aircraft, but not necessarily (or at all likely) at Guyancourt which was an operational base. Had they existed, they might have ended up there.

[Nick Beale]

Graham, Guyancourt also seems to have been very active in fitting out and repairing Bf 109s for the reconnaissance units in France, so I could picture them (say) putting all the necessary operational radio gear, cameras etc. into prototype airframes delivered to them. So not production per se but something more than pure maintenance.

[pvanroy]

Guyancourt had quite extensive facilities - before the war, Caudron had an assembly shop for their aircraft there. So, I can imagine they would have had the ability to convert a small number of G-5/U2 airframes using kits produced elsewhere - this is what they did with W.Nr. 110073.