Re: Bf 109 H WNr.110073
 

Do you mean the schematic three-view drawing dated 21.7.1943? That one indeed shows the regular three-piece canopy. An overview schematic of the Baugruppen dated 24.2.44 also shows the regular three-piece canopy. There is also another schematic side-view drawing of the proposed production version of the H (using the K fuselage), which shows an Erla Haube, but unfortunately I don't know the date for that one.

Re: Bf 109 H WNr.110073
 

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?

Re: Bf 109 H WNr.110073
 

Yes, I already said that the standard Erla Haube could not be pressurized, due to the steels used.

The prototype H model was made at the end of 1943, which is why I referenced it...I was not referring to this specific aircraft, but rather the initial design (which was based on an F initially)...so that was not me misquoting anything. I was simply stating that when it was initially designed, the pressurized Erla Haube was not even on the drawing board.

Just because an Erla Haube was said to have been installed on a G5 airframe, does not mean that they kept the pressurization. It could started WITH a pressurized cockpit (and standard canopy)...and then adapted later to take the Erla (pilot preferred) with no pressurization.

After all...none of these aircraft NEEDED pressurization. The B-17 was at mega high altitudes and was unpressurized. Though it was "convenient" for the German pilots to have this...they were already flying at high enough altitudes without it.

If it was something they "had" to have...they would have made the G3 and G5 in mass numbers.

I suspect it originally had the standard canopy, but was later changed out to the Erla...and they dropped the pressurization as it was not needed, really not that great to begin with, and had its problems.

Re: Bf 109 H WNr.110073
 

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.

Re: Bf 109 H WNr.110073
 

Actually, I think we are mostly in agreement. My comment about the standard Erla Haube was in reply to Graham Boak’s suggestion that it might have been modified for pressurization – something I agree with you would have been impossible because of its construction.

I took your 1943 reference to be with regard to 110073 at Guyancourt, hence the misunderstanding. While, strangely, the 1942 Sofort-Programm to produce a high-altitude fighter was based on the 109 F (which had ceased production in April 1942, with the G-1 entering production in February of that year), the Schnellösung of 1943 which gave rise to the 109 H was based on the G-5/U2 from the outset, with projected production versions being derived from the 109 K. Two drawings of the production 109 H based on the K fuselage both show an Erla Haube. Unfortunately, I do not have a date for those drawings, but I would assume they are from early 1944, given that the 109 H was essentially shelved by the middle of that year.

I agree that the V49 may have lost its pressurization – see my reply to Graham Boak. However, both the DB 628 and the Bf 109 H had design altitudes of 14 000 – 15 000 m. So, for testing the full envelope of both this engine, and the airframe, a functioning pressure cabin would have been indispensable. The V54 was tested extensively, also at high altitudes, and the Guyancourt W.Nr. 110073 was used for high-altitude reconnaissance. So, at least both these two airframes would have required functioning pressure cabins.

I also agree that for combating bombers over Europe, pressurized fighters were not required – which is also a reason why pressurized versions of the 109 were abandoned after the G-5 (of which about 550 were built, not an insignificant number). However, cabin pressurization is indispensable for high-altitude reconnaissance aircraft, which was one of the main roles envisaged for the 109 H besides that of extreme altitude fighter (where it could have been used to combat allied high-altitude reconnaissance machines). Remember, the 109 H was intended to operate at altitudes around 14 000 m, where cabin pressurization is a necessity.

In any case, to get back to the Guyancourt machine W.Nr. 110073: this aircraft definitely had a functioning pressure cabin, given its intended role and the quoted altitude of 14 200 m it achieved (Nick Beale's Ghostbombers website). Planning for the conversion dates at least to January 1944 (see the Bauzustand posted by piero, with a date of 24.1.44). The machine was converted at Guyancourt in Spring 1944, with Fritz Wendel making the first test flights on 5-6 April 1944 (test report by Wendel). In May it was transferred to 5.(F)/123 for operational testing, and on 12 July it was shot down by friendly FlaK (Ghostbombers website, courtesy of Nick Beale). So, while I consider it most likely that this aircraft was fitted all the time with a standard three-piece pressurized canopy, in my opinion, this timeline does not entirely exclude the possibility that it *might* have been equipped at some point with a pressurized Erla Haube. The same also goes for the V54, which made its first flight on 2 November 1943, and was damaged in a forced landing on 29 June 1944, marking its final flight (it was intended to be repaired and slated to undergo further modifications, but it seems this was never finished – see Nick Beale’s Ghostbombers page).

Re: Bf 109 H WNr.110073
 

TNA file WO208/1434

S.R.A. 5608

CS/196 – Leutnant WARTHOL (Fighter Pilot: Me 109, G6, 17+Black, 5(F)/123) Captured Dreux 16 Aug 44

CS/202 – Leutnant OTTNAD (Fighter Pilot: Me 109, G6, 9+, 8/JG 27) Captured Dreux 18 Aug 44

Information received 28 Aug 44

TRANSLATION

WARTHOL: We had the ‘H’ The ‘Kommandeur’ said: “What do you want? The ‘H’ has been up to 14200m.” The ‘Gruppenführer’ did that on the firm’s trial with the ‘H’; according to the barogram and according to the altimeter. A special altimeter had been installed, which went up to 15000 in. A special barograph had also been installed, which also registered up to 15000m. “What more do you want? With the ‘H’ you can outclimb any enemy aircraft.” We had to explain to him that we could get away for the moment by climbing, but we couldn’t remain at a height of 14200m, because we hadn’t got the petrol for it. The ‘H’ has such a heavy consumption of petrol at high altitude that you can’t keep it up. In the end the ‘H’ has to come down again. Then it is capable of 650 k.p.h.

Re: Bf 109 H WNr.110073
 

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.

Re: Bf 109 H WNr.110073
 

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.

Re: Bf 109 H WNr.110073
 

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.

Re: Bf 109 H WNr.110073
 

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.