Bf 109 H WNr.110073
 

I am trying to reconstruct what was the most probable aspect of the only Bf109 H that went into action; by reading all the documentation in my possession, including the material of the following links:

Bf 109 H (page 1)

Bf 109 H in service with 5.(F)/123 - Luftwaffe and Allied Air Forces Discussion Forum and the attached document
https://www.flickr.com/photos/162245...posted-public/

https://www.flickr.com/photos/162245...posted-public/

https://www.flickr.com/photos/162245...posted-public/

I have developed the drawing you see.

https://www.flickr.com/photos/162245...posted-public/

I would be grateful for any suggestions and/or modifications you would like to suggest.

Many thanks in advance.
Giampiero

Re: Bf 109 H WNr.110073
 

First off: many thanks for posting that Bauzustand for the Guyancourt 109 H - I had not seen that before!

Just a couple of thoughts:

- You indicate that the regular pressurized canopy was later replaced by an Erla Haube. On what information is this based? A pressurized version of the Erla Haube was developed, and prototyped, but I have never seen it installed on an actual airframe. If it was installed on the 109 H that would be really interesting.
- Since the aircraft was pressurized, there should be a small intake on the right side of the cowling for the compressor of the pressurization system (as on a regular G-5). As an aside, I have never seen images of an AS cowling with an intake for the cabin pressurization compressor.
- Since the machine was constructed on the basis of a standard G-5 converted to AS, it seems likely that it used the regular AS cowling. However, for the 109 H, a more refined cowling was planned, which ultimately saw use on the Erla produced G-10. So, it cannot be excluded entirely that the Guyancourt machine may have had the refined cowling.
- The Bauzustand report states that the radiators were positioned in the wing extension "as in the 109 H V55". According to some interpretations, the H V55 had the radiators incorporated into the leading edge of the wing extension.
- The Restabdeckungen for the main gear may not have been entirely like those of the K. Messerschmitt also designed Restabdeckungen for the G, but these were not introduced widely, although some individual machines were equipped with them (e.g. Graf's G-6). The Restabdeckungen for the G were metal, whereas those of the K were wood. Also, in the G they were actuated hydraulically, whereas in the K it was through a pulley system connected to the main gear retraction system. However, this would not really be visible in your drawings.
- Your side views show the aircraft with a regular 109 G wing (no extended tip, slats, ailerons or flaps).
- Two of the links in your post both lead to the same Bauzustand report.

Just my 2 cents!

Re: Bf 109 H WNr.110073
 

If it helps, this is the verbatim text of teleprint CX/MSS/T187/48 (TNA file HW5/484)

WEST EUROPE

TO TECHNICAL OFFICER, DATED 16/5:-

THE STAFFEL REPORTS SURRENDER OF BF 109 G-5, WORKS NO 1(B%1)0346, THROUGH SALVAGE DETACHMENT 20/IV ANVIEN(+) TO GUYANCOURT WORKSHOP ON 14/5. THE STAFFEL REPORTS ACCEPTANCE OF BF 109 H, WORKS NO. 110073 ON 16/5, FROM GUYANCOURT WORKSHOP. A/C HAS DB605-GS ENGINE MMM METHANOL INSTALLATION AND GM1- INSTALLATION, CAMERA 50/30, FU GE 16 Z, WITH HOMING ATTACHMENT ZVG 16, FA16E AND FA16S, PRESSURE CABIN, AND 1 MG 151-20.

NOTES: 1) SOURCE BELIEVES ABOVE FROM 5(F)123

2) (+) NOT LOCATED. MAY BE ANVIN, LOCATED IN PAS DE CALAIS AREA

3) AN ME 109 WITH H BUILT IN £H - EINBAU£ WAS READY TO BE COLLECTED FROM GUYANCOURT ON 10/5 (T182/3)

4) SEE T187/47 FOR TECHNICAL DEFECTS IN THE COMPRESSED AIR SUPPLY OF BF 109 G-5 (HIGH ALTITUDE A/C).

1752/17/5/44

Re: Bf 109 H WNr.110073
 

First of all, thank you for your articulate answer.
- regarding the Erla-Haube I invite you to read the first document, or the answer that Nick Beale gave immediately after you
- it seems, I say it seems, that there were Bf 109s pressurized both with that without the small intake on the right side of the cowling, in any case the refined cowling did not have it, at least in the production airplanes
- I think the radiators were positioned as on the V50 or V54
- I agree perfectly with you on the two different types of Restabdeckungen, I wrote 'K' to clarify the concept (I did not want to write too much on the drawing)
- you are also right on the side profiles, but you must know that the proposed drawing was not done by me (I absolutely do not know how to draw ), but it's a collage made with various other designs and I didn't find a good side view of the 'long wings'
- I fixed the links in the meantime.


Giampiero

Re: Bf 109 H WNr.110073
 

There are also quite a few well-known drawings on the web...

Re: Bf 109 H WNr.110073
 

Many thanks for your reply! Just some comments:

- Erla Haube: unless I overlooked something, the Ghostbombers website only states "On 11 May, 5.(F)/123 had been told that 15 all-round vision canopies were ready for collection from the ERLA works airfield at Antwerp-Deurne: the Staffel was to keep three, the rest were for Guyancourt." So, they received Erla Hauben from Erla VII, but that does not necessarily mean one of those was used on the H conversion (for which it would have needed to be a pressurized version, which was quite significantly different in a number of aspects from the regular Vollsichthaube). Also, maybe again I overlooked it, but I don't see any mention of a Erla Haube in the transcript reproduced by Nick Beale here.

- Cabin pressurization intake: interesting if there were some that lacked this intake... I just wonder, in that case: where would the compressor get its air, if there was no intake? And weren't these Erla cowlings standardized - after all, there are lots of G-6 and G-14 without pressurization that do have the bump and intake even though on those aircraft it's not needed. In the case of G-5/AS conversions, I think there is some question as to whether those retained cabin pressurization after conversion - if not, they wouldn't have needed the intake on the refined cowling anyway.

- Radiators: I tend to agree, but on the other hand I do find it interesting the document specifically references the installation of the H V55, and not the V54.

Thanks for your efforts!

Re: Bf 109 H WNr.110073
 

In the original:

CX/MSS/T181/124

Source copied document of 11/5:

With a view to fetching the 15 all-round vision cockpits for Bf 109 which have been allocated in accordance with communication of Lehr and Ersprobungskommando 24 Großenhain, the Staffel will immediately despatch a collecting detachment to the Erla Works, Airfield Antwerp-Deurne.
3 of them are intended for the Staffel and can be at once taken over. The remaining 12 are to be sent on to workshop at Guyancourt.

NOTE: Source has reason to think that 5.(F)/123 was the Staffel concerned.

Source: TNA file HW 5/481

Re: Bf 109 H WNr.110073
 

You cannot pressurize an Erla Haube.

The reason why is because of the tubular construction, and lack of seal at the BACK end of the canopy.

The construction was steel and mild steel. Mild steel was used all around the tubular construction (especially at the rear), and bent very easily (malleable with your hand). As such, there is no way to seal around the cockpit.

In addition, the only part of the 109 cockpit that was ready for pressurization was the cockpit tub (firewall to seat back).

The fuselage was not made pressurized behind the seat...and the Erla Haube extended all the way to the baggage compartment.

There would have had to be a complete re-deign of the entire cockpit to make that work...as well as a newly designed canopy and rear armour.

This is why the 3-piece canopy was only used on pressurized models...it sealed right at the seat back, where the head armor (newly-designed for the pressurized cockpit) enclosed the entire cockpit.

Soooooo...if it had an Erla Haube...it was not pressurized.

The only way it could have been pressurized, is if it had the 3-piece G3/G5 Canopy.

Re: Bf 109 H WNr.110073
 

Please read my earlier post on the topic. A pressurized Erla Haube was designed and prototyped. There are two photographs of it in Schmoll (2017, p. 173). As I noted, this pressurized Erla Haube was significantly different in construction from a regular Erla Haube. The framing was reinforced, double walled transparencies with silica gel pellets were installed, there was a pressure seal around the entire circumference, and a pressure bulkhead at the back of the Haube, in front of the luggage compartment. The windscreen was also redesigned and incorporated heating. In many respects, it was an entirely new canopy from a technical point of view - but it retained the overall lay-out of a regular Erla Haube.

Reference:

Schmoll, P. 2017. Me 109. Produktion und Einsatz. MZ-Buchverlag, Regenstauf, Germany. 312 pp.

Re: Bf 109 H WNr.110073
 

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!

Re: Bf 109 H WNr.110073
 

As a follow up to my previous message, in case you - or anyone else - is interested to see what a pressurized Erla Haube looks like: I took a quick snap of the photos on p. 173 of Schmoll (2017), and they can be downloaded here:

https://disk.yandex.com/i/q0JjZkR1z22YoQ

Apologies for the poor quality.

Re: Bf 109 H WNr.110073
 

Thanks for the image...

:)

Here is the problem though...

This was never implemented. Prototype only.

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

Re: Bf 109 H WNr.110073
 

But could you describe the Bf 109H that flew with 5.(F)/123 as anything more than a prototype or experimental model? It wasn’t in series production and it wasn’t a standard Umrüst Bausatz, was it?

Re: Bf 109 H WNr.110073
 

Given the content of post n. 1, I would be very interested.
Giampiero Piva

Re: Bf 109 H WNr.110073
 

The fotos of the pressurized Erlahaube were attached to a letter from Phänomen-Werke to Forschungsanstalt Oberammergau dated 28. Nov. 1944. They were to back up a not included report on testing the cabin 009.128-Z003/123-Z001. It is quite clear that the cabin was prototype only. IMHO a pressurized Erlahaube was not available for WNr. 110073 anyway.
One of the fotos has a handwritten note: "Windschutzaufbau 8-109.128-Z003 K3 - Z003 druckfest".

Re: Bf 109 H WNr.110073
 

Correct...

Even the Me109K never had it in 44/45. Impossible for the H model to have it in 1943 when it was not even available (and probably still on the drawing board).

Re: Bf 109 H WNr.110073
 

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.

Re: Bf 109 H WNr.110073
 

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!

Re: Bf 109 H WNr.110073
 

One more thing I thought about for your reconstruction: testing of the V54, and experience with the G-6/AS showed that the standard Fo 870 oil cooler provided insufficient cooling capacity. As a result, the V54 was to be refitted with the larger Fo 987 oil cooler, which was also introduced during G-14/AS production, and retrofitted to some G-6/AS. Therefore, 110073 possibly may have been equipped with the larger Fo 987 oil cooler. We really need to see the photographs that purportedly exist of that aircraft!

Re: Bf 109 H WNr.110073
 

I have not seen the photographs, but there is a 3-view drawing, which appears to be of Me origin on microfilm of the captured German documents at The US National Air and Space Museum. It is not a very good image, but it is pretty well dimensioned and shows some internal detail, i.e. location of the GM-1 tank, etc. Of course, the real aircraft may not appear exactly the same as the drawing, but the canopy on the drawing certainly does not appear to be the Erla type.
Best Regards,
ArtieBob

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.