I am afraid this is incorrect, I trust Bill on this, and practically all publications I`ve seen say June 1944 for the P-51D as an introduction date.
Two sources I have reference initial production delivery of March, 1944. "American Combat Planes" by Ray Wagner, and "America's Hundred Thousand" by Francis Dean, which states that the P-51D was introduced to the 8th AF. This last reference does state that the P-51D was delivered to the 8th AF in quantity in June, 1944.
The 109K was introduced in during October, units received it in huge numbers already that month (some 200 were around, even though some were wrecked during refit). It was certainly in combat by the start of November since the first combat loss is known from 2 November 1944.
My reference states that the 109K appeared in November, 1944. The reference is excellent, but I think the difference is semantics.
So, if you want to keep the playing field truely even, you need to find the first date by which at least 200 P-51Ds were in service with first line units, and, they suffered losses in combat. For the 109K, it`s November 2, even though it was in production since August 1944.
I disagree. The proper indication of when aircraft development cycle is complete, which is what we are discussing, is the date of the first production unit, in this case, March '44 for the P-51D, and October '44, for the 109K. To be really fair, since the major changes of the P-51D over the P-51B is a bubble canopy and two added guns, you really have to go back to May, 1943, when the first production P-51B appeared, to get the right design genealogy. The 109K traces directly back to the G-10 (AS?) according to my reference. I have no reference (including your site) that references the production date of the G-10, except your reference of early '44. If you have a more precise date of production start, I would like to see it. I didn't trace the lineage to the G-6 as explained in the following paragraph. In any event, this would be a six to nine month difference.
To me a couple of months seems rather indifferent, and, there were plenty of 'interim' aircraft produced since early 1944 which ensured the 109K`s absance until October 1944 was not really felt - the K itself offered mostly just cleaner lines and more importantly, a standardized airframe with rationalized internal arrangements.
There appears to be a major redesign of the Bf-109 from the G-6 through the G-10 to the K. This is manifested in almost a 900 lb reduction in empty weight (6050 lbs vs. 5161 lbs). This is not a "just cleaner lines" redesign of the G-6. This is why I did not go back to the G-6.
I think the 51F wasn`t introduced at all, or the p51H for that matter in the second half of 1944. I`d suggest you check out the new models of 109G that were introduced in the first half of 1944, especially the /AS types with methanol. By all accounts, these were excellent aircraft, and very close to the 109K in performance, albeit some 20 km/h slower due to their less clean airframes. Nevertheless, they stepped in for the 109K and DB605D since March 1944 as an interim solution.
You are correct on the 51F as it was really a XP-51F, but it and the "G" incorporated the major changes implemented in the H. Since the changes to the P-51 were in the same scope as the Bf-109G-10 (including the reduction in airframe weight including reduction in armament (two gun on the G-10?)) and the same time frame (early '44), it is indeed reasonable that the very capable North American engineers could have fielded a viable aircraft by October '44. After all, they were able to take the highly advanced new design P-51 from drawing board to first flight in only few months. In reality, the Bf-109K was to the Bf-109G-6 as the P-51H was to the P-51D. Airframe was lightened and ammo and fuel reduced and bigger engine installed (did the Bf-109H only have two guns like the G-10?). In addition, the changes were in same time frame; the only difference was that the pressure to replace the P-51D was small. A fair comparison is the Bf-109K to the P-51H.
There`s much speculation in this and grossly underestimates development problems. Germany, who was desperate to stop the hordes of P-51s, P-47s, B-17s, B-24s, and Brit planes, with advanced aircraft, as you say, was developing the 109K since March 1943. How much easy it would have been for them to have it, one may say, by late 1943...? It`s certainly very easy to say - but in It took them until late 1944 until it actually arrive at the units, and it was far less radical departure from the existing G-airframes.
Not true. There was a 889 lb reduction in empty weight from the G-6 to the K. There was only a 540lb reduction between the P-51D and P-51H. Which one was more radical?
Not to mention, that to my best knowledge, the F-series Mustang, as hot their spec are, are essentially experiemental aircraft that toyed with the idea of lowering airframe stress limits and weight in favour for higher performance. Apart from it never been realized in this form, it`s also questionable how much use such lightly stressed aircraft would be operationally, how many potential problems would be needed to be solved with the airframe and engine before it would be combat ready, how long it would take factories to re-tool etc.
The weight reduction was to reduce what the British considered over-design of the P-51D by incorporating the design loads of the Spitfire. To my knowledge, there was no complaint about the Spitfire being too lightly stressed to be an effective fighter. Remember the Bf-109G-6 lost more weight than the P-51D did.
I don`t like such speculations, and after all, the facts are on the table, we know how it was, anything else is a swamp of guesswork, riddled with dangerous intellectual traps every step. The 51F did not become an operational type just and the P-51H, which just missed the war, eventually did not produce the very impressive performance figures originally expected and calculated for it.
I don't think test results support this statement
Individual aircraft performance of course, differ from plane to plane, and it especially seems to be true w the Mustang.
I don't think this is exceptional. There certainly is more information available over a wider time frame on the P-51 performance than for German designs.
I prefer this one for the P-51D Performance since it notes that 'the data presented represent good agreement with most of the flight test results'. It`s probably a good middle-value.
It shows 368 mph at SL, and I presume the wingracks are missing (I could be wrong), which chopped some 12 mph off from top speed and were std fitting. With them it would do about 356 mph, and there`s also a test with the RAF`s TK 589 which I have which had 354mph at SL (w. racks).
I'll accept 368 mph.
The one you shown, with 375 mph claimed at SL at the same rating of 67", from June 1945, is very much higher than that. I can only guess why - perhaps an exceptionally good aircraft was tested, and/or it was polished and had special surface treatment. But I doubt it`s normal (and so do even North American, see above), it`s probably the best figure around.
The associated write up on the test indicated one wing rack per wing was included in the "clean" design (remember, you were assuming the wing racks were missing). While no modifications were mentioned regarding making it more slick, I wouldn't be surprised if gaps were filled, gun ports covered and maybe some wax. I would be surprised if the German test were not performed with similar modifications.
The 109K had 1800 PS in it`s earliest engine that was not fitted to too many aircraft though, or 1850 or 2000 PS. With the two latter ratings, it was officially rated at 370mph and 377 mph respectively, and some 8 mph if polishing was applied.
So, you are saying that the 109K, generating roughly 200 hp to 350 hp more than the P-51D (remember the P-51D engine is generating 1630 hp at 67"), can only eke out 2 to 9 mph more (using your figure for the P-51, no racks). By the way, did the 109K have wing racks on during the test? Doesn't this basically proves my point.
And of course, as in the case of the Mustang, there were worser and better planes. The tolerance was usually 3%, so theoretically you could have a production 109K anywhere between 360 mph (a plane w. the lowest rating, so badly built it just passed acceptance tests) and ~395 mph (a plane with the highest rating, with exceptionally good finish, polished by the loving groundcrew).
You seem to assign the P-51D data to the highest of the variance (your original argument was that it was the norm) and the Bf-109K to the norm of the data, when, it seems, you only have one point of data to work with on the 109K. I don't think this is a statically valid assumption. It could very easily be the top of the performance range.
In any case you can view the whole thing on my site, here : Kurfürst - Performance of 8 - 109 K4 and K6 with DB 605 ASCM/DCM This is the only thing, I dare say, most if not all of us aircraft geeks have on 109K performance.
Thanks for the site. I will get busy trying to interpret charts and convert metrics and update my data base.