Early Jet Fighter development

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boredatwork
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Re: Early Jet Fighter development

Post by boredatwork »

Production numbers prior to June 1944 was about 60 per month. In fact it was 60 units in May. The units did not begin combat operations until June 44 though. 29 units Approx. matches the Jabos reported placed into operations to Hitler in July, and not the total number available.
I suspect that your numbers are airframes not completed aircraft ready to be accepted by the Luftwaffe:
"The next month, June 1943, Messerschmitt himself was called before the RLM to report on the status of the proposed production of the Me262. While it was still in testing, he predicted that his company could not commence delivery of operational Me262s before January 1944. Messerschmitt was optimistic about the Me 262 program but he was realistic about his companies manufacturing capabilities. He predicted that his company could start production in January 1944 and be able to deliver by the end of each month 8 in February, 21 in March, 40 in April, and 60 in May. There after he promised 60 aircraft each month through November 1944. At this point he noted that these were only airframes! He specifically pointed to the fact that he was in control of pruducing the aircraft, the Junkers engines were another matter altogether. [...]"

"When Beauvis did finally fly the jet in October the RLM again expanded it's order to thirty 0-series aircraft [ie pre-production models], with the stipulation that they would be completed by the end of 1943. However Messerschmitt rejected the order on account of his lack of production capabilities; he promised only 10 airframes by the deadline."

Quoted from The Jet Race and the Second World War
I think this is the BMW engine, not the Jumo engine that was unavailable as a reliable unit until late war.
Neither was reliable. The early Jumo 004s that powered the early prototypes were hand build 004A prototypes, NOT pre-production models and were never intended for mass production - being far too expensive both in man hours and strategic materials. The delays caused by redesigning the engine for mass production - the 004B were protracted and at first cut running time from the 100+ hours of the A model to less than 10.

Galland and Milch may have been enthused about placing the Me262 into immediate mass production but Director Cambeis, the Junker's representative of the Me262 overseeing commission was totally opposed to it.

Eventually after dealing with problems with the compressor blades reliability was up to 25* hours and the design was frozen for mass production, despite continued Junker's engineer objections, in June 1944.

*the 25 hour longevity was measured on the test bench, NOT operational conditions. In actual operating units only the bomber units remotely came close to that time. In part because they began their conversion earlier and their mechanics were more experience but mostly because their missions didn't require sudden throttle actions that drastically shortened the life of the engines.

"Developing the new power unit was difficult enough, but German engineers faced a further problem. Owing to the Allied blockade; the hardening elements necessary for effective high-temperature-resistant steel alloys-in particular, chromium and nickel-were in short supply. Only limited quantities could be spared for the jet-engine program, so those who worked on the new propulsion system had to make the best of what was available. For the Jumo 004 engine that powered the Me 262, Junkers engineers used some substitute materials that were not up to the job.

For example, the combustion chambers were made of mild steel and coated with baked-on aluminum to prevent them from oxidizing. When the engine was running, these combustion chambers slowly buckled out of shape. The turbine blades were made of a steel-based alloy that contained some nickel and chromium. That material was insufficiently resilient, however, when the engine was running, the centrifugal forces used the blades to elongate, or "creep."

Limited by combustion chamber buckling and turbine blade"creep," the running life of pre production Jumo 004s rarely reached 10 hours. Throughout a flight, careful throttle handling was vital to avoid having an engine flame-out or overheat. At altitudes of above 13,000 feet, the engine became increasingly temperamental, and if it suffered a flameout, the pilot had to descend below that altitude before he attempted a relight. In its early form, the Jumo 004 had too many weaknesses to allow mass-production.

After much hard work to improve matters, late in June 1944, the Jumo 004B-4 emerged with a running life of 25 hours. That still wasn't impressive, and certain reliability problems remained, but the Luftwaffe couldn't afford to wait any longer. The design of the Jumo 0048-4 was "frozen" and the unit was put into mass production. During Sept '44, Jumo 004B-4 production reached significant levels, and that month, the Luftwaffe took delivery of 90 Me 262s"
The Jumo engine was available, however, in numbers prior to June 44, but the problem was that it was dispersed among several other projects, which held down delivers of the 262. This was once again down to Hitler. For example, Hitler had dreamed up the idea of the Salamander jet that would be flown by Hitler Youth pilots. This was a total waste of resources. The Salamader was actually more demanding of pilot skill than was the 262.
While it's true the Jumo 004 was being disperssed among many different projects, most never made it past prototype stage. The only real competitor for the Jumo 004 engines were the Arado 234. The first AR234 pre-production model did not appear until May 1944, and the type didn't become operational until Sept 1944 - total production till the end of the war only 210.

The He 162 wasn't conceived until September 1944 and was largely the brainchild of of Speer and party leader Otto Saur. It was to be powered by the BMW 003, instead of the Jumo. While undoubtably a waste of resources it in no way impacted the operational availability of the Me262 in 1944.
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Dave Saxton
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Re: Early Jet Fighter development

Post by Dave Saxton »

While its true that problems with engine reliability presisted (not just for the Germans but for all jets engines during this time frame), I'm not sure about the details and chronology in the above qouted accounts. I have seen the captured data on these issues, particularly the metalurgy issues at the national archives. In fact I know its not entirely correct.
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Dave Saxton
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Re: Early Jet Fighter development

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There seems to be much conflicting data especially pertaining to the chronology of the 004 engine development. Junkers data and Smithsonian data seem to corraborate each other though. 004B engine differed from 004A engine by using less strategic materials, with more extensive air cooling in compensation.

The chronology accordingly for 004B is:
Early 42 004B design ready for testing.
Mass Production of 004B starts summer 1943
7,916 004B engines built and delivered by Junkers Leipzig plant from mid 43.
Unknown numbers built under license by Opelwerkes.
004D also begins production in late summer 1944.
004E is 004D with afterburner first run in early 1945.
004C was more advanced afterburning prototype, never run.

Junkers official data lists a 30 hour TBO. According to Junkers records, Approx. 50% of engines overhauled at 30 hours required replacement of compressor or turbine blades. Overhaul required 100 man hours. Field Overhaul was set up to be relatively easy not requiring highly skilled labor. New production at Junkers required 50 man hours per engine.
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Re: Early Jet Fighter development

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That seems at odds with:
http://www.nationalmuseum.af.mil/factsh ... asp?id=878
The engine's development began in 1937, but large-scale production did not begin until late 1944. By the time Germany surrendered in May 1945, more than 5,000 engines had been produced.
and wiki has this to say at: http://en.wikipedia.org/wiki/Junkers_Jumo_004
The first production model of the 004B weighed 220 lb (100 kg) less than the 004A, and in 1943 had passed several 100 hour tests, with a time between overhauls of 50 hours being achieved.[2]

Later in 1943 a series of engines suffered vibration problems, and solutions dragged on. Eventually, in December, blade-vibration specialist Max Bentele was once again brought in during a meeting at the RLM headquarters, and the problem was solved by raising the blades' natural frequency by increasing their taper, shortening them by 1 millimeter, and reducing the operating speed of the engine from 9,000 to 8,700 rpm.

It was not until early 1944 that full production could finally begin. These setbacks were the principal factor delaying the Luftwaffe's introduction of the Me 262 into squadron service.

Given the lower-quality steels used in the 004B, these engines typically only had a service life of some 10-25 hours
http://tanks45.tripod.com/Jets45/ListOf ... unkers.htm does say:
In summer 1943 the serial production of these engines was started at Junkers Leipzig and at the Opelwerke at Russelsheim. A total of 7916 Jumo 004B were built by Junkers Flugzeugwerke plus an unknown number of engines at Opel.
Here's a link to a paper that might be significant: http://scitation.aip.org/getabs/servlet ... yes&ref=no
it states about 6,000 were produced.

This source: http://www.petester.com/html/ba_jumo004.html
also states:
Volume deliveries of 004s began in the fall of 1944
It may hinge on what is meant by volume deliveries and full production.
http://www.nasm.si.edu/collections/arti ... 9670124000 would seem to confirm that with:
First production engines were delivered in mid-1943, and volume production began in 1944
This page goes into some detail on the reliability problems with the 1943 Jumo engines:
http://www.456fis.org/JUNKERS_JUMO_005%20JET_ENGINE.htm

All of which suggest that large numbers of Me-262s in early 44 were not likely.
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Re: Early Jet Fighter development

Post by boredatwork »

I was going to cite the paper by C.B. Meher-Homji but lwd beat me too it.

The most relavent portions are:
During the summer of 1943, several turbine blade failures were experienced due to a sixth-order excitation (6 X No. of combustors) when operating at full speed. The Junkers team worked diligently to resolve the problems.

[...]

The Air Ministry was, however, getting increasingly impatient and scheduled a conference in December, 1943, at the Junkers Dessau plant, to be attended by turbine experts from government, industry, and academia.

[...]
The problem was solved by increasing the blade natural frequency by increasing blade taper, shortening blades by 1 mm, and reducing the operating speed of the engine from 9000 to 8700 rpm.

The leading particulars of the production engine are shown in Table 1. Volume production of the 004B-1 started in early 1944. In spite of difficult conditions, the engine was manufactured in increasing quantities. Approximately 6000 engines were built by the end of the war.


Also, though I don't recommend purchasing it, if you happen to come across the book The Messerschmitt Me262: The Production Log 1941-1945 - with brief histories of 1,200 of the 1,500 Me262s produced, by Aircraft work number it's interesting that the bulk of the pre-production aircraft were completed in January/February but had to wait until April for engines to make their first flights. Likewise large numbers of early production aircraft are listed as airframe complete, destroyed by bombing while awaiting engines. It brings up the question that if Mass production truly began in the summer of 1943 why was there such a shortage of engines in early 1944? The Arado program certainly wasn't consuming huge quantities and there were no other jet programs remotely close to production that would compete for them.
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Re: Early Jet Fighter development

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What these conflicting data sets say; is that the production of 004 engines was tied to demand. Why was the demand so langid prior to mid 44? It was because the 262 did not go into full production when the Luftwaffe leaders wanted it to, and in which had been determined was feasable. Isn't this what Galland and other have always said for decades?

Furthermore, I don't think it's coincidental that the claimed readiness for the 004B as late as mid 44 is the same chronology of the 003 and the introduction of the 004D.
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Re: Early Jet Fighter development

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Dave Saxton wrote:What these conflicting data sets say; is that the production of 004 engines was tied to demand. ....
That's not the message I got. For one thing several of them specifically state that there were reliability problems with the pre 44 engines and that some didn't consider them ready for production at that point. This is saying something considering the reliability of even the late war engines. The existence of airframes awaiting engines also rather points to unsatisfied demand.
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Re: Early Jet Fighter development

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Dave Saxton wrote:While its true that problems with engine reliability presisted (not just for the Germans but for all jets engines during this time frame), ....
From: http://en.wikipedia.org/wiki/Rolls-Royce_Welland
The Wellands were rated at 1,600 lbf (7.1 kN), with 180 hours between overhauls. The Jumo 004B, which entering service only a few weeks earlier, was rated at 1,984 lbf (8.8 kN), but required overhaul after 10-20 hours.
That's an order of magnitude difference in the time between overhauls. In Me-262 service even the improved reliability versions didn't see this rise to anywhere near 180 hours.
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Re: Early Jet Fighter development

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What these conflicting data sets say; is that the production of 004 engines was tied to demand. Why was the demand so langid prior to mid 44? It was because the 262 did not go into full production when the Luftwaffe leaders wanted it to, and in which had been determined was feasable. Isn't this what Galland and other have always said for decades?
Dave Saxton wrote:Hitler failed to catch the vision of how the Me-262 should best be used. He saw at as a Blitz Bomber that would make the invasion beaches untenable in the upcoming invasions. Hitler forbade its production as a fighter or a defensive weapon, so the program languished into 1944, and the Mustangs wore the Jagdwaffe down to impotence through early 1944.
- Goering first visited Messerschmitt to enquire as to the possibilities of fitting the Me262 with bombs on november 2nd, 1943. At that point there was ONE flyable prototype, the V3 being destroyed and the V1 and V2 seriously damaged.

- The first 004B powered prototype, V6 didn't join the flight test program until early november.

- The Demostration where Hitler first saw it fly and supposedly made his "Blitz Bomber" comment wasn't held until November 26, 1943

- On December 5th, 1944 Von Below (Hitler's Luftwaffe Aide) writes to Goering:
The Fuhrer has called our attention once more to the tremendous importance of the production of jet propelled aircraft for employment as fighter-bombers. It is imperative that the Luftwaffe has a number of jet-fighter bombers ready for front commitment by the spring of 1944. Any difficulties occasioned by labour and raw material shortages will be resolved by the exploitation of Luftwaffe resources until such time as existing shortages can be made up. The Fuhrer feels that a delay in our jet fighter program would be tantamount to irresponsible negligence.
- January 1944 16 Pre-production machines are completed but are unable to join the development program until april due to lack of engines.

- The V10 conducted trials with bomb racks in Winter/Early Spring of 1944.

- The meeting where Hitler discovers that none of the aircraft in production are equiped to carry bombs happens in March (or April?) 1944.

- The Fuhrer-Befhel stipulating exclusivity to Bomber production is issued on June 8, 1944.


If the engines were truly ready for mass production in the Summer of 1943 and all the was needed was a go on the airframe then, given the fact that both the Luftwaffe and the Fuhrer wanted the Me262 badly (albeit for different roles) why wasn't it put into production sooner? The Luftwaffe had already ignored the Furers wishes and placed it into production as a fighter and yet only a few dozen engineless preproduction and production machines had been produced before Hitler forbade further fighter production.

The excuse that it took 4-6 months to adapt the design to a bomber is a poor one as the only difference between the Schwalbe and the Sturmvogel were the simple bomb racks and bomb arming mechanisms, development of which had been completed long before the order had been issued and would have had minimal impact on producing the airframes. Bf109s had afterall been modified to Jabos in the field during 1940.

Hitler's order undoubtably delayed the Me262's deployment as an interceptor, but did little to delay the type's introduction as a whole.
Furthermore, I don't think it's coincidental that the claimed readiness for the 004B as late as mid 44 is the same chronology of the 003 and the introduction of the 004D.
I don't see similarity. The BMW003 was cleared to begin production several months after the Jumo 004B-1 production was finally beginning to achieve volume after a prolonged trickle dating back to the 004B-0 models of the previous year. Production of the 003 didn't reach volume until late in the year in response to the He162 project. I'm sure given the huge numbers of engine models and marks produced during the war you could easily find two different aero-engine models produced by different companies that shared much closer milestone dates than that.
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Re: Early Jet Fighter development

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boredatwork wrote: - On December 5th, 1944 Von Below (Hitler's Luftwaffe Aide) writes to Goering:
*December 5th, 1943
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Re: Early Jet Fighter development

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There are obviously different ways of interputing the conflicting data and chonologies. I think both perspectives show merit, and probably contain elements of the truth. Let me point out that the perspective that the program languished was mostly because of political issues rather than technical issues, was espoused and defended by Galland, who was in a position to know. There are as many authorities that agree with Galland's perspective as there are that support the view that engines were not ready for prime time.
The Wellands were rated at 1,600 lbf (7.1 kN), with 180 hours between overhauls. The Jumo 004B, which entering service only a few weeks earlier, was rated at 1,984 lbf (8.8 kN), but required overhaul after 10-20 hours.
That's an order of magnitude difference in the time between overhauls. In Me-262 service even the improved reliability versions didn't see this rise to anywhere near 180 hours.
The actual TBO (which is arbitarily set) was 30 hours and Junkers records testify that only about 50% of engines at 30 hours required much work. It was a remarkable engineering achievement considering the size and weight constraints and the elborate compensation in design to not place undue claim on strategic materials.
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Re: Early Jet Fighter development

Post by lwd »

Dave Saxton wrote:
The Wellands were rated at 1,600 lbf (7.1 kN), with 180 hours between overhauls. The Jumo 004B, which entering service only a few weeks earlier, was rated at 1,984 lbf (8.8 kN), but required overhaul after 10-20 hours.
That's an order of magnitude difference in the time between overhauls. In Me-262 service even the improved reliability versions didn't see this rise to anywhere near 180 hours.
The actual TBO (which is arbitarily set) was 30 hours and Junkers records testify that only about 50% of engines at 30 hours required much work. It was a remarkable engineering achievement considering the size and weight constraints and the elborate compensation in design to not place undue claim on strategic materials.
How do you know it was arbitrary. When the design goal is 100 hours and the bombers are getting close to that figure why would they arbitrarily set it to 30 hours for the Me-262? 50% of your engines requireing extensive work at overhaul is not a good thing. There are also reports of Me-262 frequently loosing an engine in flight. Indeed early on the repots indicate 10-20 hours was about the expected engine life in an Me-262.
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Re: Early Jet Fighter development

Post by Karl Heidenreich »

lwd:
When the design goal is 100 hours and the bombers are getting close to that figure why would they arbitrarily set it to 30 hours for the Me-262? 50% of your engines requireing extensive work at overhaul is not a good thing. There are also reports of Me-262 frequently loosing an engine in flight. Indeed early on the repots indicate 10-20 hours was about the expected engine life in an Me-262.
This is a very good evidence that the Me 262 and their pilots were great performers. If many Me 262 were lost to mechanical difficulties and their kill ratio was 1.5 to 1, it means that we need to extract those planes that crashed by their own difficulties and the rate will increase, obviously, is just mathematical certainty.
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Re: Early Jet Fighter development

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Karl Heidenreich wrote:...This is a very good evidence that the Me 262 and their pilots were great performers.
Certainly there is for the latter. For the former I'm not so sure. Do we have the data for a like group of pilots flying other fighters at that time? Was there even a like group?
If many Me 262 were lost to mechanical difficulties and their kill ratio was 1.5 to 1, it means that we need to extract those planes that crashed by their own difficulties and the rate will increase, obviously, is just mathematical certainty.
It depends on how the kill ratio was calculated. If it's all Me-262 kills divided by all Me-262's then it won't be affected at all. Likewise if it's Me-262 kills divided by Me-262 combat losses it won't be affected. Now if you want to go from the former to the latter it will yield a different number but how relevant is that? Then of course there's the question of what is a combat loss for an Me-262? Do you want to include all lost due to enemy action? Or just those destroyed by enemy airplanes? Or some subset of those?
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Re: Early Jet Fighter development

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lwd wrote:Certainly there is for the latter. For the former I'm not so sure. Do we have the data for a like group of pilots flying other fighters at that time? Was there even a like group?
Well, there were some and most noteably Hartman. He requested a transfer out of 262's because he felt he could be more productive in his 109 and stood a better chance of surviving the war. 262 pilots sometimes died trying to land or take off when they were bounced by allied pilots waiting for them.
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