Could the Luftwaffe survive against Allied attacks if the USSR had been defeated?

[Soren]

Btw, IIRC the Me-262 got outfitted with a new engine throttle control system in Dec. 1944 which prevented flame outs. Wether it improved fuel efficiency as that introduced with the D series I am not sure.

 

[fly boy]

I think it depends on when they beat the Soviets. IMO, I believe the line is 1943. Before that, the Luftwaffe would still have had significant numbers to put on only one front, which would have help to defend the factories.

After 1943, the allies advanced fighters and mass production would have drove Germany into the ground. However, I do believe it wouldn't have ended in 1945. All those men and resources on one front! wow.

Of course, I'm sure Hitler would have screwed up a one front war too!

very ture say they beat them in 42 witch we all know would never happen hitler could foucus on us england and africa

 

[namvet68]

No...with Japan being knock out all the might of the US military would be turn on Germany. Now the Luftwaffe would have to face the high flying B-29's. All American forces would be able to focus on bring Germany to her knees and lets not forget the possible of having the A-bomb dropped on her also. Turman would not be a fraid to do it.

American flight schools can turn out more pilots than Germany could and American factories can turn out more everything than Germany could.

England than could turn to all of her empire to send all the troops from the Asia to Europe.

 

[Freebird]

No...with Japan being knock out

Who said anything about Japan being knocked out?

 

[kool kitty89]

I disagree. And the German 100 hour full trottle tests seems to support what I'm saying.

The main problem plagueing the Jumo 004 production engine was the turbine blades made of substitute metals which couldn't take the heat generated above 8,800 rpm and were prone to failure even at much lower rpm's. Had the needed materials such as the special heat resistant metals been there this problem wouldn't have existed.

The problems at higher RPM were due to vibrations not heat. The resonance of the solid turbine of the 004A was at a much higher frequency than the hollow air-cooled versions and thus experienced this well above the operating RPM. (and thus it could overrev to 10,000 rpm)
(improvements on the 004D solved the vibration problem)

The reliability issues Delcyros and red admerial are reffering to aren't related to service life issues or complete failures, but the surging anf flame-out problems durring rapid throttle movements at lower rpm. The engine could be restarted of course (unlike the 003), but this was still a problem. (this was also improved on the D model iirc)

 

[Soren]

Well AFAIK the turbine blades turned soft because they couldn't take the heat, creating the problem with resonance you explained. Had the blades been made of the right heat resistant metals this problem wouldn't have existed.

And then there's the solid blades, well the D series didn't have solid blades like the A series, yet they solved the problem somehow ?

 

[kool kitty89]

Yes, Delcyros probably knows more on the specifics, but I believe the shape of the turbine blades were alter slightly and other things were alterd upstream of the turbine as well. (the turbine stator arrangement I think, and the inlets from the combustion chambers to the diffuser)

There were different vipration problems encountered on the early 004A's, but these were mainly to due with the compressor section, and not the "hot" section.



The soc-history-war-world-war-ii November 2006 Archive by thread
I think it was discussed somewhere in the couple jet engine threads listed there, or in a link poster there.

I think this is th earticle:
Anselm Franz and the Jumo 004

There's smoe interesting discussions in the aformentioned threads nonetheless. (regarding the 004, 003, and some on the HeS 006)

 

[kool kitty89]

I read through the parts I was looking for, and my explanation wasn't quite right, but read for yourself:

Anselm Franz and the Jumo 004

(on the 004A)

In the spring of 1940, the 004A made its first test run; by January 1941, the engine was brought to its full speed of 9,000 rpm and a thrust of 946 pounds. At this juncture, the engine's compressor was plagued by vibration failures in the sheet-metal stator vanes, which were originally cantilevered from the outside. Max Bentele, a renowned blade-vibration specialist, was asked to help solve the problem. The stator's design was changed, and by August 1941 a thrust of 1,320 pounds was attained. In December 1941, a 10-hour run at a thrust of 2,200 pounds was demonstrated. The engine was flown in an ME 110 test bed on March 15, 1942, and on July 18 the first flight of the ME 262 powered by two Jumo 004 jets took place. The flight lasted 12 minutes.

And the 004B

Extensive air cooling was used throughout the engine. A later version of the 004B engine had hollow air-cooled stator vanes. Compressor discharge air was used to cool the blades. With hollow blades of Cromadur sheet metal, the complete 004B engine contained less than 5 pounds of chromium. The first production model of the 004B weighed 220 pounds less than the 004A. Additional modifications were made to the first compressor stages. A series of 100-hour tests were completed on several engines, and time between overhaul of 50 hours was achieved.

During the summer of 1943, a sixth-order excitation caused several turbine-blade failures. Franz resorted to asking a professional musician to stroke the blades with a violin bow and use his trained musical ear to determine the ringing natural frequency. The air ministry, however, was getting increasingly impatient and scheduled a conference in December 1943. Bentele attended the conference and listened to the numerous arguments pertaining to material defects, grain size, and manufacturing tolerances.

When his turn came, Bentele told the assembled group that the culprits were the six combustor cans and the three struts of the jet nozzle housing after the turbine. These induced forced excitation on the turbine rotor blades where a sixth-order resonance occurred with the blade-bending frequency in the upper speed range. The predominance of the sixth-order excitation was due to the six combustor cans (undisturbed by the 36 nozzles) and the second harmonic of the three struts downstream from the rotor. In the 004A engine, this resonance was above the operating speed range, but in the 004B it had slipped because of the slightly higher turbine speed and the higher turbine temperatures. The problem was solved by raising the blade's natural frequency—increasing blade taper, shortening the blades by 1 millimeter, and reducing the operating speed of the engine from 9,000 to 8,700 rpm.

Perhaps Delcyros can shed some more light on the changes to the 004D that allowed the higher rpm's.

 

[Nikademus]

So late 43 and early 44 would have been pretty hard for the Luftwaffe and the allies but i do believe the allies would wear them down eventually.

Interestingly, much of elements regarding air strength are not really hypothetical, since the Luftwaffe, on realizing the growing threat from the USAAF by late 43, transferred a sizable portion of their fighter forces from the Med and Eastern fronts. In the end the Americans still fielded a bigger force that just kept on growing in size. On changing their tactics under Doolittle, the 8th AF wanted the Luftwaffe to come up en mass and fight it out, figuring they could win such an attrition war.

-Freebird,

As promised, I looked up the information from Blair's "Hitler's Uboat War" regarding the Uboat component thrown into the mix along with a Russian setback. At the beginning of 1942, the Atlantic portion of the Uboat force stood at 64 boats. (19 x Type IX's, 44 x Type VII's and the U-A) 22% of this force (14 boats), were not combat ready. Of the 50 remaining boats, U-A was undergoing a conversion into a U-Tanker, 1 x Type IX and 4 x Type VII's were homebound or in Germany being overhauled, repaired or being retired. Four more Type VII's were in France undergoing repairs while Artic transfer was in Germany for overhaul before joining the Atlantic group.

Due to the distances involved, only the Type IX's were considered suitable craft for Drumbeat. (Type VIIC's would be used to attack Canadian waters) At the time Hitler authorized the campaign, 8 out of 20 available Type IX's [Dec 41] were not available; (4 returning from South Atlantic patrols and requiring overhaul....1 other also returning and needing an overhaul and 3 Type IX's were being committed to the battle with Homebound Gibraltar convoy 76.)

Ultimately Donitz was able to make ready 6 x Type IX's for the first wave in Dec, 41. Of them, 1 developed an oil leak and aborted. In addition, 10 x Type VIIC's were committed to the first wave to attack shipping in Canadian waters as that was considered [barely] feasible for a total of 15 boats.

 

[Freebird]

-Freebird,

As promised, I looked up the information from Blair's "Hitler's Uboat War" regarding the Uboat component thrown into the mix along with a Russian setback.

Nikademus, thanks for the post.
I'm going to post my reply to this on the KM IJN thread, as it mainly deals with the sub question.

 

[Soren]

Well according to your qoute KK the problem was solved with the reduction in rpm from 9,000 to 8,700 rpm. So the resonance problem was solved before the Me-262 entered full service, as the Me-262's in service weren't allowed to run at over 8,700 rpm producing 8.8 kN of thrust.

Now according to my research some problems with engine service life remained because of substitute metals used in the hot section and because of the initial throttle system allowing large amounts of fuel to be dumped into the engine at once, causing a flameout. This problem was later solved, preventing the risk of flameouts and allowing more aggressive throttle control. However the problems with the metal softening in the hot section still remained as the needed metals weren't available, and IIRC full throttle flight was only allowed for 30min at a time.

The Jumo 004D series had a new throttle control system which like that on the late B series prevented flameouts and allowed aggressive throttle control. However the D series was also allowed to run at higher rpm's, suggesting a new turbine blade design amongst other things. The increase in rpm's was considerable at some 1,300 rpm, and the increase in power was noticable as-well at 1.5 kN. And all this for no increase in weight.

Performance with the D series was pretty mindblowing at 920 km/h at SL and 945 km/h at 5.5km.

 

[kool kitty89]

I think it was more due to thermal creep than softening. Continued expansion and contraction of the metals used in the hot section caused certain components (namely the turbine blades) to become distorted over time. The use of nickel alloys can mean hot section components that are virtually immune to thermal creep, as the addition of nickel in certain combinations greatly reduced the expansion with heat. (Nimonic alloys used in the british engines, in addition to being resistant to high temperatures and oxidation, were particularly good in this respect as I recall)


The blade softening problem occured in a similar manner to the flame-out behavior: too much fuel was dumped in at once and (rather than resulting in a flame-out) the ai-fuel mix was made richer (ie closer to stoichiomentric in this case), causing higher temperatures. At the same time there would be insufficient cooling air while this is occuring, worsening the problem. This results in temporarily overheating the hot section and softening/warping of the turbine. (depending on the severity of the event and the condition of the engine this may cause an immediate failure of the turbine or possibly a ruture in the combustion chamber, or simply result in more minor damage that will shorten engine life and possibly fail lter on)

 

[BIG BIRD]

I saw A show on the history chanel that said the germans could start production of 1,000 Heinkal he 162 volksjagers a month, some variants were estimated to be more than a mach for a mig 15 or f-86.

 

[kool kitty89]

Those would be the Swept wing variants with the HeS 011 engine. (He 162C)

There was also the He 162D with foreward swept wings.

 

[delcyros]

The reliability issue of the Jumo-004B was due to the fuel regulation system, which (unlike the BMW-003) was not regulating the fuel flow in correspondence to airflow but to engine rpm. Easy to burn out the turbine blades when accelerating from idle to ca. 6.000rpm. That´s why 100 hour benchtests are not very reflective, they do undergo the critical throttle setting only once and then remain fro the duration of the benchtest at high rpms. In service conditions, one has to accelerate from time to time (every take off, f.e.) and the intervals are probably related to less than one hour. Hence the avg. service lifetime of the turbine section of the BMW-003 was 200 hours instead of 25 for the Jumo-004 while both engines passed multiple benchtests in well in excess of 100 hours. Both engines used identic alloys. Check my post #23 in this thread for more details:

http://www.ww2aircraft.net/forum/aviation/heinkel-he-162-engine-1745-2.html

 

[red admiral]

A few bits to add; changing materials isn't a magic fix. Prolonged heating of a material under load will eventually result in failure. This is called creep and its probably the most boring failure mechanism possible. The blade will grow in length until it either snags the side panel or breaks from excessive stress. Adopting a nickel superalloy reduces the rate of creep it doesn't stop it so the failures will still happen, only after greater running periods. However, if you have good maintenance procedures you can reduce the failure rate by replacing the blades (or the engine more likely in this case) before this becomes a problem. This stands whether you have steel, nickel or ceramic blades. More regular engine changes for the 004 would have mostly solved this problem.

*Note, modern engines have FADEC that continously measure the clearance between the blades on the casing and move the casing outwards as the turbine blade grows.

For reliability of the engine in service use combustion is a big problem and the limiting factor in the early British designs before being mostly solved in 1941/42 (though a better burner was put into service on the Nene and subsequent designs). You're trying to burn a lot of fuel in a combined space, short time in a howling gale. Excessively quick throttle movements are going to have bad results. The US ran into lots of problems in the 50s with the adoption of on/off afterburners.

My comments with regards to reliability in service are more to do with the other end - the compressor. Rapid throttle changes (or even differences in AoA) could cause problems because of the poor surge characteristics. Rpm increases so more air has to be compressed and against a higher pressure gradient so at times it will break down and the air flow reverse direction and start coming out of the front. Its a lot more rapid and violent than that, with lots of vibration and the possibility of blades breaking. The low pressure ratio of the 004 (compared to the immediate postwar Avon) reduces the problem but fuel consumption is poor as a result.

Performance with the D series was pretty mindblowing at 920 km/h at SL and 945 km/h at 5.5km.

Pretty similar to the Meteor F.4 which is more or less constant 590mph up to 15000ft whereupon its limited to M0.82

 

[kool kitty89]

The 003, 004, and 006/HeS-30 (as well as Heinkel's centrifugal-flow engines) all had fairly low pressure ratios of around 3.0-3.2:1 (even lower on the early Centrifugal models).

The 004A/B/D/E (and iirc the 003A/E) used the relatively simple impulse blading in the compressors (with ~80% of compression taking place at the rotor blades and most of the stators acting as guide vanes only), which allowed the blades to be made of stamped sheetmetal, cheap and efficient method of construction, but a lower mechanical efficiency and greater weight. (albeit the 003 was a little more efficient than the 004's compressor)

The HeS-30/006 (as well as some versions of the 003 being devloped with much greater performance, significatly higher pressure ratio, and greatly reduced SFC; namely the 900 kp 003C and 1,200 kp 003D) used reaction blading (with compression acheived ~50/50 at the rotors and stators) with much greater efficiency and compression per stage, achiving a similar pressure ratio to the 003 and 004 but in only 5 compressor stages. With much lower specific fuel consumption, size, and weight. The downside is that the blades had to be machined and required the use of thrust bearings.

Early jet engines

I believe Delcyros has brought a lot of this up before as well.

 

[kool kitty89]

Early jet engines

I found the post I was looking for on that forum regarding the vibration and TBO. (it seems I overlooked it a while ago)


It also gives a good summary of the advantages and disadvantages of the Britich vs German engines. (ie the 004 the 004 had a much smaller frontal area at the expense of considerable weight gain)

 

[Venganza]

No...with Japan being knock out all the might of the US military would be turn on Germany. Now the Luftwaffe would have to face the high flying B-29's. All American forces would be able to focus on bring Germany to her knees and lets not forget the possible of having the A-bomb dropped on her also. [Emphasis added.] Turman would not be a fraid to do it.

American flight schools can turn out more pilots than Germany could and American factories can turn out more everything than Germany could.

England than could turn to all of her empire to send all the troops from the Asia to Europe.

I think the part about the A-bomb is the crucial part and it has nothing to do about whether of not we had knocked the Japanese out of the war. If the war had gone on into 1945, it wouldn't have mattered how many wonder weapons the Nazis had. If the bomber streams started getting hammered by these jets and the Allies started to lose their air superiority, they would have just started dropping A-bombs on the Germans and the party would have been over. It might have been a little more difficult to drop atomic bombs on people who looked like us (the Germans as opposed to the Japanese) but I'm sure we would have gotten over those qualms. If the Nazis had also had the bomb, then that would have changed everything, but even in real life, with the impetus of getting hammered by both sides, they didn't have the bomb by 1945, and if they had defeated the Soviet Union, I think their atomic research would have been put even more on the backburner, so no Nazi A-bomb by 1945. The Allies win.

 

[kool kitty89]

In a horific/terror factor kind of way, yes, but the allies (the US) had only one more bomb nearing readiness after Fat Man, after that it would have been several months before another could be completed. (so a total of 1 Uranium bomb and 2 Plutonium bombs detonated durring the war, with a third in readiness)