# Jumo 222: what's the truth?



## wiking85 (Nov 29, 2013)

I know this is more a thread for the engine subforum, but I've already broached the topic there in this thread without much in the way of answers:
http://www.ww2aircraft.net/forum/engines/jumo-213-what-took-so-long-39029.html

Anyway my question is why was the Jumo 222 really not put into production? From what I've read recently via Lutz Budrass it seems that it was a combination of being developed to death (by constantly upping the HP requirements and displacement just as the previous requirement was being met) and being placed on low priority to undermine Erhard Milch's rival, Dr. Heinrich Koppenberg, who was running the Ju 288/Jumo 222 program (he also separated the program to kill it too). Budrass pretty much states that this rivalry killed the engine, rather than technical issues being the real cause of it never entering production status.

It also seems that in April 1941 the Jumo 222 in its original design configuration (2000 hp) achieved 100 hours on a bench test, which is a strong indication that it is closing in on being production ready, though there were still some issues with corrosion and piston seizure that set in at about 50 hours (which in 1941 was better than the BMW 801 or DB 603). Eventually this original 2000hp configuration and displacement was the version, the Jumo 222E/F that was the one that actually got near production status in 1943 before Allied bombing killed it for good (though work continued on refining it until 1945). However in 1941 the requirement was upped to 2500hp in response to the Ju 288 airframe gaining weight during the development process, which required an increase in power from its engines to keep up performance. This of course set back the process and prevented the engine from getting ready until 1943 at which time the requirement was again bumped up to 3000hp, setting development back again.

So based on all of this it seems that had the original displacement and HP output been kept from 1941 on the engine would have been ready some time in 1942 for serial production, though perhaps not at the 100 hour between overhaul mark (which didn't keep the BMW 801 or DB 603 from production historically). Obviously it would be weaker than needed for the Bomber B program, which IMHO should have been killed at the point its weight jumped up too far for the engine, but it would have had plenty of other uses in the He 177B, Do-217, Ju 188, and even a FW190 version (or Ta-152 which tested with the Jumo 222 historically). The fuel consumption would have been significantly better, as the smaller cylinders were more efficient than say the DB 603 or BMW 801, and the weight and dimensions wouldn't have been that much bigger than the DB 603. 

Am I missing something here or was the Jumo 222 killed by administrative action and development rather than technical issues?

As a side subject, what would its effect have been had it entered production in March 1942 with 70 hours between overhauls and no greater requirement for strategic materials than say the DB 603 of Jumo 213? Would it have meant an earlier He 177B powered by these engines, a Do-217 not underpowered, a Me 410 with Mosquito-level speed, a FW-190/Ta-152 with altitude performance challenging the P-51, a Ju 188 with better performance than the Ju88, and a series of night fighters/intruders that actually lived up to spec (like the He-219, Ju 88G, and Ju88S)?
What becomes of the Ostmark production facility if it were actually able to start operations with its original tooling, rather than being partly retooled for the DB603 and not really ever being operational?


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## Shortround6 (Nov 29, 2013)

Basically the thing was a turkey. Color it which ever way you chose but most sources will _agree_ that around 270-280 engines (of various versions) were built. That is one *HE*** of lot of test engines. Please remember that R-R built 301 Peregrines total and kept two squadrons of twin engine fighters in combat service for around two years. The 270-280 Jumo 222s powered about 1/2 dozen air frames ( and briefly). Did somebody order a "trial" batch of a few hundred engines before they were ready? Even if we "assume" 70-80 "test engines" (P&W built about 50 R-4360 28 cylinder 4 row radial test engines, including flight test) that leaves us with about 200 Jumo 222 "semi" production engines that apparently were not deemed airworthy. Considering the number of weapons systems that the Germans bodged together out of mis-matched parts you would think that 200 or so _air worthy_ 2000hp engines would have found _SOME_ use. 

As for "The fuel consumption would have been significantly better, as the smaller cylinders were more efficient than say the DB 603 or BMW 801" there is efficiency and there is efficiency, Trying to use a bunch of small cylinders can make for better volumetric efficiency but that may not mean better fuel efficiency. 
A Jumo 222A (46.5 liters) had 1.3734 sq meters of scrubbed cylinder wall. 
A BMW 801 had 1.0698 sq meters of scrubbed cylinder wall.
A DB 603 had 1.0987 sq meters of scrubbed cylinder wall. 

Most people figure that _about_ 80% of the internal friction of an engine comes from the pistons/piston rings scrubbing the cylinder walls the Jumo 222 has about 25% more piston/cylinder friction than a DB 603 _at the same rpm_. Since friction goes up with the square of the speed and the Jumo 222 is going to faster in most cases it is burning more fuel to over come internal friction. Now _perhaps_ the Jumo can make the same power (being more efficient?) as the DB 603 while cruising at a lower rpm than the DB 603 and get back some of the fuel economy?


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## wiking85 (Nov 29, 2013)

The argument of the number of engines produced is somewhat a matter of details, as there were radically different versions due to the increase in displacement and various reengineering schemes that altered the engine so much that it needed a new set of test engines. There were four displacement changes from 1941-44, which resulted in cylinder changes each time and of course multiple different supercharger and later turbocharger designs. Cooling systems were rerouted with these changes too, which pretty much resulted in different test models all while having its priority constantly changed and switched from different proposed aircraft (it was tested with at least 7 different designs that I'm aware of). All this makes total sense why it would have so many test engines.


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## wuzak (Nov 29, 2013)

The DB 604 was better....


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## Shortround6 (Nov 29, 2013)

Not really, see:

The Hugo Junkers Homepage

Granted there may be some problems with translation but twice production is stated to be stopped? If the engine wasn't ready to go why _start?_

Please note that there are some discrepancies between the chart of engines on that page ( and some discrepancies in the chart itself) and a chart in an article in the "Torque Meter" magazine by Kimble McCutcheon on the bore and stroke of some of the models. 
Granted there were a lot of different models and bore and strokes but _why_ you would need 30-40 new test engines for a 5mm bore job is beyond me. Or 30-40 new engines with the same bore and stroke but a new supercharger set up? 

Aircraft it actually flew in seem to be one (or more?) JU 52 test bed aircraft, two (or 5-6?) Ju 288 prototypes 9 different series) , one Fw 191 prototype. A few He 219 Prototypes. And a number of these prototypes were held up by the lack of "fight cleared" engines. Something isn't adding up. 

I was also in error on the R-4360 engine, it had 15,000 hours of ground running with 23 engines, not 50, before being deemed "reliable" with no definition of 'reliable' being given. Some service users of the R-4360 may beg to differ but at least it powered service aircraft. 

Of interest may be this history of the P&W R-4360 engine. 

http://www.enginehistory.org/P&W/R-4360/R-4360History.pdf 

of note is that the first "lash up" engine was running about 5 months from the start of work and the engine was flying in a test bed aircraft in 18 months from start of work. Also note the testing done with single row and single cylinder test rigs. 

Please note that the R-4360 used a variety of supercharger set ups. 

Somehow "needing" 270-280 "test" Jumo 222s doesn't seem quite right


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## wiking85 (Nov 29, 2013)

It also flew on a He 177/277 prototype and there was a TA-152 prototype as well. IIRC there was also a Do-317 prototype the flew with it. 
As to the website...what's its source for information? There is a lot of unsourced internet information out there.


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## Shortround6 (Nov 29, 2013)

That is the problem with much of the material about the Jumo 222. Some of the information on the website may have been taken from Putnam's " Junkers Aircraft Engines 1913=1945" By Antony L Kay or perhaps they used some of the same sources. In any case the charts listing the different models on some websites are wrong. (just use the listed bore and strokes to figure out the displacement and see the errors, one model engine just needs 12 more cylinders {total 36} to reach the listed displacement with the listed bore and stroke) 

As for the 177/277 prototype or the TA-152 prototype do you have a V number? I have no doubt that plans were made, I wouldn't put money on metal not being cut but actually flown? 

Maybe my books are old and out of date but this seems like a phantom engine, lots of models and differnet sources saying confusing things ( and maybe the 289 number is a mistake and just copied form one book/site to another) but even the planes that flew with it are noted as not having flown long or without constant trouble. If the 289 number is right (or anything close to it) the program was a colossal waste of effort ( a few Allied programs got shut down before going quite as far and justly so and a few more should have been.)


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## wuzak (Nov 30, 2013)

wiking85 said:


> It also flew on a He 177/277 prototype and there was a TA-152 prototype as well.



I am reading about the He 177 now, and thus far there had been no mention of the Jumo 222. The He 274 was to be powered, from a quick glance, by 4 x DB 603 or 4 x BMW 801. 

The Ta 152 with Jumo 222 was a proposal, rather than a flying prototype.




wiking85 said:


> IIRC there was also a Do-317 prototype the flew with it.



That may be the case. 

The early Ju 288s definitely had them.

But if the Jumo 222 was indeed reliable and production ready at 2000hp, then why weren't they suggested for the Me 264? The Me 264 was designed for Db 603s (1750hp), ended up with Jumo 211s (~1200-1300hp?) and finally BWM 801s (1750hp). If a 2000hp engine was ready and waiting I'm sure Messerschmitt would have jumped at the chance.

(Curiously they didn't have DB 606/610s as an option either.)


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## wiking85 (Nov 30, 2013)

http://www.ww2aircraft.net/forum/engines/engine-quastion-about-he-177-a-11699-3.html


> The He177 B V101 was found burned out at Cheb in May 1945. It was fitted with the Jumo 222 when destroyed, thus it was not the high altitude He-277 B-5 aircraft powered by the high altitude Jumo 213E. Nor was the He-177 B V101 found at Cheb fitted with a pressurised cockpit thus it was not the He-277 at all.



http://www.ww2aircraft.net/forum/aviation/powerplants-fw-190-ta-152-a-35474.html
From GregP:


> The Ta 152H sported a Jumo 213 E/F that weighed in, as specified above, at about 1,808 pounds dry. The Ta 152 C also had a Jumo (213A) of about the same weight except for the C-0 and C-1, which had a DB 603L powerplant (see above). Cone C models had a Jumo 222 which made 2,465 HP for takeoff and 1,870 HP at cruise. It had a dry weight of 2,399 pounds.



As to the reason it wasn't reliable at 2000hp was that that version was cancelled in 1941 and upped to 2500hp before it was ready; then when it was reapproached at 2000hp in 1943 the Dessau plant was wrecked by allied bombing, which made production of the engine impossible, so the Me 264 didn't have access to the Jumo 222E/F, which, from what I've gathered, nearly entered production but for the bombing.
My point was that it could have been ready in 1942 if the order for a higher hp version didn't come down in 1941, which set the project back to getting the engine up to the new standard, in effect killing the chance to get the 2000hp version ready in a timely fashion before strategic challenges set in. The other issue is that by 1942-43 Milch had decoupled the engine from the Ju288 project, which meant it was relegated to secondary (or even tertiary) status in terms of funding and engineering resources.



Shortround6 said:


> Maybe my books are old and out of date but this seems like a phantom engine, lots of models and differnet sources saying confusing things ( and maybe the 289 number is a mistake and just copied form one book/site to another) but even the planes that flew with it are noted as not having flown long or without constant trouble. If the 289 number is right (or anything close to it) the program was a colossal waste of effort ( a few Allied programs got shut down before going quite as far and justly so and a few more should have been.)


From what I've gathered this book has the most complete info about the engine:
http://www.amazon.com/dp/3763761071/?tag=dcglabs-20
I don't have access to it, but I might be able to get it via interlibrary loan and can translate it.


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## stona (Nov 30, 2013)

Propellorhead said:


> The He177 B V101 was found burned out at Cheb in May 1945. It was fitted with the Jumo 222 when destroyed, thus it was not the high altitude He-277 B-5 aircraft powered by the high altitude Jumo 213E. Nor was the He-177 B V101 found at Cheb fitted with a pressurised cockpit thus it was not the He-277 at all.



That needs some clarification.

V101 was PROBABLY the burnt out aircraft found at Cheb in 1945. It had first flown with four DB 603 A engines way back in December 1943. It was an obvious choice to convert one four engine version (DB 603) to another (Jumo 222), probably in connection with the He 277 program. As far as I know nobody knows whether V101 ever flew in this configuration. 

I can find no evidence that the Jumo 222 was ever considered for the He 177. The B-0 was to have four BMW 801 engines. Drawings of the various versions of the B-5 all have four DB 610 engines. A specification for the B-6 calls for four BMW 801 engines with mention of a variant with four Jumo 213 Es. Finally the B-7 proposal was to have had four DB 603s. Since none of these (B-0,B-5,B-6,B-7) were ever built it's a moot point, but at no time is the Jumo 222 mentioned.

The He 277 is also irrelevant. It barely got off the drawing board and I don't believe that a single prototype was ever completed. Some sources suggest that some examples were built, but were destroyed by allied bombing, but the hard evidence for this is, politely, elusive.

Cheers

Steve


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## davebender (Nov 30, 2013)

Prototype first run for both engines was during 1939. If fully funded to production status per original 2,000hp specification I suspect both could have been in mass production during 1942. 

Daimler-Benz was working on a multitude of engine projects during WWII for Schnell boats, submarines, tanks etc. in addition to DB601/DB605 aircraft engine. IMO it makes sense to give 24 cylinder aircraft engine project to Junkers rather then burden Daimler-Benz with another major project.


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## DonL (Nov 30, 2013)

wuzak said:


> The DB 604 was better....




I have very very serious doubts about such a claim.
No 604X was ever in the air and it was also a major development project of DB since 1938 for the Bomber B.
To all german sources the DB 604X was far away from the development of the Jumo 222,


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## tomo pauk (Nov 30, 2013)

Hi, DonL, maybe you want to say that Jumo 222 was far ahead from the development of the DB-604, since no 604 ever got in the air?


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## DonL (Nov 30, 2013)

Oh sorry yes, wrong language


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## Rick65 (Nov 30, 2013)

The more I read about the German programs for 2000hp+ engines the more I realise what an achievement the Napier Sabre was, with flight in the prototype Typhoon in early 1940 and service introduction in mid 1941. It initially had reliability problems, and service models didn't offer power at height but it was in production and being used in operations when the German (and US ) equivalents were not.


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## wiking85 (Nov 30, 2013)

Rick65 said:


> The more I read about the German programs for 2000hp+ engines the more I realise what an achievement the Napier Sabre was, with flight in the prototype Typhoon in early 1940 and service introduction in mid 1941. It initially had reliability problems, and service models didn't offer power at height but it was in production and being used in operations when the German (and US ) equivalents were not.


It didn't hurt that the Sabre started development two years before the equivalent German or US designs.


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## wuzak (Nov 30, 2013)

DonL said:


> I have very very serious doubts about such a claim.
> No 604X was ever in the air and it was also a major development project of DB since 1938 for the Bomber B.
> To all german sources the DB 604X was far away from the development of the Jumo 222,





tomo pauk said:


> Hi, DonL, maybe you want to say that Jumo 222 was far ahead from the development of the DB-604, since no 604 ever got in the air?



I didn't say that the DB 604 was _more advanced_, I said iit was better than the Jumo 222.

Certainly at the time of cancellation the DB 604 would have been at least equal in power. Take-off power was listed at 2660hp and mximum 2410hp @ 20,600ft (6279m):

GED0109

Compared with 2500hp at take-off and 2490hp @ 16,400ft (A-2/B-2) or 2200hp @ 16,400ft (A-1/B-1). 

GED0116

The 3000hp version seems to require MW50 for take-off and GM-1 for altitude performance.

Max Cruise performance is slightly in favour of the Jumo 222 at sea level (1900hp vs 1830hp) but in favour of the DB 604 at altitude (1860hp @ 20,000ft vs 1750hp @ 16,400ft).

Physically they are the same capacity (depending on versions), are about the same weight (2400-2500lb/1089-1134kg), but I don't have any exterior dimensions for teh DB 604.

DB604

http://enginehistory.org/German/Jumo222/Jumo222Fig04.jpg

Plus, I think the DB 604 looks neater.


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## wiking85 (Nov 30, 2013)

wuzak said:


> I didn't say that the DB 604 was _more advanced_, I said iit was better than the Jumo 222.
> 
> Certainly at the time of cancellation the DB 604 would have been at least equal in power. Take-off power was listed at 2660hp and mximum 2410hp @ 20,600ft (6279m):
> 
> ...


I've read that the Jumo was more fuel efficient and therefore preferred, as it would give the Ju 288 the range it needed to meet spec.


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## Shortround6 (Nov 30, 2013)

This is were things get murky. We have documents that don't make sense. Please figure the capacity of the DB 604 based on the numbers given in GEDO109. If I am doing the math right the 46.5 liter capacity is correct for an engine using a 135mm bore and a 135 mm stoke. Using a 140mm bore should give you a Displacement of 49.85 or 49.88 liters. and a 135 bore and 140mm stroke DOES NOT give 50 liters. It gives 48.07 liters. 

As for fuel economy? both are 24 cylinder engines using just about the same sized (if not THE same sized cylinders) at the same max rpm ( and cruising rpm?) and depending on exact engine measured, the same compression ratio? Granted they seem to vary a bit form source to source. But one torn down Jumo 22 had a 6.75 compression ratio and one description of the DB 604 says 7:00 to 1 compression ratio? 
We are left with differences in piston/piston ring fit, bearing drag, exact power used to drive supercharger, ignition timing ( and they are going to be close also) pumping losses, etc to try to explain which engine was more "economical" and since the amount of actual flight testing ranges from Nil (DB 604) to not much ( Jumo 222) we are left with manufacturer's "estimates" (sales pitches). Maybe the Jumo was more economical but there is no "feature" that points to it. (Allison used a 6.65 compression ratio compared to the Merlins 6.00, 10% greater which _helped_ fuel economy. These engines show a 3.7% difference in compression and in the DB 604's favor?
Both engines were fuel injected. 

We are firmly in the land of "What if" just out side the city of "Maybe" next to the river "It might have" and in the shadow of the mountain peak "not sure" when dealing with these two engines 

even reports of torn down Jumo 222 engines in allied hands don't agree with each other or with German sources (150mm bore on a Jumo 222 ??) Could be a simply typo ( I make more than my fair share


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## davebender (Dec 1, 2013)

The most important achievement was keeping the engine on track for mass production @ the original 2,000hp specification. Whoever was in charge of British aircraft engine production was clearly more competent then his German counterpart.


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## Shortround6 (Dec 1, 2013)

No.

Two things:
1. British could use/plan on better fuels to increase power more than the Germans could.
2. The British were not so wedded to the twin engine concept. If more than 4000hp was needed they shifted to four 1200-1600hp engines rather than try for 2500+ engines.


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## wiking85 (Dec 1, 2013)

Out of curiosity why didn't the Lancaster ever use the Sabre?


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## tomo pauk (Dec 1, 2013)

Dry weight of the Sabre was almost 1000 lbs greater than of the Merlin 21. Add heavier cooling lubrication system, bigger prop cowling and the powerplant group goes up for 6000 lbs, or more? That added weight cuts in fuel and/or bomb load. Plus, the CoG need to be addressed, since all of the extra weight is in the front of the CoG. The counterbalance means new weight added to the aircraft. Some reinforcements will need to be added to the airframe - further 1000 lbs? Before you know it, it's 8000 lbs added to the Lanc - that would lug only 1/2 of the bomb load, or have much reduced radius.


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## davebender (Dec 1, 2013)

Probably weren't enough Sabre engines available when the Lancaster bomber entered mass production.

Do we have production data for the Sabre engine?


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## Shortround6 (Dec 1, 2013)

Lancaster was a 4 engine Manchester, When The Vulture was having troubles the Sabre really wasn't a working proposition either. The Sabre passed it's 100 hour test at 2000hp rating in June of 1940 but the production engines were still a mess and stayed a mess for quite some time.
There were projects for both a Sabre powered Manchester and a Centaurus powered version both both projects were dropped with the flight testing of the first Lancaster's.


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## Piper106 (Dec 1, 2013)

Back to our regularly scheduled program... the Jumo 222.

I think that that oh so German drive for perfection bit them big time. 

The Jumo 222 was (or would have been) a technically masterpiece. On the other hand, brute force and ignorance in the form of a doubled Jumo 211 engine in a vertical H formation i.e. two vertical cyliner flat 12s running on two standard Jumo 211 crankshafts geared to one propeller shaft would have been much more likely to have yielded a a useful result. 

For example, doubling the 1938 vintage 211B engine running at 2400 rpm would give 2400 PS / HP. Wikipedia gives the weight of an early 211 as 585 kg, doubled would be 1170 kilos (2580 pounds), compared 1088 kgs (2400 pounds) for 46.5L Jumo 222A. Plus with 70L available, development/growth of the H-24 Jumo could have followed in the foot steps of the Jumo 211 V-12, so there could have been 2600 PS / HP in 1940, and 3000 HP by 1943. 

The H-24 version could have used the crankshaft, rods, pistons, cylinder liners, and cylinders heads of the 211. About the only totally new parts needed would be the crankcase casting, and the propeller reduction gear. As the Luftwaffe outgrew 211 V-12 powered aircraft, parts production and factories could have been converted into the H-24 version for the Bomber B program. 

If you need to visualize, Google or Bing on "Arsenal H-24 engine". This was liberated France doubling of the Jumo 213 for post war.


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## wiking85 (Dec 1, 2013)

Piper106 said:


> Back to our regularly scheduled program... the Jumo 222.
> 
> I think that that oh so German drive for perfection bit them big time.
> 
> ...



How would this have been different than the DB606/10?

And what makes you think that the Jumo 222 would have been technical masterpiece?


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## Piper106 (Dec 1, 2013)

wiking85 said:


> How would this have been different than the DB606/10?
> 
> And what makes you think that the Jumo 222 would have been technical masterpiece?



The "technical masterpiece" was a bit 'tongue in cheek', or 'graveyard humor'. However had it worked I'm sure there would be plenty of posters on this board (and other boards) holding it up as proof of German technical superiority over inferior British / American iron mongers. 

Some advantages of a Jumo H-24 over the Daimler Benz DB 606 / 610 engines. First, there have been several threads about how Daimler Benz lacked production capacity, while there was 'plenty' of production capacity for the Jumo 211. A two crankshaft, 24 piston, 24 connecting rod engine eats up production capacity fast. Second, the DB 606 double engine weighed 1515 kg (3333 pounds), the DB 610 1540 kg. Considering that the Allison 24 cylinder V-3420 weighed within a few pounds of twice what their V-12 weighed, I feel my estimate of 1170 kgs (i.e double that of a Jumo 211 V-12) for a Jumo H-24 is reasonable. A 300 kg plus weight saving per engine is significant. The Damlier double engines also had a red hot exhaust collector at the very bottom of the engine cowling between the two vees, just waiting to start a fire should there be the slightest leakage of fuel or oil. On the proposed Jumo vertical H, the hot exhausts are on the outside of the cylinder banks, above the cowling bottom.


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## Shortround6 (Dec 1, 2013)

Unfortunately for a number of nations some of the engine designers of the 30's tended to get carried away with their own cleverness. Granted they were up against some real limits at times. You can only make cylinders so big for one. For a given type of fuel you can only use so much boost. This leaves you with lots of cylinders and/or high rpm as the only answers until the fuel guys hit the next level. Since small cylinders offer a number of advantages 1, better cooling due to higher cylinder wall to volume ratio. 2, better volumetric efficiency. 3, higher rpm due to shorter stroke ( less strain on parts) AND less time needed for flame front to cross smaller cylinder. It also seemed like the high cylinder count, high rpm engine offered real chances for big improvements. 
Unfortunately adding cylinders and or spinning the crank faster was NOT as easy as it seemed. That and a few designers seemed to go out of their way to complicate things. The Jumo 222 was utter simplicity compared to the Wright Tornado. The ONLY good thing you can say about the Tornado is that they didn't build almost 300 of them 

A few of our too clever for their own good designers also tried to make these high cylinder count engines as compact as possible. Granted they were looking for that _big jump_ that would carry their company for years and years instead of a short term fix. While engine and materials men had learned an awful lot in the 30 something years since the start of powered flight there was still an awful lot more to learn and these complicated engines brought that home with a vengeance. Metal fatigue was just starting to be sorted out. They were just starting to get a good handle on vibration problems (of all sorts). Most (all?) companies didn't have airflow benches that could measure the air flow through cylinder head ports. Intake manifolds and airflow through them was more art than science. Even coolant flow entailed a lot of trial and error. 

R-R used a system of run it until it breaks, fix it , then run it some more. The more cylinders you use the more stuff that can break and the more ways it can break. 

Classic story on the Griffon is that they reversed the crankshaft rotation and ground the cams and rigged the ignition to suit and promptly broke two crankshafts in less than ten hours each. Somebody noticed that they were using the _same_ layout for the crankshaft as the Merlin (the crank pins were staggered the same amount from front to back and in the same order) They made a "mirror" image crankshaft, dropped it in and ran with no problem. Not all vibration is the engine trying to bounce up and down or side to side. Harmonic vibration can do strange things, breaking parts that vibrate in harmony with the part/s causing the vibrations but located at some distance from the part/s causing the vibration. DO you try to damp the vibration to begin with or beef up the broken part/s ( which just may change the frequency at which they vibrate). 

And most of these all too cleaver engines would have been an absolute BI*CH to service in the field.


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## Elmas (Dec 2, 2013)

_“None of the studs, nuts and bolt were accessible- you couldn’t even see them!-You were feeling around corners and you’d got weirdly contorted spanners to get at them, giving it half a turn then chosing another spanner and giving it another bit of turn! oh, that was shocking!_

Peter Jago, RAF engineer, about the Napier Sabre engine


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## stona (Dec 2, 2013)

Many engines were difficult to service in the field. Goering wasn't too thrilled about the installation on the He 177, which he had inspected at Rechlin in May 1942.

"How is such an engine to be serviced on the airfields? I believe I am right in saying that you cannot even take out the spark plugs without pulling the whole engine apart."

From a transcript of a Goering Conference held on 13th September 1942. 

So bad were the problems of maintenance that a special field maintenance unit (Feldwerft Abteilung zbV 1) was set up to support the first operational He 177 unit, II./KG 40. 

Cheers 

Steve


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## cherry blossom (Dec 2, 2013)

A very interesting but biased account of Jumo 222 development is in Ferdinand Brandner's autobiography http://www.amazon.de/dp/3853391257/?tag=dcglabs-20. I haven't read it and most reviews focus on his later work but there is some mention of the effects of material shortages causing problems. The central problem that we are trying to understand is that the initial Jumo 222 model passed its 100 hours type test in April 1941 but despite that development seemed to go backwards. Could it be that the early prototypes used bearings made with alloys that could not be manufactured in quantity because of shortages of metals such as tin? Naturally changing the capacity twice may also not have speeded up the development of a reliable engine. Brandner is quoted as saying that the Jumo 222 was developed to death.


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## Shortround6 (Dec 2, 2013)

I think entirely too much is being made of the the type test.
The Napier Sabre passed a type test in 1940. hand built engine passed, production engines turned out to be another story. The Vulture passed a type test or it wouldn't have been put in the Manchester. The Centaurus was supposed to have been type tested in 1938? Or the Hercules. Wright R-3350 was type tested When? (first version, major redesign for the version that powered the B-29) Continental IV-1430 passed a type test in 1940, test flown in two types of aircraft several years later it was a dismal failure to be kind.

Germans were flying Fw 190s in combat with some rather less than reliable BMW 801 engines and yet the Jumo 222 got only limited flight time in a few prototypes despite all those engines being built?


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## delcyros (Dec 2, 2013)

just get Prof. Lutz Budraß book and please stop speculating without sources.


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## wiking85 (Dec 2, 2013)

delcyros said:


> just get Prof. Lutz Budraß book and please stop speculating without sources.


AFAIK Budrass states that the engine was killed by Milch in an administrative act rather than technical issues; is that true as far as you know?


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## delcyros (Dec 2, 2013)

Short answer: yes. It was Milchs intent to make sure that the Jumo222 fails in order to crush the special position of the Junkers company in the german military industrial aeronautic complex. Had the Ju288 succeeded it would relegate Heinkel, Dornier, Henschel and other manifacturers to the status of licensees from which they wouldn't recover. Everybody knew this.
Milch succeeded because he upped the performance requirements faster than Junkers MW could improve the output of the Jumo222.
When it eventually was about to reach the requirement of 1943 he ordered that airframe and engine should not be developed together and effectively killed both projects.
It was important that this engine fails, independent of application


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## wiking85 (Dec 2, 2013)

delcyros said:


> Short answer: yes. It was Milchs intent to make sure that the Jumo222 fails in order to crush the special position of the Junkers company in the german military industrial aeronautic complex. Had the Ju288 succeeded it would relegate Heinkel, Dornier, Henschel and other manifacturers to the status of licensees from which they wouldn't recover. Everybody knew this.
> Milch succeeded because he upped the performance requirements faster than Junkers MW could improve the output of the Jumo222.
> When it eventually was about to reach the requirement of 1943 he ordered that airframe and engine should not be developed together and effectively killed both projects.
> It was important that this engine fails, independent of application


So in your opinion could the engine have succeeded in giving 2000HP by 1942 if it had not been 'developed to death' by Milch?


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## davebender (Dec 2, 2013)

That's impossible to avoid if you want high performance. Hence the reason modern military aircraft and armored vehicles are designed for rapid replacement of the entire engine, which is then shipped back to depot for repair. This practice has it's roots in WWII.


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## Milosh (Dec 2, 2013)

So dave the engines of the He177 were removed from the a/c and sent to a repair depot to replace the spark plugs?


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## Shortround6 (Dec 2, 2013)

ROFLMAO:

Not picking on the Jumo 222 here but even the P&W R-4360 had problems, it was made "reliable" but was a maintenance hog. If the starting procedure was not _strictly_ adhered to it was possible to flood the engine and foul the plugs ( actually a common occurrence with WW II engines, or at least not uncommon) requiring that all 56 spark plugs be pulled, cleaned or replaced and re-installed before attempting to start the engine again. They don't send engines back to the shop in western country's for spark plug replacement or valve adjustment or other minor problems (leaking pipes/hoses etc. )


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## Jugman (Dec 2, 2013)

In all fairness the large number of Jumo 222 manufactured may be do to accounting practices. For example the V-1710-A1 Build 1 and Build 2 are considered the same engine by Allison yet Build 2 had every part replaced! Is it really the same engine if you do that? Junkers may have listed this as a new engine instead of a rebuilt one. Furthermore the total could include spare equivalents. For example, if one includes spare equivalents for the Chrysler I-2220 the number built goes from 6 to at least 50.


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## wiking85 (Dec 2, 2013)

From the following book:
Black Cross Volume 2: Junkers 288/388/488: Karl-Heinz Regnat: Amazon.com: Books


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## delcyros (Dec 3, 2013)

I am not qualified to have my own opinion as I haven't seen all primary sources which were abiable to Budrass but he expressed that the Jumo-222A1 was certified to be ok for mass production early 1942 based on a 30min rating of 2000hp on B4 fuel after passing bench flight tests. They even had a new factory tooled up in Vienna. It would also be ok for the proposed Ju288A to reach predicted performance.
However, already late in 41 Milch called for a change from 3men crew to 4 men crew, larger MTOW and more remote def guns requiring a larger wing and a 2500 hp class engine.


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## wiking85 (Dec 3, 2013)

Well it sounds like if the Ju288A and the original version of the Jumo 222 were stuck with then they would be in production by late 1942-early 1943. Its the increased spec requirements, done on purpose, that killed both projects; Milch apparently made this his #1 project when he took over after Udet's suicide to dismantle the system of power that was in place to ensure his authority over the aviation sector, which Koppenberg had wrestled into his control with the Ju88 program; it seems Koppenberg was aiming for total monopoly and was trying to ensure with the Ju288 that he would kill his competitors and become the defacto minster of aviation himself, because he would control the only viable aviation firm at that point. So both the Jumo 222 and Ju 288 were not killed by technical issues, but rather administrative sabotage for political reasons.


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## Jugman (Dec 3, 2013)

I dopn't think Ostmark was ever actually tooled up to produce Jumo 222s. Or at least it was converted to DB 603 before the proses was complete. Regardless of whether or not the Jumo 222 was considered production ready, the sheer size and complexity of the crankcase casting could have been grounds for cancellation. Most certainly it would have made the unmitigated disaster that Ostmark was even worse.


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## DonL (Dec 3, 2013)

I


> dopn't think Ostmark was ever actually tooled up to produce Jumo 222s. Or at least it was converted to DB 603 before the proses was complete.



Nope,

Ostmark was tooled up for the Jumo 222 inclusive all sub companys, which delivers fuel injections, supercharger and so on.

This was one of the reasons that the change of Ostmark to retool to the DB 603 cost two years.


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## wiking85 (Dec 3, 2013)

Jugman said:


> I dopn't think Ostmark was ever actually tooled up to produce Jumo 222s. Or at least it was converted to DB 603 before the proses was complete. Regardless of whether or not the Jumo 222 was considered production ready, the sheer size and complexity of the crankcase casting could have been grounds for cancellation. Most certainly it would have made the unmitigated disaster that Ostmark was even worse.


How was it any different than the Napier Sabre? That engine was just fine after the initial hiccups were worked out.


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## Shortround6 (Dec 3, 2013)

This seems a little too simplistic and pat. It also seems to assume that the both the Ju288 and Jumo222 were without any problems that could not be easily solved. Politics may very well have been involved but even in politics you need a germ of truth or an excuse. 

1937-start of work on the Jumo 222 engine
1938-planning work on the EF-73 project which becomes the basis for the Bomber B specification issued in July 1939.

Specification calls for a 600kph speed ( 373mph) and a bomb load of 4000kg (8820lbs) to be carried to any part of Great Britain form bases in France or Norway ( at least according to one source). Two 2500hp class engines are specified. Please compare specified performance to what the Douglas A-26 was able to achieve in 1943-44. 

May 1939 sees H. Hertel leave Heinkel and join Junkers to oversee the EF 73 project. The Jumo 222 ran for the first time on a test stand the moth before. The EF 73 has an extensively glazed _pressurized_ cockpit and remote control gun barbettes. The RLM requests (among other things) a larger wing and a change in the gun barbettes. 
By the end of May 1940 a full mock up of the fuselage has been inspected and orders are given for 3 prototypes ( Junkers had already begun cutting metal) fuel tanks in wings and fuselage are to house 5360 liters ( 1416 US gallons again compare to A-26) of fuel. 

Now 1940 is were things get a little strange, The Jumo 222 makes it's first flight Nov 3 1940 in the nose of a Ju 52. JU 288 V1 flies for the first time Nov 29 1940 using BMW 801 engines. The V2, V3 and V4 follow from March until May of 1941, The Jumo 222 is flown supposed to have passed it's type test in May of 1941? The JU 288 V5 with Jumo 222s flies Oct 1941 but ignition troubles keep engines from developing full power. 

It is at this point that politics may or may not rear it's head. Plans had been made to produce 380 planes a month. The RLM now changes to the 4 man cockpit and other changes, including a yet bigger wing, which is tested on V6 with Jumo 222 engines (Jan 1942) and is lost due to engine fire. The V7 goes goes back to BMW 801s and seriously under powered it too is lost due to an engine fire. The V8 is flown with Jumo 222 engines as is the V9 in May 1942 (prototype for the B series). March of 1942 had seen orders for the production of the Ju 288 go ahead but by November the the numbers were cut to 35 aircraft due to the problems with the Jumo 222 engine, the C and D versions not performing satisfactorily and the engine project is back in development. The Ju 288 V10 flies in Jan 1943 with a pair of BMW 801TJ ( turbo-charged) engines. Earlier flights were made by the V11 and V13 with DB 606 engines in July and Sept 1942. The V12 and V 14 were the last Ju 288s powered by Jumo 222 engines. 

I would note that they were using 1600hp BMW 801 engines for test flying instead of not only the later 2500hp Jumo 222 models but the earlier 2000hp models that some people seem to think were production ready ( or even built in a small production batch/s) 

According to this account 6 Ju 288 prototypes flew with Ju 222 engines. It could be in error. 

Again try compare what they were trying for to the A-26. More bombs, more fuel, a pressure cabin and more speed ( maybe achievable at the higher altitude ?) and they started 2 years earlier. By the time they got done (and saddled the plane with DB 610 engines) they had a plane that weighed more empty than the A-26 was _supposed_ to weigh ready for take-off ( A-26 cheats as the difference between _normal_ and Max weight is an easy 8,000lbs or so).

The Specification was too big a leap for the technology of the time which lead to an extended development time. The Initial design (EF 73) had a wing span smaller than an "A-20" but wanted 4 times the bomb load and more range ( fuel ) and used more powerful engines. Were ALL of the RLM requests political meddling or an attempt to bring the "design" somewhat closer to service requirements?


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## wiking85 (Dec 3, 2013)

Shortround6 said:


> This seems a little too simplistic and pat. It also seems to assume that the both the Ju288 and Jumo222 were without any problems that could not be easily solved. Politics may very well have been involved but even in politics you need a germ of truth or an excuse.
> 
> 1937-start of work on the Jumo 222 engine
> 1938-planning work on the EF-73 project which becomes the basis for the Bomber B specification issued in July 1939.
> ...



The Jumo 222 was ordered uprated in October 1941, though it had already undergone one displacement upgrade between 1939-41 (not sure when exactly) that bumped it up to 2500hp. So the initial change happened somewhere in 1941 prior to October, but the second increase which netted the C/D series of 3000hp engines (first run in summer 1942). Yet after this engine failed they went back to the original displacement in 1943 and fixed the problems, resulting in the E/F series. 

So there were problems between 1939-1941, but it was the first displacement upgrade that started the development creep that prevented it from being ready in 1942. Wikipedia has unsourced claims that Junkers ordered the displacement increase, but I think that was the start of RLM interference.
Milch was starting his political counterattack on Udet and was issuing orders in October 1941, which ultimately resulted in Udet's suicide, so its likely that he was ordering unnecessary upgrades in the weight of the airframe around this time (such as adding a fourth crew member and more defensive armament among other things), while then demanding upratings in engine performance, something he knew would set back engine development.

The article below mentions the year delay after the April 1941 test, which would have put full scale production back until April-May 1942, but by then the order to move up to 2500hp was ordered and new problems set as the old ones were being solved. So the 2000hp version would have been ready in 1942, but after the March date Dave mentioned.


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## delcyros (Dec 3, 2013)

The A-20 is a technically greatly inferior airplane design to the Ju-288 and the A-26 is not yet on par with it. I don´t know why it should be compared at all. After all, the amount of R&D which went into the combined JUMO-222&Ju-288 project was similar to that of the V-2 missile project. It had much more R&D support than the A-26. More effecient fuselage space usage (just think of bombbay and fuel tanks), more optimised structural framing, better ergonomically laid out cockpit, better preperation for section mass production and last but not least more advanced aerodynamics with much more time spent in the windtunnel for detail solutions. 



> I would note that they were using 1600hp BMW 801 engines for test flying instead of not only the later 2500hp Jumo 222 models but the earlier 2000hp models that some people seem to think were production ready ( or even built in a small production batch/s)


There were not many Jumo-222A1 produced and the A1V-11 to A1V-16 were worked very hard in the trials, logging several hundred hours of flight. A document dated to 18th of oct. 1943 lists the Ju-288V05 with it´s n´th set of engines stationed at JUMO and given care and maintenance. Most of the JUMO-222 which were produced were of -A3 subvariants and late -E2/F2 subvariants for which after start of the Jägernotprogramm all suitable carriers were canceled from production list while single engined projects with JUMO-222 were not yet developed to the degree to carry this engine.

To blame it a technical fault is incorrect and Budraß is entirely correct in pointing out that the problem lies in the decision making process. One thing which is often overlooked is that in 1941 nobody expected a long continuation of the supposed to be short remainder of the war. The Ju-288 should represent the next generation bomber, not just a mildly improved version of existing ones. And while allied engeneerers succeeded in developing good to very good solutions and bringing them to front service in record breaking times, german ones didn´t succeeded in bringing them to front service because they tried to over-improve , over-engeneer and over-develop them, in part explainable by the formidable technical challanges in front of them. But not entirely, part of it was a prevalent low tolerance to compromises. Remember, german technicians in 1941/2 experimented with strange futuristic projects, like jet and rocket propelled aircraft and bombs, guided stand off weapons, long range missiles, turbine driven submarines.

The JUMO-222V05 driven by two JUMO-222A1V engines and a span of 60.3ft was the way to go. It offered the performance required with the test flights starting in september 1941. The plane was started beeing assembled by oct. 1940. It remained to be the only test bed according to the original -A1 specification with 3 men crew and small wing. The following change in general size meant that a whole pletora of other changes had to be done (gears, wings, cockpit, structure) so that the construction of the next prototype, the -V6 was not started before july 1941. That´s 3/4 of a year delay. This means that only the Ju-288A1 had a realistic chance of production (preproduction models in 1942 mass production scheduled for 1943 with 1st frontline service in 1943).


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## Shortround6 (Dec 3, 2013)

We appear to have a timing disconnect. 
The Jumo 222 was started in 1937 as a _2000hp_ engine.
The Bomber "B" requirement was issued in 1939 ( two years later) for 2500hp _class_ engines. 
Jumo 222 is already behind the curve. Now many engines did pick up 25% in power from early models to later ones (or more) but trying to pick up 25% in power while still in development and _without_ the use of improved fuels is going to be difficult. 

AS for "The A-20 is a technically greatly inferior airplane design to the Ju-288 and the A-26 is not yet on par with it. I don´t know why it should be compared at all. After all, the amount of R&D which went into the combined JUMO-222&Ju-288 project was similar to that of the V-2 missile project. It had much more R&D support than the A-26."
I think you are missing the point. The A-20 was a "technically greatly inferior airplane design" _BUT_ it was in production in 1940 and I only used it to serve as a bench mark for what the Germans were trying to do. More speed, quadruple the bomb load and longer range in a similar size (but not weight ) aircraft. It certainly does require a more advanced aircraft. And here we hit part of the problem, perhaps it was _too_ advanced or _too_ ambitious. A 2000kg payload at the speeds and ranges requested would have been pretty challenging, trying for 4000 kg bomb load? The A-26 used a similar sized wing to the 288B and used a Laminar flow airfoil and double slotted flaps ( I know it is not true laminar flow but it was about the best air foil around at the time of it's design) and had 2000hp engines, a smaller bomb load and less fuel. You are going to need a _really_ advanced aircraft to beat it for speed, range (fuel capacity) and larger bomb load while using the _SAME_ power engines, yet the RLM is blamed for wanting 2500hp engines to meet the performance specifications. 
Using up the resources of the V-2 program for a twin engine bomber may NOT be a bragging point. The Ju 288 may very well have been more advanced than the A-26 and used up a lot more R&D but you can't have it both ways. A long, costly and complicated development program IS much more subject to political interference. 

I agree with " german ones didn´t succeeded in bringing them to front service because they tried to over-improve , over-engeneer and over-develop them, in part explainable by the formidable technical challanges in front of them. But not entirely, part of it was a prevalent low tolerance to compromises. Remember, german technicians in 1941/2 experimented with strange futuristic projects, like jet and rocket propelled aircraft and bombs, guided stand off weapons, long range missiles, turbine driven submarines."

But to put a fair amount of the blame on "politics" when you are trying to produce such long lead time weapons is not quite fair. 

"The JUMO-222V05 driven by two JUMO-222A1V engines and a span of 60.3ft was the way to go."

It might have been if they left a few things out. You have a about 58lb per sq ft of wing area with a 'Normal" loaded weight of 33850lbs. The Whole bomber "B" program was way too much of trying to be "all things to all men". A less ambitious plane might have succeeded with the original Jumo 222 engines.


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## delcyros (Dec 3, 2013)

I am curious because I have the copies of the TA Bomber B requirements right in front of me but I am sorry, there is no word of a 2,500hp engine. The specifications call for a top speed of 600km/h, a max range of 3600km with 2ts payload and max. permissable 6ts short range overload payload. No engine is specified.

This is often mixed up with Junkers initiative proposal EF-74. This preliminary proposal based upon the Ju-288 layout, but was driven by 2 x JUMO-223 Aero Diesel engines with a supposed to be 2,500hp short term 5 min power. These engines didn´t existed yet in 1939. The JUMO-223 is not comparable with the JUMO-222. The entrance of the Junkers EF-74 and EF-73 in effect triggered the decision of the RLM to summon the bomber-B competition.

The JUMO-222A1 was perfectly capable of higher short term power. The 2000HP rating is 30 minutes rating. It wasn´t ever cleared for the 2480HP -5min take off rating (they just upped the requirements so that the 30 min. rating matched this performance). That´s still a bit short of the 2000hp planned max sustainable but quite close. Just to remember, the 1,750 HP BMW-801 required C3 fuel, the JUMO-222 was fine with low grade B4 fuels. A shift to C3-grade fuel would have allowed short time emergancy powers in excess of 2,200HP. It was tested for this.



> The A-20 was a "technically greatly inferior airplane design" BUT it was in production in 1940 and I only used it to serve as a bench mark for what the Germans were trying to do. More speed, quadruple the bomb load and longer range in a similar size (but not weight ) aircraft. It certainly does require a more advanced aircraft.


The Ju88 was also in production in 1940, whats the point? Both are a generation older than the Ju-288. And a generation between 1938 and 1942 means quite a lot in terms of technical capabilities.



> A 2000kg payload at the speeds and ranges requested would have been pretty challenging, trying for 4000 kg bomb load? The A-26 used a similar sized wing to the 288B and used a Laminar flow airfoil and double slotted flaps ( I know it is not true laminar flow but it was about the best air foil around at the time of it's design) and had 2000hp engines, a smaller bomb load and less fuel. You are going to need a really advanced aircraft to beat it for speed, range (fuel capacity) and larger bomb load while using the SAME power engines, yet the RLM is blamed for wanting 2500hp engines to meet the performance specifications.



Fuselage cross section? Wetted area? iengine nacelle drag? Cooling drag? The JU-288 airframe aerodynamic studies alone took the Junkers company 60 mio. RM, about as much as 1,200 A4 missiles would have costed. They found a perfect integration between engine and nacelle which allowed for less wetted drag compared to older JUMO-211 engine installations in the Ju88, despite having a much more powerful engine. Just looking at the cockpit, the JU-288A1´s is just 97cm wide and defines the width of the hull. It´s a fighter style one person cockpit while that of the A26 offers 156cm width. The Junkers design was laid out for minimum frontal and wetted drag and high cruise speed at the expanse of rather high take off and stall speed and less stellar high altitude performance, a normal trade off by the standarts of the mid and late 40´s, but new in the late 30´s. They attempted to mediate by high lift aids and excess power (the proposed A/C was 15% heavier than the Ju88 but had 35% more power). It may, however, as a very fine tuned product have been less tolarable to structural weight changes in general.



> A long, costly and complicated development program IS much more subject to political interference.


True. but I really suggest You consult Prof. Budraß work. Just look at the critical decision making timeline between the suicide of Ernst Udet in nov. 1941 and Milch´s decision to change engine and airframe requirements in order to stop production in dec, the same year. The program was costly because of Milch´s repeated changing requirements which made sure it will never proceed beyond prototype stage. To many minutes noted how these changes compromised the performance envelope and had to be adressed by time consuming changes again... Just look how the project grew in size:

EF-73:
MTOW: 14.6t
wing area: 48 m^2

Ju-288A1 (mid 1940):
MTOW: 15.6t
wing area: 54.0m^2

Ju-288A2 (dec. 1941):
MTOW: 17.3t
wing area: 60m^2




> It might have been if they left a few things out. You have a about 58lb per sq ft of wing area with a 'Normal" loaded weight of 33850lbs. The Whole bomber "B" program was way too much of trying to be "all things to all men". A less ambitious plane might have succeeded with the original Jumo 222 engines.


Agreed but in defense of Junkers, the general trend was to go for higher wingload as it represents a tradeoff for better flight performance. The step was already taken by Messerschmidt with his Bf-109 earlier, the Focke-Wulf and Heinkel companies had very good experiences with this approach from various A/C projects, too but the Junkers company was rather late in applying this step. The approach was endorsed by Udet. Milch just rejected it.


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## Jugman (Dec 3, 2013)

DonL said:


> I
> 
> Nope,
> 
> ...



Construction of the main building did not begin until late July 1941. It was completed around March 1942. It took even longer for the power plant, test cells and warehouses to be completed. The decision to switch over to the DB 603 was made in December 1941. First DB 603 deliveries were in May 1943. The earliest projected date for Jumo deliveries I have seen is April 1943.

I do not see how retooling cost two years.


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## Shortround6 (Dec 3, 2013)

Sorry, but I do not have copy of the specification Just books that apparently have it wrong. I stand corrected. But is speaks to the confusion about the Ju 288 and the Jumo 222 engine. 



> The Ju88 was also in production in 1940, whats the point? Both are a generation older than the Ju-288. And a generation between 1938 and 1942 means quite a lot in terms of technical capabilities.



Yes it does and the point was simply how far the Design team was trying to go in one in one jump. I am making no claims as to which was better ( the Ju 88 or the A-20) just picking out a convenient benchmark. 

If you wish go from the JU-88A-1. Wing about the same size and span (or with a few %) The 288 was to go from 1680 liters of fuel in the wing to 3560 liters and while the older plane could put another 1880 liters in the bomb bay (totally blocking it) the 288 was supposed to hold another 1800 liters in the fuselage _without_ blocking the bomb bay (unless this book is in error and this tankage does block the bomb bay), this is while upping the bomb load by at least 50% (or 100%?) , fitting heavier defensive armament, the Pressure cabin and the heavier engines. And requiring about a 33% increase in speed. AND the first couple of 288 prototypes had dive brakes. 

It is a wonder they didn't require it to tell jokes and wash windows


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## wiking85 (Dec 3, 2013)

The Ju 288 carried fuel tanks above the bomb bay in special tanks, making sure to use every inch of space in the fuselage for bombs or fuel. It could also carry two external drop tanks if needed.


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## tomo pauk (Dec 4, 2013)

Why I don't think that fuel was carried in 'special tanks', seem like the whole plane was designed around it's bomb bay and fuel tanks. Was there any fuel int he wings? Plus, the pilot and co-pilot of the A-26were seated tightly side to side, while the crew compartment of the Ju-288 allows for a comfortable quarters - ie. not very much narrower than of A-26 (if any?), and the side blisters add to the drag, too.

added: there is also the lower blister, and top of the crew compartment is well above fuselage, so IMO there is no advantage in streamlining vs. A-26 front crew compartment.


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## delcyros (Dec 4, 2013)

Shortround6 said:


> Sorry, but I do not have copy of the specification Just books that apparently have it wrong. I stand corrected. But is speaks to the confusion about the Ju 288 and the Jumo 222 engine.



Definitely. One has to remain beeing sceptical with so many things in secondary accounts. 
Junkers was the single sole company which had both- aircraft and aeroengine R&D and manufacturing.





> If you wish go from the JU-88A-1. Wing about the same size and span (or with a few %) The 288 was to go from 1680 liters of fuel in the wing to 3560 liters and while the older plane could put another 1880 liters in the bomb bay (totally blocking it) the 288 was supposed to hold another 1800 liters in the fuselage _without_ blocking the bomb bay (unless this book is in error and this tankage does block the bomb bay), this is while upping the bomb load by at least 50% (or 100%?) , fitting heavier defensive armament, the Pressure cabin and the heavier engines. And requiring about a 33% increase in speed. AND the first couple of 288 prototypes had dive brakes.
> 
> It is a wonder they didn't require it to tell jokes and wash windows



They thought that they could do this by adopting new structural layout. The load was shared between frames and the counterstressed skin as opposed to all by frames in the Ju-88. As mentioned above, the tanks (blue) were carried by the main structural member (see below, red) to which the hardpoints for the bombs were attached below. One unit, two functions and spacially optimised:





This way also offered more space for the internal bomb bay, which was dimensioned in a way to just take the two of the heaviest then possible bombs, the SC2500. In addition to the four 450ltr fuselage fuel tanks, there were two inner wing tanks with 720ltr each and four outer wing tanks with 660 and 400ltr each, respectively. Additional fuel could be carried in the bomb bay (4 x 450ltr tanks) and as drop tanks at the outer wing station (2 x 900ltr drop tanks), allowing for a max fuel load of 7,160ltr. Depending on choosen bombload, the fuel tankage varied.



> there is also the lower blister, and top of the crew compartment is well above fuselage, so IMO there is no advantage in streamlining vs. A-26 front crew compartment



The blisters were rather small and teardrop shaped. The fuselage of the A-26 was (similar to the Ju-288.. likely because of space optimisation) roughly squarish with rounded corners developing 85% -288- and 83% -A26- cross sectional coverage, respectively).
The A26 fuselage was 5 ft and 2.04inches wide and 5ft, 10inches high. This translates to a width of 1.57m and a height of 1.78m.
The Ju-288 fueslage cross section was 97cm wide and 1.40m high. 
Cross sectional area of the Ju-288 fuselage (corrected for coverage) was 1.16m^2 while that of the A-26 was 2.32m^2, roughly twice as much frontal exposure.
At the position of the blisters, the width is 1.28m max and the height is 1.68m max. Still smaller than the A-26.

for the JUMO-222 I suggest the following datas aviable here:

http://www.enginehistory.org/German/Jumo222.shtml

There are still some mistakes in them. 2,500HP Powerrating 1.6 ata f.e. was never clerared for the A-1. The A-2 and A3 were run in 1942 with 1.78ata and 3000HP take off power. The Ju-288AV-05 refitted with JUMO-222 A3/B3 made 660km/h recorded top speed.

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## Shortround6 (Dec 4, 2013)

I thank you both for the pictures and information. It looks like the Junkers engineers did a great job of packaging. 

That doesn't mean that the Ju 288 wasn't a leap too far. While packaging explains how they got 50% more weight ( or more) into a Ju 88 sized plane it doesn't solve many of the other problems. 

Contemporary Henschel pressure cabin.





In 1939/40 the Germans had NO working power turrets in service and they were planning on skipping the manned power turret and jumping to the remote control power turret. Now it is easier to make the pressure cabin that way but with little or no practical experience in turret design the turrets/barbettes are not an easy solution. 

The Germans seem to have had landing gear problems, perhaps the allies had just as many and they are just not chronicled as much? But many German programs had numbers of prototypes damaged or destroyed by landing gear failures. The Ju 288 program had about 50% of the aircraft damaged/destroyed by landing gear problems, how much this was caused by compact/light landing gear trying to handle a heavy hot airplane I don't know ( and I may be reaching). The A-26 had a wing loading comparable to the Ju-288 but it took the US 3 steps to get there. The A-20/B-25 followed (Not by much) by the B-26 and then the A-26 which used about the same engines as the B-26 but in a smaller airplane. The A-26 compensated to some extent by being the first plane in service with double slotted Fowler flaps ( earlier planes had used single slotted Fowler Flaps). 

It may be pure speculation on my part but perhaps the RLM wanted bigger wings to help with field performance? Much like the Martin B-26 had both a larger wing and a change in wing incidence to help with field performance although the USAAC was willing to sacrifice flight performance to get it ( and not demand more powerful engines to get the flight performance back)

I have seen: Junkers Jumo 222

and I do have a copy of the magazine with the article referred to "Torque Meter Vol. 6, No. 3 (Summer, 2007)"

Which, while offering a 14 page article with lots of pictures of parts and a detailed description of several Jumo 222A/B and E/F engines torn down at Wright Field in 1946 in preparation for building a running example, is a bit skimpy on the history of the engine. Engines were obtained from the Navy engine test station in Philadelphia. Where they got them it not stated ( direct from Germany or engines in British possession handed over ?) Article claims 289 built but gives no source or reference for this. and no break down is given of how many of each type was made or when, which to my mind is one of the big unanswered questions so far.

1. how many were built, the 289/291 number ( and I don't care about 2 engines) or a significantly smaller number? 
2. Which models and when?
If there were even a couple dozen A?B engines sitting around in 1942/43 and they were good for 30-50 hours why weren't they being used for prototype flying? If the large number built was E/F version in 1944 and due to bombing and production schedules being jerked around (and bombing) it is a bit more understandable why the didn't get into some sort of aircraft. 

One interesting feature is that while the engine used two magnetos and had dual plugs each magneto ran 1/2 the engine. One magneto supplying ALL the plugs in 3 banks of cylinders so a magneto failure takes out 1/2 the engine.


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## wiking85 (Dec 4, 2013)

AFAIK the landing gear issues were worked out by the end of 1942 along with the structural issues; the last remaining problem by 1943 was engines. Part of the landing gear problems had to do with the increase in weight between the A-series and B-series, which required time to work out (there were also some issues during the up-weighting between A-series prototypes too). Had they stuck with the A-series, then the landing gear issues would have been worked out sooner.

Beyond that you make a solid point about the remote controlled defensive armament; it probably would have been easier to simply remove them once they proved too advanced for the time to simplify construction until they could be further developed and rely on speed and escorts to defend them. 

BTW does anyone know what that fourth crew member that was added to the B-series actually did? I can't find information about it.


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## delcyros (Dec 5, 2013)

Regarding the remote controlled turret.

The FDL-B 131/2 with FA-15 appearently never made big issues. The same system for waist guns drove the Me-210 and Me-410 and a derived system similar to the B stand was employed in the Ar-240 and He-177 B-1 stand and other Bomber-B projects had them too. Post war analysis showed the system to be mechanically reliable and offering better arcs of fire. It allowed for concentration of the crew in a better supportable compact space. 

In context to the Ju-288 it´s not known to me that problems with the RPC turrets in any form delayed the project.
Am not sure how this can be considered too advanced for the time. Heinkel, Junkers, Messerschmidt and Focke Wulf went down this path starting in the late 30´s and by the late 40´s, everybody regularely employed them.



> The Germans seem to have had landing gear problems, perhaps the allies had just as many and they are just not chronicled as much? But many German programs had numbers of prototypes damaged or destroyed by landing gear failures. The Ju 288 program had about 50% of the aircraft damaged/destroyed by landing gear problems, how much this was caused by compact/light landing gear trying to handle a heavy hot airplane I don't know ( and I may be reaching).



It´s obvious that they had a number of landing gear failures. This was aggreviated by the fact that the relatively high stall speed required harder touch down conditions. It was further aggreviated by the repeated weight increases which required fixes to the mechanical design. However, in the course of the testing phase these issues have been largely resolved and wouldn´t have been that bad had they agreed upon the original design.



> It may be pure speculation on my part but perhaps the RLM wanted bigger wings to help with field performance? Much like the Martin B-26 had both a larger wing and a change in wing incidence to help with field performance although the USAAC was willing to sacrifice flight performance to get it ( and not demand more powerful engines to get the flight performance back)



There were a couple of reasons:

The original small wing of the EF-78 proposal was found to be deficient in the V-1 by fligth testing due to comparably poor transverse and directional stability. In response, the fuselage was lengthened and the tailsurfaces reshaped. This adressed directional stability and improved transverse stability. in July 1940, the RLM following experiences at the BoB made substantial changes to the performance requirements:
Much increased defensive armement (requiring a fourth crew member) and upped max bombload by 1t. Thus, it became necessary to add two wingstations for bombs, since the internal bombbay couldn´t have carried 6t. It also required an entirely new cockpit design.
This in turn forced to insect a small new fuselage section for the lower RPC turret and an entirely new wing with 5m^2 bigger area to keep wingload down despite the massive increase in MTOW. It meant that the JUMO-222 with 2000Hp rated military power was now found a bit on the low side of performance. The take off power of 2,500Hp was required, resulting in a shift in development from JUMO-222A-1 to JUMO-222A-2 with enlarged bore. It also meant that the JU-288V05 couldn´t be used as a template for the proposed A-1 series anymore, resulting in the all-new B series (which only kept the center fuselage sections of the former A subtype).
The B-series may also have been intended for high level bombing principally (no dive bombing requirement anymore) and higher ceiling requires bigger wings, too. 
The shift from -A1 to A-2 subvariant of the JUMO-222 was unfortunate as it entailed harmonic issues which soon delayed the program and required constant care. While the performance was successfully increased (in mid 1941 the engine first run at 2,400hp and in oct that year made short time power of 3,000HP on C3-fuel), several mechanical issues appeared which prooved difficult to overcome. Spacing of the enlarged cylinders was problematic, too, requiring substantially more heat transfer to be done than in the A1 subtype. In the end, the A-3/B-3 was the fix for the harmonic issues encountered in the A2/B2. The A1/B1 on the other hand convinced by it´s smootheness of run and these problems weren´t alltogether anticipated to be caused by a slight change in bore.




> If there were even a couple dozen A?B engines sitting around in 1942/43 and they were good for 30-50 hours why weren't they being used for prototype flying?


I think they were used. The V05 alone supposedly made 1200 hours to nov 1943. This requires 2400 engine hours or about 12 engines with appox. 100 hours each between MOT and supplied back a second time. It actually was more because a couple of them were wrecked in the testing program.
I also dont know how many JUMO-222 were produced by Germany. At least the A-1 subtype was completely developed. max. sustainable power was 1850hp with 2,000HP military power and 2,500Hp take off/emergancy power (the latter never cleared on B4 fuel). A complete preseries of 50 engines were manufactured in addition to an unspecified number of prototypes. Preparation of mass production at MMF and Ostmark proceeded until late 1940 alongside preperation of mass produtction of the JU-288A1. Junkers already made over 6000 specialised tooling machines for it and all involved suppliers. From the A2/B2 and A3/B3 engines I have seen no data but according to primary sources, Milch decided against mass production of these engines in late 1942 because he didn´t wanted the Junkers company to be in charge of so many important dev engine projects (JUMO-213, JUMO-222, JUMO-004) he somehow feared overconcentration of important projects in just one company. The C3 fuel optimised C/D subtypes were just drawing board projects with one or two prototypes buildt (but not tested) and the E/F proceeded at low pace from prototype to pre-series production.
In Oberursel, a licensee, test stands were erected for JUMO-222E/F in early 1944 but only five JUMO-222E were produced here before the Jägernotprogramm killed all developmental non-jet engines for non-fighters from production lists in 1944. The -222E/F saw a rather widespread preparation for mass production in 1944 and a number of engines have to be reckoned to be from this subtype.
According to Reinhard Müller and Holgar Lorenz´s accounts, the A1/B1, A2/B2 and A3/B3 were produced in V-numbers and preseries production as was the E/F high altitude variant (if You take the A-1/B-1 number of 50 engines this makes for 200 engines not accounting for prototypes). The C/D was only in prototype stage and the -T subvariant a prototype benchtested. Thus, a total production number of in between 250 and 300 JUMO-222 appears to me as entirely believable.
Wörth mentioning, there were a couple of JUMO-222 produced after the end of war for the soviets in Köthen, too.


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## wiking85 (Dec 5, 2013)

What's your source for all of this?


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## tomo pauk (Dec 5, 2013)

And another question: how good is this book:

Vom Original zum Modell, Junkers Ju 288/388/488: Karl-Heinz Regnat: 9783763760282: Amazon.com: Books

The price is very attractive.


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## wiking85 (Dec 5, 2013)

tomo pauk said:


> And another question: how good is this book:
> 
> Vom Original zum Modell, Junkers Ju 288/388/488: Karl-Heinz Regnat: 9783763760282: Amazon.com: Books
> 
> The price is very attractive.


I have the English version, its quite good and I posted one page from it about the Jumo 222 here already, but there isn't a full history of development of the aircraft in the book, which is somewhat frustrating, though the technical information is very good and there is excellent photographs of the aircrafts.


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## tomo pauk (Dec 5, 2013)

Thanks. That would be this book?

Black Cross Volume 2: Junkers 288/388/488: Karl-Heinz Regnat: 9781857801736: Amazon.com: Books

Is there better books around, about the 288?


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## wiking85 (Dec 5, 2013)

tomo pauk said:


> Thanks. That would be this book?
> 
> Black Cross Volume 2: Junkers 288/388/488: Karl-Heinz Regnat: 9781857801736: Amazon.com: Books
> 
> Is there better books around, about the 288?



Not that I know of. There is this though:
Die Ju 88 und ihre Folgemuster: Heinz Nowarra: Amazon.com: Books


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## cimmex (Dec 5, 2013)

Interesting site oft he Ju 288, in German only 
FlugzeugLorenz: Junkers Ju 288


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## tomo pauk (Dec 5, 2013)

Thanks for the tips


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## Denniss (Dec 5, 2013)

Just a sidenote: the fuselage layout with the fuel cells above the bomb bay (with option to use larger tanks using bomb bay space) was also used in the He 177. AFAIR the A-20 and B-25 used a similar layout but favored external tanks insted of using the (limited) bomb bay space.


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## Shortround6 (Dec 5, 2013)

delcyros said:


> Regarding the remote controlled turret.
> 
> In context to the Ju-288 it´s not known to me that problems with the RPC turrets in any form delayed the project.
> Am not sure how this can be considered too advanced for the time. Heinkel, Junkers, Messerschmidt and Focke Wulf went down this path starting in the late 30´s and by the late 40´s, everybody regularely employed them.



The RPC turrets may not have delayed the Ju-288 but then so much other stuff did that any delays in the turret program got covered up. The German RPC turrets went into service when? Spring/summer of 1942? In the Me 210 if you can call that going into service. The He 177 which used similar mounts/turrets to the Ju-288 had trouble in the early models. While it is true that everybody used them in the late 40's that is just a bit too late. The British were using manned power turrets in 1939 ( cribbed from the French?) and the Americans were fitting manned power turrets to the B-17, B-25, B-26 and other aircraft starting in the spring/summer of 1941. Granted a few of the American designs (like the B-25 belly turret) were less than successful But the manufacture and use of large numbers of such turrets gives good feed back for the progression to the RPC turret. The Germans tried to jump the step and had to back track a bit with a turret that had powered traverse but manual elevation in one model ( and I am not too sure about how the traverse worked as some photos seem to show a limited lateral movement of the gun _in the turret._ Gross traverse is power and fine traverse is manual? 





> It´s obvious that they had a number of landing gear failures. This was aggreviated by the fact that the relatively high stall speed required harder touch down conditions. It was further aggreviated by the repeated weight increases which required fixes to the mechanical design. However, in the course of the testing phase these issues have been largely resolved and wouldn´t have been that bad had they agreed upon the original design.



True but we are back to wondering if the original design would really do what was wanted. 





> There were a couple of reasons:
> 
> The original small wing of the EF-78 proposal was found to be deficient in the V-1 by fligth testing due to comparably poor transverse and directional stability. In response, the fuselage was lengthened and the tailsurfaces reshaped. This adressed directional stability and improved transverse stability. in July 1940, the RLM following experiences at the BoB made substantial changes to the performance requirements:
> Much increased defensive armement (requiring a fourth crew member) and upped max bombload by 1t. Thus, it became necessary to add two wingstations for bombs, since the internal bombbay couldn´t have carried 6t. It also required an entirely new cockpit design.
> This in turn forced to insect a small new fuselage section for the lower RPC turret and an entirely new wing with 5m^2 bigger area to keep wingload down despite the massive increase in MTOW.



Now we are back to the question of _IF_ the changes were politically motivated or operationally motivated or technically motivated. Or a mix. To my mind the longer fuselage and new tail surfaces are technically motivated. (changes to make the plane work as originally intended). The increase in in defensive armament and 4th crew member _may_ be operationally motivated. Changing operational requirements in response to combat experience. I don't know how many "gunners" the 3 man crew had. One gunner can only engage one attacker at a time regardless of the number of remote gun mounts and their fields of fire. Wither they should have stuck with speed as a defense and and kept the light gun armament and 3 man crew may or may not be political. Upping the bomb load by a ton _may_ be political ( either an attempt to change enough stuff to kill the program or for bragging rights as to how good the "new" plane would be.) since the orginal could carry more bombs much further than the existing Ju-88s or He 111s it is hard to see a pressing operational need for the higher bomb load. 

Speculation on my part and I am welling to find out how close (or far) I am 





> It meant that the JUMO-222 with 2000Hp rated military power................. In the end, the A-3/B-3 was the fix for the harmonic issues encountered in the A2/B2. The A1/B1 on the other hand convinced by it´s smootheness of run and these problems weren´t alltogether anticipated to be caused by a slight change in bore.



thank you for the information. There is no question that changing the bore ( and stroke) resulted in long delays in the program. But the need for such changes still needs to be resolved. Politically motivated or would accepting a somewhat less "advanced" specification have allowed the original engines to work? Ditch the pressure cabin ( is it really needed in a plane with a service ceiling of 29-30,000ft?) keep the original 3 ton bomb load, etc. But once the changes were decided on ( and speed requirement not dropped) the 2000hp versions were a dead end. 





> I think they were used. The V05 alone supposedly made 1200 hours to nov 1943. This requires 2400 engine hours or about 12 engines with appox. 100 hours each between MOT and supplied back a second time. It actually was more because a couple of them were wrecked in the testing program.
> 
> According to Reinhard Müller and Holgar Lorenz´s accounts, the A1/B1, A2/B2 and A3/B3 were produced in V-numbers and preseries production as was the E/F high altitude variant (if You take the A-1/B-1 number of 50 engines this makes for 200 engines not accounting for prototypes). The C/D was only in prototype stage and the -T subvariant a prototype benchtested. Thus, a total production number of in between 250 and 300 JUMO-222 appears to me as entirely believable.
> Wörth mentioning, there were a couple of JUMO-222 produced after the end of war for the soviets in Köthen, too.



Well, this kind of gets back the reliability question, If you have 50 of a pre-series of 1850-2000hp Jumo 222s in addition to prototype engines why were they trying to power prototype aircraft with 1600hp BMW 801s? Specifically the Ju-288V7 ( I can understand V1-V4 but once V5 and V6 have Jumo 222s why the back step? Unless the Jumo 222s are still experiencing troubles in the spring of 1942? Which is around a year _after_ it passed it's "type test". In the Spring of 1942 they have no idea how many hours they will put on the V5 and so there shouldn't be a large stock of 'reserve' engines for one or two airframes. 
Or why in 1944 some of those other "series" production engines weren't used to power _something_ given some of the very limited production models or prototypes the Germans were flying  

One source claims that about 900+ Jumo diesel engines of the 205,206,207 and 208 series were produced and considering the numbers of aircraft powered by those 900+ engines one really has to wonder what was going on with the Jumo 222.


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## wiking85 (Dec 5, 2013)

Shortround6 said:


> Well, this kind of gets back the reliability question, If you have 50 of a pre-series of 1850-2000hp Jumo 222s in addition to prototype engines why were they trying to power prototype aircraft with 1600hp BMW 801s? Specifically the Ju-288V7 ( I can understand V1-V4 but once V5 and V6 have Jumo 222s why the back step? Unless the Jumo 222s are still experiencing troubles in the spring of 1942? Which is around a year _after_ it passed it's "type test". In the Spring of 1942 they have no idea how many hours they will put on the V5 and so there shouldn't be a large stock of 'reserve' engines for one or two airframes.
> Or why in 1944 some of those other "series" production engines weren't used to power _something_ given some of the very limited production models or prototypes the Germans were flying
> 
> One source claims that about 900+ Jumo diesel engines of the 205,206,207 and 208 series were produced and considering the numbers of aircraft powered by those 900+ engines one really has to wonder what was going on with the Jumo 222.


In late 1941 they upped the rating requirement of the Jumo 222 to 2500hp, which cancelled further construction of the 2000hp version. They hadn't yet made the 2000hp fully reliable yet, but were working them hard, which burned them out (and were used with multiple prototypes, not just the Ju288. There was the Fw191 and Do317 both made it to prototype). There were 6 Ju288s that used the 222A1 and several Fw191s and Do317s that used it.

Beyond that later versions were tested supposedly on the He177, but also the He219 and perhaps others too.


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## Shortround6 (Dec 5, 2013)

Working them hard _how_ in the spring of 1942? 

First 4 Ju 288s used BMW 801s, not a problem, it is early in the program. 

Next two Ju 288s use Jumo 222s, all on track so far.

Next Ju 288 goes back to the BMW 801s, why?

Next Ju 288 (No 8 ) uses Jumo 222 engines. and that is the end of the A series prototypes. 

No 9 (B series) flies in May 1942 with Jumo 222s followed by No 11 and No 13 using DB 606 engines, sandwiched in there is the No 12 aircraft with Jumo 222s and flying late is the No 10 aircraft with 1800hp turbo supercharged BMW 801s in Jan 1943. No 14 was last Jumo 222 powered 288 to fly in Aug 1942. 

There were 6 Fw 191 airframes started. V1 and V2 used BMW 801s. V3, V4 and V5 were abandoned and scrapped as FW got out from under the "all electric" requirement. V6 being the least finished is the easiest to convert and is the first and ONLY fw 191 to fly with Jumo 222s in the _spring of *1943*_.

The Dornier 317 never flew with a Jumo 222 engine, in fact according to some sources it never left the paper stage until 1941/42. first flight of the V1 prototype using DB 603 engines was 8 September 1943 a little late to be burning out engines in 1942.

There is no evidence that the He 177 (or any variation of it) ever flew with the Jumo 222 so no burned out engines there either. 

As for the He 219, an old book by William Greene ( and certainly subject to correction) claims ONE He 219A-7/R6 flew late summer of 1944 with Jumo 222 engines. Other airframes of the B and C series were built for the Jumo 222 engines but were still waiting for engines to be delivered when the war ended. 

By this count _eight_ airframes flew with Jumo 222 engines over a span of more than two years from beginning to end. And with some of the Ju 288 prototypes crashing or being scrapped there were never more than 4 and more likely 2-3, airworthy airframes at any one time using Jumo 222 engines. It shouldn't have been _that_ hard to keep 2-4 planes flying with several hundred engines _IF_ the engines were air worthy to begin with.


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## delcyros (Dec 7, 2013)

wiking85 said:


> What's your source for all of this?



I have compiled a number of relevant sources and the works of Budraß, Lorenz, Kay, Nowarra and others on this topic. As mentioned previously, I have by far not the wealth of primary sources aviable to Budraß but a number of them.


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## delcyros (Dec 7, 2013)

Shortround6 said:


> The RPC turrets may not have delayed the Ju-288 but then so much other stuff did that any delays in the turret program got covered up. The German RPC turrets went into service when? Spring/summer of 1942? In the Me 210 if you can call that going into service. The He 177 which used similar mounts/turrets to the Ju-288 had trouble in the early models. While it is true that everybody used them in the late 40's that is just a bit too late. The British were using manned power turrets in 1939 ( cribbed from the French?) and the Americans were fitting manned power turrets to the B-17, B-25, B-26 and other aircraft starting in the spring/summer of 1941. Granted a few of the American designs (like the B-25 belly turret) were less than successful But the manufacture and use of large numbers of such turrets gives good feed back for the progression to the RPC turret. The Germans tried to jump the step and had to back track a bit with a turret that had powered traverse but manual elevation in one model ( and I am not too sure about how the traverse worked as some photos seem to show a limited lateral movement of the gun _in the turret._ Gross traverse is power and fine traverse is manual?



How does that relate in specific? The various german projects concentrated on RPC (some like Bomber A-project well before the Ju-288) and arrived with a mechanically reliable and working solution. The Me-210 may have been a failure but certainly not because of the RPC units, which weren´t even adressed on the change to Me-410.

From what I have seen, there are a couple of issues with the Ju-288 design which developed a requirement of change in the course of testing but neither the pressurized cockpit nor the RPC were among them:
[1] landing gear hydraulic failures, corrected by a change in design
[2] stability issues corrected by new tail and lightly longer fuselage
[3] reliability issues of the leading edge evaporation cooling, corrected by adoption of annual ring coolers
[4] reliability issues of ducted hollow prop spinners for annual ring coolers, corrected by adoption of standart annual ring radiators with small spinners (external flow rather than internal within the hub)
The net effect of [2] to [4] was an improvement of flight capability as opposed to a reduction of flight performance due to an increase in drag



> (...)Speculation on my part and I am welling to find out how close (or far) I am


That´s perfectly reasonable. The three men crew had two gunners -which is ok given that there are just two positions. The four men crew, for whiches reasonability I cannot find a lot of good arguments, had three gunners and three RPC gun positions. Upping the bombload while not changing range and speed requirements isn´t reasonable at all. It will always force a more or less complete redesign.



> There is no question that changing the bore ( and stroke) resulted in long delays in the program. But the need for such changes still needs to be resolved. Politically motivated or would accepting a somewhat less "advanced" specification have allowed the original engines to work? Ditch the pressure cabin ( is it really needed in a plane with a service ceiling of 29-30,000ft?) keep the original 3 ton bomb load, etc. But once the changes were decided on ( and speed requirement not dropped) the 2000hp versions were a dead end.


It appeared to the RLM that the whole Ju-288A was to small in light of the upped performance requirements in mid 1940. This in part explains for the 3/4 of year delay between start of construction of Ju-288AV05 and Ju-288AV06 (which had the new -B wing and tested it on an -A fuselage). I agree that I too don´t see a pressing need for a pressurized cockpit in light of the bombers cruise altitude spec.
I have recently come across performance data for the JUMO-222 from the high altitude test stands. According to these curves, it appears that the rated military power of the JUMO-222A1 (half hour rate, 2900rpm) was 2240HP at SL but this power could only be attained using C3 fuel (and often caused case corrosion in exposed parts). The JUMO-222A1 on B4 fuel wasn´t cleared for more than running on 2800rpm, 2050HP power (roughly the 2 hours rate) and 1850HP max continous power. It was a derated engine. Take off power of 2,500HP and military power of 2,240 HP was never cleared for. Maybe I will post the graphs later. 2000 HP was still sufficient for the JU-288A (the -v05 made 615km/h with the derated JUMO-222A1 but 660km/h with JUMO-222A3 with both versions the max. continues cruise was 565km/h at 6000m) to fit the bomber B top speed requirements but performance would have dropped in the enlarged Ju-288B to below 600km/h with just 2x 2000HP. 

Still, I believe that the design path of the JU-288A should have been followed rather than abandoned. Keep the small wing and 3men crew but skip the pressurization requirement, skip two of the outer wing fuel tanks and limit the internal bombbay to 3t or 4t max. That way the MTOW drops sufficiently that the whole bomber could run on either JUMO-213A, Db-603A or BMW-801G properly until the JUMO-222A replaces them and restores the original spec (or until later vesions of said engines with MW-50 boost restore specs).
No need to build any JU-188/-388 or late model Ju-88. No need to keep up building of obsolete Do-215 and He-111.


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## tomo pauk (Dec 7, 2013)

I've looked around for Budrass' book, wonder whether is a lower price than 430€ (that is for for a special edition) anywhere for the 900+ pg book?


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## DonL (Dec 7, 2013)

Do you know anyone in Germany?

He can go to a public libary and copy or scanning the book, it is much more cheaper then 430€.
Also you can get the book over interlibrary loan.


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## tomo pauk (Dec 7, 2013)

I have the sister-in-law in Stuttgart. Will see whether I can trade some Dalmatian sunshine for some scanned/copied pages


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## DerAdlerIstGelandet (Dec 7, 2013)

tomo pauk said:


> I have the sister-in-law in Stuttgart. Will see whether I can trade some Dalmatian sunshine for some scanned/copied pages



Where in the Stuttgart area? That is where my family lives as well.


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## tomo pauk (Dec 8, 2013)

Don't know exactly where - IIRC just west of Feuersee.


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## wiking85 (Dec 8, 2013)

Was the Jumo 222 ever tested with GM and MW boost and what was the result?


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## delcyros (Dec 9, 2013)

I don´t know of any attempts with MW-50. However, GM-1 injection is at least present in the power graphs related to altitude from trials of the JUMO-222E/F. First stage kicks in at 12000m (39,370ft) and restores power to 1,720 HP. 2nd stage jumps in at about 13,000m and restores power to 1710HP at this altitude (both on 2900 rpm Steig- und Kampfleistung -GM-1 injection could however, also be applied to Start- and Notleistung 3000rpm). Static full pressure height is about 11,200m for this engine.


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## delcyros (Dec 9, 2013)

Some more food on timelines:

[+] mid 1940:

RLM selects mass production of JU-288A1 (with side blisters and w/o periscopes) and JU-288A2 (no blisters but periscopes to aim RPC). 
Proposed engines: JUMO-222A1 rated 2,000hp on B4 fuel, RLM funds a whole new factory in Vienna for tooling up for this aeroengine
The JU-288A has the following charcteristics:
-3 men crew, pressurized cockpit
-2 RPC turrets (alternative one double and two connected side single turrets)
-internal bombbay for max. 5ts, normal rated 3ts.
-span: 18.29m
-wing area: 54m^2
-MTOW: 15.6t
-range: 3,850km
-cruise speed: 565km/h

[+] mid 1941:
RLM selects mass production of JU-288B. 
Proposed engines: JUMO-222A2/B2 rated 2,500hp on B4 fuel, 
The JU-288B has the following charcteristics:
-4 men crew, pressurized cockpit
-3 RPC turrets
-internal bombbay for max. 5ts, normal rated 4ts, external hardpoints for 1t bombs or 1.2t drop tank
-span: 20.06m
-wing area: 60m^2
-MTOW: 18.5t
-range: 3,600km
-cruise speed: 540km/h

-ongoing problems of the JUMO-222A2/B2 lead to prototpyes beeing propelled by BMW-801, A/C appears underpowered at this weight by BMW-801.

[+] end of 1941:
Milch initially reduces then cancels orders for production of JUMO-222 and JU-288B, Vienna Ostwerke is given to DB. Milch orders seperation of airframe and aeroengine departments in Junkers.

[+] mid of 1942:
Milch informed Junkers that the JU-288B is not going to be selected for production at all with JUMO-222. Koppenberg and Brandner assure that the JUMO-222 A3/B3 will be by all means cleared for sufficient power and that the preparations went far for mass production. Koppenberg retires. Junkers tries to fit Db-606 and later Db-610 into the airframe. Improvement on JUMO-222 proceed at low pace to JUMO-222A3/B3

[+] mid of 1942:
Junkers FW change the JU-288 to accomodate Db-606 then later Db-610. The resulting Ju-288C has the following characteristics:
-4 men crew, armoured cockpit
-3 RPC turrets
-internal bombbay for max. 5ts, external hardpoints for 1t bombs or 1.2t drop tank
-span: 23.0m
-wing area: 64m^2
-MTOW: 22.8t
-range: 2,500km
-cruise speed: 570km/h


[+] end of 1943:
JUMO returns to the original JUMO-222A1/B1 configuration and changes the supercharger design, leading eventually to the successful JUMO-222 E/F series.
Preparations for poduction of JU-288C with DB-610 starts. At the same time, JU-388K is selected for production. The type has the following characteristics (K2):
-3 men crew pressurized cockpit
-2 x JUMO-222A2/B2 (alternative was BMW-801, DB-603 and JUMO-213)
-1 RPC gun, 3ts internal bomb bay
-span: 22.0m
-wing area: 56m^2
-MTOW: 14.6t.
-range 2800km
-cruise speed: 545km/h
-the plane is based on Ju-188 and Ju-88 designs and has a high degree of common parts with them. 

[+] mid 1944:
It is a not well known fact that both, the JU-388K and Ju-288C actually enter production. Next to 2 JU-388K0 prototypes and 10 Ju-388K0 first batch preproduction models an unspecified number of Ju-388K0 from the 2nd batch preproduction was partially completed, one ATG manufcatured JU-388K1 was made when the Jägernotprogramm cancels all deliveries of new bombers and shifts ressources antirely to fighter and recon forces. The few Ju-388K0 produced are rebuildt to photorecon variants in the factory, the JU-388C gets abandoned alltogether with elements offered for the JU-488 prototypes. One may ask what´s the rational in the Ju-388K at all as it returns to the JU-288A specifications with regard to crew size and general aircraft size. This indicates, for me at least, that there was a rational and a need for a bomber with 1940 JU-288A specifications still in 1944. The JU-388K is -compared with the Ju-288- an inferior and less optimized bomber design. For one thing, it kept the obsolete Ju-88 fuselage (with rather limiting space for bombs and fuel tanks) and the Ju-188 tail structure and wings (more complex and weight intensive designs, less space for fuel). The Ju-388K cockpit, however, and RPC instrumentation showed signs of Ju-288 heritage.


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## davebender (Dec 9, 2013)

I don't understand the rational behind Ju-288 airframe period. Why not just use Jumo 222 engines to power existing Do-217 (which then becomes Do-317)? The Dornier airframe was already in production, worked well and performance was similar to Ju-288 airframe when powered by similar engines.


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## wiking85 (Dec 9, 2013)

davebender said:


> I don't understand the rational behind Ju-288 airframe period. Why not just use Jumo 222 engines to power existing Do-217 (which then becomes Do-317)? The Dornier airframe was already in production, worked well and performance was similar to Ju-288 airframe when powered by similar engines.



That's factually incorrect. First of all the Ju288A could carry two 2500kg bombs internally or just about any combinations of 3000kg otherwise. The Do-217 could only take 3000kg max with a special kit out and anything more was carried externally. Also the 2000hp the Jumo 222s would only give 500hp extra combined above the DB603, which only would translate into a 363 mph top speed; the Ju 288 had a 401 mph top speed. Its even worse when you consider that the Ju 288's cruise speed was 350mph with any bomb load (all that changed was its range), while the cruise speed with the DB603 for the Do-217 was 248 mph, which might rise to 265mph cruise, which is almost 100mph more than the Jumo 222 equipped Do-217. 

The Do-217 was an evolutionary design, while the Ju 288 was revolutionary one.


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## davebender (Dec 9, 2013)

I'm under the impression Do-217 bomber airframe was produced in two variants.
2,500kg bomb bay.
4,000kg bomb bay.
Variant with the smaller bomb bay carried additional internal fuel for a greater combat radius.


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## wiking85 (Dec 9, 2013)

davebender said:


> I'm under the impression Do-217 bomber airframe was produced in two variants.
> 2,500kg bomb bay.
> 4,000kg bomb bay.
> Variant with the smaller bomb bay carried additional internal fuel for a greater combat radius.


I've never seen any info about that, though I'm aware of multiple variants:
https://en.wikipedia.org/wiki/Dornier_Do_217#Variant_list

Maybe you're thinking of the 317. Otherwise the Do-217 could carry 4000kg with external hard point mounted ordnance, which dropped performance:
https://en.wikipedia.org/wiki/Dornier_Do_217#Specifications_.28Do_217_M-1.29


> Armament
> 
> 4 × 7.92 mm (.312 in) MG 81 machine guns in nose and lateral positions
> 2 × 13 mm (.51 in) MG 131 machine guns in dorsal and ventral positions
> ...


This max internal load was very rare and only in one configuration with 500kg SD (armor piercing) bombs, which had limited utility.


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## tomo pauk (Dec 10, 2013)

The early 217s (Do-217E-1) was able to carry 2000 kg of bombs internally. For the subsequent bomber variants (starting from the E-2), the bomb bay/bomb carriers were modified, so maximum was 3000 kg of bombs (with shortcoming that CoG was moved rearward with 2800 kg of bombs an more). 

added: According to this, SD bombs were 'fargmentary bombs', BTW. The PC and PD bombs were of armor-piercing variety.


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## wiking85 (Dec 10, 2013)

Semi-armor piercing actually...which makes sense. Thanks for the resource.


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## davebender (Dec 10, 2013)

What was internal fuel capacity of Ju-288 and Do-217?


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## tomo pauk (Dec 10, 2013)

Do-217 carried 2960 liters of fuel in 'permanent' tanks, up to 1500 L were to be carried in the bomb bay if needed (2x750 L tanks), and 1800 L was capacity of 2 drop tanks (2x900 L). Ju-228 carried 5360 L in 'permanent' tanks, plus 2 x 900 L in drop tanks.


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## davebender (Dec 10, 2013)

The relatively small Me-210 carried 2,420 liters of internal fuel. Seems like Dornier crippled his otherwise good heavy bomber airframe by carrying only 2,960 liters of internal fuel.


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## tomo pauk (Dec 10, 2013)

While it's easy to see that Ju-288 carried far more, the question is what kind of powerplant is needed to lift in the air several tons of fuel and several tons of bombs. The early BMW-801s were fine with lighter weights, not so much when Do-217 was fully bombed- and fueled-up. The Do-217E-2 was able to take off with 2000 kg of bombs and additional fuel tank in the rear bomb bay (3700 L total), and it was not possible to carry the drop tanks in the same time - the maximum take off weight (just under 16,7 tons) was almost reached with that layout of payload. The cruising speed on max TO weight was 435-460 km/h with BMW 801As, at 5km.
So we have both limitations of aircraft (how much of weight was it possible to take aloft) and engine in particular (both for T.O and cruising at meaningful speed). 

Of course, I'd like to see some good data on the Do-217 bombers with DB-603A, so we can compare them with data about earlier models.


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## Denniss (Dec 10, 2013)

The Do 217 was also crippled by the dive-bombing requirement. The wing reinforcements may have been a reason for limited space for fuel tanks. It also limited the wing size which in turn led to high wing loading.

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## DonL (Dec 10, 2013)

The Do 217 was never intended as heavy Bomber also the Ju 288.

Both are medium bombers or fast medium bombers, the He 177 was the heavy bomber project.

To my opinion the Do 217 was a very good medium bomber (with Db 603 engines) and the realistic step at 1938/39, it was advanced but a normal step.
The Ju 288 was the try to get two or three steps of development with the next generation a/c and it was to ambitioned for 1938/1939 and much to complex from development and production.


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## Shortround6 (Dec 10, 2013)

Maybe Dornier didn't have a lot choice. Do 217 V1 flew over a year before the Me 210 V1 and used 1075hp DB 601 A engines ( not what was wanted but what was available) DO 217 could carry double the bomb load of the Me 210 inside and even more outside. 

You want a 3000kg bomb load and only a 522 sq ft wing with 1000-1100hp engines something has to give. 

Calling it a heavy bomber doesn't make it one. Even after they made the wing bigger and gave it BMW 801 engines you have a plane with less power than either an A-20 or a B-25, a wing in between the two (about the size of a B-26 wing) and a bomb load (nominal) higher than ether the B-25 or B-26. Weight went between 33,000 lbs "normal" to 36,299lb overload for the Do-217E-2.


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## davebender (Dec 10, 2013)

The one we are currently discussing - Jumo 222. 2,000hp for Jumo 222 which was supposed to begin production during March 1942. Superseded by 2,500hp version a year later. With that engine Do-217 and/or Ju-288 airframe can achieve their full potential.

If the choice is mine to make Ju-288 fuel capacity should earn that airframe the Bomber B contract and Do-217 ends production.


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## wiking85 (Dec 10, 2013)

davebender said:


> The one we are currently discussing - Jumo 222. 2,000hp for Jumo 222 which was supposed to begin production during March 1942. Superseded by 2,500hp version a year later. With that engine Do-217 and/or Ju-288 airframe can achieve their full potential.
> 
> If the choice is mine to make Ju-288 fuel capacity should earn that airframe the Bomber B contract and Do-217 ends production.



The problem that Milch rightly foresaw was that the Ju 288 would supersede all other bombers, save perhaps the He177B, which would put all the other companies out of business and leave Junkers as the only choice for future designs and give his rival, Heinrich Koppenberg, full authority over aviation procurement programs and neuter Milch in his job.


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## Shortround6 (Dec 10, 2013)

davebender said:


> The one we are currently discussing - Jumo 222. 2,000hp for Jumo 222 which was supposed to begin production during March 1942. Superseded by 2,500hp version a year later. With that engine Do-217 and/or Ju-288 airframe can achieve their full potential.
> 
> If the choice is mine to make Ju-288 fuel capacity should earn that airframe the Bomber B contract and Do-217 ends production.




The Do-217 wasn't really in the "bomber B" catagory, it was a low risk back up. First prototype flew Oct 4th *1938* compared to Nov 23 *1940* for the first Ju 288 and March 18th *1941* for the Fw 191. 

And even if you can wave a magic wand and get working (airworthy) Jumo 222 engines sticking them _and_ another 1800kg of fuel into a Do 217 is going to call for a major re-engineering job. 

They built 1541 Do 217 bombers and 364 night fighters before production _stopped_ in June of 1944.
The 36th production Do-217E was delivered in the summer of 1941, several months before the first flight of a Ju 288 with Jumo 222 engines.


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## stona (Dec 11, 2013)

wiking85 said:


> The problem that Milch rightly foresaw was that the Ju 288 would supersede all other bombers, save perhaps the He177B, which would put all the other companies out of business and leave Junkers as the only choice for future designs and give his rival, Heinrich Koppenberg, full authority over aviation procurement programs and neuter Milch in his job.



In what capacity do you imagine that Koppenberg could gain 'full authority over aviation procurement plans' and by implication the generalluftzeugmeister (whoever that might be) whose boss was Reichsmarschall Goering, arguably the second most powerful man in Nazi Germany ? 

Milch in particular could always appeal to Goering, he had his ear for most of the war. When he finally fell out with Goering (getting involved in typical Nazi in-fighting and far too late in the war to be relevant to this discussion) he simply went to work with Speer, the Minister of Armaments who really did control all procurement programs and who unlike any other Nazi minister had direct access to Hitler. 

It doesn't make sense to me, and contradicts the way I believe the Reich government and aviation industry worked. It was a dictatorship !

Cheers

Steve


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## wiking85 (Dec 11, 2013)

stona said:


> In what capacity do you imagine that Koppenberg could gain 'full authority over aviation procurement plans' and by implication the generalluftzeugmeister (whoever that might be) whose boss was Reichsmarschall Goering, arguably the second most powerful man in Nazi Germany ?
> 
> Milch in particular could always appeal to Goering, he had his ear for most of the war. When he finally fell out with Goering (getting involved in typical Nazi in-fighting and far too late in the war to be relevant to this discussion) he simply went to work with Speer, the Minister of Armaments who really did control all procurement programs and who unlike any other Nazi minister had direct access to Hitler.
> 
> ...



Milch and Goering hated one another, Milch because he had been bribing Goering for years and got him the job at the RLM and because he did all of the actual work, and Goering hated Milch, because Milch actually did all of the work and bragged about it publicly. Milch was sidelined in favor of Udet until his suicide, after which Milch took back over aviation armaments (which is why Milch suddenly started sabotaging the Jumo/Ju 288 project in late 1941, because he suddenly had his authority returned and wanted to reassert himself over weapons projects that were started under Udet). Goering though favored anyone that limited Milch's authority even at this point (late 1941/1942) which is just as Speer is starting to usurp Goering power over the economy (4 year plan office); it wasn't until Speer finally made an alliance with Milch that shut out Goering that Goering's influence over economic matters ended, which happened gradually over 1942; so in 1941-42 Milch was eliminating rivals that Goering might use to undercut him, which he had done since Udet in 1936. 
Koppenberg had managed to virtually kill several other projects with the Ju88 program in the meantime (he bragged about sabotaging the Do217 by monopolizing its labor). So while officially Milch had the power, given the competing bureaucracies within the Third Reich which usually issued competing orders, subordinates often had to choose who to obey when they got multiple sets of orders; Koppenberg was on the ascent due to the authority he took from Udet (who was weak and let his underlings make decisions, with the strongest amassing the biggest weapons program resources, like the Ju88, just by force of personality, which incidentally, was how Goering took over the economy from Schacht in 1936. Koppenberg did this with the Ju88 and was pretty much the guy that got his way when issuing orders to people about allocation for labor, raw materials, and machine tools). So when Milch was officially given authority over aviation again after Udet's death he worked to administratively kill his rivals' authority. Koppenberg had managed to become the de facto authority in the allocation of resources in aviation, eventually grabbing over 50% of all available resources for the Ju88 project, which meant that even if Milch issued orders about other projects Koppenberg had the gravitas with the bureaucrats to make sure Milch was disregarded. So Milch had to sabotage Koppenberg by ensuring his projects never came to fruition, so logically couldn't maintain his stranglehold over labor, raw material, and factory resources. Milch successfully played the game and was able to syphon off Koppenberg's power by changing requirements for the Ju 288 project, which meant it could never be produced, so he could swoop in and claim Koppenberg's resources for other projects, rather than let things sit idle. This of course let him reassert his power over the bureaucracy and marginalize Koppenberg to the point he could just be fired, which he was. 

https://de.wikipedia.org/wiki/Heinrich_Koppenberg
This also states that Koppenberg diversified his power to direct control over resources too, such as bauxite (used for aluminum) in Norway, becoming the director of mining firms, which gave him direct authority over its allocation. So he was ensuring he couldn't be undercut and could undercut others by controlling the direction of resource allocation. This is the way Nazi Germany worked; bureaucrats seized power from one another via such methods all the time, which ensured a production mess until Speer took over and centralized all authority in his office, which meant the German economy could function rationally instead of in constant inefficient competition. That was Speer's real 'miracle', ensuring that finally the backstabbing was under control and the war effort could be properly supplied.


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## stona (Dec 11, 2013)

I would argue whether Goering hated Milch. They used each other and I could cite dozens of instances when Goering backed Milch,_ because it suited him_. I've never seen any evidence that Goering would favour an industrialist over a senior Luftwaffe officer or member of government. 

We certainly can agree that the whole sorry bunch were playing everyone off against each other. The reason Speer was so successful was because he had direct access to Hitler, something even other high ranking Nazis found very threatening. None of them enjoyed that privilege (except Bormann). Nobody in Nazi Germany was going to oppose something that they even suspected might have the direct backing of Hitler, something Speer exploited ruthlessly.

I think the explanation of the Jumo programme, or any other, in terms of personalities is too simplistic. I don't doubt that there may be elements of truth in it, but its not the point of this thread, so I'll duck out 

Cheers

Steve


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## wiking85 (Dec 11, 2013)

Hate was not the motivation insofar as it was power; the hate came from the threats to power that Goering and Milch represented to one another. Its the same reason Koppenberg had to go; he was too powerful and needed to be dealt with so Milch could reclaim supreme authority in his sphere. So its a matter of power politics than personality:
https://en.wikipedia.org/wiki/Ian_Kershaw


> Like Broszat, Kershaw sees the structures of the Nazi state as far more important than the personality of Hitler (or any other individual for that matter) as an explanation for the way Nazi Germany developed. In particular, Kershaw subscribes to the view argued by Broszat and the German historian Hans Mommsen that Nazi Germany was a chaotic collection of rival bureaucracies in perpetual power struggles with each other. In Kershaw's view, the Nazi dictatorship was not a totalitarian monolith, but rather comprised an unstable coalition of several blocs in a "power cartel" comprising the NSDAP, big business, the German state bureaucracy, the Army and SS/police agencies (and moreover, each of the "power blocs" in turn were divided into several factions).[35] In Kershaw's opinion, the more "radical" blocs such as the SS/police and the Nazi Party gained increasing ascendency over the other blocs after the 1936 economic crisis, and from then onwards increased their power at the expense of the other blocs.[36]

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## davebender (Dec 11, 2013)

Perhaps Milch thought the Allies would give him a better deal after Germany lost the war due to his sabotaging aircraft production.


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## stona (Dec 11, 2013)

davebender said:


> Perhaps Milch thought the Allies would give him a better deal after Germany lost the war due to his sabotaging aircraft production.



He was sentenced to life in prison and served about seven years....so you may have a point 

Cheers

Steve


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## gmsw7 (May 29, 2016)

Attached are 20 pages from Ferdinand Brandner's autobiography covering the jumo 222. They are in german, I am a slow german reader and about 1/3 way through


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