Jumo 222: what's the truth?

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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.
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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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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.
 
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.
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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.
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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.
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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.
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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.
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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.
 
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.
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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.
 
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.
 
wiking85 said:
What's your source for all of this?
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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.
 
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?
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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
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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.
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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.
 
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?
 
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.
 
I have the sister-in-law in Stuttgart. Will see whether I can trade some Dalmatian sunshine for some scanned/copied pages :)
 
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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