Ju288A enters service in 1942

[Shortround6]

Performance figures I used are from Page 47 of the book listed in a previous post.
Junkers Ju 288/388/488 by Karl-Heinz Regnat. It is Black Cross volume 2.

There are stats for the 288A, the 288B and the 288C.

I used the ones from the column headed 288A and the last stat listed is the crew which says three for that version. the other two models are listed as having the four man crew.

Other sources may well vary.

I would be very questioning of performance numbers for 8000 meters altitude. The JU 222 A/B engines were single stage, two speed supercharged engines. The 288B (four man crew) is supposed to have been planned for the 222 E/F with a two stage supercharger and that is a lot more believable for top speed or cruising at 8000 meters. In the chart/table on page 47 of that book the 288B is listed as having a lower ceiling than the 288A despite the 2 stage supercharger. Of course picking up almost 4000kg of weight certainly didn't help.

I would note (and have noted it before) that just because ONE engine makes it through a type test in a test cell (on the Bench?) doesn't always mean that all production engines are going to last as long. Napier Sabre being a case in point. Not to pick on the British too much the Wright R-3350 used in the B-29 passed it's type test in 1939 and we know how well that worked out. XB-29 No 1 required 17 engines to log 99 1/2 flight hours. Perhaps one engine lasted all 99 1/2 hours and the other 3 needed frequent replacement. I don't know. I do know that there were a number of engines that squeaked through type tests that were nothing but trouble for several years in service.
Sorry but saying that the Jumo 222 passed a type test doesn't prove much of anything one way or the other. The fact that 280 something engines built only got under 9 airframes into the air says a lot more. I have noted it before, The RR Peregrine, with 301 engines built, kept two squadrons of Whirlwinds in Service for over 1 1/2 years.

I am not going to place much credence in a computer game damage model unless somebody can show how it was done. One of these popular computer games uses the same rate of fire and damage model for ALL 20mm guns in the game.

 

[wiking85]

Performance figures I used are from Page 47 of the book listed in a previous post.
Junkers Ju 288/388/488 by Karl-Heinz Regnat. It is Black Cross volume 2.

There are stats for the 288A, the 288B and the 288C.

I used the ones from the column headed 288A and the last stat listed is the crew which says three for that version. the other two models are listed as having the four man crew.

Other sources may well vary.

I have the book too, but am at work all day so won't be able to cross reference it until tonight. At this point I'm going off the original spec chart especially because the figures listed for speed and all that is lower and probably more realistic.

I would be very questioning of performance numbers for 8000 meters altitude. The JU 222 A/B engines were single stage, two speed supercharged engines. The 288B (four man crew) is supposed to have been planned for the 222 E/F with a two stage supercharger and that is a lot more believable for top speed or cruising at 8000 meters. In the chart/table on page 47 of that book the 288B is listed as having a lower ceiling than the 288A despite the 2 stage supercharger. Of course picking up almost 4000kg of weight certainly didn't help.

Why? The speed is lower at that altitude than at 6km when it should be higher due to the less dense air lowering drag. That is entirely in line with the lower capability supercharger, which the chart I posted notes says HP output was lower at the higher altitude. The weight gain would be a factor, but AFAIK the Ju288B did not plan to use the Jumo 222 E/F until very late in the war. Again I'll have to double check the book you mentioned when I get home tonight.

I have several other German language sources I can double check as well, including a 2021 series of articles in a German aviation magazine.

I would note (and have noted it before) that just because ONE engine makes it through a type test in a test cell (on the Bench?) doesn't always mean that all production engines are going to last as long. Napier Sabre being a case in point. Not to pick on the British too much the Wright R-3350 used in the B-29 passed it's type test in 1939 and we know how well that worked out. XB-29 No 1 required 17 engines to log 99 1/2 flight hours. Perhaps one engine lasted all 99 1/2 hours and the other 3 needed frequent replacement. I don't know. I do know that there were a number of engines that squeaked through type tests that were nothing but trouble for several years in service.
Sorry but saying that the Jumo 222 passed a type test doesn't prove much of anything one way or the other. The fact that 280 something engines built only got under 9 airframes into the air says a lot more. I have noted it before, The RR Peregrine, with 301 engines built, kept two squadrons of Whirlwinds in Service for over 1 1/2 years.

IIRC 2 out of 3 engines tested did. And the 100 hour test is a continuous 100 hours of operating. The B-29 engine did indeed have several issues, but it seems a lot of it was related to the areas where they were operating, since tropical climates were not helping the issue of overheating, which when coupled with the magnesium materials used in it led to fires. That was more similar to the issues of the BMW 139 and Japanese Homare engine given that all of those were air cooled radials than the liquid cooled Jumo 222.

I'll double check what Brandner had to say, as he was an engineer on the project, but my German is rusty and it will probably only be tomorrow that I have time to do that. The number of engines built really doesn't tell us much given how many different iterations and redesigns it went through to meet Milch's repeated demands of changes to the design. Plus several were used for many different aircraft prototype testing.

I am not going to place much credence in a computer game damage model unless somebody can show how it was done. One of these popular computer games uses the same rate of fire and damage model for ALL 20mm guns in the game.

They were quoting blast radius details from Luftwaffe manuals about the bombs. The details weren't the game's damage model.

 

[Shortround6]

The American type test was 150 hours, The R-3350 had to pass it several times, every major change requires a new type test. Or every power rating change requires a new type test.

US test was as follows.

At least 150 hours of running, including
10 hours at take-off power.
40 hours at rated power or 91% of take-off power, which ever is greater.
10 hours at overspeed.

The take off part of the test may be done continuously or up to 120 five minute periods alternated with 120 five minute periods at idle.

Similarly the overspeed test is may be broken into a series of 30 or 60 second periods of overspeed alternated with 5 minute periods at idle.

Passing a type test is also not really related to or an indication of average over-haul life. R-3350s started their service career (not experimental use) at about 100hrs average life.
By the end of WW II they averaging 400 hours, in airline use in the 1950s they were occasionally making it to 3000 hours. These late engines only had to have one example pass a 150 hr type test at the specified rating/s.


Point is that one engine successfully getting through a type test is no guarantee that early production (or even later production) engines will have a successful career.

Bristol Hercules passed a type test, early versions in Wellingtons sometimes didn't make 30 hours, later ones got much better, post war ones were an order of magnitude better.

 

[wiking85]

The American type test was 150 hours, The R-3350 had to pass it several times, every major change requires a new type test. Or every power rating change requires a new type test.

US test was as follows.

At least 150 hours of running, including
10 hours at take-off power.
40 hours at rated power or 91% of take-off power, which ever is greater.
10 hours at overspeed.

The take off part of the test may be done continuously or up to 120 five minute periods alternated with 120 five minute periods at idle.

Similarly the overspeed test is may be broken into a series of 30 or 60 second periods of overspeed alternated with 5 minute periods at idle.

Passing a type test is also not really related to or an indication of average over-haul life. R-3350s started their service career (not experimental use) at about 100hrs average life.
By the end of WW II they averaging 400 hours, in airline use in the 1950s they were occasionally making it to 3000 hours. These late engines only had to have one example pass a 150 hr type test at the specified rating/s.


Point is that one engine successfully getting through a type test is no guarantee that early production (or even later production) engines will have a successful career.

Bristol Hercules passed a type test, early versions in Wellingtons sometimes didn't make 30 hours, later ones got much better, post war ones were an order of magnitude better.

I get your point, but using two radial air cooled engines as an example vs. a liquid cooled engine in a different layout is not the best counter example given how different the engine styles and issues are.

I'll go through the Brandner chapter when I get a chance to figure out what the issue was from the engineer who worked on the project.

As to the Karl-Heinz Regnat book on the Ju288 I see where you got the numbers, but the author doesn't cite any sources. Frankly I'm going to stick with the original Junkers spec sheet numbers over those in that book given the lack of citations.

 

[nuuumannn]

about you stop commenting until I do so I can debunk your bullshit?

Alright, you're obviously trying to derail the thread. Stop being a douche.

Here's a trick, how about you stop the casual insults mate. We can do this without them, so be civil.

 

[Shortround6]

Well, we can look at the Allison engine in 1940. It had passed a type test and yet in US service in 1940 it had to be down rated to a max rpm of 2770rpm instead of 3000rpm while the engines were rotated out of service and sent back to Allison for a rework that involved both a new crankcase and a new crankshaft, to be done at Allison's expense. Something like 288 engines were involved. Later Allison's got a lot better.
The Napier Sabre has already been mentioned several times. The RR Vulture may have been mentioned more than once. The Continental XI-1430 has been mentioned, it passed a type test but engines delivered to Lockheed and McDonald were not only troublesome but didn't come close to making the promised power. All had passed type tests or they wouldn't have been put in aircraft for testing the aircraft. Experimental engines were put in known aircraft to keep the variables down, much like Junkers used a Ju 52 for flight trials of the Jumo 222 engine. Large, multi seat aircraft also offered room for extra instruments and engineers/technicians to monitor engines still in development while in flight.


Passing a type test didn't seem to mean as much as was hoped, engines that failed a type test could be real trouble.
The engines that are used for a type test are usually tool room samples and not built on production machinery or using normal production workers.

The ignition system on the Jumo 222 seems bizarre in the extreme, every other aircraft engine used dual ignition (two spark plugs per cylinder) for two reasons. One was safety in that should one magneto fail all cylinders still had one functioning spark plug. engine performance was reduced due to less than ideal flame front propagation the cylinder, but one could assume that some sort of cruise power (or high cruise power) was still available. Some sources on the Jumo 222 claim that each magneto fired both plugs in 1/2 the engine. If a magneto fails 12 cylinders out of 24 would still function completely as normal while 12 cylinders wouldn't function (fire) at all. Try pulling four of the plug wires on an eight cylinder car and see how it runs. Potential vibration problems are astronomical.

 

[Geoffrey Sinclair]

There was the R3350-1, -2, -4, -5, -8, -10, -13, -14, -16, -17, -18, -19, -21, -23, -23A, -24W, -26W, -26WA, -26WB, -30W, -30WA, -30WB, -32W, -34, -35, -35A, -37, -39, -41, -43, -57, -57A, -59, -65, -75, -85, -89, -91. Of these the following powered B-29s, -13 (50 engines built), -19 (31 engines built), -21 (147 engines built), -23 (1,265 engines built), -23A (22,486 engines built), -32W? (32 engines into B-29s after 1950), -41 (26 engines built), -57 (6,958 engines built), -57A (407 engines built), -59 (376 engines built), -65 (8 engines built). Fuel injection was introduced for engines built in the final quarter of 1944.

Everything to the -5 was a pre WWII engine, with very few of each type built. Everything to the -24W had at least some production in WWII, as did the -35 to -59, post WWII first production were the -26W to -34 and the -65 on. Of the 44,536 R-3350 built, 32,039 were of types out of production by the end of 1945. The -23 was built between 2/43 and 3/44, the -23A between 1/44 and 5/45, the -57 between 1/44 and 11/45. Many of the early engines went into things like experimental types, B-32, C-97 and so on.

Some 3,763 B-29s were built in WWII, 2,507 in 1945, and 378 in the final quarter of 1944. If you have a look at the number of hours on combat missions and
the number of combat sorties you find the average sortie took over 14 hours.

You find WWII history in some interesting places.

Journal of the American Statistical Association, V 41 no. 234, June 1946, pages 190 to 203. "Actuarial Analysis of the operating life of B-29 aircraft engines", by O L Altman and C G Goor.

Lots of obvious and not so obvious points.

1) R-3350's were in critical supply in 1944 and the first half of 1945. Supply problems were easing around the end of the war.
2) Air transportation was used to fly R-3350's to the US for overhaul, at best 2 R-3350's would fit in a cargo plane.
3) Overhauled engines had around 10% lower "life" before the next overhaul.
4) The -23 was the carburettor and the -57 the fuel injected versions. The -23 was modified to improve reliability.
5) The statisticians noted the standard USAAF methodology for forecasting engine life was only suitable for a reasonably static population. Not where there was a steady arrival of more strength using new aircraft.

In terms of engine life, operations in India were the worst, since each combat sortie required three reasonably rapid climbs, India to China, China to Japan, China to India. Next came training in the US, finally the best were the units in the Marianas.

Expected life prior to first overhaul, early operations from India, 163 hours, -23 engines. Using modified -23 engines this had risen to 280 hours by February/March 1945 for aircraft operating from India and 304 hours from the Marianas.

The figures for B-29s used in training were 221 hours and 310 hours versus the 163 and 280 hours figures above.

Operating from India a comparison between the modified and unmodified -23 engines showed 80% of the unmodified and 95.3% of the modified engines survived to over 100 hours, 33.9 of the unmodified and 81.5% of the modified engines survived to over 200 hours, 0.2% of the unmodified and 47.3% of the modified engines survived to over 300 hours.

In the Marianas, as of 20 November 1944 the average hours on each -23 engine removed was 91, by 20 January 1945 it was 151, as of 30 April it was 234. These figures include removals for engine model changes, modifications, accidents and battle damage. They are also under estimates of the normal engine lifetime because so many of the engines were new. The figures include new and overhauled engines, so it is either the number of hours since the engine was built for new engines or since overhaul for the overhauled engines. Engine hours before removal as of 31 May was 259 hours, and 31 July 272 hours. These figures are for engines removed because of mechanical problems only.

Even in July the steady number of new B-29s arriving drove down the average engine hours per removed engine.

A study as of 31 July 1945 noted in the Marianas the -23 engines 96.8% of new and 92.5% of overhauled logged more than 100 hours before replacement, 87.5% and 75.7% respectively logged over 200 hours, 62.7 and 43.4 logged over 300 hours, 19% and 8% logged over 400 hours, none logged over 500 hours.

As noted above the training schools in the US went through R-3350 engines quicker than the combat units in the Marianas, for example 57.9% and 36.4% logged over 300 hours, but once this mark was passed the engines in the US held up more, so 24.6% and 10.4% logged over 400 hours, and 1.2% and 0.2% managed over 500 hours. The fuel injected -57 engine had a higher time between overhauls, so in the above study 31.2% used in training logged over 400 hours, and 4.9% logged over 500 hours.

Some of the 15th Air Force 1945 monthly reports have Engine Change Reports, graphs of average running time per aircraft engine changed. Generally speaking the R-1830 radials in the B-24 and the R-1820 radials in the B-17 had at least an average of 300 hours running when changed, few had 400, with the R-1820 ahead, most having 350 or more hours. Overhauled engines usually had around half the average hours of new engines. The V-1650 Merlins and the V-1710 Allisons usually averaged over 200 hours, few made it to 300 until March/April. Overhauled Allisons were around half the new engine hours, overhauled Merlins more like a quarter.

 

[nuuumannn]

Far from attempting to derail this, all I'm attempting to do is illustrate the futility of believing that changing one or two dynamics will change the course of this aircraft's career. In simple terms, I disagree with you, wiking. Now that is okay. That's what we do here. We don't have to agree with each other all the time, that'd be boring.

Firstly, the accusations of wishful thinking. Believing that the Ju 288A was somehow ready for production and could be made so in 1942 is wishful thinking. Believing that somehow this would change if Milch was not in charge is also wishful thinking. The Ju 288A model was a prototype, not production ready. Refusing to believe that the Jumo 222 had only problems that could easily be solved if Milch hadn't interfered is also wishful thinking.

Reality is a strange, complex, multidimensional beast and with aircraft designs that fail, in retrospect it's never just one or two factors. Take the He 177, it was never just the dive bombing expectation, nor just the engines. There were design considerations that led to the engines overheating, there were other factors that often get overlooked. The Avro Manchester, it was not just about the Vultures. The Manchester had other issues and it wasn't quite ready for production, and when it was put into production, these issues had not been sorted, which, by the time the Lancaster enters production they had (largely) been sorted. The same with the Handley Page Halifax, it suffered from excess drag, but it also had other airframe issues that took over a year to sort out.

The problem I have with the Luftwaffe and its aircraft is that within this medium, i.e. the internet and forums, it has gained this mythical status of having created these terrific aircraft blessed with astonishing performance and if any one of them was done that was slightly different they could have changed the outcome of the war, or some such far fetched thing. It's far more complex than that, it always is and this German thing has become a cliche. It's everywhere on this forum, there are posts by people that state that if such and such had black crosses or was German it'd be a world beater etc, etc. This comes from this hopelessly optimistic belief that is prevalent in this thread.

If you don't agree with me, wiking, good for you, but I'm not going to stop denouncing stuff if I think it's unrealistic.

 

[wiking85]

Well, we can look at the Allison engine in 1940. It had passed a type test and yet in US service in 1940 it had to be down rated to a max rpm of 2770rpm instead of 3000rpm while the engines were rotated out of service and sent back to Allison for a rework that involved both a new crankcase and a new crankshaft, to be done at Allison's expense. Something like 288 engines were involved. Later Allison's got a lot better.
The Napier Sabre has already been mentioned several times. The RR Vulture may have been mentioned more than once. The Continental XI-1430 has been mentioned, it passed a type test but engines delivered to Lockheed and McDonald were not only troublesome but didn't come close to making the promised power. All had passed type tests or they wouldn't have been put in aircraft for testing the aircraft. Experimental engines were put in known aircraft to keep the variables down, much like Junkers used a Ju 52 for flight trials of the Jumo 222 engine. Large, multi seat aircraft also offered room for extra instruments and engineers/technicians to monitor engines still in development while in flight.

Passing a type test didn't seem to mean as much as was hoped, engines that failed a type test could be real trouble.
The engines that are used for a type test are usually tool room samples and not built on production machinery or using normal production workers.

The ignition system on the Jumo 222 seems bizarre in the extreme, every other aircraft engine used dual ignition (two spark plugs per cylinder) for two reasons. One was safety in that should one magneto fail all cylinders still had one functioning spark plug. engine performance was reduced due to less than ideal flame front propagation the cylinder, but one could assume that some sort of cruise power (or high cruise power) was still available. Some sources on the Jumo 222 claim that each magneto fired both plugs in 1/2 the engine. If a magneto fails 12 cylinders out of 24 would still function completely as normal while 12 cylinders wouldn't function (fire) at all. Try pulling four of the plug wires on an eight cylinder car and see how it runs. Potential vibration problems are astronomical.

I get what you're saying. Going through Ferdinand Brandner's memoir (he was the head engineer of the Jumo 222 project) they started the project in 1937 and had completed the first perfect 100 hour bench test in March 1940. He says it was not ready then, much as you're pointing out about other engines, and required two years to get production ready, with a start date for mass production in July 1942 set.

The first engine to fly was in November 1940 on a Ju-52 test bed though there would be several more Ju52 tests; he mentions three were used and did extensive flight tests with several engines. Obviously there was much development after that, but Milch raising the HP requirements in December 1941 effectively crippled the project. In 1942 Bradner said the Jumo 222 had completed 20 bench tests without any issue and the other issues associated with high altitude oil flow issues had been resolved and the engine was fully mature and ready for mass production.

So per the head of the project the engine was ready to enter production probably in August 1942 (he's somewhat unclear on the exact timing in the text). He says it was absolutely ready as of December 1942 when the decision was instead made to mass production the unready DB603 (it wouldn't be able to match the 2000hp output until 1944 and only then with MW injection and the 100 hours between overhauls was only achieved in 1944 at some point) and shift development focus to the Jumo 213 while the Jumo 222 was trying to meet the 2500 and later 3000 hp requirement Milch laid out (Brandner calls him out in particular) despite the protests of just about anyone involved in the project including the executives.

Even if we assume the worst and the engine at 2000hp was only ready in December 1942 for mass production given the state of the factory for the project it would have been able to enter production in large numbers quite quickly. After all the Ostmark facility was built to produce 1000 per month (overly optimistic IMHO but they really did build an American style mass production facility). Likely some series production could have commenced from August 1942 onwards at the Ostmark facility to get the first Ju288 units set up, but actual large scale mass production would have taken until December 1942 and IMHO probably only would be at 500 units per month by then, i.e. half of design capacity. That would be undertaken instead of the DB603 and the Jumo 213 would never be developed. The 603 probably would still be worked on, but given the development issues would probably remain a minor production engine.

So yeah, looks like 1943 would see the mass production of the Ju288A/Jumo 222 2000hp version and later iterations might hit that 2500hp mark before the end of the war. There should have been enough production then to cover several models of aircraft if desired, including a Ju388 and even improving the performance of the Do-217, which even with the DB603 and BMW801 was considered underpowered.

Bradner's memoir than entirely supports the thesis of Lutz Budrass (well respected historian of the German aviation industry) that Milch killed the project administratively by having both the Jumo 222 and Ju288 'developed to death'.

Edit:
Turns out things were even more complicated than I thought as there were an A/B-1, A/B-2, and A/B-3 engines, each with different power output and somewhat different construction.

The A/B-2 was the engine that Brandner said was ready by December 1942 with the following characteristics:

Junkers Jumo 222 Aircraft Engine

The Junkers Jumo 222 24-cylinder inline radial was intended to be the next generation of German aircraft engines during WWII. Developmental issues and material shortages prevented its production.

oldmachinepress.com

The Jumo 222 A/B-2's cylinder bore was increased .20 in (5 mm) to 5.51 in (140 mm), while its stroke remained unchanged at 5.31 in (135 mm). This change increased the Jumo 222 A/B-2's displacement by 214 cu in (3.50 L) to 3,044 cu in (49.88 L). The H-beam articulated connecting rods of the early engines were replaced with an I-bean articulated connecting rod design. The engine's compression ratio may have been raised to 6.735 to 1, and valve diameters may have been altered slightly. The Jumo 222 A/B-2 had a balance pipe between the intake manifolds of adjacent cylinder banks. Engine speed was limited to 2,900 rpm in an attempt to increase its reliability. The Jumo 222 A/B-2's maximum power at 2,900 rpm was 2,500 hp (1,864 kW) for takeoff and 2,490 hp (1,857 kW) at 16,404 ft (5,000 m). Climbing power at 2,700 rpm was 2,250 hp (1,678 kW) at sea level and 2,050 hp (1,529 kW) at 16,404 ft (5,000 m). Cruising power at 2,500 rpm was 1,900 hp (1,417 kW) at sea level and 1,750 hp (1,305 kW) at 16,404 ft (5,000 m). The engine's fuel consumption at cruise power was .449 lb/hp/hr (273 g/KW/h) at sea level.

The A/B-1 version sounds like it would have been ready for mass production in August 1942 and in fact flew in the V5 prototype of the Ju288 without issue:

The Jumo 222A/B-1-powered Ju 288 V5 made its maiden flight on 8 October 1941. Brandner had managed to talk his way onto the aircraft for the flight, which was completed without issue. For the Ju 288, the Jumo 222 turned a four-blade Junkers VS 7 propeller that was a 13 ft 1 in (4.0 m) in diameter. An annular radiator was positioned in the cowling, and experiments were conducted on Ju 288 V5 using a ducted spinner to deliver cooling air to the radiator.

Stats:

The Junkers Jumo 222 A/B-1 had a 5.31 in (135 mm) bore and stroke. The engine had a total displacement of 2,830 cu in (46.38 L). The Jumo 222 A/B-1 initially produced 2,000 hp (1,491 kW) at 3,200 rpm. At the expense of reliability, further development eventually pushed its maximum power at 3,200 rpm to 2,500 hp (1,417 kW) for takeoff and 2,200 hp (1,641 kW) at 16,404 ft (5,000 m). Climbing power at 2,900 rpm was 2,260 hp (1,685 kW) at sea level and 2,090 hp (1,559 kW) at 16,404 ft. Cruising power at 2,700 rpm was 1,900 hp (1,617 kW) at sea level and 1,700 hp (1,268 kW) at 17,060 ft (5,200 m). The engine's fuel consumption at cruise power was .477 lb/hp/hr (290 g/kW/h) at sea level. The Jumo 222 A-1 weighed 2,690 lb (1,220 kg), and the Jumo 222 B-1 weighed 2,745 lb (1,245 kg). The engine had a diameter of 3 ft 10 in (1.16 m) and was 7 ft 5 in (2.25 m) long.

The further development mentioned above was the A/B-2 version.

There is a reference to issues in early 1942 from January-March that were resolved by the end of the period, but I cannot tell from the text if that was the 1 or 2 version:

Work on the Jumo 222 would continue, but the engine was no longer a priority. Brandner stated that, at the time, various Jumo 222 engines had completed 20 100-hour test runs, and many at Junkers felt that the engine was basically ready for production. However, further issues with the connecting rod bearings caused a developmental delay that extended from January to March 1942. The connecting rod bearing failures took a long time to resolve with experimentation of different bearing materials and lubrication techniques. Ultimately, a new connecting rod design was employed, the antimony alloy bearing material was replaced with a tin alloy, and the synthetic engine oil used was switched to a natural oil with an increased sulfur content. Due to tin shortages, antimony had been substituted early in the engine's development.

Now as to why there were so many Jumo 222 engines produced:

Various versions of the Jumo 222 were flown in approximately 11 aircraft: three Ju 52 test beds, six Ju 288s (V5, V6, V8, V9, V12, and V14), one Fw 191 (V6), and one He 219 (V16). Jumo 222 engines were also planned for the Heinkel He 219B and C and the Hütter Hü 211 heavy fighters. Engines were not ready for the He 219B and C airframes, and the two Hü 211 prototypes were destroyed while under construction during an Allied bombing raid in December 1944. Some sources state that Jumo 222 engines were fitted to a four-engine Heinkel He 177 (V101), as the burned out remains of this aircraft were found at Cheb in Czechoslovakia. However, examination of the aircraft reveals the engine's exhaust stacks were in the standard four and eight o'clock positions for a Daimler-Benz DB 603 engine rather than the 2, 6, and 10 o'clock positions for the Jumo 222. The Jumo 222 was proposed for numerous other aircraft designs ranging from fighters, like the Focke-Wulf Ta 152, to bombers, like the Heinkel He 177. However, none of these plans came to fruition. A total of 289 Jumo 222 engines were built.

Now the contention that the engine was developed to death:

While the Jumo 222 was not trouble-free, its development progressed as well as could be hoped for considering it was a new engine design, the repeated changes to engine requirements and design, and that the ongoing war resulted in material shortages. Some contend that the changing Ju 288 and Jumo 222 requirements were intentionally made to cause the aircraft and engine to fail.

Heinrich Koppenberg was the managing director of Junkers, the only German company producing both aircraft and aircraft engines. Koppenberg had become a powerful man who worked himself into various positions that gave him control over many strategic resources. Erhard Milch was the Air Inspector General of the Luftwaffe and in charge of aircraft production. He had gained increasing control over aircraft procurement in Germany. Milch felt that Koppenberg and Junkers would have an aircraft production monopoly and economically ruin other companies if the current Ju 288, Jumo 222, and other company projects were successful. New large-scale Junkers production orders meant that resources at other companies would be allotted to produce Junkers products under license rather than develop their own. Some contend that Milch began to alter the official requirements just as they were about to be met by Junkers. After Ernst Udet, head of the T-Amt (Technisches Amt, Technical Office of the RLM), committed suicide on 17 November 1941, Milch took his place. Milch now had the power to dictate programs for the Luftwaffe. Acting as the RLM's authority, Milch continued to change project requirements, which left Junkers to perpetually chase the goal. Koppenberg was imprisoned in April 1942 when Junkers repeatedly failed to achieve what the RLM asked of them. While the above may be true, it is also true that the Jumo 222 had its own design issues. Brandner felt the engine was "developed to death" with its numerous displacement changes and constant design revisions.

The balance of the evidence is that the engine was ready for mass production in 1942 at least with 2000 hp, perhaps with as much as 2500hp for take off due to increased RPMs and bore.

Still, for the sake of argument and the OP scenario let's do a conservative scenario say it stays with the 2000hp version and enters mass production in August 1942 as intended in the Ostmark facility with 500 units per month. The original 3 man Ju288 should have been ready for mass production around then anyway too and probably pre-production models have been used to help set up a test squadron.

So conservatively we have a 2000 hp engined Ju288A enter frontline service around January 1943. Even using the lower performance estimates in the chart I provided earlier it would still have DH Mosquito performance in terms of speed with a 2000kg payload, but greater range (double?) and the ability to carry up to a 3600kg load internally (not sure with what performance though). Looks like reasonable operating altitude would have been around 6km. No way the Soviets could have intercepted that even as late as 1944 provided it stays above 5km altitude. The Wallies also would have had a problem dealing with it, but they'd be much better positioned to be able to intercept it over Britain given their air defense system. Outside of Britain though the Wallies could well struggle to intercept it, seeing as they'd lack an integrated air defense system. Ju288s in Italy would be a major headache to deal with.

 

[Shortround6]

Well, as far as the Russians intercepting it, you may be right. By 1943 there weren't a whole lot of MIG-3s left in service. Perhaps a bit over 300 defending the Moscow area?
Development was continuing at a slow pace and the Russians could have come up with something (and diverted some production of AM engines from the Il-2) if the Ju 288 was causing a big problem.


I am not sure about translations between "bench tests" and type tests.

For the P & W R-2800 it was first run Sept 13, 1937 (this may have been a 9 cylinder single row test rig).
By Nov 18th 1937 they had 100 hours of running time.
By Aug, 15th 1938 they had 1000 hours of running time.
By July 1st 1939 they completed two type tests, Engine No1 at Wright Field and engine No 2 at the Pratt & Whitney factory. At the completion of the type tests they had 3300 hours of run time on the test/development engines. All was ground running.

July 12, 1939 was the first test flight in the Vultee Y-19.

Feb 12, 1940 say 5000 hours of running time completed.

March 25th 1940 was when the completed the model test of the first contract model.
Granted Production R-2800s were a lot more trouble free than Wright R-3350s.

However problems with high cylinder count engines seem to go up near exponentially.

P & W had 15,000 hours of ground running on the 28 cylinder R-4360 to get to about the same stage of development as the R-2800 had with 3,500 hours. And remember. the R-4360 used R-2800 cylinder barrels, R-2800 cylinder heads (and valve gear) and either R-2800 pistons and rings or darn close to it (connecting rods were probably different).

So in the US you had bench running, bench tests, type tests, model tests, and flight tests. How that translates to German practice I don't know. Or how different letters/memos/documents were translated.

Wright had some of their troubles (but certainly not all) with the R-3360 because of the almost 6.5 million dollars (62.5 million in year 2000 dollars) flushed down toilet on the Tornado project which included 1,632.35 hours of testing on six 42 cylinder engines, 1,200 hours on two 14 cylinder engines and 130 hours on a 6 cylinder test engine. The Tornado project didn't come close to resulting in a useable aircraft engine. This division of effort (and work on the later R-2600 and R-1820 models) certainly did nothing for the R-3350.

 

[wiking85]

Well, as far as the Russians intercepting it, you may be right. By 1943 there weren't a whole lot of MIG-3s left in service. Perhaps a bit over 300 defending the Moscow area?
Development was continuing at a slow pace and the Russians could have come up with something (and diverted some production of AM engines from the Il-2) if the Ju 288 was causing a big problem.

Problem is the point defense system they had and how quickly any fighter could not only rise the to the appropriate altitude (6km probably), but then close the distance and get into attack position. And hope the bomber didn't spot them and dive away. Even then I'm not sure the MiG-3 could catch even the 2000hp version with the lower spec sheet given that it's top speed was only slightly higher than the Ju288, but it wouldn't matter largely because MiG-3 was largely withdrawn from most service by 1943.

The British did send some Spitfires in 1944, but they saw very limited use, apparently only around Leningrad and Moscow later in 1944:

British Aircraft in Russian Service

There were PR Spitfires, other Spitfires, Hawker Hurricanes and two seater conversions of both. There were A.W. Albermarles ...

soviethammer.blogspot.com

Those might have a chance to intercept, but they showed up so late it might not make a difference and by then the 2500hp version of the Jumo 222 might well be available.

I am not sure about translations between "bench tests" and type tests.

For the P & W R-2800 it was first run Sept 13, 1937 (this may have been a 9 cylinder single row test rig).
By Nov 18th 1937 they had 100 hours of running time.
By Aug, 15th 1938 they had 1000 hours of running time.
By July 1st 1939 they completed two type tests, Engine No1 at Wright Field and engine No 2 at the Pratt & Whitney factory. At the completion of the type tests they had 3300 hours of run time on the test/development engines. All was ground running.

July 12, 1939 was the first test flight in the Vultee Y-19.

Feb 12, 1940 say 5000 hours of running time completed.

March 25th 1940 was when the completed the model test of the first contract model.
Granted Production R-2800s were a lot more trouble free than Wright R-3350s.

However problems with high cylinder count engines seem to go up near exponentially.

P & W had 15,000 hours of ground running on the 28 cylinder R-4360 to get to about the same stage of development as the R-2800 had with 3,500 hours. And remember. the R-4360 used R-2800 cylinder barrels, R-2800 cylinder heads (and valve gear) and either R-2800 pistons and rings or darn close to it (connecting rods were probably different).

So in the US you had bench running, bench tests, type tests, model tests, and flight tests. How that translates to German practice I don't know. Or how different letters/memos/documents were translated.

Wright had some of their troubles (but certainly not all) with the R-3360 because of the almost 6.5 million dollars (62.5 million in year 2000 dollars) flushed down toilet on the Tornado project which included 1,632.35 hours of testing on six 42 cylinder engines, 1,200 hours on two 14 cylinder engines and 130 hours on a 6 cylinder test engine. The Tornado project didn't come close to resulting in a useable aircraft engine. This division of effort (and work on the later R-2600 and R-1820 models) certainly did nothing for the R-3350.

I'll stick with the opinion of the head engineer of the project about it being production ready, especially since the version in question was good enough to be fitted to 5 prototypes and worked in that role and the engineer in question felt confident enough about it to ride in the first flight it was fitted to a Ju288 prototype. Also note in the Karl-Heinz Regnat book you cited earlier that the last prototype of the Ju288 fitted with the Jumo 222 worked perfectly. That would be the V14 prototype (288B variant) that entered testing in August 1942. Earlier ones apparently also worked very well as well.

 

[wiking85]

Back to the runway issue, it looks like most bomber rated bases were paved 2000m runways. That was the case with the eastern most base in Belarus as of 1944 near Bobruysk, which were operational until overrun in Bagration. Tartu also had an airbase, but it was not as capable as the one in Belarus, but still had a 1200m paved runway. So either, assuming any strategic bombing plans for the eastern front mature ITTL before summer 1944, could be used by the Ju288 to strike Moscow or Yaroslavl. Or even theoretically a Jumo 222 equipped Do217.

As an aside about the reliability of the engine in 1941-1942 for development, it seems a lot of the issues that people mention the engine had were for the bore increased A/B-2 engine, as the A/B-1 and -2 types are often not differentiated. Things like the vibration and corrosion issues were related to the A/B-2 version as of late 1941/early 1942 due to the increase bore and rpms. Still it looks like that version (limited boost up to 2500hp for short durations) was still fixed by mid/late 1942, but the RLM held out for the A/B-3 version that had a regular 2500hp rating, not a boosted rating that high, which wasn't supposed to enter mass production until October 1944, despite the 'lesser' versions being ready in 1942.

We've also not talked about that side of the equation here if the 2000hp Jumo was ready and produced at a rate of 500 or more per month from January 1943 onwards: it could be used in other aircraft since the ramp up production time for the Ju288 would be considerably more than for the engines. The Do217 is one example, but as mentioned in one of my previous posts the He219 was to use the Jumo 222, same with a 4 engined version of the He177. That would have eliminated the need to worry about using the coupled DB601/5 and dramatically increased performance for a marginal increase in weight. Beyond that there is the option for a Ju388 with the 222 and as also mentioned above a fighter version using it. The Ta-152 is mentioned, but the Fw190 should have been able to use it as well, effectively becoming a Luftwaffe version of the Tempest:

Jumo 222 installations??

Specifically, cowl and radiator configuration for the Jumo 222 fitted to the Ju388 and He219B. While the He219 might be a really iffy one-of, though a whole family of versions was proposed, there were several Ju388 prototypes fitted and flown with Jumo222s.

www.secretprojects.co.uk

Focke Wulf Fw 190/Ta 152 Projects & Variants

Thank! :)

www.secretprojects.co.uk

The Fw190 used the BMW801D, which required the expensive C3 fuel, for 1700hp and could hit 2000hp later with MW injection or C3 fuel injection for short periods; the Jumo 222 used B4 fuel to achieve 2000hp without boost. With boost it got up to 2500 as we see above. A Fw190D with Jumo 222 capable of boost up to 2500hp would be extremely formidable even in 1944. Since the dimensions of the engine and overall weight even 'full' was very similar to the BMW801 modifications shouldn't be nearly as extensive as the FW190D, plus it being available to start testing in 1942 and available in numbers in 1943 should make it ready sooner than the OTL FW190D, since the Jumo 213 engine was only made available for fighters later in 1944.

 

[nuuumannn]

Again, the problem I have with this is the assumption that the Ju 288A is going to be worthy of production and service at the end of 1942 beginning of '43, for the reasons discussed in the other thread. The type has no defensive armament, which it was designed to have and which was not subject to interference from Milch or anyone for that matter, Junkers never got it to work. Expecting this bomber, with its three man crew and no defensive armament to be put into production for service in 1943 is fantasy. As for the argument the RLM messed it up, well, Junkers wanted it to be funded by the RLM:

Cesscotti (2001) states "Fully expecting the RLM to provide the funding for the construction of the prototype Ju 288, in February 1940 (i.e. almost four months before the RLM contract was formally awarded) the Junkers company had already begun work on the prototype."

With the accusations of sabotage, it might be worth going to the archives in Germany to find out if there is any surviving documentation that states why the RLM made changes to the design in the first place, rather than simply assuming it deliberately set out to sabotage the design. That simply holds no water and is not logical. The RLM is paying for it, why would it sabotage it? It has a requirement to fulfil.

 

[Shortround6]

A number of US projects failed to meet the initial requirements in some fashion.

The USAAC/USAAF had three basic choices.

1. Accept the less than desired performance and put the plane/s into production with the engines as they then existed (or were promise0.
2. Delay production and demand either new engines or more powerful versions (not developed yet) of existing engines be used to meet the desired performance.
3. Throw everything out and start over with either a more advanced air frame or both new air frame and new engines with even more delay.

Germans and actually everybody was sometimes faced with the same problems. However when you are already using the most powerful engine (promised) in the supply chain switching engines is not an option.

Most nations had service engineers/officers that would look at manufacturer's proposals and evaluate how close to reality they were. If there was a big discrepancy in estimated performance the project might be dropped or changes demanded before metal was cut.

I would note that few project engineers were going to admit in their memoirs that project "X" was a turkey.

The Jumo 222 was not the only engine (or airplane) that was canceled just as success was achieved on the test stand or on the last test flights........at least according to project managers/engineers.

There was a fair amount of finger pointing at Wright about the failed Tornado program. At least three US fighter programs were supposed to use the engine and perhaps other aircraft.

Actually the Tornado was the 3rd engine chosen for the XP-58 after it was decided the IV-1430 was too small and the P & XH-2600 was canceled. With the Tornado also canceled the XP-58 fell back on the Allison V-3420 for actual flight trials.

If the RLM evaluators decided the JU 288 wasn't going to meet the performance goals with the early Jumo 222 engine then you are back to the choices listed earlier. Accept the lower performance. Delay production and demand new versions of the engine with more power. Scrap the whole program and start over.

Are their any documents that say Milch made the decisions on his own evaluation or was he relying on reports from engineering staff? Granted he could exert pressure on such a staff but few manufactures are going to admit their own estimates are a wrong. Look at Bell and the "aircraft that must not be named".

 

[nuuumannn]

If the RLM evaluators decided the JU 288 wasn't going to meet the performance goals with the early Jumo 222 engine then you are back to the choices listed earlier. Accept the lower performance. Delay production and demand new versions of the engine with more power. Scrap the whole program and start over.

Yes, indeed. The Jumo 222 might have been ready, but it couldn't put out 2,500 hp, which was stipulated in the original specification for the Bomber B, which is why the DB engines were examined. They produced better performance at height and with changes made to the airframe, that performance was definitely required.

Are their any documents that say Milch made the decisions on his own evaluation or was he relying on reports from engineering staff? Granted he could exert pressure on such a staff but few manufactures are going to admit their own estimates are a wrong.

This is the crux of the matter. I'm pretty certain Milch didn't just wander in and demand changes. They were not made in isolation. There was definitely some motivating factor behind them and it would be interesting to find out why they were made before accusations of sabotage are made. Increasing the crew number was because a fourth individual was required for the two remote defensive gun positions required, there was a bomb aimer, radio operator and pilot, adding another gunner helped, which made sense and the Ju 288B stipulated two remote defensive positions:

Cesscotti (2001) says: "For armament it was planned to make use of remote controlled gun stations sighted with periscopes on the dorsal and ventral fuselage areas. These included the A-Stand under the tip of the cockpit, also called the chin position. The B-Stand just behind the pressurised cockpit. Both stations were to have two 13mm MG131 twin guns each. The rear position, also with a remotely operated gun, either an MG 131 twin barrelled machine gun, standard or an MG 151 (15mm) or an MG 151/20(20mm)."

The C model was in fact anticipated by Junkers and it was Hertel himself who began changing the aircraft to take the DB engine before the RLM had instructed him to do so. Changes included adding another remote gun position aft of the bomb bay, or C-Stand.

 

[cherry blossom]

Has anyone else noticed that the original design of the three man crewed Ju 288 A, which I had originally thought was a unique concept, has some characteristics in common with the Douglas XB-42 Mixmaster, which is also three seat and also carried two remotely controlled pairs of heavy machine guns. For example, the max take off weight of the Ju 288 A was 38,900 lb (manufacturer's estimate) and that of the Mixmaster was 35,702 lb (from Wikipedia). The wing areas were 581.25 sq. ft. for the initial Ju 288 A and 555 sq. ft. for the XB-42.

 

[NevadaK]

I went back and reread the original post before composing my answer. Assuming the Ju288 was production ready in 1942 my response to the question "how would it perform?" is:

1) My first thought is that the conversion to the full scale production and implementation of the Ju288 would have had an overall detrimental impact on the Nazi war effort. German industrial capacity at the time would have been focused on existing bomber types (He111,Ju88,Do217) and it would be impossible to shut down any existing production lines to convert over to the new bomber. This would require diverting resources to construct new factories and infrastructure. That strain, would be felt somewhere in the German armaments system at a time when they could least afford any dips in production.

2) Assuming the Ju288 is proven ready in first half of 1942, meaningful numbers of aircraft would not be available until 1943. This can be shown through the growth in numbers of B-17's and B-24's stationed in the UK. The US had begun building new factories for both aircraft in late 1940 through the Arsenal of Democracy program and even with America's production capacity, we don't see large numbers of these aircraft until late 1943. Germany with fewer resources would have greater difficulty fielding a resource intensive aircraft such as the Ju288 in meaningful numbers in less time without diverting all resources from existing production. Something they would not be able to do.

3) In a tactical role, the Ju288 does not offer such a leap in capability as to definitely alter the course of battle. Yes, it would be faster and carry more bombs, but as Germany in 1942 still commanded the air over the eastern front in 1942 and was competitive in 1943, the improved tactical capability would not affect the overall course of the war.

4) Germany does not have the resources to adopt a strategic air campaign. As is demonstrated in western Europe, strategic air campaigns require massive resources in terms of numbers of planes and supporting infrastructure. Point targets are much harder to destroy than planners believed and plans such as Operation Eisenhammer rarely proved successful.

5) The Ju288 would not be immune to interception and without long range escort would suffer high loss rates. It is true that USSR manufactured aircraft did not perform well at the projected operational altitudes of the Ju288. On the other hand, the USSR did use Spitfire MkV's and IX's for high altitude and strategic air defense. These aircraft were provided through lend lease and would have been more than capable of intercepting the bomber. Without air escort, the Ju288 would have suffered the same kind of loss rates as USAAF bomber's did over western Europe. Additionally, if the threat of a Nazi high altitude bombing campaign were real the USSR would have been able to acquire large numbers of P-47's which would have excelled as high altitude point interceptors.

The Ju288 is a provocative aircraft and the proposed performance criteria are impressive. But, as with many "wonder" weapons the technological challenges were insurmountable. There have been very few aircraft (or weapon systems) that have altered the course of the war despite improvements in performance. The cost of bringing the Ju288 into service in meaningful numbers would have been difficult for the German war industry to bear and interruptions in existing aircraft production in 1942 -1943 would have been disastrous. Not to mention what increased bomb production to support an increased bombing campaign would have on other needed munitions. There is also the mistaken belief that it would have been immune to interception over the USSR. That overlooks the fact that the USSR did indeed have sufficient high altitude capability to limit Ju288 effectiveness. Just not made in the USSR. So, to answer the question "how would it perform?" as an individual aircraft it would be formidable assuming the projected performance criteria were met. As a weapons system, I think the results would have been less than hoped for.

 

[nuuumannn]

So, to answer the question "how would it perform?" as an individual aircraft it would be formidable assuming the projected performance criteria were met. As a weapons system, I think the results would have been less than hoped for.

I read your synopsis, NevadaK, it works and I agree with what you are stating here. The problem with the three man Ju 288A is that it is operationally a non-starter, despite what the original poster asserts. The aircraft was intended on being a replacement for the pre-war twin-engined medium bombers, with the He 177 assuming the mantle of heavy bomber, but both these projects evolved into muddled messes. Goring had reason to be disappointed with the industry, they over-promised and under delivered, but of course, Udet was a big part of the whole dive bomber capability saga, so that definitely came from within. As for Milch's role, his purpose was to shake the industry up and standardise programmes, as was necessary, so his intent was to get something workable, which the Ju 288A simply wasn't. In hindsight, the Germans were good at inadvertent self-sabotage.

The bigger heavier aircraft that Milch wanted, the Ju 288B could have been a viable replacement for the Ju 88, but, as you point out, to what end, nevertheless, the Germans needed such a thing if they wished to continue - they were planning for a permanent replacement after all, but they needed to solve the armament and engine issues - despite what the original poster states, the Jumo 222 engines were not issue free in 1942 and remained troublesome throughout their various incarnations.

All things being equal, if the engines played ball and the armament was actually built, the type would have been a good aircraft. Would it have made a difference to Germany's fortunes? Definitely not, but that's not part of the original hypothesis of the thread.

 

[tonycat77]

i don't see the reason why germany couldn't do a reliable 18 cylinder for 2000hp+ applications.

 

[SaparotRob]

Neither could they but here we are.