Ju388 any good?

[wiking85]

Junkers Jumo 222
In terms of the technical info the Allied post-war looks into the engine is perhaps as authoritative as we are going to get online in English.
TMV6N3

The Junkers Jumo 222

Early in 1946, the USAAF Power Plant Lab at Wright Field obtained several captured Junkers Jumo 222A/B and E/F engines from US Navy Engine Test Station in Philadelphia, Pennsylvania. The Jumo 222 was a 24-cylinder, liquid-cooled engine with six banks of four cylinders each arranged radially about a common crankcase. The Navy had performed a cursory examination and planned to test the engine, but due to the lack of facilities and other difficulties, little was done. Wright Field personnel began detailed inspection of the engines and translated several technical papers about the Jumo 222 from German to English. According to German test information, later versions of the Jumo 222 performed extremely well at high altitudes. One object of the inspection and testing was to discover whether this was true and why. There was also considerable interest in the fuel injection and engine control systems. Pratt Whitney, Allison and Lycoming, all with large engine developments under way, wanted information on the engine.

Now if we take this info and mesh that with the work of Lutz Budrass, who claims the original engine was set to be ready in 1942 but for a new spec being issued in November 1941 by Milch that setback development, which was done again in 1942/3, it would have been ready. That is also from the head engineer of the engine:
Ein Leben zwischen Fronten: Ferdinand Brandner: 9783853391259: Amazon.com: Books
And also in the previously mentioned Ju288 book. I'm inclined to agree that the engine would have been production ready in 1942 some time but for Milch's struggle with Koppenberg and the constantly changing specs on the engine setting back development when bombing further complicated things.

 

[Shortround6]

Thank you. I have a copy of the magazine. The Wright field personnel disassembled the Ju 222 and measured and photographed it but while they reassembled it the intended test running never happened. Other things had take priority.
The technical description is nice but the history (numbers produced of each model) and performance are not there. One item of note however is the ignition system. It used two magnetos and each cylinder used two spark plugs but contrary to just about every other aircraft engine in the world
each magneto handled half the engine, firing the plugs in 3 cylinder banks. If a magneto craps out you have lost half the engine and are fighting the dead cylinders instead of an engine running on all cylinders but at reduced power.
The engine torn down and described was a 222E. Wright Field had 3 222A/B engines torn down for parts.

 

[Koopernic]

The USAAF obtained Jumo 222E/F and translated German documents. Al the translations say that all the Jumo 222 types had a 135mm stroke though bores varied. The story of varying strokes seems to come from German POW and are therefore not totally reliable since the POW are either working from memory or trying to please their interrogator.


The Jumo 222A1/B1 were the defective ones 135 bore by 135 stroke.
The Jumo 222A2/B2 had and increased bore of 140mm and fixed the basic problems, they were to be produced in September 44 but early versions did fly in prototypes.
The Jumo 222A3/B3 differed in details and in improved supercharger fluid dynamics but shared the bore and stroke of the jumo 222A2/B2
The Jumo 222E/F was a Jumo 222A2/B2 with a two stage supercharger and intercooler and the same 140mm bore and 135mm stroke of the A3/B3. The first stage intercooler had two mechanical speeds while the second had an infinitely variable hydraulic drive.

It was not vapourware and units were taken to the USA. See the following links:
TMV6N3
Junkers Jumo 222

Although the Jumo 222E/F was rated at 2500hp it was generating 2900hp on B4+MW50 on the bench.

The Jumo 222C/D still had the 135mm stroke but increased bore to 145. It received its own funding in 1944. It's basic rating of 3000hp was considered essential.
The Jumo 225 was a 36 cylinder engine with a bore equal to the Jumo 222A1/B1 135 x 135.

Apart from the POW discrepencies these are radials and so have a king rod and i think all cylinders have slightly different strokes. I guess its the king rod whose stroke is quoted.

 

[Shortround6]

It's vaporware in the sense that it never seemed to show up. That is fly with any degree of regularity.

The British built 538 RR Vultures according to one source. Maybe they shouldn't have but it powered not only a few prototypes but about 200 Avro Manchesters. The 289 Ju 222s powered only a handful of prototypes and often a later prototype of a given airplane had to revert to a lower powered engine due to a lack of airworthy Ju 222s.

 

[Koopernic]

I don't mean to digress too much, but what was the point of the Ju 488? It didn't seem like too great of an a/c considering it could only carry 11,020 lbs at 2,795 miles (nothing compared to the B-29 or the He 277, it's contemporsries) albeit it had a decent service cieling and was pretty fast at a proposed 428 mph, and supposedly very easy and fast to build (due to its very high amount of parts commonality with other aircraft in service.

I think you've already analysed that but my opinion and reading is

1 Unlike any version of the Heinkel He 177B, He 277B, Me 264 etc. it had and exceptional service ceiling (48000ft for the BMW801TJ version, surely more for the 801TQ) and speeds of up to 421mph for versions powered by the Jumo 222E/F at only slightly less service ceiling (13650m i.e. 45100ft).

The Luftwaffe would have realised that the Allies were going to deploy aircraft equal to the Ta 152, or an improved Mk XIV Spitfire (eg Mk 22 Spitfire) or High altitude Tempest. Fighters with 4 gun 20mm Hispano armament are not light matter. I don't think you can fend of these kind of fighter aircraft in B-29 or He 277 style aircraft using gun turrets with big lavish 10 man crews, the armament of these fighters is too deadly and you must avoid it as much as possible. You cant avoid a 460mph fighter in a 360mph B-29 or He 277. You essentially must be almost as fast as the interceptor to be very hard to intercept and force the attacking fighter into essentially a tail chase. The Ju 488 was to have a pair of electro hydraulically aimed 20mm guns in the tail to defend against that.

There were broadly two versions of the Ju 488
A/ the BMW801TJ powered versions had the Ju 388 nose and Ju 288 tail and used a fabric covered steel tube fuselage with an extended Ju 388K bomb panier. The engine nacelles all had undercarriages in them. This version cruised at 385mph and had a max speed of 428mph. The prototypes the V401 and V402 were almost ready for flight testing in France when the factory was over run. B/ The Jumo 222E/F version was expected to cruise at 395mph to 421mph. No maximum speed is given min Black Cross Ju 288/388/488 but it must have been high as the Jumo 222A2/B2 was estimated as having a speed of 422mph at 6000m. This version had a normal monocoque fuselage and internal bomb bay. The engine had room for improvement.


2 It was likely to be quick to enter service and efficient to build because most of the parts came from the Ju 388 program. The nose is Ju 388 the tail from the Ju 288 empennage.

It's very important it enter service quickly and without too much tooling up because within 1-2 years it would be replaced by the Ju 287 jet.

If they can remove the dorsal 20m guns and install radar for directing the tail guns it probably stays viable for a year or two.

 

[SpicyJuan11]

I think you've already analysed that but my opinion and reading is

1 Unlike any version of the Heinkel He 177B, He 277B, Me 264 etc. it had and exceptional service ceiling (48000ft for the BMW801TJ version, surely more for the 801TQ) and speeds of up to 421mph for versions powered by the Jumo 222E/F at only slightly less service ceiling (13650m i.e. 45100ft).

The Luftwaffe would have realised that the Allies were going to deploy aircraft equal to the Ta 152, or an improved Mk XIV Spitfire (eg Mk 22 Spitfire) or High altitude Tempest. Fighters with 4 gun 20mm Hispano armament are not light matter. I don't think you can fend of these kind of fighter aircraft in B-29 or He 277 style aircraft using gun turrets with big lavish 10 man crews, the armament of these fighters is too deadly and you must avoid it as much as possible. You cant avoid a 460mph fighter in a 360mph B-29 or He 277. You essentially must be almost as fast as the interceptor to be very hard to intercept and force the attacking fighter into essentially a tail chase. The Ju 488 was to have a pair of electro hydraulically aimed 20mm guns in the tail to defend against that.

There were broadly two versions of the Ju 488
A/ the BMW801TJ powered versions had the Ju 388 nose and Ju 288 tail and used a fabric covered steel tube fuselage with an extended Ju 388K bomb panier. The engine nacelles all had undercarriages in them. This version cruised at 385mph and had a max speed of 428mph. The prototypes the V401 and V402 were almost ready for flight testing in France when the factory was over run. B/ The Jumo 222E/F version was expected to cruise at 395mph, max speed is 421mph. This version had a normal monocoque fuselage and internal bomb bay. the engine had room for improvement.


2 It was likely to be quick to enter service and efficient to build because most of the parts came from the Ju 388 program. The nose is Ju 388 the tail from the Ju 288 empennage.

It's very important it enter service quickly and without too much tooling up because within 1-2 years it would be replaced by the Ju 287 jet.

If they can remove the dorsal 20m guns and install radar for directing the tail guns it probably stays viable for a year or two.

Thanks, so it would be best to cancel the He 274 and replace it with the Ju 488 which would be used as a low and high altitude bomber until the He 277 is up and running (and then the 488 would be built as a purely high alt bomber, canceling the high alt 277 variants)?

 

[SpicyJuan11]

Sorry, double post.

 

[Koopernic]

Thanks, so it would be best to cancel the He 274 and replace it with the Ju 488 which would be used as a low and high altitude bomber until the He 277 is up and running (and then the 488 would be built as a purely high alt bomber, canceling the high alt 277 variants)?

I wouldn't like to say as I know little of the He 274's performance, was it better than the Ju 488. It has nice features such as standard ejection seats and a small crew. The Ju 488 would seem further along and easier to get into production, which is crucial. Both the He 274 and the BMW engine Ju 488 V401 and V402 were being built in France and were lost.

The He 277 I think is old school, even with a speed of around 360+ it's too slow to avoid or limit interception by the enemy and takes too much manpower to defend.

 

[SpicyJuan11]

I wouldn't like to say as I know little of the He 274's performance, was it better than the Ju 488. It has nice features such as standard ejection seats and a small crew. The Ju 488 would seem further along and easier to get into production, which is crucial. Both the He 274 and the BMW engine Ju 488 V401 and V402 were being built in France and were lost.

The He 277 I think is old school, even with a speed of around 360+ it's too slow to avoid or limit interception by the enemy and takes too much manpower to defend.

The He 274 had lower service ceiling than the Ju 488 at barely 47,000 ft, was substantially slower at 360 mph, and only carried 8,818 lbs @ 2,137 miles, the critical aspect of parts commonality with the He 177, I do not know.

 

[Gixxerman]

Is the real (as opposed to the unreliable projected) performance data for the He274 (AAS 01A/01B) available?
IIRC the DB603 engines used the TK11 turbo-charger in French service, how did they get on with them?

I can see why the Ju488 might look attractive from the ease of production point of view but as far as I can make out everything about it is projection, I think this is very relevant given the design included (at least at the start) turbo-charged BMW engines and we have seen umpteen times projections inflated manufacturer claims in this period fall well short.

Someone can correct me if I'm wrong but did Germany ever actually have a developed reliable turbo-charged engine? I don't think so.
I know they had designs testbeds for them but given how long it took engine manufacturers in the USA to perfect them merely having started is in my opinion a long way off actually having service-ready engines.
Ditto having sufficient materials to make enough to be of much use.

Later versions (like several aircraft) were supposed to use the Jumo 222, again hardly a design that had proven itself reliable ready for military service, regardless of how many prototypes were made.

 

[Shortround6]

Later versions (like several aircraft) were supposed to use the Jumo 222, again hardly a design that had proven itself reliable ready for military service, regardless of how many prototypes were made.

near as I can figure 8 aircraft flew with Ju 222 engines. a Ju 52 test bed, 6 different Ju 288 prototypes and 1 Fw 191. There may be a possibility that a He 219 flew with them.

I don't don't doubt that the Germans could design a turbo charger. I don't doubt they could build one or a dozen. The problem comes with building 100 or 200. You run smack into the problem that troubled them with jet engines. A shortage of high temperature alloys for the turbine.On US turbos inlet temperature of the exhaust gases to the turbo could (or exceed, 1750 degrees was the limiting temp) reach 1750 degress F. I doubt the German units were much different.

The Americans wrecked a few (or more than a few) planes with exploding turbos as did the Russians. Getting turbos to work reliably is a bit different.

 

[kool kitty89]

I don't don't doubt that the Germans could design a turbo charger. I don't doubt they could build one or a dozen. The problem comes with building 100 or 200. You run smack into the problem that troubled them with jet engines. A shortage of high temperature alloys for the turbine.On US turbos inlet temperature of the exhaust gases to the turbo could (or exceed, 1750 degrees was the limiting temp) reach 1750 degress F. I doubt the German units were much different.

Air cooled turbine blades was the route BMW took there, and their turbocharger design work pre-war was folded into the (originally Bramo) design that became the 003. (with Bramo's planned 600*C inlet temperature increased to 770*C -albeit that would still be significantly lower than 1750*F)

I don't believe any of the major turbocharger projects used radial inflow turbines, but given their cooperation with Heinkel, it would have been interesting if Hirth's developments had taken that direction. (with or without air cooling, radial turbines handle load/stress better at given power and temperature and also tend to be easier to engineer for smaller turbines than their axial counterparts -should be more useful for turbochargers and less advantageous for larger gas turbines, and probably not a great idea for anything larger than the HeS 3/6/8 Ohain worked with -the HeS 8 itself probably would have been better off with an axial configuration given its straight-through flow arrangement and aims at minimizing diameter and weight)

 

[Koopernic]

The alloy used in the turbocharged BMW801 was sicromal by Boehler, the same alloy used in the BMW 003 turbojet. In general small turbines for turbochargers suffered from non of the problems their larger turbojet variants suffered from and could even be fabricated by different techniques such as welding of the blade shank to the disk. In general I think they had much more problems with the ducting and perhaps housing.

The German's had major turbo charger and high altitude engine program, there was the massive Hubertus facility which provided air conditioned high altitudes wind tunnel chambers able to simulate full flight conditions and a full range of altitudes that was unmatched by the Allies. I think even the J79 was developed in this facility.

The desire for turbo chargers was at least as motivated by civilian needs. The treaty of Versailles was designed to damage Germany economically (to keep it weak) and had in part done so by creating an order that left a poorly functioning trade system that harmed all of Europe as well. To overcome these problems German business reached out to neutrals in Sth and Central America, China, Japan, Africa with considerable success. Anywhere Anglo or French colonialism could not interfere. Lufthansa provided transport for Iran and turkey.

As a result a significant need for long range Aviation arose. Diesel powered sea planes with ranges of 3000 to 5000 miles, catapult launched sea planes that could be retrieved and in the ocean by Blohm and Voss as well as Dornier.

The Fw 200 Condor was the first of the long range passenger aircraft. It was designed to fly at 10,000ft (where pressurisation wasn't needed) over 1600km to 2000km routes over water (hence 4 engines). With the rear cabin filled with fuel tanks ranges of 4000 miles could be reached with 9 passengers in large business class lounge seats. That meant Berlin to New York, Berlin to Africa and then Across the ocean to Sth America with important passengers and mail. This lubricated business.

However pressurisation and operational altitudes of at least 25,000ft was needed. One outcome was that Lufthansa had the Ju 252 converted from a mere improved Ju 52 into a pressurised enlarged trimotor.

Another was the Heinkel He 116 with Hirth Trubo chargers that was to fly over the Himalays at 25,000ft.

The collection of "Luft46" books I have invariably shows that German aviation firms had grand prewar plans for pressurised 100-150 passenger aircraft with turbo charged spark ignition engines or more likely diesels that could ply the Atlantic, Far Eastern, Sth American trade.

The war rather than accelerating technical progress may in fact have arrested it in some areas. (note the Boeing 307 stratoliner)

The point is there had been quite a lot of research into turbo charging prior to the war and valuable experience gained.

These German turbo charger experts invariably ended up being drawn into jet development.

The German high altitude program seems to have been after service ceilings of 50,000ft so was of a different nature. Thee reality is the tactical ground support requirements for the Luftwaffe made ultra high altitude of secondary concern in importance.

 

[Shortround6]

The German planes, as built, were propaganda machines. They did not make money on their own and relied on subsidies from the German government. To be fair so did most other airlines. Rapid communication was deemed to be of national importance ( as was prestige) and the subsidies of various forms (very generous air mail contracts for one) supported the Air line Industry. The DC-3 was the first plane that could operate without subsidies. This relied on a number of factors. Number of passengers vs fuel burned per hour/mile, maintenance costs, cruising speeds ( on short runs a fast plane could squeeze in an extra trip per day). Could the plane make not only enough money to support the operating costs but to actually repay it's initial cost in a timely fashion.

That was the Holy Grail of the airline industry. A plane that could pay it's operating expenses, re-pay the initial investment or loan for it's purchase and pay the initial investors/owners a profit. The Holy Grail for the air plane companies was a plane that would be sold in large enough numbers to not only make payroll but pay for the initial investment in tooling/factory space and pay the initial investors/owners a profit.

You don't do that by building 3 of this and 6 of that and 8 of another design. Same for the engine makers, you make money by building engines by the hundreds and hopefully thousands. A couple of dozen trick engines either loose money for the engine maker or run up the cost for the airplane buyer/s making it harder for them to pay-off the plane. If you have a rich uncle with deep pockets (government) interested in headlines things get a lot easier.

Not to pick on the Germans too much. I don't believe the whole Concorde thing ever made money for anybody except maybe the advertising agencies
Too few air-frames built, too few engines built, operating expenses through the roof. Ticket sales may not have covered operating expenses at times let alone repay investment.

Many companies sketched/drew large, long ranged airliners just before and during the war. The concept was there, the details often were not.

I think the US had built and flown around 100 turbo-charged aircraft by either 1940 or 1941 (the 50 Consolidated P-30s obviously made up 1/2) but there had a been a pretty steady succession of turbo aircraft from about the mid 20s onward. Most of these were single stage systems, there was no engine driven supercharger. But with 70-80 octane fuel there was only so much boost you could use. The US might not have had a large ground laboratory but it had thousands of hours of actual flight experience. Granted some of it was rather dated, some of the early turbo chargers were lubricated by squirting grease into them through zerk grease fittings with a grease gun, not something you want to do on long duration flights

Record setting flights by low capacity mail planes made head lines. They were not a commercial necessity.

 

[kool kitty89]

The alloy used in the turbocharged BMW801 was sicromal by Boehler, the same alloy used in the BMW 003 turbojet. In general small turbines for turbochargers suffered from non of the problems their larger turbojet variants suffered from and could even be fabricated by different techniques such as welding of the blade shank to the disk. In general I think they had much more problems with the ducting and perhaps housing.

This seems very possible. The materials required for high temperature turbines themselves would be similar to what the jet engines were working with but used in smaller quantities (and when supply shortages -especially Nickel- weren't so severe) and while those same alloy components were important for aircraft piston engine production to a very substantial degree, I could much more easily see issues with effective exhaust ducting being more severe. (that's a LOT more stainless steel than you'd need for the turbocharger hot sections alone and possibly even more difficult to engineer suitable non-strategic substitutes -exposing the exhaust ducts to slipstream or cowl-ducted cooling air might help but also reduce temperature/pressure of the exhaust gases and useful power available to the turbine -though also reduced thermal stresses on the turbine- while keeping ducting as short as possible would be even more significant than in contemporary American designs)

The installation used on the Jumo 207 seems to have been very compact with the turbocharger mounted directly against the rear of the engine and keeping the exhaust ducting very short. (and I believe the Jumo 207 was the only engine type implementing turbocharging in active military -or civil- operations in Germany prior to the end of WWII)

It's not as often cited as the concern over thrust losses, but the issue of material usage (or poor serviceability of alternatives) seems to be one of the reasons Heinkel moved away from jet engines buried in the fuselage with long exhaust ducting. (granted, that also wouldn't have precluded buried or semi-buried arrangements like the P-59, Mig 9, and Vampire used -or Heinkel's own proposed configurations for the P.1078) Admittedly, the external nacelle arrangement also made the issue of frequent engine changes more practical. (though the Vampire and P-59 didn't seem to limited in that regard either)

 

[Shortround6]

The temperature of the exhaust gases from a diesel are cooler than the exhaust gases from a spark ignition engine which makes it a bit easier to use turbos on a diesel.

 

[Juha]

...

The Fritz-X bomb was very accurate and reliable when it could be used. CEP's were in the 10s of meters and operational hit rates around 50%...

That's only possible in test enviroment, according to Martin Bollinger's recent book the real success rates of the Fritz X unit III./KG 100 were little under 6% of weapons carried, little under 10% of weapons launched and 14% of weapons guided, rather far cry to 50%.

 

[Koopernic]

That's only possible in test enviroment, according to Martin Bollinger's recent book the real success rates of the Fritz X unit III./KG 100 were little under 6% of weapons carried, little under 10% of weapons launched and 14% of weapons guided, rather far cry to 50%.

I have Bollinger's book on my kindle. Unsurprisingly you seem to have found (what page I can't find) the worst passible unit performance with the worst possible performance.

Bollinger also gives the success rate of the Hs 293 at 30% near misses that caused damage (page 172) which could be raised to 50% if a charitable interpretation that included near misses that caused light damage.

As far as the Fritz-X is concerned it had its greatest success by 1943 and wasn't used much for nearly a year. When it was it was at over allied invasion beaches at night or in the face of stiff fighter opposition. At this time the He 177 units were suffering a minimum of 20% monthly losses and often as high as 50%.

 

[Juha]

Difficult to see on what you are complaining, III./KG 100 was the Fritz-X unit and I gave the the results of it. That covers both the Do 217 and He 177 periods. And you first put forward the accuracy of Fritz-X on that thread but forgot to mention that that was the accuracy during the tests not that of combat situation. As usual the first ones were considerable better than the latter. The Graph is 12.1 and is it on the page 173 in the printed book. IMHO you should also read the text right after Graph 12.4 that might bring some reality to your appraisal of the effectiveness of the guided weapons of the WWII. They were a step forward but not yet a gigantic leap forward.