Jumo 222: what went wrong?

[davebender]

A standard bureaucratic means to destroy or stonewall a project that cannot be canceled outright. Anyone who has spent several years pushing paper for the U.S. Government will recognize the technique.

The original April 1937 specification required 2,000 hp while running on B4 fuel. This specification was met in only 4 years. April 1941 100 hour endurance test @ 2,000 hp. IMO that's a fantastic achievement. Junkers should have been lauded for their good work and the engine should have been rushed into production. Instead Milch kept changing specifications until Junkers finally gave up.

 

[Shortround6]

It seems to me that perhaps politics is the reason that so many useless engines were actually manufactured. manufacturing engines by the dozens that will never be fitted to aircraft sure smacks of something besides good sense.

You make a lot of the 1941 100 hour "endurance test". was it really 100 hours at 2000hp or was it a standard type test in which the 2000hp rating is only 10-15% of the run time?

Both the Sabre and the Centaurus had passed type tests at over 2000hp by 1940 yet neither one was ready to actually go into service aircraft.

I don't know if Milch was behind the requirement that all these "advanced" German aircraft stay steadfastly twin engine aircraft or not. With the weight growth of many of the project aircraft the desired performance could not be meet with a pair of 2000hp engines. With the 4 engine option off the table there are two options left, accept reduced performance using the 2000hp engines or ask for more powerful engines to restore performance. Since any production manager of aircraft programs with the brains god gave a gnat knows full well that whatever weight escalation prototypes show in development, things will only get worse with the production models. This rather limits the practical application of option two, accepting lower performance with the 2000hp engine.
This leaves Milch with option 3 or perhaps with part option 2 and part option 3. OK production of the 2000hp version, accept lower performance of the production aircraft and hope Junkers can pull more power from the engine later before too many production aircraft are made or ask Junkers more more power as soon as possible to ensure that what ever service aircraft are made are really combat capable.

Unless Milch was the guy who insisted on changing the various bombers and other aircraft so they gained 10-20% in weight from initial estimates to flying prototypes he was caught in the middle.

 

[tomo pauk]

Kyrill von Gersdorff in "Flugmotoren und Strahltriebwerke". Hope your facility in the German language is up to snuff...

The most authoritative information available on this "beast".

Thank you, will check it out.

BTW, can you toss a sentence or two about the beast?

 

[Siegfried]

The Jumo 222 made tremendous progress. Development was started in 1938 or 37 depending in account. By comparison Sabre developement started in 34/35 and the CW R-3360 was already running in 1937 (and was still unreliable in 1943).

The lead engineer was Ferdinand Brandner, latter famous for leading production of the Jumo 004 turbojet before being taken as forced labour to the Soviet Union where he developed the giant NK-12 turbo-prop used in the Bear bomber(the soviets kept moving the development to various Bueros). After being free from captivity Brandener developed the E-300 turbo jet for the supesonic Hispano HA-300 (essentially a Messerschmitt Me 300 equal to the Mirage III and MiG 21).

Brandner wrote a memoir "Mein Lebben Zwichen Zewi Fronten" (My Life Between two fronts) in which he talks about the Jumo 222. I don't have the book but it is paraphreased on "Black Cross Ju 288/388/488" unfortunatly only briefly by non technical experts.

Essentially he says that in order to rashly achieve the 2500hp output requirement it was "developed to death" with 5 bore and 3 stroke changes.

The orginal approximetly 46L engine of the Jumo 222A1/B1 and A2/B2 was inreased to 55L in the form of the Jumo 222C/D, this used a more Daimler benze style of design. This too didn't work out in time anyway.

In the end, after a suspension from production and a low priority development program the original bore and stroke in the form of the Jumo 222A3/B3 and the two stage intercooled supercharger version the Jumo 222E/F achieved 2800hp and were back on the production schedule in 1944.

The engine has ignition problems and hot gas errosion problems, but these were overcome very early though I believe the ignition problems were remained difficult.

Milch eventually decoupled the Jumo 222 from the Ju 288 aircframe and proposed using the DB610, the coupled engine also used in the latter He 177A5, which was troublesome but powerfull. This variant of the Ju 288 was faster but much shorter range. Eventually when the Ju 288 was cancelled the Jumo 222 didn't have an airframe customer.

An German aviation historian Budras puts the seperation and cancellation down the Milch strategy to breakdown the Junkers/Jumo conglomerate. Milch was also known for perfering quantity of quality.

In the end the first airframe for the Jumo 222 would have been the Ju 388, essentailly a pressurised Ju 88/188 with remote controlled tail armament, estimated speed was 440mph.

The He 219 could also have been a 'customer' while the Do 335, Ju 488 and Ta 152 could have taken the engine.

Put that engine into a He 219 or Ju 88G or S even with only 2000hp and its a killer aircraft.

The engine was actually cleared for 2200hp short term takeoff by the time it was used in Ju 288 test flights.

Another issue was bearing materials, which were sleave bearings presumably using white metal since tin was an issue. Apparently bearing materials (tin) was in short supply and this was used to decide against Jumo 222 production as well. The Daimeler Benz engine had the unque characteristic of all WW2 engines of having roller bearings even for the big ends.

 

[davebender]

Why not the Do-217? The 2,000 hp Jumo 222A engine might have turned the promising but underpowered bomber into a winner.

 

[Siegfried]

Why not the Do-217? The 2,000 hp Jumo 222A engine might have turned the promising but underpowered bomber into a winner.

A variant of the Do 217 known as the Do 217M managed 347mph on a pair of 1750hp DB603A engines.

A cube law rule suggests the following speeds
1 With 2000hp 363mph
2 With 2200hp 374mph
3 With 2500hp 390mph

The Jumo 222E/F by virtue of its two stage supercharger was able to sustain power to much higher altitudes. It was estimated to drive the Ju 388L3 from about 410 to 440mph over the Jumo 222A3 version. This would push the Do 217 to about 420mph.

The Luftwaffe didn't have the luxury of large formations supported by hundreds of tons of windows/chaff and hundreds of jammers so high penetration speed, to delay interception and reduce warning time was critical. During the baby blitz Luftwaffe use of Duppel, their version of windows, almost managed to shutdown the British radar system due to specular reflection. There simply wasn't quite enough tonnage of it.

This is within the interception capabillity of the deadly Mosquito NF however the interception will occur much latter in the mission if at all, it will take more radar controller time. German night bombers had an effective tail warning radar; the FuG 217, it didn't just ring a bell, it gave range on a trace and was observed by the pilot (rather than gunner). Germans bombers that were intercepted seem to have been aware of the interception and returned fire as well as undertook evasive manouvers. Since the NF Mosquito had armoured glass and nose as well as 4 x 20mm Hispano guns the odds didn't favour the bombers weaker armament and lack of blind fire tail radar.

 

[davebender]

Perhaps so but as someone once explained to me, the larger engine allows higher cruise speed with payload and greater total payload. That's what really matters for a bomber.

If the Do-217 were powered by Jumo 222 engines and produced in greater numbers RLM could probably cancel the troublesome (as of 1942) He-177A bomber. It would also free up a few of the scarce (as of 1942) DB603 and BMW801 engines for other aircraft types.

 

[Shortround6]

not really, a 4000hp bomber with a 613 sq ft wing cannot do what a 6000hp bomber with an 1100sq ft wing can do.

This is a bit like saying that if a B-26 had 2000hp engines the British could have canceled the Lancaster...........oh, wait, the later B-26s did have 2000hp engines.

 

[Siegfried]

not really, a 4000hp bomber with a 613 sq ft wing cannot do what a 6000hp bomber with an 1100sq ft wing can do.

This is a bit like saying that if a B-26 had 2000hp engines the British could have canceled the Lancaster...........oh, wait, the later B-26s did have 2000hp engines.

USAAF bombers tended to have inadaquetly thought through bomb bay arrangments. Some German aircraft did as well but the Do 217 was well thought through. The Ju 88 had a small internal bay but had always been designed for external carriage (which actually made the aircraft faster even with bombs by allowing a narrowed down fueselage). The He 111 was essentially a high speed mail plane airliner had vetical bomb storage due to the spars of the wing interfering with the bomb bay.

As far as the B-26 was concerned, it wasn't that great in the bomb bay area, but it was still good enough to say that the B-26 could carry as much tonnage as the B-17 though not as high or as far. Had the B-26 received the planned for turbo charged R-2600 engine it would have been a 400mph machine able to fly as high as the B-17. Range probably still would have been somewhat less but one immagines somewhat more fuel could be squuezed in.

The Do 217 out performed the B-26 in every parameter: total bomb load, range, range vs payload, speed etc and it did so on less power. In return the B-26 offered a manned twin gun tail turret that i9n effect cost 62 mph in top speed if the B-26G is compared to the Do 217M. That is a lot of speed to sacrifice. This is not to say the Do 217 was unarmed: it had a ventral gondala which in combination with the dorsal turret and twin tail gave reasonble tail protection. Even the tail turret deficiency could likely have been dealt with by remote controlled tail armament.

As far as higher wing loading is concerned; its main effect is to increase takeoff run, which can be compensated for by more power though this only reduces the takeoff run, not the takeoff speed. Higher wing loading means less parastic drag which means more speed and in fact often more range.

 

[wuzak]

Doesn't high wingloading make for higher landing speeds also, which was more of a problem for the B-26 if I understand correctly.

 

[Denniss]

High wing loading also affected the max altitude - The Do 217 night fighter was extremly disliked as it barely reached 7km altitude if fully loaded with fuel. A known problem for the He 219 as well.

 

[Siegfried]

High wing loading also affected the max altitude - The Do 217 night fighter was extremly disliked as it barely reached 7km altitude if fully loaded with fuel. A known problem for the He 219 as well.

Indeed, but add 10% extra power, then one can fly 3% faster. However having 3% more speed also means 10% more lift. It basically translates into higher ceiling.

Both He 219 and Do 217 were underpowered.

The DB603A (used in most He 219 and many Do 217) had a power of 1750hp full pressure altitude of only about 5.3km. There was also the DB603AA which was tuned to a higher altitude (about 7km) but gave up some low altitude power (about 1585) but seems to have been little used. Thie DB 603A was the engine that powered most Do 217M/N and He 219

The He 219 had been designed around anticpation of the Jumo 222. The DB603 was a weaker alternative but the engine was supposed to be the 1900hp DB603G but this engine never became available (apparently used C3 fuel). The DB603G seems to be a DB603AA running of C3 so the aircraft ended up with a 1750hp engine with a full pressure altitude of only 5.3km.

(full pressure altitude is a figure of merrit where the supercharger maintains 1 atmosphere of pressure)

The DB603E which had 1850hp and a full pressure altitude of 7.3 on B4 fuel but was too late to see much service and a variant of this was the DB603EM with MW-50 and 2260hp, it needed C3 (initially) so it too never entered service.

This left the 2260hp DB603LA with its two stage supercharger and abillity to produce this with only B4 fuel. I believe 3 were delivered as part of the Ta 152C

The two most promising engines DB603 and Jumo 222 were somewhat inexplicably retarded.

 

[FLYBOYJ]

A cube law rule suggests the following speeds
1 With 2000hp 363mph
2 With 2200hp 374mph
3 With 2500hp 390mph

Providing that the extra horse power involves no more addition of weight which in the real world doesn't always happen. Additionally airframe stress must be calculated for the additional power. If one is adding 500hp more to an airframe and has to add 500 pounds more to the weight, things become more complicated

 

[johnbr]

I so a document a long time ago it had a drawing of a Do-217 with the BMW 802 in it.The 802 the designer said would have no trouble getting 3000hp out of it.

 

[davebender]

I suspect that wasn't the only reason.

You don't turn a heavy bomber into fighter simply by changing the model designation. IMO the Do-217 had no business being used as a night fighter.

 

[Siegfried]

I so a document a long time ago it had a drawing of a Do-217 with the BMW 802 in it.The 802 the designer said would have no trouble getting 3000hp out of it.

A fascinating engine, it was an 18 cylinder radial built on the bore of the 14 cylinder BMW 801 but with a longer stroke. It would have been known as an R-3600 under an American designation system. (Possibly an R-3560 as the master rod had a different stroke?). One unique planned feature of the engine was variable exahaust valve timming. It had a two stage three speed supercharger and a turbo was also planned. There is more than one way to skin a cat. Out of the three 'hyper engines' the X-24 DB604, the 24 cylinder 4 row water cooled Jumo 222 and the BMW 802 only the Jumo 222 seems to have gotten as far as an airframe. The engine did run on the Bench but The 802 seems to have been abandoned in 1943 as the focus went to the BMW 801. However some engineers at BMW though it was pointless pushing the BMW 801 and it was better to transfer to the BMW 802.

 

[davebender]

I don't think they had any choice. The BMW801 required a long time to perfect.

If the BMW801 had produced 1,750hp during 1941 running on B4 fuel with an endurance of 100 hours then BMW might have shifted development resources to their next generation engine.

 

[Denniss]

The DB603A (used in most He 219 and many Do 217) had a power of 1750hp full pressure altitude of only about 5.3km. There was also the DB603AA which was tuned to a higher altitude (about 7km) but gave up some low altitude power (about 1585) but seems to have been little used. Thie DB 603A was the engine that powered most Do 217M/N and He 219

The DB603E which had 1850hp and a full pressure altitude of 7.3 on B4 fuel but was too late to see much service and a variant of this was the DB603EM with MW-50 and 2260hp, it needed C3 (initially) so it too never entered service.

Several correction here:
1) DB 603A rated alt was 5.7 km
2) take-off power of the 603AA was 1670PS and rated alt was 7.3 km
3) take-off power of the 603E was 1800PS and rated alt was 7 km
4) Most He 219 A-0 used the 603A, A-2 used 603AA, A-7 had 603E

 

[davebender]

The success of Daimler-Benz V20 marine engines has me wondering about the DB604, Daimler-Benz's competitor to the Jumo 222.

Most sources quickly dismiss the DB604 as inferior to the Jumo 222 but is that really true? The Daimler-Benz V20 was considered very reliable. That experience should have given them a development edge over Junkers for making large engines. It's nothing but a hunch but I suspect politics was the primary reason for selection of the Jumo 222 over the DB604.

 

[johnbr]

Do's any one here have info on the Db-h16 that was also made .All I now is it put out 2000hp.