Junkers Ju288 as four engine bomber

[Deleted member 1487]

What is as a backup project in case the He177 or the Jumo 222 engine didn't work out the Ju288 was also developed into a four engine version starting in 1940 using existing Jumo 211 engines? It's performance wouldn't have been as great as that projected for the Ju288, but it would likely have been production ready by 1942 and considerably better performance than the Ju88/188/388 and Do217 using existing mass produced engines. IOTL the Luftwaffe did try this approach too late with the Ju488 and relied on using the Jumo 222 for it, but I don't see any reason why it wouldn't have been viable with four lower powered engines. It could retain the playload of the Ju288, which was considerable, though not quite as good as the He177, but be lighter, use some parts from the Ju88 developments, while the Ju288 was designed around being a mass produceable, assembly line product.
http://www.flugzeug-lorenz.de/index.php?id=109

If operational in 1942 as a fast, high altitude long range bomber and recon aircraft what sort of impact could it have had?

 

[brazen]

Nothing really to be fair, it's going to get chopped to pieces of it trys to attack the UK due to the air defence system.

Against the Russians it will probably be almost invunerable at altitude for the majority of the time but It would never be deployed in the numbers needed to have a decisive influence.

 

[Deleted member 1487]

Nothing really to be fair, it's going to get chopped to pieces of it trys to attack the UK due to the air defence system.

Not so sure in 1942 that would be the case, though it would more likely than not have to attack at night. From 1943-45 though yes. The thing is it could be used in the Mediterranean to attack deep British targets in Egypt, which could be very profitable. There is also the Battle of the Atlantic where the speed and altitude, not to mention range would be very useful.

Against the Russians it will probably be almost invunerable at altitude for the majority of the time but It would never be deployed in the numbers needed to have a decisive influence.

I'm not so sure about that given how much effort was put into optimizing the aircraft for mass production (the Bomber B after all was to replace all 2 engine bombers and most of the need for a four engine) and how resources were wasted IOTL on the He177/Ju290/Ju390/Ju188-488.
1200 Ju188s were built IOTL, about 1200 He177s, about 100 Ju388s, 65 Ju290s, 2 Ju390s, 276 Fw200s, etc.

Cancelling the Ju 188 (IOTL built as a stand in for the 288) and He177 in 1941-2 saves a lot of production resources for the Ju288 four engine. Plus all the OTL resources pushed into tooling up for the Ju288 aren't wasted either (hundreds of millions of Reichsmarks worth). No reason then that they couldn't have made several thousand of them just on the OTL resources put into the Ju288 project+no Ju188/388+a cancelled He177 before it enters production. Plus you could arguably cut some of the He111, Ju88 (H series long range variant for naval and recon use), and Do217 production to get more resources, as IOTL those aircraft were shoe-horned into strategic or at least long range operational bombing that could be done better by something like a four engine Ju288. Even a limited number of long range bombers in 1942 would be helpful and by 1943 you'd have a lot of them to launch a more serious series of long range attacks.

 

[Coiler]

Against the Russians it will probably be almost invunerable at altitude for the majority of the time but It would never be deployed in the numbers needed to have a decisive influence.

Assuming they don't build or (more likely given the expense and niche) get lend-leased high altitude interceptors of their own.

 

[Deleted member 1487]

Assuming they don't build or (more likely given the expense and niche) get lend-leased high altitude interceptors of their own.

The issue there is whether those aircraft as fast climbing enough to intercept at high altitudes and of course what sort of GCI/radar network they have in place to get fighters airborne in time. The Soviets badly lagged on that front IOTL and only got the necessary equipment in quantity via LL in 1944. Even then there were problems with Soviet intercept ability, as the bombing of Poltava in 1944 showed.

 

[tomo pauk]

What is as a backup project in case the He177 or the Jumo 222 engine didn't work out the Ju288 was also developed into a four engine version starting in 1940 using existing Jumo 211 engines? It's performance wouldn't have been as great as that projected for the Ju288, but it would likely have been production ready by 1942 and considerably better performance than the Ju88/188/388 and Do217 using existing mass produced engines. IOTL the Luftwaffe did try this approach too late with the Ju488 and relied on using the Jumo 222 for it, but I don't see any reason why it wouldn't have been viable with four lower powered engines. It could retain the playload of the Ju288, which was considerable, though not quite as good as the He177, but be lighter, use some parts from the Ju88 developments, while the Ju288 was designed around being a mass produceable, assembly line product.
http://www.flugzeug-lorenz.de/index.php?id=109

If operational in 1942 as a fast, high altitude long range bomber and recon aircraft what sort of impact could it have had?

From technical and risk stanpoints, going with 4 mass-produced engines on a bomber has many of advantages vs. a bomber that relies on just 2 spanking new engines - obviously, there is no risk that engines will not be there when needed, 4-engined bombers usualy have superior lift capacity than 2-engined types, engine-out situation on a heavily-laden A/C is a managebale thing. Less diluted development work on engines is also a benefit. Just see Manchester vs. Lancaster.
4-engined bombers are also better use of crew - one gets better payload/range vs. crew needed.
As far as lift capacity, we can take a look at Halifax I - on 4x Merlin X (1150 HP each), it was good for 13000 lbs, 1000 miles range.

The 4-engined spin-off of the Ju 288 would not be a high altitude long range bomber in the vein of B-24, meaning still requiring escort.

 

[Zheng He]

Operational in 1942? It has no impact at all - the Allies overwhelming advantages are starting to kick in and it will be a resource intensive weapon system to build, operate, crew, and maintain and those resources are not going toward other things.

 

[Deleted member 1487]

From technical and risk stanpoints, going with 4 mass-produced engines on a bomber has many of advantages vs. a bomber that relies on just 2 spanking new engines - obviously, there is no risk that engines will not be there when needed, 4-engined bombers usualy have superior lift capacity than 2-engined types, engine-out situation on a heavily-laden A/C is a managebale thing. Less diluted development work on engines is also a benefit. Just see Manchester vs. Lancaster.
4-engined bombers are also better use of crew - one gets better payload/range vs. crew needed.
As far as lift capacity, we can take a look at Halifax I - on 4x Merlin X (1150 HP each), it was good for 13000 lbs, 1000 miles range.

The 4-engined spin-off of the Ju 288 would not be a high altitude long range bomber in the vein of B-24, meaning still requiring escort.

It wouldn't have the range or payload of the B24 for sure, but it certainly would have a major speed advantage, while the 1942/3 Jumo 211F/Js would still have pretty solid altitude. Plus if we are also considering a power egg so that DB engines saved from the He177 could be used as well (the Do217 had that to drop in either the BMW or Jumo 213 and DB603 engines), we can look at the performance of the DB605 and later 603 engines.

For reference the top speed of the B24 is 303mph, the Ju288 wouldn't be less than 350mph, probably closer to the 388mph of the Ju288B with DB606 engine considering it is going to maintain a similar power output, but increase in weight due to the larger wing span (though two Jumo 211s actually are lighter than one DB606). Also the Ju288 was at max 21,000 kg loaded, the B24 normal loaded weight was 25,000kg. 4 tons savings with a more powerful engine (Jumo 211F/J was 150-200hp hundred HP more powerful than the B24's Twin Wasp) mean considerably improved performance.

For 1942-43 it would be about as fast as the contemporary Mosquito bomber with larger payload. With increased power DB605's with improved supercharger it would still at least match the 1944 Mosquito too.

And Tomo you'll love this, the Ju288 could carry two 2500kg bombs internally.

Operational in 1942? It has no impact at all - the Allies overwhelming advantages are starting to kick in and it will be a resource intensive weapon system to build, operate, crew, and maintain and those resources are not going toward other things.

Against Britain sure, but in the Atlantic, Mediterranean, and Russia it would have a lot of use due to the range, speed, and payload. By 1944 outside of the East or at night it would be likely too vulnerable even with better engines.

 

[tomo pauk]

It wouldn't have the range or payload of the B24 for sure, but it certainly would have a major speed advantage, while the 1942/3 Jumo 211F/Js would still have pretty solid altitude. Plus if we are also considering a power egg so that DB engines saved from the He177 could be used as well (the Do217 had that to drop in either the BMW or Jumo 213 and DB603 engines), we can look at the performance of the DB605 and later 603 engines.

Jumo 211F & J were making 1060 and 1100 PS at best altitude of 5-5.5 km, respectively, 30 min rating, or 900-950 PS max continuous. Granted, the Db 601E/605A will do better.

For reference the top speed of the B24 is 303mph, the Ju288 wouldn't be less than 350mph, probably closer to the 388mph of the Ju288B with DB606 engine considering it is going to maintain a similar power output, but increase in weight due to the larger wing span (though two Jumo 211s actually are lighter than one DB606). Also the Ju288 was at max 21,000 kg loaded, the B24 normal loaded weight was 25,000kg. 4 tons savings with a more powerful engine (Jumo 211F/J was 150-200hp hundred HP more powerful than the B24's Twin Wasp) mean considerably improved performance.

B-24 have had 1200 HP from SL to 25000 ft (military power), or 1000-1100 HP max continous - the turbosupercharger investment paying off there nicely. The Jumo 211F & J were making 800-850 PS at 25000 ft, 30 min rating, or 750-800 PS max cont.
The weight of 4-engined Ju 288 will go up vs. 2-engined historical Ju 288, since there will be chnages and strengthening of the wing and U/C.

For 1942-43 it would be about as fast as the contemporary Mosquito bomber with larger payload. With increased power DB605's with improved supercharger it would still at least match the 1944 Mosquito too.

The resulting A/C would've probably been in-between with the DB-610 powered He 117 and Ju 288 versions, indeed at least 350 mph at ~6 km.
We should be wary of manufacturer's estimates, though.

And Tomo you'll love this, the Ju288 could carry two 2500kg bombs internally.

I love it alredy.

 

[Deleted member 1487]

Jumo 211F & J were making 1060 and 1100 PS at best altitude of 5-5.5 km, respectively, 30 min rating, or 900-950 PS max continuous. Granted, the Db 601E/605A will do better.
B-24 have had 1200 HP from SL to 25000 ft (military power), or 1000-1100 HP max continous - the turbosupercharger investment paying off there nicely. The Jumo 211F & J were making 800-850 PS at 25000 ft, 30 min rating, or 750-800 PS max cont.
The weight of 4-engined Ju 288 will go up vs. 2-engined historical Ju 288, since there will be chnages and strengthening of the wing and U/C.

How long could the B24's engines sustain that vs. the Jumos? The engine power of the B24s relied on 100 octane fuel and full boost, which IIRC was only sustainable for about 5 minutes at a time. I'd also like to see that Twin Wasp max continuous at altitude rating in a chart if you have one.

The Ju288B weight I listed was for the DB606 model, where the engine was already 1,500kg, about the weight of two Jumo 211s. The wing would have to be lengthened of course with 4 engines, but the wings were already modified to take the heavier DB606 engines and more powerful torque.

The resulting A/C would've probably been in-between with the DB-610 powered He 117 and Ju 288 versions, indeed at least 350 mph at ~6 km.
We should be wary of manufacturer's estimates, though.

Not really, as the performance and weight listed were for the Ju288B, which was using the 1.5 metric ton DB606 and was actually flown. If anything it would have been very close to the already modified Ju288B's weight and performance considering it is maintaining a similar overall power and weight, just increasing the drag due to the extra nacelles and having greater span. The He177 was much bigger and heavier.
The Ju288C (with DB610 engines) was actually production ready by 1943 and planned to be phased in in 1944, but the fighter emergency program cancelled the project.
https://de.wikipedia.org/wiki/Junkers_Ju_288#Ju_288_C
The max speed was apparently 655km/h or ~407mph with the pre-production model. Granted that was using the more powerful twinned DB605 engines, which put out about 2900hp and 2x 1943 Jumo 211Fs aren't going to quite match in output, especially when driving separate props.

 

[tomo pauk]

How long could the B24's engines sustain that vs. the Jumos? The engine power of the B24s relied on 100 octane fuel and full boost, which IIRC was only sustainable for about 5 minutes at a time.

The supercharger system used on B-24s (turbosupercharger + engine-stage S/C) was superior than supercharger system of Jumo 211s (engine-stage S/C only). Hence better altitude power.
Max continuous is the power that engine is supposed to make as long as there is enough of fuel and lubricant.

I'd also like to see that Twin Wasp max continuous at altitude rating in a chart if you have one.

No problems:

The Ju288B weight I listed was for the DB606 model, where the engine was already 1,500kg, about the weight of two Jumo 211s. The wing would have to be lengthened of course with 4 engines, but the wings were already modified to take the heavier DB606 engines and more powerful torque.

Wing will probably receive the 'plug' next to the fuselage, obvioulsy at each side. That will add weight and drag (= bad), and probably lower the wing loading (=good for a bomber).

Not really, as the performance and weight listed were for the Ju288B, which was using the 1.5 metric ton DB606 and was actually flown. If anything it would have been very close to the already modified Ju288B's weight and performance considering it is maintaining a similar overall power and weight, just increasing the drag due to the extra nacelles and having greater span. The He177 was much bigger and heavier.
The Ju288C (with DB610 engines) was actually production ready by 1943 and planned to be phased in in 1944, but the fighter emergency program cancelled the project.
https://de.wikipedia.org/wiki/Junkers_Ju_288#Ju_288_C
The max speed was apparently 655km/h or ~407mph with the pre-production model. Granted that was using the more powerful twinned DB605 engines, which put out about 2900hp and 2x 1943 Jumo 211Fs aren't going to quite match in output, especially when driving separate props.

4x DB 605A at 5.7 km = 5000 PS at 5.7 km, 30 min rating, or 4300 PS max continuous.
On same altitude, 4x Jumo 211F & J will do 4000-4200 HP at same altitude, 30 min rating, or 3700-3900 on max cont. Going for 4 separate engines vs. 2 twinned will should also mean additional engine drag, that we add to the greater drag of the now bigger wing.

 

[Carl Schwamberger]

...

Against Britain sure, but in the Atlantic, Mediterranean, and Russia it would have a lot of use due to the range, speed, and payload. By 1944 outside of the East or at night it would be likely too vulnerable even with better engines.

If used in significant numbers over the Atlantic it might prod the Allies into providing more VLR ASW aircraft sooner & in larger numbers.

 

[iani]

Wouldn't Wetland just have made more Welkins?

 

[Deleted member 1487]

If used in significant numbers over the Atlantic it might prod the Allies into providing more VLR ASW aircraft sooner & in larger numbers.

Not sure how that follows given that the VLR ASW would be for fighting submarines rather than aircraft. CAM ships and escort carriers would be a better counter to VLR Luftwaffe aircraft.

 

[Deleted member 1487]

The supercharger system used on B-24s (turbosupercharger + engine-stage S/C) was superior than supercharger system of Jumo 211s (engine-stage S/C only). Hence better altitude power.
Max continuous is the power that engine is supposed to make as long as there is enough of fuel and lubricant.

Right, for boosting I thought. I found a chart from GE that supports what you're saying, I'm just trying to understand how it increases performance at high altitude outside of the boosted performance numbers.

No problems:

Thanks. The weights are considerably higher than that listed on wikipedia, which makes just the engine (not sure if that includes the turbosupercharger) much closer to the Jumo 211.

Wing will probably receive the 'plug' next to the fuselage, obvioulsy at each side. That will add weight and drag (= bad), and probably lower the wing loading (=good for a bomber).

"Plug"?

4x DB 605A at 5.7 km = 5000 PS at 5.7 km, 30 min rating, or 4300 PS max continuous.
On same altitude, 4x Jumo 211F & J will do 4000-4200 HP at same altitude, 30 min rating, or 3700-3900 on max cont. Going for 4 separate engines vs. 2 twinned will should also mean additional engine drag, that we add to the greater drag of the now bigger wing.

I wonder what the wing alterations would look like given just how massive the DB606/10 was.

Versus the Ju488 (used bigger engines than the Jumo 211 or Db605 and a larger, longer fuselage):

 

[Deleted member 1487]

Wouldn't Wetland just have made more Welkins?

Not sure they were really any better than the Mosquito for bomber interception, plus they only entered service in mid-1944.

 

[tomo pauk]

Wouldn't Wetland just have made more Welkins?

Welkin, at altitudes where it was supposed to fight (30000-40000 ft) was probably more of a threat to itself than to an enemy aircraft.
RAF will be better served with hi-alt Spitfires and Mosquitoes.

Right, for boosting I thought. I found a chart from GE that supports what you're saying, I'm just trying to understand how it increases performance at high altitude outside of the boosted performance numbers.

Thanks. The weights are considerably higher than that listed on wikipedia, which makes just the engine (not sure if that includes the turbosupercharger) much closer to the Jumo 211.

I don't get the bolded part.
Boosting is not a dirty word, any meaningful aircraft engine used boost - as much as S/C can provide it, and engine can stand it. Greater boost means that engines have more air that runs towards cylinders; more air = more power. Air is very thin above 20000 ft, compressors are needed to compress it.
Jumo 211 have had just one stage of supercharging (engine-stage S/C; pressure ratio of 3:1 max) = not a great power above 15000-20000 ft. Engines on B-24 have had 2 stages of supercharging (turbo + engine-stage S/C; pressure ratio of perhaps 5:1) = good power above 20000 ft.
Engines listed at the doc above are without turbo system. For liquid-cooled engines, there is also weight of cooling system to accout for.

"Plug"?

An insert to increase wing size, sorta what the Bf 109H got.

 

[Deleted member 1487]

I don't get the bolded part.
Boosting is not a dirty word, any meaningful aircraft engine used boost - as much as S/C can provide it, and engine can stand it. Greater boost means that engines have more air that runs towards cylinders; more air = more power. Air is very thin above 20000 ft, compressors are needed to compress it.
Jumo 211 have had just one stage of supercharging (engine-stage S/C; pressure ratio of 3:1 max) = not a great power above 15000-20000 ft. Engines on B-24 have had 2 stages of supercharging (turbo + engine-stage S/C; pressure ratio of perhaps 5:1) = good power above 20000 ft.
Engines listed at the doc above are without turbo system. For liquid-cooled engines, there is also weight of cooling system to accout for.

I didn't mean it is a dirty word, just that boost was something that could only be sustained to a limited degree to avoid heat build up. That is, WEP. Of course I suppose it makes sense that greater air pressure matching that of low altitude pressures would boost performance, but any idea what max continuous power was at 1000m or so?
Any idea why the Jumo 211 didn't get a two stage supercharger?

An insert to increase wing size, sorta what the Bf 109H got.

Gotcha, thanks, though it looks from the comparison pics I posted that there might not need to be much wing span increase.

 

[tomo pauk]

I didn't mean it is a dirty word, just that boost was something that could only be sustained to a limited degree to avoid heat build up. That is, WEP. Of course I suppose it makes sense that greater air pressure matching that of low altitude pressures would boost performance, but any idea what max continuous power was at 1000m or so?

In-service R-1830s were never cleared for WEP, whether on fighters or on bombers. On R-1820 and R-2800, it took water/alcohol injection to achieve WER; also for the planned turboed R-2000.
Max continuous power on the turboed R-1830 of ww2 era was 1000-1100 HP from sea level to 20000-25000 ft, depending on version.

Any idea why the Jumo 211 didn't get a two stage supercharger?

A million dollars question. Especially when we recall that "Junkers motoren" was making 2-stage superchargers in 1930s for altitude records.
When it is about military-service-worthy 2-stage supercharged engines for ww2, German aero-engine companies (not just them, of course) lagged behind RR, P&W and Allison in design & production of those.

 

[thaddeus]

when the "power system" scenario did not work for JU-288 wonder if a trimotor arrangement might have served? (using the Jumo 211s)