WWII MISTERIES: What happened with the JU390?

[Soren]

Soren - by the same logic LW leaders could not believe a single engine fighter like the Mustang, with extremely high performance, could escort daylight bombers past Berlin..

I've never heard of the Germans displaying any disbelief on that subject, esp. seeing they had captured quite a few examples of this a/c and thuroughly tested it in both flight and windtunnel tests. The tests ending with the conclusion the airfoil was disadvantaguous in all other aspects but drag reduction in straight flight.

The range of the Mustang was mostly due to its fuel capacity, a/c with similar fuel capacities flying similar distances.

[drgondog]

Originally Posted by Soren

I've never heard of the Germans displaying any disbelief on that subject, esp. seeing they had captured quite a few examples of this a/c and thuroughly tested it in both flight and windtunnel tests. The tests ending with the conclusion the airfoil was disadvantaguous in all other aspects but drag reduction in straight flight.

The range of the Mustang was mostly due to its fuel capacity, a/c with similar fuel capacities flying similar distances.

You took me a little too literally.

On the other hand the Luftwaffe didn't capture a Mustang until 3 months after the first Berlin escort mission. June 6, Cambrai. So they performed zero wind tunnel tests on the airframe until after June, 1944. The first one crashed and both the pilot and a/c were lost after Lerche flew it for some time. Look to pages 117-119 of his book.

Note his comments that of all the Me and Fw series of piston engine fighters flown by Luftwaffe aces in comparative tests, only the Dora and the 109G-10 'could more or less keep up with it.

As to the analogy I used. It was only after wind tunnel tests that they had a true understanding of the extremely low drag of the Mustang.

May I also draw your attention to the flat plate and wetted drag comparisons you showed a couple of weeks ago? The range was Definitely not Only due to fuel capacity.

Look to P-38, P-47 and F4U internal fuel capacity versus Mustang and re-think the point?

As to 'quite a few'captured, the number was IIRC two or three B's and one or two D's... the very first example on D-Day as noted above. The one picture I have seen of the first P-51D before LW colors were applied indicated September-October timeframe based on the Invasion stripe scheme and lack of nose cowl/rudder color scheme assigned to each fighter Group

[pbfoot]

Originally Posted by Soren

You'd need to know either the time or cruise speed along with distance to establish this Pbfoot.

So where did you get the 187 knot figure from ?

32 hours 6000 miles

[drgondog]

Originally Posted by Soren

Btw, the figures from U-boat.net are interesting, noting a top speed of 515 km/h at 6,200m. Now top speed is never anywhere close to the service ceiling so somehing aint right.

Sources are very different on this bird...

I think you are seeing several of my points as well as the questions that arise from the data.

Personally, I am inclined to believe that the ceiling was higher than the 'stated' 19,600 feet... and closer to B-29 for equivalent payloads. The real noticeable components of the 390 that might yield higher base drag components are a greater AR, 6 engine nacelle/wing body versus 4 for B-29, and what looks to be a thicker wing/chord..

Those factors MIGHT cancel out the lower wing loading.

Note also that one source says 267MPH cruise speed, and another says 267mph max speed with external load?

That smells like 200-220 max cruise speed for range calculations but no way of telling without the other data we have been looking for?

I'm strictly guessing when I say I THINK that the Ju 390 had to a.) have more fuel capacity than the B-29, which for block 25 forward according to Baugher had 9438 gallons for Ferry. Kiwi stated 10,000 gallons for the Ju 390.

If true for internal capacity of the Ju 390, I MIGHT be led to believe that the Ju 390 would have a max ferry range slightly greater than the B-29. Again, Baugher says 5800 miles max ferry with full internal fuel and no bomb load... but 3200 miles with 'normal' bomb load - which I think was closer to 12,000 pounds. Operations and ferry figure include reserve for climbing and also contingency at destination... usually 30 minutes minimum

So, I look at the Ju 390 one last time and I come to a "Guess" that a.) the BMW801E was at least 80% of the power of the B-29 at 25,000 feet, and b.) it had to cruise at the higher altitude to get 200-220 cruise speed, than the stated ceiling.

If the 801E was close to the power profile of the D-2 at 15,000 to 20,000 feet I just can't come close to believing any of the range figures..

Last - the Merlin 65/Packard 1650-7 fuel consumtion figures for the Mustang is 48 gallons per hour at 18,500 feet? Is there any way a very powerful radial matches the Merlin for fuel consumption/cruise settings? Kiwi stated 40-55gph at cruise? Another hard one to understand absent the real data.

Hence my 'suspicion' on all the link data on this bird. Call me a suspicious guy but those are the factors which had me scratching my head.

[Soren]

The high AR of the B-29's wing will increase lift whilst decreasing the drag, increasing the L/D ratio, a great advantage. I haven't looked into the difference in AR though, but even small differences have very noticable effects.

I too believe that the service ceiling of the Ju-390 was higher than 6 km, probably 8-9 km, but no more as the BMW-801 lost performance rapidly above 20,000 ft.

As for the P-51, we agree.

[drgondog]

Originally Posted by Soren

The high AR of the B-29's wing will increase lift whilst decreasing the drag, increasing the L/D ratio, a great advantage. I haven't looked into the difference in AR though, but even small differences have very noticable effects.

I don't have the Mean Chord for either but the Span>>2/Area gives 10 for the 390 and 11.5 for the 29, so it is significant.

I too believe that the service ceiling of the Ju-390 was higher than 6 km, probably 8-9 km, but no more as the BMW-801 lost performance rapidly above 20,000 ft.

As for the P-51, we agree.

I still wish we could find the data on the 801E. By all anecdotal accounts the 801Q was yet another boost to the 801 series and a direct derivative of the 801E

[Soren]

The 801E wasn't really any better than the D-2 at high alt, the 801F proves that. The 801 would need a turbo-supercharger to help it at high alts, just the like the R-2800 in the P-47.

Better L/D ratio of the B-29 also helped increase ceiling over the Ju390.

[Kiwikid]

Thank goodness I missed this ridiculous bun fight.

The Ju-390 has been quoted as using both the BMW-801D and BMW-801E engine. The "E" engine was experimental and never saw widespread use. The "E" engine had 2.5% better fuel performance.

The "E" engine differed in gearing for higher altitude and a better cooling fan/compressor. The figures for a BMW-801E are so marginally different as to be minimal and if you insist on the Ju-390 having flown to New York with BMW-801E engines then so much the better because that engine had slightly better fuel performance.

Drgndog you've quoted figured like 56 inches boost. That's claptrap!

drgndog said:

You believe a Truth but you don't have any of this to demonstrate you have an assembly of relevant facts? Nor does Kiwi.

I see however where you've made the mistake drgndog and it is understandable.

Yes you've published a report on BMW-801D performance in a range of rpm settings from 2150rpm to 2750rpm. (post#93)

What you seem unaware of Drgndog is the BMW-801D (and E) had an automatic fuel control system.

When run above 2150rpm the automatic fuel control switches the supercharger from low to high gear and fuel from lean to rich. That is why you have a table with much higher fuel consumption. It pays to cite facts in context.

The context is that this engine would not have been run at such settings by the Ju-390 except on take off and even then only for limited time.

You've cited a table for a fighter plane performance at high boost, high rpm and rich fuel mixtures. That does not translate to a Ju-390 at lower rpm with lean mixture and low boost.

I got involved because I saw an analysis that seemed reasonable to me based on the numbers presented. I got into this in more detail when Kiwi posed that nobody knew what they were talking about and proceeded to a.) get the math wrong by nearly 20% on his own figures and assumptions - much less any assumptions based on a referencable source that applied to the case in question.

As I have stated before I did not get the math wrong. I rounded down because I did not accept given the low wing loading that the climb would have been so protracted.

An Fw-190 A5 would reach 20,000ft in 15 minutes. I calculated that a Ju-390 would reach 20,000ft in 25 minutes because that is the time a fully laden B-29 needed to reach 20,000ft.

Then I rounded it down as you say by 20% because the Ju-390 has only 55% of the B-29's wing load and 18% more power. The Ju-390 also had an 85% better power to weight ratio than the B-29.

A realistic figure for the ju-390 to reach 20,000ft would be about 20 minutes, so please stop misleading people.

I did not get the maths wrong. I rounded down because I knew that the fuel consumption for a 25 minute climb was excessive and not supported by fact.

The math which you say I got wrong was an "ESTIMATE" for the climb. The maths for the cruise was essentially correct. the climb to altitude was an estimate... nothing more ...nothing less.

If you want to split hairs drgndog, had I assumed the same 15 minute time to altitude figures I could have halved the fuel estimate for the climb and you'd be none the wiser so please stop engaging in cheap shots.

If you want an honest debate then don't use intellectual dishonesty to win the debate.


In an altitude range of 14,000ft to 20,000ft with the early two stage supercharger used on "D" and "E" engines the manifold pressure at cruise settings of 1700hp and leaned fuel was 27 inches of mercury.

The supercharger did not change gear until 2150 rpm.

I'm willing to believe any performance figures based on either well founded calculations based on exhaustive wind tunnel results with at least one test flight to reference areas of agreement versus differences from the theoretical.

I am glad to hear that drgndog because NACA performed the tests you've referred to on the BMW-801D2

My information comes from the National Advisory Committee for Aeronautics (NACA) forerunner to NASA, Memorandum report #E5D19 "Characteristic of the BMW 801D2 Automatic Engine Control."

Flying at lean cruise settings and supercharger low gear up to 20,000 ft, the BMW-801D engine only burned 56.66 US Gals per hour. The "E" engine used 2.5% less fuel per hour.

I too believe that the service ceiling of the Ju-390 was higher than 6 km, probably 8-9 km, but no more as the BMW-801 lost performance rapidly above 20,000 ft.

Soren the BMW 801D2 would reach 36,000ft if pushed, but that tripled the fuel consumption. Critics of the New York flight cite BMW-801 fuel consumption at maximum power with rich fuel mixtures and high boost to justify claims that the flight couldn't have happened.

It's intellectually dishonest to cite such power settings as typical of a New York flight. No aircraft cruises at maximum power on a long range flight.

Through a process of logical deduction the cruise speed for such a mission appears to have been a very slow 167 knots at 20,000ft.

BMW-801E

The BMW801E engine: Version E was in fact modified D-2 used for prototype testing. It would have developed 2000hp in bench tests. It seemed to be produced in small number and to be delivered under designation TG and/or TH.

At take off power the BMW-801D used 200 US Gal per hour but could only maintain this for 3 minutes before overheating required throttling back.

At take off power the BMW-801E used 195 US Gals per hour. It also used water methanol injection to the supercharger intake at take off.

The biggest difference was a centrifugal air compressor which pushed air pressure from 1.39 atmospheres for the BMW-801D up to 1.62 atmospheres for the BMW-801E.

[Denniss]

Some "facts" need to be corrected:
1) The 4-stage BMW 801G was never built. The only G built was the 801G-2 and that was a D-2 geared for use in bombers while the D-2 was geared for use in fighters.
2) The Ju 390 did at least use the G-2, you can't use a D-2, geared for small and fast aircraft, in an aircraft that big and slow. Maybe it got uprated engines or not.
3) The Fw 190 A-9 did use the BMW 801S, that's a D-2 with improvements from the 801E/F program and with an improved(thicker) armored oil cooler ring.
4) The BMW 801 performance chart is for the engine without subtracting the power needed for the cooling fan, that's about 70 to 100 PS. This small note is missing on the US chart but visible on the german one.
5) The 801S or later are not to be identified by a 14-bladed fan, it was tested but it proved to suck too much power without improving cooling that much and they reverted back to the standard 12-bladed fan.
6) The often cited take-off power of the 801D-2/G-2 was 1700 PS, the 1730 PS were available at about 600m. The 801 A/B/C/L power was similar, 1560PS at sea level and the often cited 1600PS at about 1000 m

BTW: Dont trust "facts" from a site stating the BMW 801 was an 18-cylinder engine.

Another thought: Maybe it was possible to shut down one engine pair once at cruising altitude to conserve fuel ?

[Kiwikid]

This site gives a run down of distinctions in BMW801 engine types.

focke wulf 190 moteur bmw bmw801 bramo

There may also be confusion about the BMW-801E and BMW-801G because the BMW-801E was also known as the "TG"

2) The Ju 390 did at least use the G-2, you can't use a D-2, geared for small and fast aircraft, in an aircraft that big and slow.

Not quite correct Denniss as the Ju-290 sisters of the Ju-390 all had the BMW-801D engines.

I have seen references that the Ju-390 had both D and E type engines and one supposes that the E type was introduced after the first Ju-390 flights as an attempt to get better performance.

The gearing was in the supercharger and I have read of 4 stage superchargers late in the war.

[drgondog]

Originally Posted by Kiwikid

Thank goodness I missed this ridiculous bun fight.

The Ju-390 has been quoted as using both the BMW-801D and BMW-801E engine. The "E" engine was experimental and never saw widespread use. The "E" engine had 2.5% better fuel performance.

And your irrefutable source for this is?

The "E" engine differed in gearing for higher altitude and a better cooling fan/compressor. The figures for a BMW-801E are so marginally different as to be minimal and if you insist on the Ju-390 having flown to New York with BMW-801E engines then so much the better because that engine had slightly better fuel performance.

Depends on who you think is insisting?

Until i see cruise figures for the Ju 390, designer specs for fuel, real cruise settings for the BMW 801E for both max endurance and max distance - all of this discussion is essentially a 'legend'? IIRC You were the one that jumped in, insisted that it did and proceeded to screw up the math for your own assumptions

Drgndog you've quoted figured like 56 inches boost. That's claptrap!

??? are you referring to the P-47D-10 test figures I posted for Soren? Otherwise what are you talking about



I see however where you've made the mistake drgndog and it is understandable.

Yes you've published a report on BMW-801D performance in a range of rpm settings from 2150rpm to 2750rpm. (post#93)

Wiki - you have established three things so far.

1.) you can't do math to validate your own assumptions, 2.) you can't post anything of relevance to back up your assumptions, and 3.) you can't sort out who did what in this discussion.

I haven't posted ANYTHING on either the 801E or D or D-2 other than to refer to multiple references citing the multiple versions that independently claim the Ju 390 only flew in the V1 version, then the A1 version, then an A1 and A2 then a V1 and V2 then one cited the only one to fly of the V1 had a BMW801E.

Soren posted a performance chart for the D-2. So far you have posted nothing to back up your statements>

What you seem unaware of Drgndog is the BMW-801D (and E) had an automatic fuel control system.

You are correct. What I KNOW about the 801E can be written on the back of a matchbook cover with a paintbrush. I have not claimed expertise in the 801 of any series. You and Soren are having the expert discussion. So far he has posted data to back up the D-2, and you???

When run above 2150rpm the automatic fuel control switches the supercharger from low to high gear and fuel from lean to rich. That is why you have a table with much higher fuel consumption. It pays to cite facts in context.

Agreed. See above. Also note that facts without source of 'facts' is often dealt with some degree of scepticism.

The context is that this engine would not have been run at such settings by the Ju-390 except on take off and even then only for limited time.

On the other hand a P-47D-10 with an R-2800 might..

You've cited a table for a fighter plane performance at high boost, high rpm and rich fuel mixtures. That does not translate to a Ju-390 at lower rpm with lean mixture and low boost.

Maybe because the table for fighter performance at high boost, high rpm and rich fuel mixtures were for a P47D-10? Last time I checked that WAS considered a 'high performance' fighter in its day?



As I have stated before I did not get the math wrong. I rounded down because I did not accept given the low wing loading that the climb would have been so protracted.

You got the math wrong. This is a fact. You cleverly walked us through your own calculations

An Fw-190 A5 would reach 20,000ft in 15 minutes. I calculated that a Ju-390 would reach 20,000ft in 25 minutes because that is the time a fully laden B-29 needed to reach 20,000ft.

While Soren and I still believe the stated ceilings are wrong (6,000 m), that would suggest that 20,000 feet is un attainable under ordinary circumstances with a full load?

Then I rounded it down as you say by 20% because the Ju-390 has only 55% of the B-29's wing load and 18% more power. The Ju-390 also had an 85% better power to weight ratio than the B-29.

If the stated 801E reference is more reliable than you, then 1970Hp was achieveable... so which Hp table for the 801E do you wish to use? and at what altitude? Please post a reference chart.

A realistic figure for the ju-390 to reach 20,000ft would be about 20 minutes, so please stop misleading people.

See above. A realistic figure would be Never if the data are correct for the Service Ceiling. If you wish to refute the stated service ceilings then produce a fact based reference to show they are wrong and you are right.

I did not get the maths wrong. I rounded down because I knew that the fuel consumption for a 25 minute climb was excessive and not supported by fact.

So far everything you have written falls short of 'fact'

The math which you say I got wrong was an "ESTIMATE" for the climb. The maths for the cruise was essentially correct. the climb to altitude was an estimate... nothing more ...nothing less.

I fully understand a.) you were making assumptions, b.) you have nothing to back up your assumptions, and c.) your math based on your own assumtions was wrong

If you want to split hairs drgndog, had I assumed the same 15 minute time to altitude figures I could have halved the fuel estimate for the climb and you'd be none the wiser so please stop engaging in cheap shots.

My lack of wiseness in this discussion is based soley on conflicting references, no data from an accomplished pilot like yourself, no credible flight plan for a Ju 390 attempting a flight to New York, etc - THAT WOULD SUPPORT anything you have written so far.

If you want an honest debate then don't use intellectual dishonesty to win the debate.

Go find 'dishonesty' if you please?


In an altitude range of 14,000ft to 20,000ft with the early two stage supercharger used on "D" and "E" engines the manifold pressure at cruise settings of 1700hp and leaned fuel was 27 inches of mercury.

The supercharger did not change gear until 2150 rpm.



I am glad to hear that drgndog because NACA performed the tests you've referred to on the BMW-801D2

ROFLMAO - find ANY spot in the universe where I posted that!!

My information comes from the National Advisory Committee for Aeronautics (NACA) forerunner to NASA, Memorandum report #E5D19 "Characteristic of the BMW 801D2 Automatic Engine Control."

Flying at lean cruise settings and supercharger low gear up to 20,000 ft, the BMW-801D engine only burned 56.66 US Gals per hour. The "E" engine used 2.5% less fuel per hour.



Soren the BMW 801D2 would reach 36,000ft if pushed, but that tripled the fuel consumption. Critics of the New York flight cite BMW-801 fuel consumption at maximum power with rich fuel mixtures and high boost to justify claims that the flight couldn't have happened.

It sure wouldn't take a Ju 390 to 36,000 feet... not if Soren's figures on the D-2 are correct

It's intellectually dishonest to cite such power settings as typical of a New York flight. No aircraft cruises at maximum power on a long range flight.

Finally you have made a statement I agree w/o facts to base it

Through a process of logical deduction the cruise speed for such a mission appears to have been a very slow 167 knots at 20,000ft.

And you arrive at this how?

BMW-801E

The BMW801E engine: Version E was in fact modified D-2 used for prototype testing. It would have developed 2000hp in bench tests. It seemed to be produced in small number and to be delivered under designation TG and/or TH.

At take off power the BMW-801D used 200 US Gal per hour but could only maintain this for 3 minutes before overheating required throttling back.

At take off power the BMW-801E used 195 US Gals per hour. It also used water methanol injection to the supercharger intake at take off.

The biggest difference was a centrifugal air compressor which pushed air pressure from 1.39 atmospheres for the BMW-801D up to 1.62 atmospheres for the BMW-801E.

Before you complain about 'bun' fights, you ought to research who said what to whom.

[Denniss]

Originally Posted by Kiwikid

This site gives a run down of distinctions in BMW801 engine types.

focke wulf 190 moteur bmw bmw801 bramo

There may also be confusion about the BMW-801E and BMW-801G because the BMW-801E was also known as the "TG"



Not quite correct Denniss as the Ju-290 sisters of the Ju-390 all had the BMW-801D engines.

I have seen references that the Ju-390 had both D and E type engines and one supposes that the E type was introduced after the first Ju-390 flights as an attempt to get better performance.

The gearing was in the supercharger and I have read of 4 stage superchargers late in the war.

The site you linked has lots of errors. No large (bomber) aircraft used a 801D-2 or similar fighter engines, they all used the G-2 or similar bomber subtypes. 801A/L are the bomber subtypes of the 801C fighter engine. Even the famous Ju 88 G-1 landing with a functional FuG 220 Lichtenstein SN-2 radar on RAF Woodbridge in 1944 was equipped with 801G-2 engines.
There was no 801 with anything more than two superstarger stages/speeds in production, maybe excluding the turbocharged 801J and I really don't know the setup of the 1945 production 801F.

[Kiwikid]

You mean like you took me too literally about Ju-390 climb to 20,000ft to suggest I got my maths wrong ?

Originally Posted by drgondog

You took me a little too literally.

On the other hand the Luftwaffe didn't capture a Mustang until 3 months after the first Berlin escort mission. June 6, Cambrai. So they performed zero wind tunnel tests on the airframe until after June, 1944. The first one crashed and both the pilot and a/c were lost after Lerche flew it for some time. Look to pages 117-119 of his book.

Note his comments that of all the Me and Fw series of piston engine fighters flown by Luftwaffe aces in comparative tests, only the Dora and the 109G-10 'could more or less keep up with it.

As to the analogy I used. It was only after wind tunnel tests that they had a true understanding of the extremely low drag of the Mustang.

May I also draw your attention to the flat plate and wetted drag comparisons you showed a couple of weeks ago? The range was Definitely not Only due to fuel capacity.

Look to P-38, P-47 and F4U internal fuel capacity versus Mustang and re-think the point?

As to 'quite a few'captured, the number was IIRC two or three B's and one or two D's... the very first example on D-Day as noted above. The one picture I have seen of the first P-51D before LW colors were applied indicated September-October timeframe based on the Invasion stripe scheme and lack of nose cowl/rudder color scheme assigned to each fighter Group

... Well that's a very interesting assertion (that no Mustang was flown by Germans prior to 6 June 1944. Try this autobiographical account from Walther Dahl about a captured Mustang being flown by Zirkus Rosarius in 1943 complete with pictures.

Walther Dahl flys the P-51

Hungarian pilots were taught mock combat against captured Mustang T9+HK. That would date these flights to before Hungary capitulated to the Allies in March 1944.

Mustang T9+CK was being tested at Rechlin long before the Normandy landings.

[Kiwikid]

The site you linked has lots of errors. No large (bomber) aircraft used a 801D-2 or similar fighter engines, they all used the G-2 or similar bomber subtypes.

Except Deniss that it is well established the Ju-290 did use the BMW-801D so how do you explain this ?

[Soren]

The Ju-290 used the BMW-801D according to all my sources as-well.