WWII MISTERIES: What happened with the JU390?

[pbfoot]

Originally Posted by Kiwikid

Well sad to say Richard leonard got the calculations grossly wrong because he assumed 150 US gals per engine for the cruise and then multiplied that by 6 engines.

The truth is that the true figure is 45-55 US Gals per hour x 6 engines.

You have to start with the right consumption assumption. Sorry couldn't resist that.

I used your numbers and did some quick math with the available weight , weight of gas and 55 gph per engine overall rounded off to take account of climb etc. Its all rough numbers but so would the flight planning be without proper consideration for winds aloft and other factors that would affect things the 390 wouldn't have knowledge of , considering it would be tough to climb over weather with the low service ceiling

[Kiwikid]

Hi Pb,

All I did was calculate take off and climb to 20,000ft and then the fuel needed for 31 hours of flight.

The endurance would easily permit a return Atlantic mission. Jetstreams would not figure much at 20,000 feet. I have to pop out for an appointment, but will be back later to discuss it.

There is a rumour which I am unable to substantiate that the flight may have been from Norway to Michigan then past new York on it's return to Mont de Marsan, but I can't contact the source for this.

[drgondog]

Originally Posted by Kiwikid

Operational notes for the Ju-390 including payload range charts, from one of it's test pilots, Han Pancherz have been published in a couple of books including the autobigraphy of Pancherz who lives in Barcelona. From time to time Pancherz gives interviews about the Ju-390 to Spanish newspapers.

If you're not prepared to accept the data from the aircraft's test pilot then you're unlikely to accept any amount of evidence.

Kiwi - data from a single source, and a personal one at that, unmatched by other sources would lead me to at least hold belief in suspension. I'm glad you aren't a cynic like me

Incidentally since you ask drgndog the Ju-390 had a service ceiling of 20,000 feet.

Yes, I believe that is what the link I posted said.. back to this later

A any pilots will know the take off and climb are always the most thirsty part of a flight whether it's a WW2 Ju-390 or Boeing 737. Most aircraft burn a lot of fuel climbing to cruise altitude and then generally fuel flow reduces to around 30% but that is variable according to the type of aircraft and it's specific engines.

I'm quite well aware of that, but thanks for helping me further understand. The fuel flow from max power to optimal cruise varies quite a bit. For a P-51D the max is around 240 Gallons per hour and minimum cruise fuel consumtion was approx 48gph at 18K/1800rpm and 23" for a combat load

References ?
Because I don't speak German I have not read his autobiography, but there is a book called FlugPancherz. Pancherz's figures and charts are also published in "Target America, Hitler's plan to attack the United States" by James P Duffy, Pub 2004 by Greenwood Press ISBN 0275966844

There are numerous other references so I only refer you to those from the test pilots own notes.

As a pilot though, you saw enough data to believe the claims? What was the test pilot's stated optimal cruise altitude and speed for the Ju 390? As a pilot you know that the best cruise is never at max altitude?



Yes I fumbled some figures from the climb. As I recall when I calculated it I rounded some of the numbers because you can't be precise about the climb f you don't know the exact time to climb. In general my figures are more real than Leonards which I suspect are based on Kossler and Ott's figures.

And why is that? Did Leonard fumble his figures also? And what assumptions that you made are any more valid than his. So far this whole discussion including mine, are laced with 'assumptions' - said assumptions leaning to one side or the other in the debate - but assumptions nevertheless?

55 US gals per hour is per engine incidentally in case that was not clear.

I believe you stated 45-55 as the BMW801E fuel flow for your assumptions. What is not clear are two factors not in your assumptions - first is the cruise speed at that fuel flow, the second is the rated altitude for best cruise efficiency

As a pilot drgndog I do understand the difference between long range cruise and economical cruise. I also understand the difference between ferry range and max payload range thank you.

Actually I wasn't directing that comment at you.

Seek and ye shall find. The fuel consumption figures for BMW801 engines are well known and widely published for all to see.

Back to your point about the Ju 390 ceiling at 20,000 feet.

As a pilot isn't it curious to you that an aircraft with greater horsepower and lighter wing loading than a B-29, as presented above....

but can barely climb to 60% of the ceiling of the higher flying, faster B-29 which has less power and a higher wing loading (according to the 'published data)?

As a pilot, wouldn't you want to know more about the flight test data gathered before an alleged flight to New York, so that you had a lot of cofidence in matching a landing on land with a take off on land?

Wouldn't you want to know the specific altitude and rpm and boost and fuel flow to optimize your range - and what that cruise speed was? And wouldn't you be more confident in your beliefs if you had that data?


I look at the widely varying data available on the Ju 390 and keep asking myself fundamental questions.

Why would an aircraft like this, with 6 x 2000 hp and a wing loading less than a B-29 attain such poor performance unless the aircraft was seriously dirty, aerodynamically speaking. Particularly when you have made the point that this engine was one of the very best the LW had in Hp/wt ratio and performed well up to 40,000 feet. So it couldn't be that the engines would not perform.

So either the specs as given are wrong, or the aircraft was an enormous hog and NEEDED that much hp just to get it to 20,000 feet.

As a pilot, what conclusions do you draw?

[pbfoot]

Originally Posted by Kiwikid

Hi Pb,
The endurance would easily permit a return Atlantic mission. Jetstreams would not figure much at 20,000 feet. I have to pop out for an appointment, but will be back later to discuss it.
.

That is an extrodinary time aloft if my recollection is correct I believe the record for that amount time aloft without refuelling goes to the CP 07 Argus at 31 hours using the same powerplants as the B29 but much uprated to 3700 hp and thats a record only surpassed by Bert Rutans Voyager

[Soren]

The ceiling of the Ju-390 was low because of the very poor high alt performance of its BMW-801 engines. At SL it climbed allot faster than the B-29.

Hence the short take off & landing roll of the Ju-390 Kiwikid.

At any rate the He-277 was a much better bomber, with a payload capacity larger than that of the British Lancaster, an amazingly high service ceiling, cruise speed and a good defensive armament & top speed, it was technically the best bomber of WW2.

[Kiwikid]

Soren raises a valid point that the Ju-390 was in response to an RLM specification for the so called Amerika bomber issued about 1942 and it was dated by 1945.

Better aircraft were available by 1944/45 including the He-177 with many engine overheating issues and the French built He-277. A conventional four engined version of the He-177

Soren you may have heard of the airport built near Oslo in the middle of a forrest called Gardermoen ?

At the end of the war 40 large bombers were found at the airfield in preparation for a mission to attack the United States. They were described as He-177 but may have included about 6 or 7 missing He-277. There is little accurate information available about Gardermoen, except that it had a very long purpose built runway for attacks on USA.

Re earlier Ju-390 posts, I can't recall the source at present but I understand the Ju-390 had a cruise around 240 knots. The maximum speed is often cited, but maximum speed is unhelpful.

Warbirds Resource Group refer to the Ju-390 with external bomb load at 267 knots cruise. The Ju-390 V1 coded RC+DA had a bomb aimer's gondola and appears to have been the maritime patrol bomber.

[Kiwikid]

drgndog asked:

So either the specs as given are wrong, or the aircraft was an enormous hog and NEEDED that much hp just to get it to 20,000 feet.

The wing loading is easily calculated from the Ju-390's wing area and MTOW, both of which are well known and documented with corroboration by the test pilot after the war.

The issue is limited engine performance at altitude. The B-29 for it's faults had massively supercharged air intakes optimised for high altitude.

And why is that? Did Leonard fumble his figures also? And what assumptions that you made are any more valid than his. So far this whole discussion including mine, are laced with 'assumptions' - said assumptions leaning to one side or the other in the debate - but assumptions nevertheless?

I slightly rounded down the climb figures. The Ju-390 could undoubtedly reach 20,000 feet much faster than a B-29 with 18% more power, 55% lower wing loading and 85% better power to weight ratio than the B-29

You should note that even by including the slightly extra fuel for climb which you calculated the total fuel still does not exceed the Ju-390's known fuel capacity of 65,000lb.

On the other hand Richard Leonard's miscalculation is gross and excessive. He calculated fuel burn for the cruise at 500% more than was correct.

Thank goodness Richard Leonard is not a pilot, least I hope not.

The same is true of modern jet aircraft that you can optimise aircraft and engines for high or lower altitudes. The Rolls Royce Tay engine is built on the same core engine but has different versions with different fan sizes.

As an example the Fokker F-100 airliner used the Tay 650 engine with a wider Low pressure fan for shorter flights at lower altitudes has a service ceiling of just 35,000 feet.

The Gulfstream IV private jet designed to fly higher and for longer range uses the Tay 611 with a much narrower LP fan, but it can reach 45,000 feet service ceiling on basically the same engines with similar thrust and similar gross weights.



At Nationwide Air we flew ATL.98 Carvairs. They had astonishingly good fuel consumption. People who have never flown old radials just don't understand how much more fuel efficient a piston radial is over turboprops.

[drgondog]

Originally Posted by Kiwikid

The wing loading is easily calculated from the Ju-390's wing area and MTOW, both of which are well known and documented with corroboration by the test pilot after the war.

Yes if the data is correct, the wing loading is easily calculated

The issue is limited engine performance at altitude. The B-29 for it's faults had massively supercharged air intakes optimised for high altitude.

So you are willing to say that the BMW801E essentailly 'stopped' performing at 20,000 feet. the same engine used in the Fw 190A-9 and you believe this why? And did the personal account of a former test pilot have anything to say about this curious characterisic of an otherwise fine engine?

I slightly rounded down the climb figures. The Ju-390 could undoubtedly reach 20,000 feet much faster than a B-29 with 18% more power, 55% lower wing loading and 85% better power to weight ratio than the B-29

But you somehow find it plausible that the aircraft engines delivered 10,000+ plus hp, but failed to deliver enough to get past 20,000 feet?

Which set of figures do you believe - 10,000+ combined hp at some unspecified altitude, but not past 20,000 feet?

Or significant performance issues with the airframe design that was more than 6 robust engines could not compensate for lower wing loading despite 20+ more hp than a B-29

Or the data is wrong.

BTW if the BMW801E was failing to deliver its rated hp at 20,000 feet, where else was it 'short' and why would any data regarding performance be believeable? If the engines couldn't deliver the Hp at 20,000 feet, where did it fall off from design specs?


You should note that even by including the slightly extra fuel for climb which you calculated the total fuel still does not exceed the Ju-390's known fuel capacity of 65,000lb.

I did note that. Somehow I struggled my way through that to arrive at approximately 10,000 US gallons based on your suppositions. Now, having said that can you point to a surviving desing spec that states that 10,000 gallons were part of the design, or failing that a modification to create a 'tokyo tank' in the fuselage?

On the other hand Richard Leonard's miscalculation is gross and excessive. He calculated fuel burn for the cruise at 500% more than was correct.

.

I honestly don't know who is correct. You haven't showed any engine performance data, no fuel consumption vs altitude or output horsepower

No cruise speeds as function of Gross weight for either max range or max endurance.

Why are you more believable if you can't produce optimal cruise speed and altitude?

I don't doubt your intelligence, or flight experience, but you are trying to suspend belief in this discussion by pointing to an alleged personal account which to this day has never been cooroborated by either surviving Junkers test data or another series of credible witnesses.

I am really agnostic on this subject but how in heck do you expect to prove your thesis? BTW your figures for 40-55 is about right for lowest cruise fuel consumption on a Packard Merlin 1750-7 at 48gal hour.

Is the same 'flawed' BMW801E that low on fuel consumption, and if it is what is the rated hrosepower and altitude for 40 gallons (or 55) gallons per hour.

[Soren]

Kiwikid,

The He-277 is like the He-177 a German built a/c made & designed by the Heinkel Flugzeugwerke, the French had nothing to do with it.

As for the He-177 or He-277 attacking the US, well that would've been a one way trip seeing that max range was 6,000km.

If any bomber was going to bomb the US it would've been either the Me-264 with its 15,000 km range, or the Ju-390 with its 9,700 km range. (Would've been some VERY tiring missions though, flying for that long)

Bill,

The Ju-390 used the BMW-801D series engine, NOT the E series as in the FW-190 A-9. And the performance of the D-2 engine as we know fell off VERY sharply at high altitudes, hence the Ju-390's low ceiling.

[Kiwikid]

This is pretty tiresome hairsplitting Drgndog. You yourself refer to the Mustang having hi fuel flow on take off and dropping to quite low fuel flow in cruise.

I'm quite well aware of that, but thanks for helping me further understand. The fuel flow from max power to optimal cruise varies quite a bit. For a P-51D the max is around 240 Gallons per hour and minimum cruise fuel consumtion was approx 48gph at 18K/1800rpm and 23" for a combat load

Bit of an own goal don't you think ?

Kiwi - data from a single source, and a personal one at that, unmatched by other sources would lead me to at least hold belief in suspension. I'm glad you aren't a cynic like me

A single source ?

Hans Joachim Pancherz and his wartime notes which are published only happen to be the single most authoritative source in the world on the Ju-390 and you say the aircraft's test pilot is not a good enough source.

You just seem to be arguing for the sake of arguing.

Or the data is wrong.

Drawing a long bow based on nothing more than your conjecture.

BTW if the BMW801E was failing to deliver its rated hp at 20,000 feet, where else was it 'short' and why would any data regarding performance be believable? If the engines couldn't deliver the Hp at 20,000 feet, where did it fall off from design specs?

More conjecture by you. Who said the BMW801 failed to deliver it's rated hp at 20,000ft ?

It was limited to that altitude and could not blow enough air into the cylinders above that altitude. It was a known fault of the engine. You're trying to build a thesis that the Ju-390 could not reach USA because you personally don't accept an aircraft with limited engine performance could fly that far.

May I remind you of the giant Dornier Do X which flew the Atlantic pre war never climbed much above 1500ft ?

the flying boats

So you are willing to say that the BMW801E essentailly 'stopped' performing at 20,000 feet. the same engine used in the Fw 190A-9 and you believe this why? And did the personal account of a former test pilot have anything to say about this curious characterisic of an otherwise fine engine?

I wouldn't dare say it myself. Just to prove to you drgndog that this is not just what I say let me refer you to what others say about the BMW801 characteristics.

The BMW801 was well known for limitations at altitude because of it's engine driven superchargers. This was addressed late in the war with the BMW801G and that model's hydraulically driven 4 stage supercharger, but that engine was not fitted to the Ju-390 in early 1944.

BMW 801: Information and Much More from Answers.com

The supercharger was rather basic in the early models, using a single-stage two-speed design directly geared to the engine (unlike the DB 601's hydraulically-clutched version) which led to rather limited altitude performance, in keeping with its intended medium-altitude usage.

With the engine now being used in higher-altitude fighter roles, a number of attempts were made to address the limited performance of the original supercharger.

The BMW 801 Radial Engine

The BMW 801 twin row radial engine formed the basis of the Focke Wulf fw190 design. This engine has the reputation as being among the better engine designs of WW2 regardless of limitations in German supercharger technology which lead to some failings at high altitude.

I don't know some of the facts you demand answers to. The warbirds resource group is the only reference point which i can point to from off my head that refers to a cruise speed as opposed to maximum speed for the Ju-390 and that was 267 knots which i find a bit excessive.

The DC-4/Carvair cruised about 220 knots. I recall reading somewhere that the Ju-390 cruised at 240 knots but can't give you the source.

I expect the Ju-290's cruise was similar to a Ju-290's so that may be a starting point for investigation.

I'm not trying to close down debate Drgndog. If Rich's claim were subjected to the same scrutiny it would be obvious that he overestimated the fuel consumption.

Take some equivalent aircraft like the DC-4 and look at their fuel consumptions because you'll find the same applies.

[Kiwikid]

The He-277 is like the He-177 a German built a/c made & designed by the Heinkel Flugzeugwerke, the French had nothing to do with it.

Hiya Soren, I can't quote a source at the moment but before the invasion of france He-177 airframes were sent to a French aircraft manufacturer and had the wings modified for a conventional 4 engine installation.

I stand to be corrected but I am pretty confident that I have read an authoritative source on this. No arguments that it was the best German bomber.

Had Ernst Udet not persuaded Goering to drop the 1936 specification for a Urals bomber after Webel's death and instead focus on tactical dive bombers like the Do-17 and Ju-87, Germany would have had a fleet of strategic bombers in 1939.

I have read that the Ju-390 was originally fitted with the BMW 801D and at some point later was fitted with the BMW 801E, but the altitude issues were not fully solved until the BMW 801G and BMW 801R.

I have no idea which engine type was fitted in January 1944 and you may well be correct Soren.

My fuel calculations and comparison with the B-29 incidentally were based on the BMW 801D of 1730hp per engine.

[Soren]

The He-277 is completely German Kiwikid, designed in Germany by the Heinkel design team as a further development of the He-177. The aircraft itself was built in Austria.

Regarding any French involvement you must be remembering wrong Kiwikid, cause the French didn't get a hold of any He-177, and by the time the invasion was over the French completely ceased designing a/c. The He-177 first entered service in 1942. Another a/c, the He-274, was however built by Heinkel in France, but the design was completely German, the labor being only thing French. It was simply a case of the Germans utilizing captured production facilities instead of spending funds on building them themselves.

As for the Ju-390, it was powered exclusively by BMW-801 D-2 engines.

[Njaco]

The French Air Force had one He 177 - after the war.

[drgondog]

Originally Posted by Kiwikid

This is pretty tiresome hairsplitting Drgndog. You yourself refer to the Mustang having hi fuel flow on take off and dropping to quite low fuel flow in cruise.

Yes I did. I gave them to you in the conditions and altitudes and rpms and boost for a very efficent in line engine which has 15-20% less hp than the 801E. You have given me zero in return for a very large and powerful radial engine

You said the following to start this discussion


Now that you've read Richard Leonard's figures... here's the true figures:

The Ju-390 used six BMW 801E engines which were identical to the BMW 801D except the E version was geared for better performance at altitude. The 801E was geared for lower engine revolutions.

Nice statement, rich in promise..

In all other regards one can consider fuel consumption the same or slightly superior fuel consumption for the 801E. The E version had about a 100hp superiority at altitude.

But where is the 'beef' - Nice assumption, no facts

The BMW 801E also had a boost function for take off, by injection of a water methanol mixture into the left supercharger inlet. This could only be used for 10-15 minutes. Only at these boost settings does the fuel consumption rise to 221 US Gals PH.

So, at what altitudes do the BMW 801E operate most efficiently? and at what boost settings, rpm and fuel flow - for the Ju 390 V2 - to either obtain maximum range or maximum endurance. As a pilot you will know those are usually two different settings, (and altitudes and cruise speeds)

A single source ?

Hans Joachim Pancherz and his wartime notes which are published only happen to be the single most authoritative source in the world on the Ju-390 and you say the aircraft's test pilot is not a good enough source.

You just seem to be arguing for the sake of arguing.

I'm arguing because you haven't produced the above detail that would make it possible to verify either endurance or range. Apparently neither has the test pilot? This story has been around a long time w/o corroboration.

Drawing a long bow based on nothing more than your conjecture.

Skepticism based on many claims, vague assumptions and few facts,

More conjecture by you. Who said the BMW801 failed to deliver it's rated hp at 20,000ft ?

Actually - Soren did, then you.

This illustrates the above skepticism.

Actually I find it extremely hard to believe that a 801E 'dies' at 20,000 ft. Soren just stated that the E had 'well known' altitude problems but I hadn't heard that. Hell, that engine was designed to go into Fw 190s as well as other applications - so No I don't believe this

But when performance data of a 'marvelous' aircraft with nearly 50% more horsepower than a B-29, has a wing loading 10% less than a B-29, (according to all the sketchy references available so far) BUT ONLY HAS A SERVICE CEILING of 20,000 feet - well below a B-29 - doesn't that give YOU pause that something is fishy??


You're trying to build a thesis that the Ju-390 could not reach USA because you personally don't accept an aircraft with limited engine performance could fly that far.

Well, No. I'm building a thesis that either the aircraft was very dirty aerodynamically if it couldn't go past 20,000 feet with six very powerful engines, or

The published ceiling data is wrong (and what else is wrong), or

The published engine for the aircraft is wrong, or

The engines actually failed altogether with second stage boost and ceiling WAS severely limited - I'll check your references for the latter... but if true the V1 with BMW801D should speculatively cruise farther than a V2

May I remind you of the giant Dornier Do X which flew the Atlantic pre war never climbed much above 1500ft ?

Ah, no. The Panama Clippers did not fly very high of very fast either

the flying boats



I wouldn't dare say it myself. Just to prove to you drgndog that this is not just what I say let me refer you to what others say about the BMW801 characteristics.

The BMW801 was well known for limitations at altitude because of it's engine driven superchargers. This was addressed late in the war with the BMW801G and that model's hydraulically driven 4 stage supercharger, but that engine was not fitted to the Ju-390 in early 1944.

BMW 801: Information and Much More from Answers.com





The BMW 801 Radial Engine



I don't know some of the facts you demand answers to. The warbirds resource group is the only reference point which i can point to from off my head that refers to a cruise speed as opposed to maximum speed for the Ju-390 and that was 267 knots which i find a bit excessive.

Actually, the other resources show the Max speed with external weapons as 267 mph. That is a far cry from optimal cruise speed either for range or for endurance.

The DC-4/Carvair cruised about 220 knots. I recall reading somewhere that the Ju-390 cruised at 240 knots but can't give you the source.

IF true, that would represent a range close to 7500 miles. Is that your thesis? A very clean, no bomb load B-29 was capable of 5400 miles ferry - similar to a Recce -

I expect the Ju-290's cruise was similar to a Ju-290's so that may be a starting point for investigation.

The Ju 290 with four engines should be cleaner. Having said that with the four BMW801G, it seemed to also have a 6000m ceiling



I'm not trying to close down debate Drgndog. If Rich's claim were subjected to the same scrutiny it would be obvious that he overestimated the fuel consumption.


I have no problem with this statement. On the other hand we have yet to establish any solid data for the Ju 390.

Take some equivalent aircraft like the DC-4 and look at their fuel consumptions because you'll find the same applies.

If we go to trying extrapolate the performance against the DC-4, we have to establish the baseline for Both ships to determine actual reasonableness

1. Either the Test Cruise curves for altitude, sfc, rpm, boost, TAS as a function of payload, or

2. Published data for optimal cruise speed for a.) endurance or b.) range

But as a pilot you know that you need far more than fuel consuption data for the engine - you have to know how the aircraft as a SYSTEM performs with respect to engine, payload, aerodynamics and altitude.

[Soren]

Listen are you guys interested about knowing the truth or do you just want to argue ??

For the last time the Ju-390 was equipped with the BMW-801 D-2 series NOT the E series!

And here's the power curve of the BMW-801D2, as you can see performance decreases rapidly at high alt: