WWII MISTERIES: What happened with the JU390?

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To date you have

a.) presented your arguments based on 'Belief system' that the notes and data presented by a former pilot of the Ju390 are accurate and reflect the 'facts' of the aircraft's performance and it's flight to NY.

b.) have no other flight test, design specifications by Junker, actual 'as built' configuration for the Ju 390 or any usually reliable reports from say the LW to corroborate your belief systems.

c.) no clue what the operating performance envelope is for the aircraft, what its' mission configuration was for the 'Ny Flight', no idea concering the actual specified cruise settings for the BMW801E (or D if it was used) in the Ju 390 for either max range or max endurance.

d.) no clue what the alleged fuel load, version type (passenger, recce, bomber) was for the 'trip'. Somehow for the mission, believe there was enough remaining load capacity to carry another 10,000 pounds as a bombload? And hang it where? and still fly for 32 hours?

e.) made many assumptions about the cruise and take off/climb fuel consumption rates when you have no data to support them (we still aren't sure which 801 engine was used) - and base them on your pilot 'credentials'?

f.) blown away Rich's analysis based on your own unfounded assumptions and poor math.. and ready to tell him the 'Real story"

But you question my skepticism (and Rich's) of those that present "better information"??

When are you going to get around to asking questions a 'real pilot' would ask if someone said 'Take this Ju 390 to New York - bring it back if you can?"

There are a LOT of 'real pilots' on this forum that would ask the same questions I have to just get to the point where
a.) I decide it is a credible accomplishment based on the facts, or
b.) I decide it is patent BS because there are no facts (much less 'plenty, but not enough') to support a conclusion.

To summarize'

Your math was bad - deal with it.
Your flight profile assumptions have no substance, no data and no credibility
Your 'belief system' is credible relative to the Ju 390 pilot - entered into evidence - but still not a verified fact!
You don't like me when I ask you tough questions about Real Flight Performance data necessary to generate analysis.
You didn't 'like' others questioning your flawless logic or 'information'.
You frequently confuse statements made by me with statements made by others!

And you accuse me of not being objective? Did I hurt your feelings? I am sorry about that.
 
The B-29 did not have a 80% higher wing-loading than the Ju-390, that's for sure. The difference in wing-loading was closer to 60%, which is still allot, BUT here's what I know:

The Ju-390 either used the BMW-801D or E engine, both were at a disadvantage at high altitudes, power decreasing rapidly above 22 - 23,000 ft. So although I do believe/know that the Ju-390's service ceiling was higher than 6km, it couldn't have been much higher than 8 to 9 km seeing that the performance of the BMW-801D E engines completely evaporated at those altitudes.

As for the B-29, well alone because that its engines are fitted with turbo-superchargers it's no surprise that its ceiling was higher. Furthermore the B-29 benefitted from a more efficient wing, the higher AR increasing lift whilst decreasing drag, raising the L/D ratio.

Here's the effect AR has on the lift drag of an a/c and thus the L/D ratio:

With similar CLmax figures let me demonstrate just how important wing AR is;

L/D ratio = Cl / Cd

Cd = Cd0 + Cdi

Cd0 = {Negligable as it always lies in the 0.02 -0.025 area}

Cdi = (Cl^2)/(pi*AR*e)

So for the comparison we assume a Clmax of 1.3 for both and Cd0 of 0.02 for both, now note the difference wing AR alone has on the L/D ratio (one of the most crucial factors to high turn performance), and the higher the L/D ratio the more efficient the wing is.

Wing with AR of 8

(1.3^2)/(pi*8*.85) = 0.0791093688

0.0791093688 + 0.02

Cd = 0.0991093688

1.3 / 0.0991093688 = 13.1168225

L/D ratio = 13.11

Wing with AR of 6

(1.3^2)/(pi*6*.85) = 0.105479158

0.105479158 + 0.02

Cd = 0.125479158

1.3 / 0.125479158 = 10.3602863

L/D ratio = 10.36
_______________________________

L/D ratio Differential: 35.9 %

Additionally two graphs showing the difference in L/Dmax between a wing with an AR of 4 vs a wing with an AR of 9:

AR 4


AR 9


Now the B-29's wing was of a very high AR, 11.53 infact, which meant it was a very efficient wing with a very high L/D ratio, something which was also needed if the B-29 was to be a good performer at altitude.

The Ju-390's wing was of 9.96, also high but still lower than the B-29's by 1.47, which is noticable in lift drag.

In short, the higher ceiling of the B-29 can attributed to its turbo-supercharged engines and more efficient wing. The Ju-390 no doubt could've gone higher than the B-29 had it had turbo-supercharged engines, however it didn't.
 


And your source for this is?
 
 

I agree the part about the Wright 3350-23A engines. If Baugher's data is correct, they had more Hp at 25,000 feet than at SL for Max Take Off Hp boost. Clearly the D-2 data you showed had a remarkable fall off at 15-18K ft..still have no comparable data for the 801E
 
I used the following figures to calculate wing loading:

Ju-390:
Gross weight: 53,500 kg
Wing area: 254 m^2

B-29:
Gross weight: 54,000 kg
Wing area: 161 m^2

That gives a 60% difference in wing-loading.
 
Soren said:
I used the following figures to calculate wing loading:

Ju-390:
Gross weight: 53,500 kg
Wing area: 254 m^2

B-29:
Gross weight: 54,000 kg
Wing area: 161 m^2

That gives a 60% difference in wing-loading.
Click to expand...

from Uboat

Specifications
Junkers Ju 390V2

Six 1970hp BMW 801E radial engines Wing span 50.32m, length 33.6m Empty weight 36900kg, max. take-off weight 53112kg Max. speed 515km/h at 6200m, cruising speed 357km/h. Max. range 9700km.

From Warbirds

Engine:
Model: BMW 801E
Type: 18-Cylinder two-row radial
Number: Six Horsepower: 1,970 hp

Dimensions:
Wing span: 165 ft. 1 in. (50.30m)
Length: 112 ft. 2.5 in. (34.20m)
Height: 22 ft. 7 in. (6.89m)
Wing Surface Area: N/A

Weights:
Empty: 81,350 lb. (36,900 kg)
Loaded: 166,448 lb. (75,500 kg)

from Military Factor

Length: 112.20 ft | 34.20 m
Wingspan/Width: 165.03 ft | 50.30 m
Height: 22.60 ft | 6.89 m
Empty Weight: 87,083 lbs | 39,500 kg
MTOW: 166,449 lbs | 75,500 kg

From Wikipedia

Specifications (Ju 390 V1)
Data from[citation needed]


General characteristics
Crew: 10
Length: 34.20 m (112 ft 2 in)
Wingspan: 50.30 m (165 ft 1 in)
Height: 6.89 m (22 ft 7 in)
Wing area: 254 m² (2,730 ft²)
Empty weight: 39,500 kg (87,100 lb)
Loaded weight: 53,112 kg (117,092 lb)
Max takeoff weight: 75,500 kg (166,400 lb)
Powerplant: 6× BMW 801D radial engines, 1,272 kW (1,730 hp) each

In other words - at 166,000 pounds the WL of the Ju 390 is 10#/sq ft less than the 133,000 pound ferry condition of the B-29. In other words 11% difference for the 'NY Run" we have been debating?

what is the real story on anything to do with the Ju 390?
 
Errr, why are we comparing the a/c at different loads ?

The gross weights of both a/c were very similar.

As for the NY run, well that certainly wouldn't have been carried out at max take off weight.

Btw, if talking about bombing the US then the Ju-390 wasn't the ideal choice with its low ceiling. The Ta-400 would've been ideal, however funding was cut as the LW initiated the fighter program.
 

Soren - I put them out for the very reason you just asked the questions..

  1. We don't know what the alleged NY run load conditions were.
  2. We don't know what Maximum Gross Take Off conditions were with respect to any version that actually flew... so we don't know W/L would have been for the 'Ny Trip" at takeoff and climb
  3. We don't know if a flying Ju 390 had either a bomb bay, or auxilliary tanks to store additional fuel in the fuselage, and don't know what the weight would have been in that case.
  4. We don't know if the Service ceiling was at minimum fuel to get to the highest altitude possible, or whether that was a Service Ceiling for planned combat load.
  5. We don't know power loading because we don't know the engine or the flight conditions we are calculating
  6. We don't know what any version specifications were for cruise as function of weight and range and engine setting/altitude to achieve the cruise value

So why should anyone get excited about speculation on W/L comparisons, or ceiling calculations, or cruise speed/altitude for maximum range, etc.

What we know is one person claimed to have made a run to NY in one version of this airplane and we have no facts to judge the veracity of the guy.
 
Fair enough.

However with no bombs the Ju-390 could've easily made to the US and back, but with a big bomb load I doubt it. If the US was to be bombed by bombers flying from Germany or France the Ta-400 would be needed.

As for the service ceiling, well all German figures are for full weight conditions, that I know. However since we don't have the service ceiling of the Ju-390 we can only speculate as to what it was, and my guess is 8 to 9 km.

What are your thoughts Bill ?
 
Regarding the engines: Most authors focussed on the aircraft and their design but not on engines or specific subtypes. Many authors still believe the Messerschmitt Bf 110 was powered by DB605A engines were in fact it was powered by DB605B engines. The same is with the BMW 801 powered Ju 88/Do 217 types, they used the 801A/L subtypes of the 801C or the G-2 subtype of the D-2.

The initial Ju 290 (prototypes/A-1) used 801A or 801L engines (yes, the bomber/multi-engined subtypes). At least with the A-5 they switched over to the BMW 801TL (Triebwerksanlage L containg the 801G-2 engine).
 

I have opinions, and questions.

The opinions are: At least one Ju 390 was built in a passenger version originally, was tested and accepted - but contract was cancelled somewhere between one prototype and two. If the second one was built I suspect it was in a Recce version with provisions for internal tanks to extend loiter and range.

Because there is so much confusion regarding engines, I Suspect w/o any shred of proof that the first one was built with 801D and never intended to climb higher than 6000 meters, with the design passenger load. I suspect this version was closer, but less than a B-29 Ferry range.

I further Suspect that if the second one was built (either A-2 or V2) that it was equipped with 801E's to attempt a higher ceiling and cruise range for the Recce version.. I also suspect this is the one that is theorized to make the flight to US and back.

Based on the large capacity above the empty weight, I suspect that the quoted figure was for a version with internal fuel in fuselage for Recce version where passengers was not a factor. If that bird ever lifted 166,000 pounds at take off, this was the reason - pure long distance 'Ferry' condition.

The data presented agree on 87,000 pounds empty and 117,000 Gross Take Off (which I take for 'design internal payload' weight. So speculatively 30,000 pounds of ammo, crew and fuel for the original prototype is my Opinion.

So it seems the difference between 117,000 and 166,000 has to largely be additional INTERNAL fuel from my perspective - close to doubling the fuel capacity.

Even with more powerful 801E's this airplane would neither fly very high nor be efficient in cruise until it burned 2/3 of its fuel... but if it could carry 7-8000 more gallons of fuel, and actually get off the ground, I suppose it is possible to make that trip...

Questions still come back to the fundamentals - max fuel load, cruise speed and fuel consumption and altitude for the initial leg of the trip while burning down the extra fuel, then remainder of trip at 'standard' cruise and altitude after half the fuel is burned at lower cruise speed, lower altitudes and higher fuel consumption rates.

I still ponder the efficiency of this airframe/engine combination for cruise optimals. The 51 was a VERY efficient airframe/engine combo and able to optimize cruise Range at about 48gal/hr, 18,000 feet at low boost and rpms.

Do we believe that a series of BMW801s at near that fuel consumption as the efficient/powerful Merlin? I have no inkling or clue. An R-2800 sure couldn't come close which is why the Jug had to have 2x the internal fuel to fo as far.

This would be an interesting Performance Test for students..

As to your first question - if we guessed right that a.) first version prototype with the performance based on 117,000 pounds and 6km service ceiling, and a second one was built with primary difference being internal mod for fuel and BMW801E's - and w/o a chart to show relative Hp/altitude between the two, I would guess that with 200hp 'extra per engine that another 1 - 2 Km could be stretched... but at 117,000 not the 166,000 pound gross weght.

The 801E sgould cruise slightly faster for same sfc as the 801D, and higher for same fuel consumption - giving it probably a little more range - all things equal.
 
I read a little bit on the 390 at the hanger today by a gent named Heinz Nowarra and he states the 390 ferry range was 6000miles at 218 mph and 4900miles with a load ,
 
I read a little bit on the 390 at the hanger today by a gent named Heinz Nowarra and he states the 390 ferry range was 6000miles at 218 mph and 4900miles with a load ,
Click to expand...

That puts it's long range cruise about the same as a DC-4 / Carvair.

the NACA report on a BMW 801D2 engine from 1944 tests:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930093290_1993093290.pdf



Since last being online I read some further data at another forum on the BMW801E.

Phillip Willaume is a leading authority on the BMW engine and has done extensive research from various archives including the Simithsonian and British Archives. Some commentary on the BMW 801E engine based upon the engine's manual is available here:

A Complete Waste of Space Forums-viewtopic-bmw801

I have compressed the essential detail into a table here:


I have elsewhere seen figures for the BMW801D with a fuel flow of 55 US Gals per hour at 1700 rpm which based on this data would be at lower altitudes.




The Ju-390 V1 was converted from Ju-90 V6 with civil registration D-AOKD. This may be where the suggestion of a passenger transport arises.

Ju-290 A1 werke nr J900155 became the second Ju-390 with converstion at the Letov plant near Prague.
 
As I understand it , this entire debate hinges around the question of how the so called Ju-390 could have even made a round trip from Europe to America given that its range is some what short of what would seem to be required.

After some internet searching I gave up on the military forums and warplane sites and read up on civil aviation sites. Back in the 1980s I used to get AWST weekly and know that most aircraft range figures are theoretical calculations. For prop driven planes, the wind is by far the greatest factor that determines range.

When I pulled up my aviation charts for 5000-18,000 feet, it became painfully clear that if you know you wind streams at altitude you can vary your altitude and ride the wind currents across the Altantic [since they head west] and add up to 120 knts to your air speed and then drop to lower altitude heading back in the direction of Spain and negotiate around the winds ranging from 5-35knts with wind directions ranging from westerlies swinging around to northerlies, that could eventually push you back towards France.It would require a skilled crew that knew their winds at altitude...so it could be done in theory.

On a heavy weather day you can add an average of 50-60 knts to any round trip from France to America, which means in theory Ju-390 should be able to do the round trip with extra fuel tanks etc. As I recall they added some internal fuel tanks when the modified the Ju-290 to the 390 design. In fact after some tinkering it was also possible to get the Ju-290 to do the trip.... at a pinch ...also econo cruise at altitude, often had only a couple of engines running to conserve fuel
 
the only problem is the LW would have no.... absoulutely no knowledge of those winds aloft the best info the might get would be surface winds from U boats flying the pond was a relatively new sport and the only ones that might be aware of those winds and their trends would be the Ferry Command guys and MATS
 
pbfoot said:
the only problem is the LW would have no.... absoulutely no knowledge of those winds
Click to expand...

The Focke Wulf Condor transatlantic flights of 1938 must have gleaned some information on the wind forces for the Germans?

psteel said:
On a heavy weather day you can add an average of 50-60 knts to any round trip from France to America
Click to expand...

From..Transatlantic flight - Wikipedia, the free encyclopedia

"August 10, 1938 - first non-stop flight from Berlin to New York. The Focke-Wulf Fw 200 needed 24 hours, 56 minutes and did the return flight three days later in 19 hours, 47 minutes."

How did that Condor return faster on the return flight?
 
Prevailing winds but to know the winds aloft is still some what of a mystery to this day for example wind shear , look at the local winds aloft for your location they can vary a number of degrees from surface winds the winds here vary by 30 degrees at 3000 ft and are 20 knots faster at this location right now
 
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