WWII MISTERIES: What happened with the JU390?

[Soren]

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 ?

[Denniss]

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).

[drgondog]

Originally Posted by Soren

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 ?

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.

[pbfoot]

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 ,

[Kiwikid]

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 ,

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/ca...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 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.

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.

[psteel]

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

[pbfoot]

Originally Posted by psteel

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

[Graeme]

Originally Posted by pbfoot

the only problem is the LW would have no.... absoulutely no knowledge of those winds

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

Originally Posted by psteel

On a heavy weather day you can add an average of 50-60 knts to any round trip from France to America

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?

[pbfoot]

Originally Posted by Graeme

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



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

[Graeme]

Originally Posted by pbfoot

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

Roger that pb.

[Njaco]

I was thinking the same thing. I believe the jet stream and associated winds weren't really discovered until just before the war ended.

[psteel]

So that when the Japanese floated balloon bombs across the Pacific they had no idea where they were going? Surely they knew of the streams of wind at altitude and the rough direction or they would have had no idea where they would end up?

Wind currents can change 100knts over the first 5000-20,000 feet that were common flight routes . Heres a web site where you can track wind currents at altitude and predict flight routes. After a short while you notice predictable general paths . Not saying it would work every time but could explain ideas behind experimental flights.

Aviation Weather Center (AWC) - IFFDP Text Products--Winds and Temperatures - ICAO Area H

Click on the FL number [39 = 39,000 feet] and it gives you a north Atlantic polar view map of wind currents. The blue dot on each selection gives a closer-bigger map to view. The directional arrow indicates the wind direction and the figure beside it is temperature [I believe they are below zero unless otherwise mentioned]. The symboles indicate the air speed. As I recall, each flag is 50knts and each long dash is 10knts while each short dash is 5knts.

The wind channels are all over and couldn't go unnoticed. All prop flight is controlled by these winds so any range figures you see quoted are purely theoretical limits and not practical figures to debate about.


PS the wind stream was first reported in December 1934 , according to this web link....so they should have known about it.

http://www.todayinsci.com/12/12_07.htm

In 1934, Wiley Post is credited with discovering the jet stream when he flew into the stratosphere over Bartlesville, Oklahoma. With the financial backing of Oklahoma oil pioneer Frank Phillips, Post planned flights to test the "thin air" in the stratosphere above 50,000 feet. The Winnie Mae, made of plywood, could not be pressurized so Post developed the pressurized flying suit, forerunner of the modern space suit. Made by B.F. Goodrich, it was of double ply rubberized parachute fabric, with pigskin gloves, rubber boots, and aluminium helmet, pressurized to 0.5 bar. In Mar 1935, Post flew from Burbank California to Cleveland Ohio in the stratosphere using the jet stream. At times, his ground speed exceeded 550 kph in a 290 kph aircraft.

Germans had artic weather out posts for a good part of the war that gave them an ability to predict weather patterns effecting the North Atlantic and Europe.

[FLYBOYJ]

Originally Posted by psteel

PS the wind stream was first reported in December 1934 , according to this web link....so they should have known about it.

But it was basically ignored until the B-29........

[Kiwikid]

Actually during 1944, the U-boat rusting at Liverpool U-534 was posted to perform weather reporting patrols south of Greenland, not to mention other weather bases in the high Arctic.



When first certified in late 1943, the Ju-390's Maximum Take Off Weight (MTOW) was cited as 75,500kg with an 8,000km range. According to pilot Hans Joachim Pancherz, the aircraft was put through a weight reduction program in May 1944 and re-certified with an MTOW of 80,500kg with a range of 11,000km.

Crittics however remain unconvinced so I made an effort to track down an April 1945 report on bench testing of the BMW 801D engines by NACA, forerunner of the agency now known as NASA. Early flights by the Ju-390 used BMW 801D engines. The BMW 801E engine was an experimental engine often mentioned as being fitted to the Ju-390. It was in fact intended for the Export aircraft planned for production by Japan. The BMW 801E had modified gearing on the supercharger to give better fuel consumption and an extra 100hp at altitude.

Page 29 of that NACA report discloses an individual engine on lean settings below 21,000 feet altitude consumes either:

* 250 L/hr (40.83 US Gal/hr) at 1600rpm (1469.9lb/hr for six engines), or
* 275 L/hr (45.83 US Gal/hr) at 1800rpm (1649.9lb/hr for six engines)

Above 21,000 feet the supercharger cut in automatically and almost doubled fuel consumption.

Reichsluftministerium (RLM) performance specification for the Ju-390 were to carry 10,000kg (22,000lb) over 8,000 kilometres. Fuel capacity with such a payload when the aircraft's empty weight is subtracted from MTOW results in 57,268lb.

Interestingly 32 hours worth of fuel consumption at 1800 rpm equates 52,797lb of fuel. Thus a 32 hour endurance attributed to the Ju-390 is well within known take off weight and fuel consumption.

A Ju-390 therefore could carry 10,000kg from France to New York and back with a 4,471lb weight buffer, though some of this spare weight capacity may have been consumed in take off power at the start of such a flight. Fuel consumed by a Focke Wulf 190A fighter powered with a BMW 801D engine to reach 19,000 feet, equates 1152lb for six engines.

Remember that this was calculated keeping in mind a 10,000kg payload so the Ju-390 was not anywhere near the limits of it's performance had the flight been performed without a payload.

What is clear is that the flight would have been below 21,000 feet most of the way and early in the flight unlikely to have been above 12,000 feet.

Jetstream headwinds apply to jet aircraft above 30,000 feet. Not unpressurised aircraft below 21,000 feet.

Sources:

* UK Air Ministry report PRO AIR40/53 (for BMW 801D)
* UK Air Ministry report PRO AIR40/55 (for BMW 801E)
* NACA Technical Memorandum Report MR E5D19 (archived by Nasa as PDF #19930093290_1993093290)

[Kiwikid]

A question has been raised how the Ju-390 compared with the B-29 ?

Ju-390:

10,380 hp Installed horsepower
75,500 kg (166,400 lb) MTOW weight
254 m² (2,730 ft²) Wing area
0.17 kW/kg (0.10 hp/lb) Power to weight ratio

B-29:

8,800hp Installed horsepower
60,560 kg (133,800lb) MTOW weight
161.3 m² (1,736 ft²) Wing area
(0.6577hp/ib) Power to weight ratio

B-36:

21,000hp Installed horsepower
190,000kg (410,00 lb) MTOW weight
443.3 m.2 (4,772 sq.ft) Wing area
120 kW/kg (0.086 hp/lb) Power to weight ratio


The Ju-390 had 17.95% more power than a B-29 and 79.7% more wing area. The Convair B-36 with less power to weight ratio but similar large wings managed to take off at maximum weight in just 1500 metres.

The B-29 with less power and smaller wings could manage such ranges so why not the Ju-390 ?