WWII MISTERIES: What happened with the JU390?

[kool kitty89]

I was tinking more in terms of a large (bomber) aircraft though, fighters tend to have more "extra" power relatively speaking. (again, it would have to be on the edge of being underpowered at take-off for the comparison to work)

And in the Merlin's case, max economical cruise power would be well above the 500 hp power setting, ~800 hp in low blower at crit alt iirc. (max power for the minimum SFC range)
The P-40K's V-1710-73 had a max of 670 hp ar ~15,000 ft (at 28" MAP and 2,280 rpm) with just under 45 lb/hp/hr, but max range cruising was at ~400 hp at ~15,000 ft iirc. (with similar SFC -actually slightly higher). It's take-off power was 1,325 with WEP of 1,570 hp at ~3,000-5,000 ft -depending on ram conditions-. (60" Hg MAP)


Thanks again for that link, it was a lot simpler than the one I was looking at.

 

[drgondog]

I was tinking more in terms of a large (bomber) aircraft though, fighters tend to have more "extra" power relatively speaking. (again, it would have to be on the edge of being underpowered at take-off for the comparison to work)

And in the Merlin's case, max economical cruise power would be well above the 500 hp power setting, ~800 hp in low blower at crit alt iirc. (max power for the minimum SFC range)

KK - I had a little time in the 51D w/1650-7 and the setting I gave you was pretty close to max endurance for the weights I was flying. What is your source to the contrary? (I could have been screwing up)

The P-40K's V-1710-73 had a max of 670 hp ar ~15,000 ft (at 28" MAP and 2,280 rpm) with just under 45 lb/hp/hr, but max range cruising was at ~400 hp at ~15,000 ft iirc. (with similar SFC -actually slightly higher). It's take-off power was 1,325 with WEP of 1,570 hp at ~3,000-5,000 ft -depending on ram conditions-. (60" Hg MAP)


Thanks again for that link, it was a lot simpler than the one I was looking at.

You keep using economical - and that does have a meaning when time is more important than $$. Is that the 'economical cruise speed" you are referring to for the 51

 

[kool kitty89]

I meant ~800 hp is the maximum power setting for minimum SFC. I wasn't saying that would be the power setting for optimal range. (like with the P-40K, max of 670 hp, but max range was somwhere arround 400 hp)

This power setting is usually synonymous with "maximum cruise power" (USAAF) and "max weak mixture" cruise setting. (the latter in British doccuments) The term "economical maximum" was also used, at least for the USAAC.

However, in some circumstances "max cruise power" was actually in auto rich, with SFC much higher than the minimum range. (though ususally significantly lower SFC than at max continuous)

http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/1710-33.pdf (uses "economical maximum")
http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/1710-39.pdf (has max cruise listed as auto rich)
http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/1710-73.pdf
http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/1650-1.pdf (has some rather odd cruising SFC figures across the board)

 

[Ome_Joop]

Did anybody check Kiwikid's comparison facts/statements here?

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 ?

First of all a B-36 with a MTOW of 190,000kg (410,000 lb) would have been the B-36J wich had 6 x Pratt Whitney R-4360-53 (3800 hp each....22800 hp but also 4 x 5200 lb.s.t. General Electric J47-GE-19 turbojets)

a B-36B without those had a MTOW of 311,000 lb (but still would have had 6 R-4360-41 wich deliver 3500 hp each! )

a B-36D with 4 x 5200 lb.st. General Electric J47-GE-19 turbojets had a MTOW of 370,000 lb

let's say in this little game we are comparing the B-36B:

141067kg (311,000 lb) MTOW weight
21,000 hp / 311,000 lb = 0,0675 hp/lb
(21000 x 746) / 141067 = 111,05 W/kg

wich is ofcoarse better than the Ju-390 and the B-29!
102,56 W/kg Ju-390
108,4 W/kg B-29

I don't know much about maths....but i begin to wonder about those other calculations!

 

[drgondog]

Did anybody check Kiwikid's comparison facts/statements here?




First of all a B-36 with a MTOW of 190,000kg (410,000 lb) would have been the B-36J wich had 6 x Pratt Whitney R-4360-53 (3800 hp each....22800 hp but also 4 x 5200 lb.s.t. General Electric J47-GE-19 turbojets)

a B-36D without those had a MTOW of 311,000 lb (but still would have had 6 R-4360-41 wich deliver 3500 hp each! )

a B-36D with 4 x 5200 lb.st. General Electric J47-GE-19 turbojets had a MTOW of 370,000 lb

let's say in this little game we are comparing the B-36B:

141067kg (311,000 lb) MTOW weight
21,000 hp / 311,000 lb = 0,0675 hp/lb
(21000 x 746) / 141067 = 111,05 W/kg

wich is ofcoarse better than the Ju-390 and the B-29!
102,56 W/kg Ju-390
108,4 W/kg B-29

I don't know much about maths....but i begin to wonder about those other calculations!

good catch

 

[Ome_Joop]

This one is a classic...

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.

B-36B...
Takeoff run 6000 feet at sea level. Takeoff run over 50-foot obstacle 8000 feet.

6000 ft = 1828.8 meters
8000 ft = 2438.4 meters

at Combat weigth that is (227,700 lb or 103282 kg)!

The B-36D (with those jet engines remember) did better!

Takeoff run 4400 feet (1341.12m), 5685 feet(1732.79) over 50-foot obstacle. (at 250,300 lb or 113533 kg)!

 

[Kiwikid]

So how many of you ever picked up that the Ju-390 was developed from the Junkers EF100 wind tunnel tests ?

The projected weights and performance for the EF100 are almost identical with the Ju-390 and the RLM sponsored EF100 project led directly to the Ju-390.

The EF100's gross weight was 74,500kg. It's landing speed was calculated to be 66 knots. It could land in 510 metres. It could take off in 550 metres at Gross weight.

Therefore it follows that the Ju-390 could easily use the 1200 metre runway at Bodo in 1945.


The B-36 data is simply an illustration that such a large and heavy aircraft could manage 1500 metre runways. Enjoy your nitpicking.

 

[pbfoot]

Thats a pretty short take off run , maybe empty and downhill with a 30knot headwind , if you look at runways made for B36's of which I'm familar they are about 12000 feet long and very thick, was the rwy in Bodo designed for that weight of aircraft

 

[drgondog]

So how many of you ever picked up that the Ju-390 was developed from the Junkers EF100 wind tunnel tests ?

The projected weights and performance for the EF100 are almost identical with the Ju-390 and the RLM sponsored EF100 project led directly to the Ju-390.

The EF100's gross weight was 74,500kg. It's landing speed was calculated to be 66 knots. It could land in 510 metres. It could take off in 550 metres at Gross weight.

Therefore it follows that the Ju-390 could easily use the 1200 metre runway at Bodo in 1945.


The B-36 data is simply an illustration that such a large and heavy aircraft could manage 1500 metre runways. Enjoy your nitpicking.

You wouldn't be nitpicked if you dealt strictly from published facts instead of your logic and/or opinions.

Like another person not to be named - you select a POV then find facts which may be supportive but insufficient to make the case, or may be incomplete or unsubstantiated to support your claim - then declare victory.

Your 'logical' progression from Ju 390 to B-29 to B-36 to demonstrate your irrefutable conclusions turned out to be flawed because you didn't get the math right. Ome_joop caught it, showed the error of your 'logical conclusion' and rather than say "Oops, My Bad" you imply he is enjoying nitpicking?

Above, you enter a mysterious 'exhibit', make a claim about supportive or directly comparable performance to the Ju 390 and then extrapolate a conclusion?

Do you happen to have the Drag Polars for the Ju-390 for different Gross Weights?

 

[Ome_Joop]

This would be nitpicking:
Bodo was 1200 meters long that would mean even a Ju-290A7 could not take of with a 99,180 lb / 45000 kg takeoff weight (takeoff distance would be 4,092 ft/ 1240meters)!
A Ju290A7 would have had a better power to weight ratio (114,72 W/kg) than a B-36 or a Ju-390!

(6920 x 746) / 45000 = 114,72 W/kg (i adjusted this because i first had used the 1700 hp info i got from the Mogram close-up 3 is used for info).

So you are telling that a Ju-390 with a 5000 kg increase in weigth (you were talking about an 80500kg Ju-390) would be outperformimg a much lighter Ju290...

Ju-390:

10,380 hp Installed horsepower
75,500 kg (166,400 lb) MTOW weight + 5000kg = 80500kg MTOW (40000 kg heavier than that Ju-290A7with only a 3460 increase of hp)
(10380 x 746) / 80500 = 96,19 W/kg ...Bodo we got a problem!

Ef-100 suposedly info (as it was only a model, no real aircraft had flown and there was only one JuMo223 built....):
15,000 hp (6 x 2500 hp JuMo 223)
74,500 kg weight
(15000 x 746) / 74500 = 150,20 W/kg and a wing area of 350 m² or 3767 ft²

 

[Maximowitz]

Interesting thread this one, the whole of the internet in a microcosm.

Someone starts a thread asking a question.

The resident forum experts reply in the negative.

Someone else replies in the positive.

The whole thing dissolves into pointless technicalities, argument and name calling.

Result. No one is any the wiser.

 

[FLYBOYJ]

Interesting thread this one, the whole of the internet in a microcosm.

Someone starts a thread asking a question.

The resident forum experts reply in the negative.

Someone else replies in the positive.

The whole thing dissolves into pointless technicalities, argument and name calling.

Result. No one is any the wiser.

I think the recent posts here have brought valid points and those who are on one side of the argument have presented compelling data to back up their claims, so with that said I'd invite you to view another thread.

 

[Maximowitz]

I think the recent posts here have brought valid points and those who are on one side of the argument have presented compelling data to back up their claims, so with that said I'd invite you to view another thread.

Sensitive type are you? I was merely pointing out that circular unprovable arguments such as displayed here can be found on any internet forum regardless of subject. More an observation on mankind in general whose main preoccupation appears to be "winning" as opposed to "learning."

 

[drgondog]

Sensitive type are you? I was merely pointing out that circular unprovable arguments such as displayed here can be found on any internet forum regardless of subject. More an observation on mankind in general whose main preoccupation appears to be "winning" as opposed to "learning."

Learning is often obstructed by knowledge. Are you teaching or lecturing?

 

[Ome_Joop]

Sensitive type are you? I was merely pointing out that circular unprovable arguments such as displayed here can be found on any internet forum regardless of subject. More an observation on mankind in general whose main preoccupation appears to be "winning" as opposed to "learning."

I donnu...i've learned 3 things in a few moments just watching these pages!

1. that Bodo was 1200 meters...

2. that the Ju-390 was developed from the Ef100 and not a development from the Ju-290/90

3. some people can't be convinced of anything!

 

[Maximowitz]

Learning is often obstructed by knowledge. Are you teaching or lecturing?

I was making a Socratic philosophical observation of the human condition.

 

[drgondog]

I was making a Socratic philosophical observation of the human condition.

I believe he was also the author of "learning is hindered by knowlede.." but I have been wrong before.

 

[Maximowitz]

I believe he was also the author of "learning is hindered by knowlede.." but I have been wrong before.

I stole this from that well known fountain of wisdom Wikipedia but it's accurate enough:

"According to Plato's Apology, Socrates' life as the "gadfly" of Athens began when his friend Chaerephon asked the oracle at Delphi if anyone was wiser than Socrates; the Oracle responded that none was wiser. Socrates believed that what the Oracle had said was a paradox, because he believed he possessed no wisdom whatsoever. He proceeded to test the riddle through approaching men who were considered to be wise by the people of Athens, such as statesmen, poets, and artisans, in order to refute the pronouncement of the Oracle. But questioning them, Socrates came to the conclusion that, while each man thought he knew a great deal and was very wise, they in fact knew very little and were not really wise at all. Socrates realized that the Oracle was correct, in that while so-called wise men thought themselves wise and yet were not, he himself knew he was not wise at all which, paradoxically, made him the wiser one since he was the only person aware of his own ignorance."

I apologise for derailing this thread, so I'm off to the "Breaking News" thread to look at some tit...er, observe the female form. Definitely.

 

[kool kitty89]

2. that the Ju-390 was developed from the Ef100 and not a development from the Ju-290/90

Did we really establish that? It may have used some of the data in its development (stll just speculation), but the Ju 390 certainly was a development of the Ju 290. (leading back to the Ju 90 and Ju 89)

Junkers Aircraft of WWII

 

[Ome_Joop]

Did we really establish that? It may have used some of the data in its development (stll just speculation), but the Ju 390 certainly was a development of the Ju 290. (leading back to the Ju 90 and Ju 89)

Junkers Aircraft of WWII

No that (the Ef100 - Ef 53 part ) was just a sarcastic remark
Design maybe related to the Ef100 but the Ju-390 was a Ju-290 development (enlargement of the Ju-90/290 airframe )