DerGiLLster
Airman
- 70
- May 1, 2015
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It would have been an awesome sight taking off but it would have had an epic fuel consumption. Still going to be a big lumbering not quite so slow target.
Thank you Koopernic! You answered my thread and another question that has been bothering me. How to convert thrust into horsepower!
Also, what if the Ju 390 had six Walter rockets to assist in takeoff? It had a durable thick wing-frame, I would assume it would be able to take the stress of rocket takeoff.
I'm sure you are right, the world of bomber versus fighter was changing
The Ju 290A5 wasn't particularly fast, about the same 280 mph performance league as a Lancaster but its larger brother the Ju 390 was fairly sprightly at 314 mph with a range of 6000 miles. S
Both versions if pressurised and equipped with the turbo charged BMW801TJ were expected to be have an impressive fast cruise at 11000m. Thin air forgives a big fuselage. This is the Ju 290B or Ju 390C
As you say, it would have been a target. It would have been satisfactory only for maritime patrol, by 1945 or 46 there might have been some standoff missiles that would give it some assault capability. Passive radar homing glide bombs such as the BV-246 which one might expect to get active radar homing like the USN's BAT missile or TV guidance. The range of these missiles, well in excess of 100km might work on some targets.
I think its main use would have been to support the Type XXI U-boats.
Koopernic, how much of a speed increase would the 290/390 with Jumo 222'z have?
Most web pages give the speed of the Ju 290V1 as 314mph with 1700hp BMW801G2/D2 engines. The aircraft flew in 1943 and that was certainly the maximum power available at that time. It's possible these ratings are for the more powerful BMW801E but I doubt it.
Assuming the Jumo 222A2/B2 had the same full throttle height and drag and that the extra weight has not effect (a fair assumption) the speed increase would be
314 x (2500/1700)^0.33 = 357mph.
Assuming 1900hp was available 344.
The Jumo 222E/F at least 10% faster again due to the operation in thinner air, about 392mph.
The aircraft had much lower wing loading than the B-29. With the Jumo 222/EF or BMW801TJ it would have good altitude and speed.
The Ju 290 has its origins in the Ju 89 bomber which was like the B-17 a low wing monoplane. The bomb bay would have to go between the wing spars as on the B17, He 111. I do not see that as a problem for a long range aircraft. A B17 bomb load out might be 6 x 1000lbs and surely the bigger Ju 290 could do better in terms of size and number. Nevertheless the Ju 290/390 was I believe to receive a pannier for carrying bombs. I suspect since the pannier could be used to carry a ventral gun it would allow the elimination of the ventral gun gondola leading to a minimal increase in drag.
A typical B17 load out was load 6 x 1000lb, the Ju 290 surely could have carrier more and bigger bombs if it had been given an internal bomb bay. However if you can make a pannier act as a ventral gun station then it makes sense to go with the pannier.
Thank you very much, Koopernic. You say that the bomb bay would not have been a problem at long ranges, but what about shorter ones? Also, could bomb bays have been added in the engine nacelles as the Fw 200 used?
The Ju 390 actually had fantastic performance in all aspects: range, speed, operational ceiling bomb load and armament.
I'm not sure if I quite catch you there. Perhaps as a maritime patrol aircraft, but as a bomber it was outclassed by its competition whether it be on paper (Ta 400, He 277), or actually flying (Me 264, B-29), not just in bomb-load but also being a full 35-40 mph slower than all of them, and having a measly service cieling of 20,000 ft, compared to the average of 30,000 of it competitors.
The Ju 290 or 390 when fitted with the turbo charged BMW801TJ or TQ would have had superb speed and altitude performance. This engine did see service in some Ju 88S3 and a few evaluation Ju 388L1 however the speed of the Ju 390 of of 314mph with plane jane mechanically supercharged BMW801 is quite good. The Ju 290 or 390 (non turbocharged non intercooled) can't compete with a B-29 (turbo charged) however an turbo charged BMW801 was available and could no doubt be fitted with relative ease. Similar performance could be expected from the Jumo 213E1 that was used on the Ta 152H and Ju 88G7.
Non of the above aircraft would in my view be survivable.
One aircraft which might have been survivable was the Ju 488. Black Cross Ju 288/388/488 gives speed estimates for the Ju 488, they seem initially unimpressive (low 400+ mph range) until you realise these are cruise not maximum speeds, its range was however less.
The Ju 390 had a big advantage over the He 277 and Ta 400. In that it could be actually gotten into production very quickly.
Would there be any possible use of auxiliary jet engines applied for take-off boost? From my understanding the advantages of non-jettisonable JATO units (be it rocket or turbine) was relatively high thrust relative to weight and static drag added and high fuel consumption being a non-issue given they weren't intended for sustained use in-flight.
But perhaps the relatively poor thrust to weight ratio and fuel consumption of the Jumo 004 or even BMW 003 would preclude it from such applications.
I still wonder if pulse jets would make decent JATO units. You'd need to address vibration issues, but that might be somewhat less problematic for short-term only use. Static thrust should be improved if the jets were within range of the prop wash as well. (expendable jettisonable pulse jet units should also be cheap enough to just throw away rather than worrying about recovery chutes as walter rockets used)