Boeing B-52J / B-52 Re-Engining

Isn't the B-52J designation used for a proposed, dedicated jammer version just a few years ago?
 
zjz said:
Isn't the B-52J designation used for a proposed, dedicated jammer version just a few years ago?
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Just discussed, not formally assigned.
 
zjz said:
"I" has been used for Israeli F-16 and F-15 .... but I cannot recall its use anywhere else ....

IIRC, the proposed Indian F-16 uses F-16"IN" ....
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Those are marketing designations assigned by the manufacturer or designations assigned by a non-US operator. They have no relevance to the US designation system.
 
Any indications that the re-engined B-52s are going to be redesigned as B-52J?
 
Well I am not surprised at that I was thinking that the re-engined B-52s would be called the B-52J for a number of years.
 
I suppose given the conversion is a massive rebuild that each airframe will be subject to a very detailed structural survey with any identified fatigued components being replaced?
 
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
 
BlackBat242 said:
The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...

I suppose the new engine-nacelles will be less draggy too?
 
BlackBat242 said:
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...
You have to be careful with SFC numbers. I’m guessing these are test cell numbers, roughly equivalent to takeoff conditions. Cruise SFC at altitude (typically rated at 35,000 ft, 0.8M) is different and usually higher than the test cell number. The F130 will still be better than the TF33, but the difference at cruise may not be as great as the numbers quoted. If these are the cruise numbers, great!
 
BlackBat242 said:
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...
Not necessarily, partly as F119Doctor noted, and there will be greater frontal area more surface area from the nacelles themselves which would mean a slightly higher drag count as well. Also, I assume the entire assembly will weigh a little more than the previous set up, so induced drag would also rise a little. It won't be a lot, percentage wise, but it isn't nothing. So, you would be better off updating the Breguet Range equation for the B-52J, than just exchanging SFC differences.
 
Sundog said:
BlackBat242 said:
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...
Not necessarily, partly as F119Doctor noted, and there will be greater frontal area more surface area from the nacelles themselves which would mean a slightly higher drag count as well. Also, I assume the entire assembly will weigh a little more than the previous set up, so induced drag would also rise a little. It won't be a lot, percentage wise, but it isn't nothing. So, you would be better off updating the Breguet Range equation for the B-52J, than just exchanging SFC differences.
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Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.

TF33-3*: 3,900 lb (7,800 lb for 2); 53" engine diameter; cruise SFC .780 [4,000 lbf thrust, M 0.82, 35,000 ft]

F130-125*: 3,605 lb (7,210 lb for 2); 50" fan diameter (engine casing will be a little bigger, but not much); cruise SFC .657 [M 0.85, 45,000 ft]

So 84% fuel use at cruise... not quite as good, but still significantly better.



* Specific variant used in the B-52 - F130 is military version of BR700-725.
 
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I remembered reading that they are removing the 2 chin turrets from the nose, and that would reduce the drag further, possibility leading to better fuel economy too ....
 
BlackBat242 said:
Sundog said:
BlackBat242 said:
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...
Not necessarily, partly as F119Doctor noted, and there will be greater frontal area more surface area from the nacelles themselves which would mean a slightly higher drag count as well. Also, I assume the entire assembly will weigh a little more than the previous set up, so induced drag would also rise a little. It won't be a lot, percentage wise, but it isn't nothing. So, you would be better off updating the Breguet Range equation for the B-52J, than just exchanging SFC differences.
Click to expand...
Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.

TF33-3*: 3,900 lb (7,800 lb for 2); 53" engine diameter; cruise SFC .780 [4,000 lbf thrust, M 0.82, 35,000 ft]

F130-125*: 3,605 lb (7,210 lb for 2); 50" fan diameter (engine casing will be a little bigger, but not much); cruise SFC .657 [M 0.85, 45,000 ft]

So 84% fuel use at cruise... not quite as good, but still significantly better.



* Specific variant used in the B-52 - F130 is military version of BR700-725.
Click to expand...
Thanks for the cruise SFC numbers, this is the type of shift I was expecting between takeoff numbers and cruise performance.

What is your source for the cruise SFC numbers? I was unable to find those with a Google search.
 
Try Googling around for G-550 Direct Operating Costs. I found one with Cruise SFC for the BR-710-10 @ 35K feet (but being late at night, didn't save it. GRRR). You could probably chase something similar with the Global 6000 et al.
 
zjz said:
I remembered reading that they are removing the 2 chin turrets from the nose, and that would reduce the drag further, possibility leading to better fuel economy too ....
Click to expand...

Yeah, I remember reading somewhere that removing the chin turrets restore the B-52's original cruise-speed.
 
NMaude said:
zjz said:
I remembered reading that they are removing the 2 chin turrets from the nose, and that would reduce the drag further, possibility leading to better fuel economy too ....
Click to expand...

Yeah, I remember reading somewhere that removing the chin turrets restore the B-52's original cruise-speed.
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I’ve posted that here several times, the bumps and blisters disturb the pitot-static system above .86M. Yes, I’ve flown the jet out to .92M and 390 KCAS with a Pacer for a safe separation test.
 
BlackBat242 said:
Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.
Click to expand...

I have no inside knowledge here, but there might well be good reason to make the nacelles/pylons "unnecessarily" heavy. Perhaps now they weigh X, and with the new engines and modern materials they could weigh 0.5 X. But then not only would balance for the airplane be off... so would the dynamics of the wing. Lighten the pylons and the wings respond differently to flexing, gusts, etc. Maybe that's an issue, maybe it's not. But I've seen the result of "we can do it better with modern materials" without thinking everything through, and sometimes the results aren't pretty. (A crappy old, heavy steel rocket nozzle was replaced with a shiny new lighter, higher melting temperature titanium one: the new nozzle melted right off.)

There might well be depleted uranium ballast added Just Cuz.
 
BlackBat242 said:
Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.

TF33-3*: 3,900 lb (7,800 lb for 2); 53" engine diameter; cruise SFC .780 [4,000 lbf thrust, M 0.82, 35,000 ft]

F130-125*: 3,605 lb (7,210 lb for 2); 50" fan diameter (engine casing will be a little bigger, but not much); cruise SFC .657 [M 0.85, 45,000 ft]

So 84% fuel use at cruise... not quite as good, but still significantly better.



* Specific variant used in the B-52 - F130 is military version of BR700-725.
Click to expand...
Apples and oranges, that’s a pretty significant difference of altitude and slightly less of Mach number. Still it’s pretty impressive that the F130 only produces 590 lbs less thrust 10 kft higher, the TF33’s fell off pretty badly above 40 kft.
 
Orionblamblam said:
I have no inside knowledge here, but there might well be good reason to make the nacelles/pylons "unnecessarily" heavy. Perhaps now they weigh X, and with the new engines and modern materials they could weigh 0.5 X. But then not only would balance for the airplane be off... so would the dynamics of the wing. Lighten the pylons and the wings respond differently to flexing, gusts, etc. Maybe that's an issue, maybe it's not. But I've seen the result of "we can do it better with modern materials" without thinking everything through, and sometimes the results aren't pretty. (A crappy old, heavy steel rocket nozzle was replaced with a shiny new lighter, higher melting temperature titanium one: the new nozzle melted right off.)

There might well be depleted uranium ballast added Just Cuz.
Click to expand...
Almost certainly there will be a full up flutter evaluation. Lighter definitely affects the natural frequencies, the aero will be different as well so the DU anti-flutter weights may well be in order. Time will tell.

I’ve long since left the BUFF so I never saw anything about the dynamic loads other than for new stores, even then it was more Seek Eagle stuff worried about if the new store would hit another weapon or the jet.
 
mkellytx said:
BlackBat242 said:
Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.

TF33-3*: 3,900 lb (7,800 lb for 2); 53" engine diameter; cruise SFC .780 [4,000 lbf thrust, M 0.82, 35,000 ft]

F130-125*: 3,605 lb (7,210 lb for 2); 50" fan diameter (engine casing will be a little bigger, but not much); cruise SFC .657 [M 0.85, 45,000 ft]

So 84% fuel use at cruise... not quite as good, but still significantly better.



* Specific variant used in the B-52 - F130 is military version of BR700-725.
Click to expand...
Apples and oranges, that’s a pretty significant difference of altitude and slightly less of Mach number. Still it’s pretty impressive that the F130 only produces 590 lbs less thrust 10 kft higher, the TF33’s fell off pretty badly above 40 kft.
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Those were engine WEIGHTS, provided for the part of the discussion about nacelle differences.

Both engines are listed as having the sane 17,000 lb thrust at max power, no mention of max thrust at altitude.
 
F119Doctor said:
BlackBat242 said:
Sundog said:
BlackBat242 said:
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...
Not necessarily, partly as F119Doctor noted, and there will be greater frontal area more surface area from the nacelles themselves which would mean a slightly higher drag count as well. Also, I assume the entire assembly will weigh a little more than the previous set up, so induced drag would also rise a little. It won't be a lot, percentage wise, but it isn't nothing. So, you would be better off updating the Breguet Range equation for the B-52J, than just exchanging SFC differences.
Click to expand...
Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.

TF33-3*: 3,900 lb (7,800 lb for 2); 53" engine diameter; cruise SFC .780 [4,000 lbf thrust, M 0.82, 35,000 ft]

F130-125*: 3,605 lb (7,210 lb for 2); 50" fan diameter (engine casing will be a little bigger, but not much); cruise SFC .657 [M 0.85, 45,000 ft]

So 84% fuel use at cruise... not quite as good, but still significantly better.



* Specific variant used in the B-52 - F130 is military version of BR700-725.
Click to expand...
Thanks for the cruise SFC numbers, this is the type of shift I was expecting between takeoff numbers and cruise performance.

What is your source for the cruise SFC numbers? I was unable to find those with a Google search.
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https://en.wikipedia.org/wiki/Rolls-Royce_BR700#BR725 (cruise SFC here)

https://en.wikipedia.org/wiki/Rolls-Royce_BR700#Specifications (diameter, weight, thrust)

https://en.wikipedia.org/wiki/Pratt_&_Whitney_JT3D (thrust)

https://en.wikipedia.org/wiki/Pratt_&_Whitney_JT3D#Specifications_(JT3D-8A_/_TF33-P-7) (diameter, weight, cruise SFC)
Yes, the specs are for the TF33-7 installed in the C-141, but should be pretty close to those of the TF33-3 in the B-52H.
 
jsport said:
TomS said:
NMaude said:
Any indications that the re-engined B-52s are going to be redesigned as B-52J?
Click to expand...

Click to expand...
www.airandspaceforces.com

It’s Official: The Re-Engined B-52 Will be the B-52J

As soon as they get new engines, B-52H bombers will be designated as B-52J aircraft, Air Force budget documents show.
www.airandspaceforces.com www.airandspaceforces.com
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If the C-130J is the Super Hercules, does that now make the B-52J the Super Stratofortress?:p

​

 
Just to note: with engine diameter specs, anything other than fan (tip) diameter (which is obviously well defined) is fraught with difficulties when comparing. For example, per the engine TCDS the maximum radius of the BR700-725 envelope is 950mm. Is that a valid comparison to the TF33 diameter statement of ~1.35m? I don't have the faintest idea (which is exactly the point), but the BR700 delivers the same thrust with triple the BPR - intuitively there should be a non-trivial difference in fan diameter between the two.

Unfortunately, I could not find the JT3D TCDS online - too old I guess!
 
BlackBat242 said:
F119Doctor said:
BlackBat242 said:
Sundog said:
BlackBat242 said:
TF33 specific fuel consumption (lb fuel/lb thrust/hr) = .520

RR F130 SFC = .39

That is a 25% reduction in fuel use, which should mean a 25% increase in range with the same fuel load - just on the engine improvement.

The released artist conceptions of what the fully-modified aircraft will look like shows the removal of the undernose electro-optical sensors in their draggy blisters - this should reduce drag measurably, further increasing range.
Click to expand...
Not necessarily, partly as F119Doctor noted, and there will be greater frontal area more surface area from the nacelles themselves which would mean a slightly higher drag count as well. Also, I assume the entire assembly will weigh a little more than the previous set up, so induced drag would also rise a little. It won't be a lot, percentage wise, but it isn't nothing. So, you would be better off updating the Breguet Range equation for the B-52J, than just exchanging SFC differences.
Click to expand...
Why would you assume heavier and larger frontal area nacelle assemblies?
Modern materials are normally stronger and lighter than the late 1950s materials used in the B-52H's nacelles, and the engines will be lighter as well.

TF33-3*: 3,900 lb (7,800 lb for 2); 53" engine diameter; cruise SFC .780 [4,000 lbf thrust, M 0.82, 35,000 ft]

F130-125*: 3,605 lb (7,210 lb for 2); 50" fan diameter (engine casing will be a little bigger, but not much); cruise SFC .657 [M 0.85, 45,000 ft]

So 84% fuel use at cruise... not quite as good, but still significantly better.



* Specific variant used in the B-52 - F130 is military version of BR700-725.
Click to expand...
Thanks for the cruise SFC numbers, this is the type of shift I was expecting between takeoff numbers and cruise performance.

What is your source for the cruise SFC numbers? I was unable to find those with a Google search.
Click to expand...
https://en.wikipedia.org/wiki/Rolls-Royce_BR700#BR725 (cruise SFC here)

https://en.wikipedia.org/wiki/Rolls-Royce_BR700#Specifications (diameter, weight, thrust)

https://en.wikipedia.org/wiki/Pratt_&_Whitney_JT3D (thrust)

https://en.wikipedia.org/wiki/Pratt_&_Whitney_JT3D#Specifications_(JT3D-8A_/_TF33-P-7) (diameter, weight, cruise SFC)
Yes, the specs are for the TF33-7 installed in the C-141, but should be pretty close to those of the TF33-3 in the B-52H.
Click to expand...
The TF33-P-7 has a larger fan and a extra stage of low compressor than the P-3, so the SFC numbers won’t be exactly right, but they will be in the right ballpark
 
BlackBat242 said:
Those were engine WEIGHTS, provided for the part of the discussion about nacelle differences.

Both engines are listed as having the sane 17,000 lb thrust at max power, no mention of max thrust at altitude.
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Thank you for the correction, I misread. Thrust lapse will be as will be off max SFSC’s, my 1-1B52H is currently unavailable otherwise I’d hit the charts to get the TF33 data…
 
Lots of pilots look over their shoulder to land these. B-52s are as much train cars as airframes.

They don't rotate the nose either except with X-15s.

Land and take off flat.
 
Orionblamblam said:
I have no inside knowledge here, but there might well be good reason to make the nacelles/pylons "unnecessarily" heavy. Perhaps now they weigh X, and with the new engines and modern materials they could weigh 0.5 X. But then not only would balance for the airplane be off... so would the dynamics of the wing. Lighten the pylons and the wings respond differently to flexing, gusts, etc. Maybe that's an issue, maybe it's not. But I've seen the result of "we can do it better with modern materials" without thinking everything through, and sometimes the results aren't pretty. (A crappy old, heavy steel rocket nozzle was replaced with a shiny new lighter, higher melting temperature titanium one: the new nozzle melted right off.)

There might well be depleted uranium ballast added Just Cuz.
Click to expand...
The DU ballast would be for flutter concerns, or to keep empty CG where the engineers wanted it.

When we were doing hush kits on 727s, it required something like 125lbs of DU bolted to the radome bulkhead to drag CG forward. The new engines were something like 4ft longer, with an exhaust mixing area surrounded by hi temp sound deadener.

Trident said:
Just to note: with engine diameter specs, anything other than fan (tip) diameter (which is obviously well defined) is fraught with difficulties when comparing. For example, per the engine TCDS the maximum radius of the BR700-725 envelope is 950mm. Is that a valid comparison to the TF33 diameter statement of ~1.35m? I don't have the faintest idea (which is exactly the point), but the BR700 delivers the same thrust with triple the BPR - intuitively there should be a non-trivial difference in fan diameter between the two.

Unfortunately, I could not find the JT3D TCDS online - too old I guess!
Click to expand...
More a matter of a much smaller diameter core than the old JT3D, and much better acceleration/compression in the fan stage(s).
 
Scott Kenny said:
The DU ballast would be for flutter concerns, or to keep empty CG where the engineers wanted it.
Click to expand...

Almost certainly flutter, the BUFF wing is pretty flexible and the tip tanks are there as flutter weights. Not to mention there’s enough ballast elsewhere to move/remove.

When we were doing hush kits on 727s, it required something like 125lbs of DU bolted to the radome bulkhead to drag CG forward. The new engines were something like 4ft longer, with an exhaust mixing area surrounded by hi temp sound deadener.
Click to expand...

Once upon a time I interviewed for a job with a now acquired airline for a performance engineer role where we discussed weight and balance for the 727. Turns out to ferry them in an airline configuration they’d have to move all of the galley carts to the front so the CoG would be in limits. So, totally believable that you’d have to put DU out front to make up for the weight aft of the CoG.
 

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