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

[Scott Kenny]

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.

Oh, that's funny!

When we were shuffling the beasts around the hangar there were always 10-15 mechanics riding in the forward baggage bay as ballast.

 

[publiusr]

Maybe batteries instead of DU?

 

[Scott Kenny]

Maybe batteries instead of DU?

DU is a much smaller package physically. That ballast I mentioned? It was about 6"x10"x10".

 

[publiusr]

Seems a waste being inert an all.

 

[Scott Kenny]

Seems a waste being inert an all.

That's why it was so small. To fit on the antenna bulkhead and not take up lots of volume.

Other engineering changes do use things like batteries as ballast. Or change air duct tube materials for a lighter one, or whatever. It's an option, but when you're already doing a fairly extensive change like that at the aft end of the plane, you want to keep the total overall weight gained down to a minimum. Adding batteries would also require adding bus bars and/or electrical wiring.

 

[GTX]

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[Scott Kenny]

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Kinda surprised that they aren't planning on fitting that internally, replacing the existing internal jammers. B52s have plenty of space for that, since they were designed around 1950s sized electronics!

My vote would be to fit the entire Growler electronic warfare package as internal systems on the B52Js.

 

[Josh_TN]

I’m surprised they are even considering it. I wouldn’t think USAF would ever risk one being close enough to opponent defenses for EW to be effective.

 

[Scott Kenny]

I’m surprised they are even considering it. I wouldn’t think USAF would ever risk one being close enough to opponent defenses for EW to be effective.

Long endurance, lots of electrical power available to drive the jammers, and it can also pack an absurd amount of boom to send to whatever radars light up.

 

[TomS]

Kinda surprised that they aren't planning on fitting that internally, replacing the existing internal jammers. B52s have plenty of space for that, since they were designed around 1950s sized electronics!

My vote would be to fit the entire Growler electronic warfare package as internal systems on the B52Js.

If you can find the budget, sure. But hanging off-the-shelf pods on the existing pylons is way cheaper and faster.

 

[Scott Kenny]

If you can find the budget, sure. But hanging off-the-shelf pods on the existing pylons is way cheaper and faster.

I mean, they're overhauling the aircraft as they install the new engines, pulling the EOTS from under the nose entirely, and I'm assuming replacing much of the internal jammers as well (the electronics upgrades aren't exactly clear).

So if you're already replacing the internal jammers, might as well install the current top of the line stuff!

 

[Josh_TN]

Long endurance, lots of electrical power available to drive the jammers, and it can also pack an absurd amount of boom to send to whatever radars light up.

The B-52 always brings payload and endurance to the table, but in a PRC-US conflict I would imagine they would be exclusively used as stand off platforms no where near Chinese defenses.

 

[Scott Kenny]

The B-52 always brings payload and endurance to the table, but in a PRC-US conflict I would imagine they would be exclusively used as stand off platforms no where near Chinese defenses.

Oh, definitely their primary mission... But when you have enough generator output to gray out half the hemisphere, using a beast as a stand-in EW/SEAD bird is an option. Think Dale Brown's Megafortress.

 

[TomS]

I mean, they're overhauling the aircraft as they install the new engines, pulling the EOTS from under the nose entirely, and I'm assuming replacing much of the internal jammers as well (the electronics upgrades aren't exactly clear).

So if you're already replacing the internal jammers, might as well install the current top of the line stuff!

Redesigning the emitters to fit in places other than the pod they are currently fitted in is a non-trivial cost.

 

[Scott Kenny]

Redesigning the emitters to fit in places other than the pod they are currently fitted in is a non-trivial cost.

Granted.

 

[mkellytx]

I mean, they're overhauling the aircraft as they install the new engines, pulling the EOTS from under the nose entirely, and I'm assuming replacing much of the internal jammers as well (the electronics upgrades aren't exactly clear).

So if you're already replacing the internal jammers, might as well install the current top of the line stuff!

Who's to say that they replace it? The Growler's NGJ may very well augment what's already there. Now given just about anything I know about that system is more likely than not covered by NDA's I signed, no comments about the system.

Best guess is that if they're serious, they go the route of SOJ and put the pods in place of the external tanks. They're more or less flutter weights and the new engines really make that fuel surplus, the field of view there is pretty good as well.

 

[Josh_TN]

Oh, definitely their primary mission... But when you have enough generator output to gray out half the hemisphere, using a beast as a stand-in EW/SEAD bird is an option. Think Dale Brown's Megafortress.

AFAIK NGJ uses ram air for power, not the parent platforms. So the B-52s power is likely immaterial.

 

[TomcatViP]

Well, nothing says that the pod is not adapted to get more power from the 8 turbines.

 

[Josh_TN]

Well, nothing says that the pod is not adapted to get more power from the 8 turbines.

No, but it seems unlikely since it was a USN tactical aircraft program. Moreover I doubt the emitter and cooling systems are designed with a higher peak power in mind. I’d be shocked if B-52 capability was any different than that EF-18.

 

[TomcatViP]

More fun:

 

[NMaude]

I’d be shocked if B-52 capability was any different than that EF-18.

Actually it's the EA-18G not EF-18.

Is that some sort of air-pressure loading of the B-52G's airframe, @TomcatViP ? And those nacelles appear to be the ones containing the TF-33 turbofan.

 

[TomcatViP]

Yes
But it shows that attention was paid to existing configuration (often in the past, bidders and services just didn't care - when you have a major aero upgrade on an airframe that have been flying 60+ years, you need to ensure that there is continuity in the surrounding airflow).

 

[Josh_TN]

The B-52J upgrade is supposed to remove a lot of equipment from the nose (ECM gear, EVS blisters) so hypothetically the upgrade will be a bit slicker, though I don't think in a way that really would significantly matter. I wonder if the high altitude performance will be markedly superior though? MKellyTX mentioned several times the TF-33s struggled above 40k feet; I'd think business jet engines would do much better given that most of them seem to operate fine at 40-50k feet. I was thinking that might be a big deal with regards to HACM deployment - I have a pet theory that the reason the F-15 is the threshold platform is because the B-52 wouldn't be able to lift a significant amount of them to a high enough altitude for their booster envelope. Looking at X-51, the launch was at 50k feet with a 4000 lb stack (dry) plus 270 lbs of fuel. The new 3D printed combustors are a generation or two ahead of X-51 and said to be half the weight, but assuming they want to slim down the whole package to ~20 feet and 3000-3500 lbs, I would guess the launch envelope is still similar.

 

[F119Doctor]

Interesting comment about the TF33 struggling above 40K. There is nothing inherent with the engine about operating above that altitude. RB-57G with TF33 operated regularly at 60K, and the first U2 flew above 70k with J57 (same core engine as TF33) with only fuel controls modified to allow stable operation at the extremely thin atmosphere.

The TF33 provided 5k more static thrust than the J57 on the B-52G, and while the altitude thrust lapse rate may be higher with the turbofan vs turbojet, it should still have higher thrust at 40K, 0.9M cruise. Maybe the blisters and pod add-one added so much drag that the aircraft became thrust limited above 40K. Don’t know if the new higher bypass F130 engines will capable of more thrust than the TF33 at altitude unless they are severely flat rated at 18K takeoff thrust for engine out controllability and wing structure limits.

 

[Scott Kenny]

The B-52J upgrade is supposed to remove a lot of equipment from the nose (ECM gear, EVS blisters) so hypothetically the upgrade will be a bit slicker, though I don't think in a way that really would significantly matter. I wonder if the high altitude performance will be markedly superior though? MKellyTX mentioned several times the TF-33s struggled above 40k feet; I'd think business jet engines would do much better given that most of them seem to operate fine at 40-50k feet. I was thinking that might be a big deal with regards to HACM deployment - I have a pet theory that the reason the F-15 is the threshold platform is because the B-52 wouldn't be able to lift a significant amount of them to a high enough altitude for their booster envelope. Looking at X-51, the launch was at 50k feet with a 4000 lb stack (dry) plus 270 lbs of fuel. The new 3D printed combustors are a generation or two ahead of X-51 and said to be half the weight, but assuming they want to slim down the whole package to ~20 feet and 3000-3500 lbs, I would guess the launch envelope is still similar.

I suspect that's more due to drag from all the junk on the external pylons.

 

[TomcatViP]

Test Team Researches Human Factors Integration into B-52 CERP

A test team from the Global Power Bombers Combined Test Force recently began research into human factors integration as part of the B-52 Stratofortress Commercial Engine Replacement Program, on Edwards Air Force Base, California. (Air Force video by Giancarlo Casem)

www.dvidshub.net

B-52 Pilots Test New Instruments To Make BUFF Flying Easier

A test team at Edwards Air Force Base is redesigning the engine gauge clusters and cockpit for the upcoming B-52 tech upgrades.

www.airandspaceforces.com

 

[NMaude]

I wonder if they'll ever fit HUDs or HMDs for the pilots?

 

[FighterJock]

I doubt that they will fit HUDs to the B-52 upgrade NMaude, a Helmet Mounted Display would be a good idea though.

 

[Josh_TN]

I wonder if they'll ever fit HUDs or HMDs for the pilots?

I can't image a HUD is even useful in this type of aircraft. A helmet might be useful, but if it isn't part of the J upgrade, then it seems unlikely to occur for the next decade or two.

 

[archipeppe]

it seems unlikely to occur for the next decade or two.

Ok it will come with late XXI Century's upgrade package for B-52s (2040-2075)....

 

[TomS]

I can't image a HUD is even useful in this type of aircraft. A helmet might be useful, but if it isn't part of the J upgrade, then it seems unlikely to occur for the next decade or two.

I'd go the other way -- I can see some value in a simple HUD like some civilian aircraft use to improve landings in low-viz conditions.* But I can't see what a helmet-mounted display would be good for. The B-52 isn't carrying high off-boresight weapons aimed by the pilots, and indeed most or all of the weapon targeting is done by crew sitting in the back facing a wall of electronics with no outside view at all. They don't need the "look to kill" capability an HMD gives a single or two-person crew flying head-up in the cockpit. The pilots already have NVGs anyway for night flying.

 

[Byeman]

I can't image a HUD is even useful in this type of aircraft. A helmet might be useful, but if it isn't part of the J upgrade, then it seems unlikely to occur for the next decade or two.

C-17 has a HUD.

 

[Archibald]

Dassault Mercure airliner had HUD (from memory).

 

[tinlail]

I'd go the other way -- I can see some value in a simple HUD like some civilian aircraft use to improve landings in low-viz conditions.* But I can't see what a helmet-mounted display would be good for. The B-52 isn't carrying high off-boresight weapons aimed by the pilots, and indeed most or all of the weapon targeting is done by crew sitting in the back facing a wall of electronics with no outside view at all. They don't need the "look to kill" capability an HMD gives a single or two-person crew flying head-up in the cockpit. The pilots already have NVGs anyway for night flying.

The B-52 has some wild crosswind capability, and getting comfortable flying sideways takes practice. Maybe a helmet display is needed for off-boresight landing?

 

[TomS]

The B-52 has some wild crosswind capability, and getting comfortable flying sideways takes practice. Maybe a helmet display is needed for off-boresight landing?

Clearly not needed, because they do those landings without one. There hasn't been any official hint of either HUD or HMD being considered; this just us BSing on the internet.

 

[tinlail]

Clearly not needed, because they do those landings without one. There hasn't been any official hint of either HUD or HMD being considered; this just us BSing on the internet.

"needed" was poor wording, useful maybe even cost effective considering the training time?

 

[Scott Kenny]

I can't image a HUD is even useful in this type of aircraft. A helmet might be useful, but if it isn't part of the J upgrade, then it seems unlikely to occur for the next decade or two.

Gulfstream business jets have a HUD. Helps when landing in bad weather.

 

[mkellytx]

The B-52J upgrade is supposed to remove a lot of equipment from the nose (ECM gear, EVS blisters) so hypothetically the upgrade will be a bit slicker, though I don't think in a way that really would significantly matter. I wonder if the high altitude performance will be markedly superior though? MKellyTX mentioned several times the TF-33s struggled above 40k feet; I'd think business jet engines would do much better given that most of them seem to operate fine at 40-50k feet. I was thinking that might be a big deal with regards to HACM deployment - I have a pet theory that the reason the F-15 is the threshold platform is because the B-52 wouldn't be able to lift a significant amount of them to a high enough altitude for their booster envelope. Looking at X-51, the launch was at 50k feet with a 4000 lb stack (dry) plus 270 lbs of fuel. The new 3D printed combustors are a generation or two ahead of X-51 and said to be half the weight, but assuming they want to slim down the whole package to ~20 feet and 3000-3500 lbs, I would guess the launch envelope is still similar.

@Josh_TN Without looking at the thrust data for each engine it's tough to say off of the top of my cranium. That said, after completion of a test mission we took Balls 50 up as high as we could and topped out in the mid 40's. Some of the "old" SAC guys said the straight jet BUFF's did better higher. I also helped mission plan X-51 and the drop was 49/49.5 they didn't quite make it up to 50. Have no clue what altitude the new fangled HACM want's to play, suffices to say though as an operational weapon is should play nice lower.

 

[mkellytx]

Interesting comment about the TF33 struggling above 40K. There is nothing inherent with the engine about operating above that altitude. RB-57G with TF33 operated regularly at 60K, and the first U2 flew above 70k with J57 (same core engine as TF33) with only fuel controls modified to allow stable operation at the extremely thin atmosphere.

Both of those birds have better wing loading and the 57 had some spare turbojets for extra umph. The H is heavier than prior models so that raises the stall speed, while all the blisters and what not lowered the top speed from .92 M to .88 M. That's not insignificant when you fly up in coffin corner. The TF33's also create more drag so that doesn't help. It's worth remembering that the second-generation U-2's had to have J75's, which is a scaled up J57 to maintain performance. Later those were replaced by specially modified F118's which are non-afterburning versions of the F101 (another engine I have first had experience with), but the inlets didn't change too much which may be why drag wasn't as big of a deal for that installation.

The TF33 provided 5k more static thrust than the J57 on the B-52G, and while the altitude thrust lapse rate may be higher with the turbofan vs turbojet, it should still have higher thrust at 40K, 0.9M cruise. Maybe the blisters and pod add-one added so much drag that the aircraft became thrust limited above 40K. Don’t know if the new higher bypass F130 engines will capable of more thrust than the TF33 at altitude unless they are severely flat rated at 18K takeoff thrust for engine out controllability and wing structure limits.

It will be interesting to see. The installation, like the business jets will use a mixed flow duct so I'd love to see the detailed engineering data. Another thing to consider is that the F130's have digital engine controls while the TF33's were still hydro=mechanical. Again, if the airflow around the nose is clean again, then the top speed may go back to .92 M if the Air Force wants to spend the money to recertify.

 

[NMaude]

Some of the "old" SAC guys said the straight jet BUFF's did better higher.

Are you talking about the earlier J-57 powered models?