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Buckeyetech
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Feb 27, 2020 11:16 pm

I still don’t see the practicality of this. Even if the USAF started today on these mods, it would take well over a decade to finish every one, which by that point their money will mostly have dried up from buying KC-46s, B-21s, prototypes for C-17 replacements, standing up the space force, etc.
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Slug71
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Re: New advertisement: B-52 re-engine back in the mix?

Fri Feb 28, 2020 1:42 am

Buckeyetech wrote:
I still don’t see the practicality of this. Even if the USAF started today on these mods, it would take well over a decade to finish every one, which by that point their money will mostly have dried up from buying KC-46s, B-21s, prototypes for C-17 replacements, standing up the space force, etc.


Agreed.
I think the money is better spent bringing the B-21 online quicker.
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Fri Feb 28, 2020 7:31 am

First of all, throwing money at the B-21 won't necessarily bring it online any quicker. The limiting factor will be the lead time for the various subassemblies and the production space available at PMD. Secondly, the B-52 is scheduled to remain in the inventory well into the 2050 time frame. That is still 30 years of service. The Buff has a much better Mission Ready rate than the B-1 or B-2. The B-1 is clapped out and needs major structural work just to keep it flying.
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LyleLanley
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Re: New advertisement: B-52 re-engine back in the mix?

Fri Feb 28, 2020 10:11 pm

mmo wrote:
First of all, throwing money at the B-21 won't necessarily bring it online any quicker. The limiting factor will be the lead time for the various subassemblies and the production space available at PMD. Secondly, the B-52 is scheduled to remain in the inventory well into the 2050 time frame. That is still 30 years of service. The Buff has a much better Mission Ready rate than the B-1 or B-2. The B-1 is clapped out and needs major structural work just to keep it flying.


Solid. Also, the B-52 is a bomb-truck that is perfectly happy flying 8-12 hour sorties chucking spears when needed, whereas the B-21 is supposed to be a penetrator. Do we really want to have the B-21 loitering and burning up hours when an alternative (the BUFF) is right there?
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Ozair
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Re: New advertisement: B-52 re-engine back in the mix?

Sun Mar 01, 2020 1:16 am

In line with the upgrade discussion the USAF seems very keen on moving forward with just the B-52 and the B-21. The article also indicates, as others have mentioned already, how much of an upgrade the USAF is considering for the B-52. New engines obviously, apparently a new radar and as discussed in this and previous threads additional structural work on the upper wing skins etc.

Air Force general: Two-bomber fleet is the future

The future of the Air Force’s bomber fleet will be the B-21 Raider, now under development, and a heavily modified version of the Cold War-era B-52 Stratofortress, Lt. Gen. David Nahom, deputy chief of staff for plans and programs, told lawmakers on Thursday.

Nahom said getting to that two-bomber fleet is important as the Air Force shifts to a strategy focused on what the Pentagon calls “great power competition” — preparing for a conflict with a peer or near-peer nation such as China or Russia.

“On the bomber fleet, there’s nothing more important to the Air Force,” Nahom told the House Armed Services subcommittee on seapower and projection forces. “If you look at what the bombers bring, no one else brings it. Our joint partners don’t bring it, our coalition partners don’t bring it.”

The B-1B Lancer and B-2 Spirit are important in the meantime, and each bring important capabilities, Nahom said. The B-2′s ability to penetrate enemy airspace and carry nuclear weapons, and the volume of ordnance the B-1 can carry, make each aircraft crucial for now, he said. The Air Force needs to keep the B-2 until the B-21 is delivered and nuclear-certified, he said, which will likely take about a decade.

...

https://www.airforcetimes.com/news/your ... 2F#jwvideo

Given what we know about what the USAF wants to do and how long they want the B-52 to last, easily now to the mid 2050s, then what else does the B-52 need to take it to that point?

- New engines coming
- New radar mooted, any ideas what they will do, perhaps an APG-81 derivative or a radar with multiple panels across the aircraft?
- Enhanced EW
- EO/IR sensor upgrade

Thoughts on anything else?
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Sun Mar 01, 2020 6:43 am

Ozair wrote:
Thoughts on anything else?


IIRC, there will also be the following upgrades:
Installation of new ejection seats, at least the upward ones.
Revamp of pneumatic system
Increased electric generation capacity by adding Gens to either 2 or 4 more engines
Revamp of the cockpit and going "glass" where ever possible
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JayinKitsap
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Re: New advertisement: B-52 re-engine back in the mix?

Sun Mar 01, 2020 9:41 am

If going in for wing skins and the like, as well as new engines is it good to replace all of the wiring at some point. I would think the insulation is getting brittle and easy to crack.
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Sun Mar 01, 2020 11:03 am

They are going to have to do the upper wing skins as they are a time expiration issue. IIRC, 2030 the upper wing skins have to be done, so if they are planning another 20 years they will have to have it done.

To be honest the wiring should be in pretty good shape as there have been so many mods done the wiring would have been replaced.changed to handle the mod.
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JayinKitsap
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Re: New advertisement: B-52 re-engine back in the mix?

Tue Mar 03, 2020 7:02 am

mmo wrote:
They are going to have to do the upper wing skins as they are a time expiration issue. IIRC, 2030 the upper wing skins have to be done, so if they are planning another 20 years they will have to have it done.

To be honest the wiring should be in pretty good shape as there have been so many mods done the wiring would have been replaced.changed to handle the mod.


I should have thought of that, in this big of a mod I would suspect the navigation and landing lights would jump to a LED version. But the wiring would have changed with each new system under the wing, except for the engine wiring which comes out in this mod.

I came across a B-52 re engine article that covers the history, interesting. Some ugly looking concepts too.

https://fighterjetsworld.com/air/re-eng ... ber/20478/
 
Ozair
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Re: New advertisement: B-52 re-engine back in the mix?

Mon Apr 27, 2020 11:49 pm

The RFP for the B-52 re-engine has been released with a contract award expected in May 2021.

US Air Force issues draft request for proposal to replace B-52 engines

The US Air Force (USAF) released a draft request for proposal to replace the engines of the ageing Boeing B-52H Stratofortress.

The notice brings the B-52H re-engine programme one step closer to kick off.

The service plans to buy 608 commercial engines – plus additional spare engines and support equipment – enabling it to operate the heavy bombers until at least 2050, a 23 April notice says. The USAF plans to award a contract in May 2021. The engines are to be delivered over 17 years.

...

GE Aviation, Pratt & Whitney and Rolls-Royce have expressed interest in bidding on the programme.

...

https://www.flightglobal.com/fixed-wing ... 99.article

As many have suggested, GE is apparenlty going to offer both the CF-34-10 or the Passport engine while P&W are going to offer the PW800 while RR will offer the F130.
 
744SPX
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Re: New advertisement: B-52 re-engine back in the mix?

Tue Apr 28, 2020 3:01 pm

The CF-34 is a 50 year old design
 
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Nomadd
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Re: New advertisement: B-52 re-engine back in the mix?

Tue Apr 28, 2020 4:43 pm

744SPX wrote:
The CF-34 is a 50 year old design

You can call the 787 a 66 year old design if you want. It has about as much to do with the 707 as the newest CF34 has to do with the original.
 
aumaverick
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Re: New advertisement: B-52 re-engine back in the mix?

Tue Apr 28, 2020 5:12 pm

744SPX wrote:
The CF-34 is a 50 year old design


The B-52 took its first flight 68 years ago.

Does their age make either one of them irrelevant in the context of this discussion?
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Channex757
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Re: New advertisement: B-52 re-engine back in the mix?

Tue Apr 28, 2020 6:54 pm

My bet is on the GE Passport. The USAF might find this modern engine ticks all the right boxes, or alternatively the Rolls offering which the USAF has experience of. RR USA (Allison) would be ideal to manufacture them and provide support.
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Tue Apr 28, 2020 10:00 pm

RR should have the inside track due to fitting perfectly, and in inventory already, unless they bid the support/maintenance bit comparatively high.
 
rlwynn
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Re: New advertisement: B-52 re-engine back in the mix?

Wed Apr 29, 2020 12:42 pm

I do not know why the CF-34-10 is even called a CF-34. I has nothing to do with a CF-34.
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744SPX
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Re: New advertisement: B-52 re-engine back in the mix?

Wed Apr 29, 2020 4:28 pm

Nomadd wrote:
744SPX wrote:
The CF-34 is a 50 year old design

You can call the 787 a 66 year old design if you want. It has about as much to do with the 707 as the newest CF34 has to do with the original.



You're hilarious my friend. The CF-34-10 core is directly derived from the CFM-56 core, which is derived from the F101 core which is 50 years old.
 
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Nomadd
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Re: New advertisement: B-52 re-engine back in the mix?

Wed Apr 29, 2020 6:57 pm

744SPX wrote:
Nomadd wrote:
744SPX wrote:
The CF-34 is a 50 year old design

You can call the 787 a 66 year old design if you want. It has about as much to do with the 707 as the newest CF34 has to do with the original.


You're hilarious my friend. The CF-34-10 core is directly derived from the CFM-56 core, which is derived from the F101 core which is 50 years old.

And I'm derived from a 19th century German sailor who was designed 200 years ago. So what?
 
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bikerthai
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Re: bNew advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 2:58 am

Nomadd wrote:
And I'm derived from a 19th century German sailor who was designed 200 years ago. So what?


So other than the knowledge that you posses in your gray matter, that German Sailor probably has you beat on every other attribute. :lol:

So the basic core configuration may be the same, but can you say the materials, airfoil shape, cooling mechanism are the same? All these advances makes these engines more efficient and reliable.

Question though, even if the core is the same, does it really mean the same, as in same number of compressor and turbine stages?
bt
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rlwynn
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 1:32 pm

I doubt it is anything the same. The TF-34 that we think of on the A-10 weighs 1500lbs. The CF34-10 weighs 3700lbs.
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smithbs
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 2:40 pm

744SPX wrote:
Nomadd wrote:
744SPX wrote:
The CF-34 is a 50 year old design

You can call the 787 a 66 year old design if you want. It has about as much to do with the 707 as the newest CF34 has to do with the original.



You're hilarious my friend. The CF-34-10 core is directly derived from the CFM-56 core, which is derived from the F101 core which is 50 years old.


Either way, it would be fitting to fit a bomber that my grandfather would have flown with engines that my father might have designed, such that my kids could fly it into the future.

I think the RR option is the best from an engineering perspective, but let's not forget this is USAF procurement at work. They take their own twists and turns.
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 6:37 pm

The only problem with the RR is they are 1,000 lbs heavier than the others and that will have a fairly large effect on the CG.
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angad84
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 7:53 pm

mmo wrote:
The only problem with the RR is they are 1,000 lbs heavier than the others and that will have a fairly large effect on the CG.

Surely the closer an engine is to the weight of the original TF33, the better from an integration/CG perspective? More thrust/efficiency at similar weights will probably be the best way to spend re-engine funds.

We had the same problem with our programme to upgrade the engine on the Jaguar -- the RR Adour growth option did not offer enough improvements in the same weight/size class. The Honeywell F125 was an awesome leap in thrust (something like 20%) and efficiency, but so dramatically lighter than the outgoing Adour that the cost of recertifying the F125+Jaguar combination became obscenely expensive.
 
mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 8:01 pm

The RR is almost 1000 lbs heavier than the TF33.
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Tugger
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 9:12 pm

mmo wrote:
The RR is almost 1000 lbs heavier than the TF33.

Still I find it difficult to think an additional 8,000 lbs on the wings will be any kind of real issue. For CG you just shift/change/add some counterweight in the front or rear to adjust for it. And it is only 1.5% of the max weight capacity so the added weight isn't a real issue.

Am I missing something that the BUFF is really sensitive on this? I mean she drops bombs so a changing CG is something she lives with.

Tugg
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mmo
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 9:19 pm

Given where the engines are with respect to the CG, yes. The bomb bay is right in the just about the middle of the CG and there are some configurations if you have mines or ALCMs on the wing racks or where you have to keep fuel in the center wing. So, it does make a difference.
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Ozair
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 9:19 pm

Tugger wrote:
mmo wrote:
The RR is almost 1000 lbs heavier than the TF33.

Still I find it difficult to think an additional 8,000 lbs on the wings will be any kind of real issue. For CG you just shift/change/add some counterweight in the front or rear to adjust for it. And it is only 1.5% of the max weight capacity so the added weight isn't a real issue.

Am I missing something that the BUFF is really sensitive on this? I mean she drops bombs so a changing CG is something she lives with.

Tugg

You could also argue the reduced fuel burn of a newer engine would offset a weight gain, so the aircraft could take off with a lower max fuel weight but likely still achieve a greater range based on engine efficiency.
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 11:49 pm

Any modern engine will be heavier, and the B-52 was of course designed to be pretty neutral in an old-school control system (the rudimentary equivalent of the B-29 fly by cable tech scaled up 10 years). Just as the M-14 (or garand) are still capable weapons when properly wielded by trained soldiers on the battlefield, there’s really little doubt that the B-52 can continue to deliver ordinance at stand off distances or low threat environments for decades to come. In truth, stand-off ‘ordinance’ are the types that are now, more than ever, replacing the role of manned combat aircraft, and the need is increasing as a result for platforms that can orbit/deliver them to the combat area (UCAV).

The US-built, in USAF inventory, nacelle-compatible RR is easily the favorite here, though I don’t blame GE for throwing everything they can at the bid given the size of the acquisition.
 
angad84
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Re: New advertisement: B-52 re-engine back in the mix?

Thu Apr 30, 2020 11:53 pm

mmo wrote:
The RR is almost 1000 lbs heavier than the TF33.

Got a link for that? I was under the impression both were in the 4000-lb range. Admittedly not following this very closely.
 
JayinKitsap
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 01, 2020 5:00 am

mmo wrote:
Given where the engines are with respect to the CG, yes. The bomb bay is right in the just about the middle of the CG and there are some configurations if you have mines or ALCMs on the wing racks or where you have to keep fuel in the center wing. So, it does make a difference.


To continue your thought, hardpoints on the wings will be on center line of the wing structure, always minimize torsion in structures. The engine intakes need to be ahead of the wings so there will be a moment arm twisting the wing. On an existing wing this moment should be matched, either by adjusting the arm or counter weighting. Each added pound requires an added pound of counterweight times the ratio of the arms.

Does anyone know if this RFP is to award to multiple bidders, then down select like FARA or just selecting one like the T-7A? I prefer the multiple approach, real world experience keeps out the projects that look good on paper but are lemons in real life.
 
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bikerthai
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 01, 2020 12:04 pm

JayinKitsap wrote:
Does anyone know if this RFP is to award to multiple bidders, then down select like FARA or just selecting one like the T-7A?


But wouldn't a second round if down selected means delayed implemenration? The FARA program expects development issues. Isn't this program supposed to use a proven engine? The risk would then only be on the integration side. Thus I would think they would lean toward the engine that is the most mature.

bt
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
Ozair
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 01, 2020 12:40 pm

JayinKitsap wrote:

Does anyone know if this RFP is to award to multiple bidders, then down select like FARA or just selecting one like the T-7A? I prefer the multiple approach, real world experience keeps out the projects that look good on paper but are lemons in real life.

A single vendor, winner take all...
 
CX747
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Re: New advertisement: B-52 re-engine back in the mix?

Sat May 02, 2020 7:48 pm

texl1649 wrote:
Any modern engine will be heavier, and the B-52 was of course designed to be pretty neutral in an old-school control system (the rudimentary equivalent of the B-29 fly by cable tech scaled up 10 years). Just as the M-14 (or garand) are still capable weapons when properly wielded by trained soldiers on the battlefield, there’s really little doubt that the B-52 can continue to deliver ordinance at stand off distances or low threat environments for decades to come. In truth, stand-off ‘ordinance’ are the types that are now, more than ever, replacing the role of manned combat aircraft, and the need is increasing as a result for platforms that can orbit/deliver them to the combat area (UCAV).

The US-built, in USAF inventory, nacelle-compatible RR is easily the favorite here, though I don’t blame GE for throwing everything they can at the bid given the size of the acquisition.


I love the fact that you brought up the M14 and Garand!!! A while back I was doing some training at work with another guy. Had all the bells and whistles the USG could put on an M4 and a Garand. Not a big distance (25 yards) but the Garand was more accurate with Iron Sights!!! In the end as you said, it comes down to training.

With the virus now in effect, I think GE and PW have a better shot than 3 months ago. Billions out the door that eventually go overseas may not be the flavor of the day at this time if all specs are in the same ballpark.
"History does not long entrust the care of freedom to the weak or timid." D. Eisenhower
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Sun May 03, 2020 11:56 am

Heh, well, I would just point out that the RR F130 (BR725) is produced in the US (Indianapolis). It’s funny, but I read just the other day that FN America (a subsidiary of Belgian FN) was just awarded a FMS contract for M-16A4 production (huge number of rifles, generally it’s the older/non-carbine version of the M16). That’s what made me laugh thinking about how the role for the B-52 is sort of timeless (plus, the USAF must know after the tanker bid wars that it is practically impossible to replace in the next 30 years).

https://www.rolls-royce.com/products-an ... /f130.aspx

https://cbs4indy.com/news/rolls-royce-s ... 2-engines/
 
JayinKitsap
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Re: New advertisement: B-52 re-engine back in the mix?

Mon May 04, 2020 10:13 am

CX747 wrote:
texl1649 wrote:
Any modern engine will be heavier, and the B-52 was of course designed to be pretty neutral in an old-school control system (the rudimentary equivalent of the B-29 fly by cable tech scaled up 10 years). Just as the M-14 (or garand) are still capable weapons when properly wielded by trained soldiers on the battlefield, there’s really little doubt that the B-52 can continue to deliver ordinance at stand off distances or low threat environments for decades to come. In truth, stand-off ‘ordinance’ are the types that are now, more than ever, replacing the role of manned combat aircraft, and the need is increasing as a result for platforms that can orbit/deliver them to the combat area (UCAV).

The US-built, in USAF inventory, nacelle-compatible RR is easily the favorite here, though I don’t blame GE for throwing everything they can at the bid given the size of the acquisition.


I love the fact that you brought up the M14 and Garand!!! A while back I was doing some training at work with another guy. Had all the bells and whistles the USG could put on an M4 and a Garand. Not a big distance (25 yards) but the Garand was more accurate with Iron Sights!!! In the end as you said, it comes down to training.

With the virus now in effect, I think GE and PW have a better shot than 3 months ago. Billions out the door that eventually go overseas may not be the flavor of the day at this time if all specs are in the same ballpark.


Like the Garand and the B-52, the KC-135 could be a candidate for a re-engine in a similar manner. The KC-46 for now is a 170+- frame program. But there are over 500 tankers. Something like 100 be re-engined and updated like what is being done with the BUFFs.

The virus is going to make this a very competitive RFP, 608 engines in this market would be quite big.
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Mon May 04, 2020 1:38 pm

I don't want to make this a tanker derail but it doesn't make sense to re-engine the KC-135's (again). The airframes/wings are about shot, and while it will be difficult to replace them all in the 2030's now it is a real need. They are just too old to soldier on into the 2040's, and can't be easily modified to enable that (realistically the KC-10's could but again that's another long tanker war topic; my prediction is the KC-10 fleet will be taken back up from AMARG in around 12 years).
 
JayinKitsap
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Re: New advertisement: B-52 re-engine back in the mix?

Mon May 04, 2020 3:09 pm

texl1649 wrote:
I don't want to make this a tanker derail but it doesn't make sense to re-engine the KC-135's (again). The airframes/wings are about shot, and while it will be difficult to replace them all in the 2030's now it is a real need. They are just too old to soldier on into the 2040's, and can't be easily modified to enable that (realistically the KC-10's could but again that's another long tanker war topic; my prediction is the KC-10 fleet will be taken back up from AMARG in around 12 years).


Somewhere I missed the second engine replacement program for the KC-135 that retrofitted 354 aircraft with new CFM International CFM56 (military designation: F108) from the TF33. No engine replacements beyond that, but agreed that this goes to the tanker discussions.

So on the BUFF the existing TF33-P-3 has 17,000 lbf (75.62 kN) thrust, weight of 4,605 lb, 53"D x 142" long.

The replacements proposed are:

GE Passport: 18,900 lbf thrust, weight of 3,950 lb, 52"D x 103" long.
GE CF-34-10: 20,360 lbf thrust, weight of 3,760 lb, 53"D x 88.7" long.
RR F130 (BR725) 16,900 lbf thrust, weight of 3,605 lb 50"D x 130" long.
PW 800: 18,000 lbf thrust, weight of 3,190 lb 50"D x 130" long.

So all are lighter than the current engine, the lightest saves 5,400 lb per aircraft. Do any of these engines have a real advantage over the competition?
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 19, 2020 11:42 am

B-52 mix vs. ‘arsenal plane’ sounds like it is back in the...mix, to operate beyond 2050. I’m posting here just because it seems the re-engine program is a full throttle ahead priority now;

In retrospect, the new number for the Air Force’s objective bomber fleet quantity was revealed carefully. Last September, Gen. David Goldfein addressed the annual convention of the Air Force Association. In his speech, Goldfein reiterated the Air Force requirement to field a total of 175 bombers, but noted that “ideally” the actual number should be 220. The Air Force adopted no funded path to increasing the overall fleet by 45 aircraft, but set it as a goal.

Gen. Timothy Ray, the head of Global Strike Command, went even further during a teleconference with reporters in early April, saying the 220-bomber objective should be regarded as a minimum, not a ceiling.

“We know that the requirement for long range bombers is north of 220. In the past, we said it was 175, but that was a programmatically-derived approach. We as the Air Force now believe it’s over 220,” Ray said.

The Air Force has committed to operate 75 B-52s and 100 B-21s beyond 2050. With the B-52 out of production for 60 years, the easiest way to add more than 45 aircraft to the bomber fleet would be to increase the number of B-21s. But Ray would not commit to the obvious route.


https://aviationweek.com/defense-space/ ... 8d89032b0a
 
744SPX
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 19, 2020 4:58 pm

I like the PW 800 option. Lightest of the bunch by far and plenty of thrust margin. ...and it keeps the B-52 a Pratt aircraft like it has always been, and Pratt could use some good news right now.
 
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747classic
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Re: New advertisement: B-52 re-engine back in the mix?

Tue May 19, 2020 8:08 pm

JayinKitsap wrote:
texl1649 wrote:
I don't want to make this a tanker derail but it doesn't make sense to re-engine the KC-135's (again). The airframes/wings are about shot, and while it will be difficult to replace them all in the 2030's now it is a real need. They are just too old to soldier on into the 2040's, and can't be easily modified to enable that (realistically the KC-10's could but again that's another long tanker war topic; my prediction is the KC-10 fleet will be taken back up from AMARG in around 12 years).


Somewhere I missed the second engine replacement program for the KC-135 that retrofitted 354 aircraft with new CFM International CFM56 (military designation: F108) from the TF33. No engine replacements beyond that, but agreed that this goes to the tanker discussions.

So on the BUFF the existing TF33-P-3 has 17,000 lbf (75.62 kN) thrust, weight of 4,605 lb, 53"D x 142" long.

The replacements proposed are:

GE Passport: 18,900 lbf thrust, weight of 3,950 lb, 52"D x 103" long.
GE CF-34-10: 20,360 lbf thrust, weight of 3,760 lb, 53"D x 88.7" long.
RR F130 (BR725) 16,900 lbf thrust, weight of 3,605 lb 50"D x 130" long.
PW 800: 18,000 lbf thrust, weight of 3,190 lb 50"D x 130" long

So all are lighter than the current engine, the lightest saves 5,400 lb per aircraft. Do any of these engines have a real advantage over the competition?


To keep the re-engine costs in limits (without a very expensive wing redesign), the weight of the replacement engines must be approx the same as the original TF33 engines , otherwise the load distribution of the wing will change and flutter may emerge.
Most cost effective will be double pods with exactly the same aerodynamic shape and weight. (incl engines with ballast weights !)
Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
Ozair
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Re: New advertisement: B-52 re-engine back in the mix?

Wed May 20, 2020 11:20 pm

The RFP has now officially been released to the three vendors with contract award by June 2021.

US Air Force launches contest to replace the B-52 bomber’s engine

General Electric, Rolls-Royce, and Pratt & Whitney will compete for the chance to outfit the U.S. Air Force’s B-52 bomber fleet with new engines, with a contract award projected for June 2021.

The Air Force released a request for proposals for the B-52 Commercial Engine Replacement Program to the three companies on May 19. The engine makers are already under contract to create digital prototypes, and they have until July 22 to submit final proposals, the solicitation stated.

...

https://www.defensenews.com/air/2020/05 ... 2s-engine/
 
JayinKitsap
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 6:06 am

747classic wrote:
JayinKitsap wrote:
texl1649 wrote:
I don't want to make this a tanker derail but it doesn't make sense to re-engine the KC-135's (again). The airframes/wings are about shot, and while it will be difficult to replace them all in the 2030's now it is a real need. They are just too old to soldier on into the 2040's, and can't be easily modified to enable that (realistically the KC-10's could but again that's another long tanker war topic; my prediction is the KC-10 fleet will be taken back up from AMARG in around 12 years).


Somewhere I missed the second engine replacement program for the KC-135 that retrofitted 354 aircraft with new CFM International CFM56 (military designation: F108) from the TF33. No engine replacements beyond that, but agreed that this goes to the tanker discussions.

So on the BUFF the existing TF33-P-3 has 17,000 lbf (75.62 kN) thrust, weight of 4,605 lb, 53"D x 142" long.

The replacements proposed are:

GE Passport: 18,900 lbf thrust, weight of 3,950 lb, 52"D x 103" long.
GE CF-34-10: 20,360 lbf thrust, weight of 3,760 lb, 53"D x 88.7" long.
RR F130 (BR725) 16,900 lbf thrust, weight of 3,605 lb 50"D x 130" long.
PW 800: 18,000 lbf thrust, weight of 3,190 lb 50"D x 130" long

So all are lighter than the current engine, the lightest saves 5,400 lb per aircraft. Do any of these engines have a real advantage over the competition?


To keep the re-engine costs in limits (without a very expensive wing redesign), the weight of the replacement engines must be approx the same as the original TF33 engines , otherwise the load distribution of the wing will change and flutter may emerge.
Most cost effective will be double pods with exactly the same aerodynamic shape and weight. (incl engines with ballast weights !)


Instead of ballast weights could the engine CG location be moved to keep the wing torque the same. The engines are all shorter, not sure of the flow issues would be caused by moving the inlet of the nacelles forward or back. It would probably be good to keep as much of the nacelle wetted surface the same. Flutter has struck many a time.

Another article on the B-52 RFP in Air Force Mag.

https://www.airforcemag.com/usaf-releas ... july-2021/
 
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747classic
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 7:43 am

JayinKitsap wrote:

Instead of ballast weights could the engine CG location be moved to keep the wing torque the same. The engines are all shorter, not sure of the flow issues would be caused by moving the inlet of the nacelles forward or back. It would probably be good to keep as much of the nacelle wetted surface the same. Flutter has struck many a time.

Another article on the B-52 RFP in Air Force Mag.

https://www.airforcemag.com/usaf-releas ... july-2021/


The relative thin wing with two engine pairs installed will cause some serious issues if the load distribution is changed due installation of engines with significant less weight and/or aerodynamic shape.
It's always possible to (partially) re-design the wing platform to accept the new, lower weight, engines, but than the re-engine program may become very expensive.
On top of that : If the the wing platform has to be changed (strengthend) to accept the new engines, all external weapon loads presently certified, would have to be re-certified.

Note : In the past we have seen many wing flutter issues at other 4+ engined planes, eg. B-47, B707, B747, all series up to the 747-8.
Most wing flutter issues were caused by wing load distribution changes due engine weight, external stores, all combined with different (wing) fuel loads
Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 1:18 pm

At least RR has claimed theirs will fit in the existing pod. As such, at similar thrust settings any torsional differences should be minor, given the very similar weights.
 
744SPX
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 2:01 pm

texl1649 wrote:
At least RR has claimed theirs will fit in the existing pod. As such, at similar thrust settings any torsional differences should be minor, given the very similar weights.


Not sure how that will work as the RR engine has a mixed exhaust and the TF-33 does not.
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 2:14 pm

744SPX wrote:
texl1649 wrote:
At least RR has claimed theirs will fit in the existing pod. As such, at similar thrust settings any torsional differences should be minor, given the very similar weights.


Not sure how that will work as the RR engine has a mixed exhaust and the TF-33 does not.


I don't understand all of the details but that is their graphic/claim per this piece from last year; The TF-33 is after all basically one of the very first generation of turbofans.

Image

The Rolls-Royce F130 proposal would fit inside the existing TF33 nacelle to minimize modification requirements. (Photo: Rolls-Royce)


https://www.ainonline.com/aviation-news/defense/2019-03-02/new-life-b-52

The T33 was the first turbofan engine designed and produced by P&W, and some drawings date back before 1959. The JT3 commercial variant first flew on the Boeing 707 on 22 June 1960 and the TF33 powered the B-52H’s first flight one year later on 6 March, according to the company.
 
744SPX
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 7:05 pm

Hmmm... I see.

I'm kinda hoping for a new nacelle along the lines of the B and D model J-57 nacelles. The TF-33 nacelle always looked kind of ghetto to me (and does in that pic)
 
texl1649
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Re: New advertisement: B-52 re-engine back in the mix?

Thu May 21, 2020 7:26 pm

Well, I'd agree it's not the most graceful thing to ever sit on a combat aircraft, but then again the Buff is anything but; no one has ever accused it of being a 'spitfire' of it's day. The other thing about a quad-powered wing is any flutter issues could also be somewhat more easily 'tweaked' via power adjustments per engine/pod.

The theoretical weight savings is great, per engine, but I think most of us recognize more 'stuff' will wind up being added to the wing/wiring/pods making the net weight per pair of engines pretty close.
 
LightningZ71
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 22, 2020 1:29 pm

I suspect that any mass saved by the newer, lighter engines will be "Spent" on improved, nacel mounted countermeasures. Why add useless dead weight when you can actually make it productive?
 
Buckeyetech
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Re: New advertisement: B-52 re-engine back in the mix?

Fri May 22, 2020 4:08 pm

I can see the USAF completely overlooking the nacelle and cowlings, mount the new engines, have a problem, then realize they should have bought new ones. Coming from maintenance, the H model lower and upper body cowls are awful! The most over engineered piece on that aircraft. Fingers crossed they redesign them around the new engines.
B-52H, C-141C, C-5A, C-17A

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