Moderators: richierich, ua900, PanAm_DC10, hOMSaR
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.
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.
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.
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Ozair wrote:Thoughts on anything else?
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.
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.
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GE Aviation, Pratt & Whitney and Rolls-Royce have expressed interest in bidding on the programme.
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744SPX wrote:The CF-34 is a 50 year old design
744SPX wrote:The CF-34 is a 50 year old design
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.
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.
Nomadd wrote:And I'm derived from a 19th century German sailor who was designed 200 years ago. So what?
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.
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.
mmo wrote:The RR is almost 1000 lbs heavier than the TF33.
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
mmo wrote:The RR is almost 1000 lbs heavier than the TF33.
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.
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?
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.
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.
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.
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).
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.
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?
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.
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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 !)
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/
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.
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.
The Rolls-Royce F130 proposal would fit inside the existing TF33 nacelle to minimize modification requirements. (Photo: Rolls-Royce)
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.