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Once Again The USAF Is Looking To Re-Engine Its B-52 Fleet

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  • MadRat
    Rank 5 Registered User
    • Aug 2006
    • 5032

    Once Again The USAF Is Looking To Re-Engine Its B-52 Fleet

    http://foxtrotalpha.jalopnik.com/onc...-fl-1685747978

    Once Again The USAF Is Looking To Re-Engine Its B-52 Fleet


    The USAF is kicking around 'creative concepts' under which it could re-engine its fleet of 74 ever evolving B-52H Stratofortresses. With the bombers remaining in front-line service until at least 2040, and considering that flying with eight 1960s vintage TF33 engines is far from fuel efficient (burning 3k gallons an hour), re-engined B-52s should make great financial sense.

    Defensenews.com quoted Lt. Gen Mike Holmes, deputy chief of staff for Strategic Plans and Requirements, telling reporters at a February 6th event:

    "To go out and buy new engines for the B-52, you'd have a really hard time fitting that into our program, but that's why we're interested in a public-private partnership, which would be a different way to amortize those engines over time and pay for them in the savings that they actually generate, instead of paying for them out of savings that you hope for.... The idea is in a public-private partnership, somebody funds the engine and then we pay them back over time out of the fuel savings, which are generated out of the new engines. Our government has a way to do that with facilities. We don't have a way to do that with airplanes, and we are exploring whether there are alternative ways that would let us do that... Look at what the airline industry is doing — they're all re-engining. Why? Because it saves you a lot of money. If there is a commercially available engine which can give a 25-30 percent increase in either range or loiter, you have my attention."


    See also: https://www.google.com/url?sa=t&rct=...86475890,d.aWw

    My opinion:

    I personally believe that they should aim for a pair of CF6-80C2, because they already own a stock of them. The outboards would still require weight, therefore place - for takeoffs emergency use only - a single F404 or F1x0 on each outboard. That would give them plenty of power on takeoff and in the event of an emergency to stay airborne albeit at greatly reduced range. The B-52E began life with 10,000 lb st J57's that were later upgraded to 13,000 pound static thrust each. The TF33's currently give takeoff thrust up to 17,000 pound static thrust. It's been possible on more than one occasion to remain airborne in older models with four engines. Even if one CF6-80C2 gave out, the remaining engine would suffice to remain airborne. Look at swapping out the 700-gallon wing tanks for the 1,000 gallon wing tanks from previous models to prevent wing flap on the lighter wing loading.

    I built a list of weights and engines to compare:

    1 ea. 3,000-gallon wing tanks (B-52C only) approx. 25,000 pounds each
    1 ea. 1,000-gallon wing tanks (B-52A to B-52G) approx. 8,000 pounds each
    1 ea. 700-gallon wing tanks (B-52H only) approx. 6,000 pounds each

    1 ea. i-TF33-P-3 approx. 4,200 pounds ea. dry (Take-off 17,000 / Continuous ?) Fan 52" dia.

    1 ea. CF6-80C2 approx. 9,000 pounds ea. dry (Take-off 62,100 / Continuous 53,000) Fan 93" dia.
    1 ea. Trent 768 approx. 10,600 pounds ea. dry (Take-off 67,500 / Continuous ?) Fan 98" dia.
    1 ea. GEnx-2B67 approx. 12,500 pounds ea. dry (Take-off 67,400 / Continuous 58,500) Fan 105" dia.
    1 ea. Trent 875 approx. 13,100 pounds ea. dry (Take-off 75,000 / Continuous ?) Fan 110" dia.
    1 ea. GEnx-1B67 approx. 12,800 pounds ea. dry (Take-off 69,400 / Continuous 61,500) Fan 111" dia.
    1 ea. Trent 1000-A approx. 12,700 pounds ea. dry (Take-off 69,300 / Continuous 64,100) Fan 112" dia.
    1 ea. GP7270 approx. 14,800 pounds ea. dry (Take-off 81,500 / Continuous 74,700) Fan 116" dia.
    1 ea. Trent 970B-84 approx. 13,800 pounds ea. dry (Take-off 78,300 / Continuous 72,000) Fan 116" dia.

    1 ea. GE F404 approx. 2,300 pounds ea. dry (Dry 11,000 / Wet 17,700) Max. 35" dia.
    1 ea. GE F414 approx. 2,500 pounds ea. dry (Dry 13,000 / Wet 22,000) Max. 35" dia.
    1 ea. F100-PW-220 approx. 3,800 pounds ea. dry (Dry 14,600 / Wet 23,800) Max. 47" dia.
    1 ea. F110-GE-129 approx. 4,400 pounds ea. dry (Dry 18,000+ / Wet 29,400) Max. 47" dia.
    Attached Files
    Last edited by MadRat; 24th February 2015, 04:22.
    Go Huskers!
  • obligatory
    Senior Member
    • Oct 2008
    • 7043

    #2
    perhaps USAF can buy trusty Tu-95 as replacement

    Comment

    • TomcatViP
      Rank 5 Registered User
      • Nov 2011
      • 6127

      #3
      Vey intersting Madrat.

      Given the numbers, I would go for a similar arrangement as original (8x engines) but with F414. Adding rear fan (decoupled) to the inboard doublets might suffice for a TO out of reheat and cruise. Reheat on the outboard will increase TO, climb rate and in general add kinetic cap to the old bird.

      A rear mounted decoupled fan arragement had been studied and tested for the Convair's series of airliner. It's not as eco but the added advantage of simplicity and having a similar weight and geometry vis vis of the airframe behavior after engine swap could prove a determining factor by preventing damaging the wings (years of similar solicitation and then a major modal modification is not really good for a metal assembly)

      So 8x F414 with 4 inboard having a rear Fan and two pack of twin outboard mounted straight (no fan) but keeping reheat cap.

      ..or something like that
      Last edited by TomcatViP; 24th February 2015, 07:22.

      Comment

      • Hotshot
        Rank 5 Registered User
        • Jul 2014
        • 1127

        #4
        How about replacing the 8 engines with 2 very large, and using the unused pylons for more weapons? And add winglets.

        Comment

        • obligatory
          Senior Member
          • Oct 2008
          • 7043

          #5
          the structure is already fatigued so they cant carry max load anyway,least not on the wings

          Comment

          • mrmalaya
            Generation 4.75+++
            • Jan 2010
            • 4664

            #6
            Are they likely to go for a brand new engine or just get an incremental improvement from a 1980s technology engine held in stock ?

            Comment

            • MadRat
              Rank 5 Registered User
              • Aug 2006
              • 5032

              #7
              Boeing has put on the table eight CF34-10, but I'm not sure -10A or -10E. It is already overpowered in the TF33 layout, so either one will suffice.
              Go Huskers!

              Comment

              • Cherry Ripe
                Rank 5 Registered User
                • Jul 2009
                • 564

                #8
                Hard to believe the best-funded air force in the World has to go crawling for public-private funding to re-engine the Buffs.

                Anyway, I believe the wing needs the outboard engines to provide bending-relief.

                I'd propose four F117s ( PW PW2040 ) at 7,100 lb dry-weight each providing commonality with the C-17 fleet and plenty of commercial spares.

                Comment

                • FalconDude
                  Rank 5 Registered User
                  • Sep 2010
                  • 1172

                  #9
                  4 commercial engines would do just nicely.

                  Comment

                  • Alpha Bravo
                    Rank 5 Registered User
                    • Mar 2012
                    • 627

                    #10
                    I'm surprised this hasn't been done earlier, given the demands placed on the 52s ever since the end of the cold war, and considering the length they are likely to stay in service.

                    I would perhaps go for something along the lines of the PW4000-94, which could provide commonality with the KC-767 if it ever enters service.
                    Last edited by Alpha Bravo; 24th February 2015, 14:40.

                    Comment

                    • mrmalaya
                      Generation 4.75+++
                      • Jan 2010
                      • 4664

                      #11
                      Sticking with the Bear theme, perhaps they could look to re-engine with TP400s?

                      And if not, can you frankenplane that one Madrat?

                      Comment

                      • topspeed
                        Get on uppah !
                        • Jan 2009
                        • 2660

                        #12
                        Originally posted by mrmalaya View Post
                        Sticking with the Bear theme, perhaps they could look to re-engine with TP400s?

                        And if not, can you frankenplane that one Madrat?
                        Should be easy !
                        Attached Files
                        If it looks good, it will fly good !
                        -Bill Lear & Marcel Dassault


                        http://max3fan.blogspot.com/

                        Comment

                        • djcross
                          Rank 5 Registered User
                          • Jan 2000
                          • 5467

                          #13
                          High airflow engines close to the ground would be an issue unless the parking ramps, taxiways and runways are immaculate.

                          Comment

                          • Dragonflyer
                            Rank 5 Registered User
                            • Sep 2014
                            • 66

                            #14
                            Originally posted by Cherry Ripe View Post
                            Hard to believe the best-funded air force in the World has to go crawling for public-private funding to re-engine the Buffs.
                            It's been looked at several times, and I think it's not exactly a cost issue as much as a budgeting and politics issue. In the US, I regret that our Congress is not generally focused on long term efficiency as much as looking good for the next election campaign, which is frequently only a year away from the last election, and starts about a year from the next one (on our House of Representitives two year schedule). Since Congress is generally in a "cost savings" mode most of the time, supporting a multi-billion dollar engine replacement program which costs money now but doesn't save money until years down the road (after the next election) doesn't placate the "cut now" appetite of Congressmen who have to get elected again in the near term. So they keep kicking the can down the road as long as the existing equipment is working, however inefficiently. Given the need to fund the F-35 and replace the old KC-135s with the new KC-46, the AF's budget is straining to survive!

                            Also, when thinking about a replacement engine keep in mind that it isn't just about thrust, but also electrical generating capability (the BUFF uses a lot of power), so you have to get the right combination of available thrust and electrical generating capability. I'm not educated enough to understand the dynamics of that game off the top of my head.

                            Comment

                            • sandiego89
                              Rank 5 Registered User
                              • Feb 2008
                              • 354

                              #15
                              Agree, not just an exercise in replace x lbs of thrust with a similar amount of thrust. Weight, thrust lines, center of gravity, engine/wing dynamics, torsion/bending, FOD all come into play. Massive twins on the inners, or mixed powerplants are not the solution. 4 (or 8) well known engines, placed in about the same place is the way to go.

                              Comment

                              • topspeed
                                Get on uppah !
                                • Jan 2009
                                • 2660

                                #16
                                Originally posted by djcross View Post
                                High airflow engines close to the ground would be an issue unless the parking ramps, taxiways and runways are immaculate.

                                Buff would go close to 900 km/h wih TP400 engines.

                                http://en.wikipedia.org/wiki/Airbus_A400M_Atlas

                                But it would not carry as much as before; http://en.wikipedia.org/wiki/Boeing_B-52_Stratofortress
                                Last edited by topspeed; 24th February 2015, 20:13.
                                If it looks good, it will fly good !
                                -Bill Lear & Marcel Dassault


                                http://max3fan.blogspot.com/

                                Comment

                                • Levsha
                                  Rank 5 Registered User
                                  • Jan 2006
                                  • 2857

                                  #17
                                  Originally posted by djcross View Post
                                  High airflow engines close to the ground would be an issue unless the parking ramps, taxiways and runways are immaculate.
                                  That wouldn't be the case for the high-wing B-52. I thought there was a plan 10 years ago or so to reengine the B-52 with RR RB211 - but I don't think they make that engine anymore.

                                  Comment

                                  • MadRat
                                    Rank 5 Registered User
                                    • Aug 2006
                                    • 5032

                                    #18
                                    Four engines is far easier to maintain than eight. But two is better yet than four. The only reason I can see going big like CF6-80C2 is because its well known to the USAF. If you were leaning towards modernization and cost was no issue then surely go eight CF34-10. But cost really is an issue and man hours drive costs of B-52H second only to fuel.

                                    The TF33's are only ran about 80% of their potential, so there is leeway to drop overall thrust, too. And if you only hit 100,000 pounds of static thrust then you still reach the power of all previous B-52's that came before the TF33 engine was installed. The key is fuel efficiency and that pretty much means a good twin spool high bypass turbofan.
                                    Go Huskers!

                                    Comment

                                    • TomcatViP
                                      Rank 5 Registered User
                                      • Nov 2011
                                      • 6127

                                      #19
                                      Don't forget kinematics. A large fan doesn't provide you as much possibility of trajectory than a turbojet or a small fan (hence my proposal). And a bomber is a launching platform.

                                      Imagine the bird fitted with 4x414 having reheat for example (see above). The Buff could climb and maintains speed giving it's weapon more range hence more safety for the launcher. That would be more difficult with a large turbo fan given the inherent limitation of such engines (AoA, G etc...).

                                      Not speaking about a possible increase in ceiling (more range or surface for CAS).

                                      IMOHO this is on ef the reason why the USAF has stuck so long with the TF33
                                      Last edited by TomcatViP; 25th February 2015, 00:25.

                                      Comment

                                      • MadRat
                                        Rank 5 Registered User
                                        • Aug 2006
                                        • 5032

                                        #20
                                        It's penetration speed at low altitude is a modest 360knots: http://www.dept.aoe.vt.edu/~mason/Mason_f/B52S05.pdf

                                        They need to remove the tail gun and install an EODAS for self protection. You would be far more protects using LOAL air-to-air missiles If it went two large engines and two asymmetrical smaller ones (F100?) then it gives reason to reinstall 1,000 gallon (pre- B-52H) or 3,000 (B-52C) gallon fuel tanks on the wings. How about each F100 has a pair of F-15E FASTpacks to lug around external LGB's and/or SDB's.
                                        Go Huskers!

                                        Comment

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