New Engines Could Propel The B-52 Beyond Its 100th Birthday

First taking to the skies in April 1952, and introduced into the US Air Force in 1955, the B-52 Stratofortress has since become a mainstay of American air power. Originally developed as a nuclear bomber to carry out the critical deterrence role, changing realities saw it delivering solely conventional munitions in actual operations.

Of 744 B-52s originally built, 76 remain in service with the Air Force and Air Force Reserve. This fleet is set to go on flying beyond the type’s 100th birthday, into 2050 and beyond. To reach that milestone, a new engine package will be key to keeping these birds in the air.

Built Nuclear Tough

A U.S. B-52H Stratofortress in flight over the Persian Gulf in 2019. Note the black contrails commonly seen from the eight engines of the B-52.

Despite its age, the B-52 is still regularly flown and kept in prime combat readiness. Part of the reason for its long service is that the Buff, or “Big Ugly Fat Fella”, as it’s known, was intentionally overengineered and overbuilt. Created in the era of slide rules, designers wanted to ensure that the plane would be able to deal with the stresses of the high-altitude nuclear attack mission. Leaving enough margin in the design has meant that despite flying for decades, the B-52s still in service still have plenty of structural life left in them.

The B-52 is known for its distinctive layout of eight engines in four separate two-engine pods. Equipped with Pratt & Whitney TF33-PW-103 engines, the bomber boasts a range of 8,800 miles (14,162 kilometers) without refueling. However, the last of these engines was built in 1985, and continuing to produce parts and maintain the engines is becoming a hassle.

Thus, the Air Force seeks a new engine with which to power the remaining fleet. Indeed, it’s not for the first time either. The first B-52s built actually flew with a variety of Pratt & Whitney J57 turbojets, before the TF33 turbofan was rolled out with B-52H production in 1961. Since then, the USAF has investigated the prospect of engine replacement multiple times. Once ahead of the development of the B-1 bomber, and again in 1996, and both times, the project was rejected. Since then, the engines have only gotten older, thus leading to the USAF opening up its request for proposals once more in 2020.

Flying Farther and Smarter

In order for the refit to make sense, the Air Force is seeking a replacement program that will net an engine that is cheaper to operate. These savings could come from increased reliability, easier maintenance, or simply better parts availability. The engine should also be quieter, and perhaps most importantly, more fuel efficient. Jet engine technology has moved on a long way since the TF33 was developed in the 1950s, and thus newer designs could bring great benefits to the B-52 platform.

The B-2 Spirit, pictured here flying next to a B-52 Stratofortress, is a more modern and stealthier aircraft than its predecessor. However, high running costs and the fact only 20 were built mean that the B-2 is not able to supplant the B-52 in regular operations.

There’s little desire for more thrust or greater speed, due to the limitations of the aging B-52 airframes. However, a more efficient engine could enable even longer range and greater loiter times than are already possible with the B-52. The hope is to boost range by 20-40 percent, up to 12,320 miles without refueling. This could allow the B-52 to reach any point on Earth without support from a tanker aircraft.

The other major benefit is that the new engines will come with digital engine controls. These systems monitor every aspect of an engine’s health, from turbine inlet and outlet temperatures, to shaft speeds, and just about everything else. When dealing with the maintenance of eight engines on each aircraft, having a digital system to monitor what’s failing and what needs to be changed is a huge help to ground crews. As a bonus, any problem fixed ahead of time is one that doesn’t derail a training program or active mission. Given the cost of these operations, it’s a saving that’s difficult to quantify accurately, but one that pays dividends nonetheless.

May The Best Engine Win

The Air Force aims to order 608 new engines for its fleet, with General Electric, Rolls-Royce, and Pratt & Whitney are the three players vying for the contract. Based on those numbers, that’s eight engines for each of the 76 B-52s still in service today. Thus, it seems likely the plan is to stick with an eight-engine setup, despite four larger engines being a more typical solution on modern aircraft. Each company proposed an engine in the 20,000 lbf thrust range. General Electric put forward its CF34-10 and Passport engines, Rolls-Royce the F130, and Pratt & Whitney a version of its PW800. These are all smaller engines that one would typically see in applications such as small regional or private jets.

It’s hoped that greater fuel efficiency could reduce the B-52’s dependency on aerial refueling during its missions.

Each company is obviously eager to win the lucrative contract to re-engine the B-52. Rolls Royce have already been testing their F130 contender since 2019, well before the official announcement of the program, while GE and Pratt & Whitney are also busy touting their respective engines. Military procurement is big business, and fierce battle will go on behind closed doors before the ink is dry on the contracts.

Ask any engineer who worked on the B-52 program back in the 1950s as to whether their aircraft would be flying in 100 years time, and you’d likely draw a chorus of raucous laughter. However, it just so happens that the B-52 does a job and does it well. Given that replacing it would require the development of an expensive new aircraft, something that the Air Force has struggled with in recent decades, it’s clear the Buff will still soar the skies for a while yet. For the pilots and crews responsible for running the grand machine, hopefully new engines will make that duty a little easier in the years to come.

86 thoughts on “New Engines Could Propel The B-52 Beyond Its 100th Birthday

      1. True but I would also expect stealth being a big thing here.

        This kind of bomber is generally positioned against the most advanced powers with nuclear capability, that would have strong radar defenses as well. Strategic bombers are not the kind of thing used in asymmetric warfare.

        I’m surprised this bomber is still considered viable until 2050.

        1. Stealth is only a thing when an adversary has a robust and sophisticated air defense network. Iraq’s wasn’t really sophisticated or robust and the Taliban has nothing effective to more than a couple thousand feet, at most, and damned few of those. B-52s at 25-50,000 feet have been flying missions over those countries with total impunity for over three decades.

          If there is a mission that does require stealth again, the USAF still has B-2s and F-35s that can fly it, as well as F-15E Strike Eagles that can streak in underneath radar coverage. B-52s are loitering bomb trucks, not dash-and-smash interdictors.

        2. And B-52s, as well as B-2s, have proven a lot more valuable in asymmetrical warfare than you think. Having one loaded up with small precision guided bombs, loitering for hours on end, is often just what the guys on the ground need.

    1. They serve two different missions. One is precision engagement and the other, well, levels cities…

      The B-1 was lauded as “The Bomber of the Future”, but it was/is a PoS and there are more in desert storage than anywhere else. Whenever one would come for an Air Show, we would always have to reserve an extended parking spot for it because it would always either hard break on landing or red-ball on take-off. Junk.

      Nothing can or will replace that beast for a very long time.

    1. Boneyards, as well as many destroyed to fulfill nuclear arms limitation treaties.
      The ones destroyed were cut into several large pieces, and left where they lay for a few months so Soviet satellites could confirm they were destroyed.

    2. The B-52G was actually broken up to meet treaty obligations.

      My last assignment was a B-52G base (Griffiss AFB that was in Rome NY) working on the EW systems. By that time they had first-generation “glass cockpits” and the ALQ-172 was new. of course, we thought the “replaceable stack” hard drive we used was “high tech.”

  1. A side note for those wondering “why eight engines again?”

    Re-engining he plane requires eight engines instead of the more obvious solution of just replacing them with 4 because the B52 has kinda marginal lateral stability.

    Originally designed to fly in the stratosphere, early versions sported a very large tail. When the planes were forced to fly fast at lower altitudes in Vietnam (due to the introduction of Russian surface-to-air missiles) that large tail showed flutter problems in the thicker air, and about 10 feet was removed.

    The smaller tail and huge slab sides of the plane mean that it’s pretty sensitive to asymetrical engine torque, especially in the outboard pods. There’s an old joke about an engine-out leaving the pilot with the “dreaded seven engine emergency landing”, but there’s a grain of truth in it. Loosing both engines in one outboard pod (or a single big engine in a re-imagined 4-engine setup) can be a real controlability issue.

    Also, to a lesser extent, for such a big plane with a high wing, the engines aren’t really that high off the ground, so there’s limited space for one big, modern, turbofan.

    Hence, the apparently baffling plan to use 8 engines again where the obvious solution is to just replace them with four.

    1. Thanks for that comment. I realized the reengineering for 4 engines would be an expensive change. Then wondered if using 8 higher powered engines would allow turning off some of them on long flights for efficiency.

      1. I can’t imagine a situation in which you would ever purposely shut down a correctly functioning engine in flight. No amount of efficiency is worth the risk of a failed restart in an emergency

        1. In maritime surveillance it’s pretty common. The NZ airforce has a fleet of P3 Orions that routinely shutdown an engine (out of 4) when loitering offshore to reduce fuel consumption and increase endurance. That engine doesn’t have an electrical generator fitted for that purpose. They then crank it back up for the higher speed trip home.

        2. There is a very old joke that during WWII a Mustang was escorting a flight of B-29s somewhere and the pilot was bored so he did some extra maneuvering and the got on the radio with the bombers and said, “There’s not a damn thing you guys could do that I couldn’t do better.” The lead bomber pilot answered, “ok, watch this.” For several minutes, nothing happened. Finally the fighter pilot radioed, “watch what? What did you do?” The bomber replied, “I just shut down one engine.”

        3. A correctly functioning engine has no problems restarting. A boeing 747 can maintain level flight with any 1 of its 4 engines, and while I don’t think they shut off 3 at a time, they regularly shut down 2 of them after takeoff because there is more than enough power available, and realistically, an engine out event is not that dangerous for a jumbo jet.

          That’s a 747, which is a bit different from a stratofortress, but not *that* different. I wouldn’t be surprised at all if they shut off 4 or more engines during level flight.

          1. A turning engine that isn’t powered produces a tremendous amount of drag. There is no situation that shutting down an engine on a 747 would be done “regularly” outside of a few minutes of engine-out training.

        4. 3 and 4-engine passenger planes will power off engines all the time. Once the aircraft is up at altitude and at speed, you end up in a situation where either you are gaining too much altitude, too much speed, or your engines are spooled down so low that they are at a high risk of flaming out. For something like a 747-400, its common to fly most of the route with only two engines running at 60-80% power with the other two shut down.

          Also, with the fuel burn rates, once the aircraft has completed its initial climb, two engines are more than sufficient to provide some excellent climb rates. Below 25% fuel, the 747-400 and -8 just two engines are enough for an emergency climb.

          1. I think perhaps some people may be thinking of a idle-thrust glide condition, where the engine is throttled back to be thrust-and-drag neutral but is still powering hydraulic & electrical generation? Technically though, the engines are still running. Still cuts way back on noise and fuel consumption.

          2. I don’t know where in heck people come up with idea that 747s shut down engines in flight to save fuel. Seriously.

            The first thing that happens when you lose just one engine at altitude is you go to max continuous power and turn off the track so you don’t hit someone below you on the same track, because you are going to come down. Period. You are about to descend unless you can rescind the laws of physics.

            Your new altitude will probably be in the low 20 thousands and your range will go to crap.

            The only place “3 and 4 engine passenger planes will power off engines all the time” is at the gate.

            Just retired after 37 years of part 121 (airline) flying, including a couple of models of 747 and years instructing/checking. And yes, I know about the BA 747 that continued on three (and barely made it across the pond.)

            P3s are a completely different game – low altitude, well below service ceiling while hunting subs. They do shut one down regularly.

          3. Airliners never shut down an engine in flight to save fuel that is just crazy. A shut off engine will have a huge amount of drag and it will probably not be too happy to restart after sitting a few hours at 20 or 30 below zero for a few hours. Plus it just makes no sense. The most efficient way for a jet engine to function is as high as it can fly. You never want to cut an engine in climb because you want to get climb at your best rate. You never want to cut one at cruise because you will increase drag and drop altitude plus that below zero soaking of the engine.
            Yes P3s do it all the time. But they are not going for range they are going for loiter time. They can also feather the prop to cut drag and they are at low altitude and low speed. The exact opposite of how an airliner flight. The amount of crazy I have seen in this thread is impressive.

        5. afaiu there are other issues with shutting down a jet engine in flight. Turbine engines don’t like to be cooled down fast, it promotes cracking of blades and stators and can even make it seize up from the case shrinking faster than the rotors. And in a multi spool engine you probably don’t want the fan windmilling at high speed while the oilpump driven by the core doesn’t run

    2. The B-52 was not used in a low level mode in Vietnam. That was limited to to nuclear attack on the Soviet Union. They also didn’t remove 10 feet of the vertical stabilizer because of flutter at low altitude. They did have to be modifed because of fatigue from low level flight.
      The simplest reason for using the 8 engines is because that would require the least amount of modifications to the aircraft. They did look at going with 4 engines but it was not practical. BTW the clearance is not a big issue since the B-52 was used to test the engines for the 747.

        1. They have but you could still power the B-52 with four of them. There is enough clearance. They real reason that they are going with 8 is far more simple. It reduces risk. If you went for four you would need to design new pylons, and deal with changes to weight and balance as well as nacelles. Not to mention changes to the controls and training for the pilots and flight engineers. Risk = cost and delays. So keeping it as close to how it currently is is the safest and fastest way to reengine the B-52. If they could find an engine that would be a 1 to 1 replacement for the TF-33 except that it burns less fuel and makes a bit more thrust it would be ideal.

    3. The height of the tailfin was reduced by eight feet, but when that was done, the chord (fore-aft length for those who don’t know aircraft terms) of the rudder wasn’t increased to make up for its reduced height. Should have been done but for whatever reasons it wasn’t.

      1. Hey, that’s actually pretty funny!

        I would like to comment that the 7-hour orbiting may have been needed to reduce gross weight (fuel load) before the “dreaded 7-engine approach” Steve S mentioned above.

        Another comment: the B-52 has been around for so long (even the last model, the H-model) that some B-52 crewmembers are flying the same aircraft their *grandfathers* flew. Not just same model — same tail number!

        1. Same tail number, but you wonder if an atom of that metal came out of the Boeing plant on official date of production, or whether it’s all 100% Crew Chief’s patches by now :-D

          1. Note: This may be out of date. My grandfather flew bombers but retired a loooong time ago.

            The B-52 simply doesn’t have a dump system unless they recently added one. Of the two accidents in the last 40 years, neither superficially appear to be situations where a fuel dump would have saved them or even helped.

            Interesting to note new airplanes are always less reliable than old airplanes; the 737max had as many crashes in twelve months as the B-52 had in the last 40 years, thus the incredible lack of motivation to replace the B-52.

            The EPA wants a report of fuel dumps; there’s about “one hundred” per year over the usa on average. No one wants to fill out the paperwork LOL.

            Quite a few docs for the C and D models (OLD!) from 1958 were declassified in 1970 and are on archive.org and are pretty easy to find. The MTOW per that unclassified paperwork for the C/D model was 450K pounds and MLW was 270K pounds. I am not convinced the MLW of current models B-52 is unclassified (why?) and it seems unavailable in open sources.

            I suspect the pilot was being prudent and every pound burned in the engine is a pound that can’t burn in a “bad landing”. Certainly, very few airplanes handle better while heavy so its prudent to get rid of your fuel unless you have a very good reason not to. All aircraft have an ideal landing weight; why not achieve it?

          2. plenty of passenger planes with MTOW above MLW and no fuel dump system. You can do an overweight landing if you have to. The plane will have to be inspected for damage afterwards but it’ll likely be fine because MLW is based on the hardest “regular” landing

  2. According to wikipedia, in the early 1960s the B-52 had to be strengthened due to stress failures. So much for “overdesigned and overbuilt.”

    I wonder if a good argument could be made for returning the B-52 to active production: increase the size of the bomber fleet to accommodate losses in a major war, negligible design costs, low production costs, sales to dependable allies.

    My knowledge of aerodynamics is very limited, but don’t conventional aircraft like the B-52 have an inherent substantial lift/drag advantage over body-wing stealth aircraft like the B-2?

    1. The B-2 has a much, much better lift-to-drag than the B-52 since, as a flying wing, it has no drag induced by the fuselage. But the thing is so unstable that a slightly moistened air pressure sensor will turn it into a billion-dollar-barbecue.

      Really, in the modern age, drones, ICBMs, and SLBMs have rendered bombers obsolete. All that space used to support a crew adds an immense amount of drag to the aircraft and increases the weight of the aircraft and/or reduces the overall payload capacity.

        1. Current drones no, but you could make a drone the size of a B-52.

          I think the issue is also a drone the size of a B-52 would be a big risk if an enemy would gain control of it somehow.

          1. If it costs 5K pounds to keep a man alive, then on a 20K pound F-16 sized plane there is a HUGE performance advantage in droning it and turning it into a giant dumb cruise missile.

            On the other hand, for a 500K pound bomber, the performance gain is minimal little more than a rounding error.

            Ironically, cheap drones and cheap electronics mean we’re probably permanently exiting the era of unjammed communications in all fields from armor to naval to aircraft, making something like an B-52 sized drone essentially useless.

            Something like a B-52 could dump an astounding number of small drones. Imagine something like a Maverick missile but one hundredth the weight so you carry one hundred times as many. If you can only hit within 50 feet of a tank using 1980s technology, you need a 500 pound missile. IF you can toss a 5 pound missile thru an open hatch reliably, then five pounds is plenty.

    1. B70 was optimized to fly si high and fast SAMs couldn’t hit it, but SAMs improved way faster than bomber design did so that’s no longer a viable design criterion.
      Now it’s all flying low and stealthy so if they see a bomber it’s already hit its target and is heading out.

    1. I had a co-worker who did electronics maintenance on B-52s (Vietnam era) at Loring AFB (now a Pearl Jam/Phish concert venue) in Limestone ME. He said it got pretty boring up there in the winter. One night they decided to “test” the jammer they had just re-installed. They activated it during the punchlines of a late night host’s monologue. The base commander was not amused. Only one TV channel up there, you see.

      The wife is from South Hadley, MA. Her parents’ house was right off the end of the Westover AFB. She said they were *really* low when they came over her house, on the way to Vietnam.

      1. I’ve driven down Rt 90 through there many times when the large jets are landing and taking off. So impressive.

        One time I was riding my motorcycle a few miles North of there and a C-141 was doing a valley run. Now that was an experience.

        1. Last time I went through there, the “Low Flying Aircraft” signs had been removed from the Pike. Kind like losing an old friend. It was C-130s and C-5s when I was at UMass in the 70s. I think it’s C-17s now.
          I have seen aircraft below me while hiking in the Whit Mountains in NH.

          When I worked at Data General, their Portsmouth NH plant was right off the end of the Pease runway. I flew up there in the DG chopper one day and had the phones on, heard “B-52 on 10 mile final”, so I waited around after I disembarked and was rewarded by having an up-close look at a B-52 underside. “Aluminum overcast”, indeed.

          1. I lived in Hadley, MA when I was a child/teen and I recall seeing various aircraft over the years flying in and out of Westover AFB. One time I was riding my bike as a teenager in South Hadley in a rather quiet residential area with lots of trees. All of a sudden, an A-10 attack plane came screaming by from out of nowhere at tree top level. I almost crapped my pants, that thing startled the hell out of me.

  3. The crew space in a B52 is miniscule. The volume is nearly entirely fuel, avionics and weaponry.

    My late father-in-law was flying B-52s during the Cuban Missile Crisis. He used to tell the story that having done well in flying school he was given the choice of B-52 Bombers or KC-135 Tankers. He didn’t much like the idea of flying a tanker full of avgas, so chose B52s. It was only during later training that he learned that it took multiple tankers to fill a B-52.

    1. Technically the tankers carry JP-8, not avgas. JP-8 is used in aircraft with turbine engines , while avgas is a form of gasoline used by piston driven aircraft engines. But either way, your story is still great.

  4. “… I wonder if a good argument could be made for returning the B-52 to active production…”

    Most people, unless they’ve worked in or around the aerospace industry, don’t realize that almost the entire initial production cost(s) of the airframe itself consists in building the “jigs” required for the specific airplane; that building a production aircraft is NOT a “prototype” operation.

    Many years ago, the idea was floated about increasing the size of the C-141 ‘Starlifter’ fleet. That idea quickly and quietly disappeared when Lockheed pointed out THE one small problem with that proposal: that the jigs required for production had been cut up for scrap when the Air Force decided to not issue a new contract for more C-141s when the last contract had expired–building the new jigs and activating a production line would be almost as expensive as building a new, “ground-up” aircraft.

    1. Exactly. In some cases, it may be necessary to start over even if the original tooling still exists, because the machines that the tooling went on are worn out or so old that they’re completely outdated. Then, the manufacturing planning and other technical documentation is probably gone as well.

    2. I was reading last night about JOVIAL, which is an ALGOL-derived language used in the 1960’s and 1970’s for practically everything military or space.
      Which includes the software running the F22’s engines, and the whole control system/avionics on the F15, F117, and various other aircraft that are not all that old.
      The group responsible for maintaining the documentation and specifications for it was disbanded in 2010.

      This is ubiquitous: “let’s rebuild exactly the same thing only with just a few updates” and once you look, *nothing* is still in stock or usable, and you end up doing a complete redesign that happens to look like the original, or you go ahead and design something new.
      There is a significant reason to do the complete redesign: both the military and congress are way more likely to provide money for “the same thing but better” than they are for something that’s actually better. In many cases (more in the Soviet sphere) complete redesigns were commonly given the same number and touted as upgrades precisely because they’d get funding that something presented as a new design would not get.

    3. Starlifter production run was about “three hundred” over five years IIRC. So figure 60 per year you need a serious factory assembly line to squirt them out that fast. That’s like one complete plane every working week for five years. Probably gonna need overtime for that…

      We don’t mass produce aircraft anymore. The B-2 production run was 21 over what seems classified but somewhat over two decades figure less than one per year.

      We’re crashing B-52 at the rate of 0.5 per decade so we have 20 years to make one to keep up. If you’d like to replace the entire fleet every half century we need to produce slightly over one per year.

      We produced something like 5000 P-51 per year during WWII… Those days are over. The future of aviation looks like naval ships today, one off, one at a time, not too many, all semi-custom.

      If you want me to produce 120 B-52 per year using 1950s technology I need to reinvent the expensive technology of the 200 foot long manual operated horizontal milling machine, its going to cost hundreds of millions by the time I’m done, but I’ll eventually be able to squirt out wing spars at a rate of ten per month or one about every three days. Actually that’s VERY pessimistic and I bet I could squirt out a wing spar every eight hour shift given infinite supply of money to set up. Working three shifts I could trivially produce enough wing spars to replace the entire fleet every month or so.

      On the other hand if you want me to produce one B-52 every twenty year long machinist career, I could trivially rig up a system of modern COTS machining centers and conveyor belts to squirt out one wing spar per machinist career. OR I could work hard and quite easily make one wing spar on a machining center per year. Its all COTS and its cheap. I would never, ever, be able to produce a 185 foot wing spar every three days using that technology, but it seems I’ll never have to…

      Eventually aviation manufacture will merge with the technology of aviation restoration. There are guys hand making essentially entire B17 and B24 from hand, takes years, but thats how fast we produce B-2 and similar so thats “OK”.

      In the old days you increased production speed by making a bigger factory. In the future, you’ll just contact more general purpose machine shops and work in parallel, just like naval ships build modular hulls or WWII warbirds are restored. Its far cheaper to have 100 WWII warbird restoration shops each build one B-52 over the course of a decade than to have one giant factory that can produce 100 B-52 per month that shuts down after one month of production.

      Mass production is obsolete in aviation.

  5. I seem to recall that all of the previous attempts at this have failed because they have enough TF33’s to last till the heat death of the universe.

    Newer engines will reduce fuel consumption but with a fleet this small the cost will be far more than the fuel saved.

    1. There’s kind of a subtle secondary issue in that they still have TF33 engines aside from the ones on the Buff.

      There are a handful of other AF aircraft still using these engines, and that means that even if the B52 all went to the boneyard the Air Force would still have to maintain at lest some facilities to work with these engines.

      If re-engining the B52 could entirely prune this branch of the maintenance tree, the decision might be a no-brainer, even for a large military bureaucracy. But when the continued maintenance of a B52’s engine is an incremental cost to a facility that has to still exist anyhow… and that facility exists in some congressman’s home district… then it’s not such an obvious call.

      1. I once, out of the blue, got an email from someone who claimed to be working for the Air Force, maintaining some aircraft. The problem was that they were using a Data General mini as the core of a piece of test equipment. Which meant that it used a DG terminal I had helped design, and the terminal had failed. He wanted help to repair it so they could use the equipment. And they had no repair budget :-)

        I ended up pointing him to a DG serial terminal emulator program that ran on a PC (DG terminals used non-standard ASCII codes for cursor positioning) instead of trying to repair a frankly unrepairable 25-year old terminal.

      2. There are only two, the E-3 and E-8, both derived from the B707 and trivial compared to the B-52 to convert to turbofans, particularly the CFM56 (aka F108 in USAF-speak), which now powers all KC-135 Stratotankers in USAF service, as well as the E-6 Mercury, which is also a B707 derivative.

      1. 642 of those B-52s used J57 turbojets. Only 102 were built with TF33 turbofans. Turbojets are far less efficient and entirely obsolete. The last aircraft in service to exclusively use turbojets was the Concorde. That aircraft’s flight regime was the only application where a turbojet was more efficient than a turbofan. Even modern fighters use turbofans because they spend very little of their time in the air in supersonic flight.

    1. Because the new engines will use Arduinos as part of the fuel management system.

      And because it help us to appreciate the concept of design tradeoffs. Or about thinking about systems that have long lives. Heck, they were speaking about upgrading the B-52’s engines when I was in the USAF, and I left in 1990.

  6. A university roommate of mine and I used to joke the there would come a point when we would tell our grandkids that “We were old enough to remember when B-52’s landed.” This was back around 2004 and both of us were studying aerospace engineering.

    The thing that Combat Controllers like about the B-52 is that it can carry just about everything in the dropped ordinance category; so it can function as a munitions buffet. Given the time it would take to develop a new airframe and that the tooling would need to be recreated. We thought it might be easier to keep the same design, but you would gain structural benefits from composite or composite reinforced components. (They had been playing with this on DC-3’s and other planes of that generation with some success at the time.) Re-engine and then automate it as a drone (hence the landing comment).

    1. No but I once saw 2 B-52’s climbing from ~3000ft over monument valley belching out black exhaust. Quite a sight – it takes a plane that big to look impressive above the rock formations.

  7. ICBM in a hole – pretty cheap even the training is simulated, the high price is just digging and reinforcing the holes and because military pork aerospace pricing
    SLBM in a boomer – expensive to keep out at patrol but the missiles themselves are maybe 2x the price of a missile in a hole
    bombers – very expensive as they require live training on an aircraft, the bombs(standoff cruise missiles) themselves are pretty much the same price as the other warheads but you have to keep the aircraft fueled and in shape and the aircrews in deep practice this is even if you don’t go full Chrome Dome keeping a force of nuclear armed bombers in the air in the arctic ready to go; that is exceedingly expensive.

  8. “… four larger engines being a more typical solution on modern aircraft.”

    The reason they are specifically not doing this is the change in the air flow field around the nacelle would be significantly different than the current implementation. “So what?” you ask… well.

    By changing the flow field, ALL stores (bombs, missiles, fuel tanks, etc.), will need to be re-qualified for release. That’s tens of millions of dollars and years of effort to make sure that when an object is release, the air flow over the new configuration doesn’t toss the object back into the plane!

    Another issue with the changed flow-field is the structural response of the wing; it was designed with a specific slung load at each pylon. Without that load, the dynamic response of the wing changes; sometimes with very, very bad consequences.

    So keeping the same eight engine configuration with engines that weigh about the same, have about the same thrust, yet have far better fuel efficiency and are still in production for parts and services, is the cheapest solution, both from an installation, logistics and a maintenance point of view.

    ‘Cool’ doesn’t win a fight. Bringing the most capable people and equipment to the fight the quickest does; as long as the politicians have the stomach for it… unlike resent events.

  9. At what point does it make more sense (from a cost perspective) to forget about these ancient (in aviation terms) air-frames and build something brand new that does the same job but better?

    Brand new modern avionics (rather than the retrofit job the B-52s have), modern materials that can provide the same strength as a B-52 with less weight (or more strength for the same weight), modern fuel efficient engines, a design that incorporates the latest advances in aerodynamics and an all-around better airplane.

  10. “At what point does it make more sense (from a cost perspective) to forget about these ancient (in aviation terms) air-frames and build something brand new that does the same job but better?…

    We have, unfortunately, reached the point where MOST aircraft manufacturers can NOT “build something brand new that does the same job but better”. It is simply not possible.
    The ‘point’ occurred when airframe manufacturers started getting rid of their older workers who knew precisely what it took to design a reliable and safe craft. The manufacturers allowed the ‘bean-counters’ to start running the companies, and individual operations, which had previously been the sole domain–and rightly so–of “engineering”.
    The airframe manufacturers (some; not all) have lost one of their most valuable assets: “institutional memory”.

    The ‘new order’ has fallen victim to the siren-song of “all design can be performed, and all problems solved, with/by
    software”
    ; even to the extent of believing that software can take the place of doubly- and triply-redundant hardware which is required for safe operation. This was once a part of the design, with never a second thought–because it was simply known that “this is the way it is done; end of discussion”.
    After all, lines of code cost far less than three pitot tubes, or three voting CADCs (Central Air Data Computers), right? Riiiiiiiight! Those devils are EXPENSIVE!!

    Does “Boeing 737 Max” ring a bell?

    End of discussion.

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