Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 17. High hanging fruit.

April 10, 2020, ©. Leeham News: We have since December 13, discussed why e in ePlane should not stand for electric and covered a lot of areas explaining why electric aircraft or hybrids are not the best way to environmentally friendly air transport.

We now recap what we learned and then wrap the series.

Figure 1. The Gartner hype cycle. Source: Wikipedia.

The subject to discuss

In the first Friday Corner on December 13 I wrote;

“The electric aircraft hype comes from the fact it works for cars. Applying electric propulsion to aviation is seen as the most promising way to get us to an air transport system that has a lower environmental footprint. On a number of Fridays, I will argue why it doesn’t.”

The electric route is “a route with high technical hurdles, and it involves a lot of unknown unknowns on the risk side. We are still at the first peak in the Gartner hype curve (Figure 1) and we need to pass the trough of disillusionment before we make real progress. There are lower hanging fruits in the tree, but the electric hype stops us from seeing them and from directing our efforts more intelligently.”

The high hanging fruit

We summarize our insights by listing the highest hanging fruit first and then work our way to the lower levels in the tree:

  • The highest hanging fruit is the 100% battery-based electric aircraft. Only teams with no experience in developing air transport aircraft are still pretending this is a viable technology. They embarked on almost a mission impossible as it needs a certifiable battery system that has 10 times (this is 1000%!) higher energy density than the best research individual cells of today. It will not be achieved this side of 2040. Structural batteries might help but bring their own problems.
  • The next level down goes to the electric hybrids. It’s once again the batteries that drag them down. It doesn’t matter if it’s a parallel or serial hybrid. The first that happens, we lose 10% in efficiency just because the battery’s weight stays fixed during the mission. A hybrid propulsion system has yet to prove it can achieve any improvement over what already know technologies delivers.
  • The third branch from the top holds the different aerodynamic wonders that electric technologies shall enable. We proved they are better realized with existing technologies, present for decades. Yet we have no implementations. Could it be because they don’t work?
  • To the high hanging fruit, we must add hydrogen-fueled aircraft. Here the technology holds promise; we just have a long way to go to explore and mature it. We need an environmentally correct ecosystem with production, distribution, and in-plane storage. The process of driving fuel cells with hydrogen still needs development, but the burning of hydrogen in a gas turbine combustion chamber works, it predates the use of jet fuel in gas turbines.

The above list is the highest hanging fruit, yet this is where the attention is. This is consistent with Gartner curve observations from other industries. The exiting stuff catches the imagination, then reality catches up.

In five years the hype media will explain why electric and electric hybrid airliners don’t work and what to do now.

In next week’s Corner, we summarize the low hanging fruit.

 

42 Comments on “Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 17. High hanging fruit.

  1. The Gartner Curve should have an up front depression were
    keeping up protective interest in existing solutions depresses initial evaluation of new technologies.

    After that depression
    The “Peak of Inflated Expectations” is synthetic and not necessary.

    To even out the curve shoot some of the PR folks and associated profiteers and development will be much more realistic.

  2. The psychological aspects are more than just the “Gartner Hype Cycle”. I recently investigated BMW announcement of joint plans with Toyota to launch Fuel Cell Electric Hybrid vehicles (more as a backup) and was quite surprised at the angry reaction this provoked from pro battery electric vehicle persons. Fuel Cell vehicles using compressed hydrogen have advantages that may fill the weak areas of Battery Vehicles. They can be refilled in 3 minutes, fuelling station can be as simple as an electrolyser, compressor and some tanks in a half container that can be built into existing petrol station or even for home use, the range of the vehicles is great, the vehicles can tow, the electrolysers can use renewable electricity when it is available at odd times or it can be transported from say sunny production facilities in Australia.

    It seems battery electric vehicles have become the “one true panacea solution” for many of religious zeal and if scepticism is expressed or a supplementary solution is offered they can be seen as an enemy of the one true religion. That is something new and bad.

    The same has happened with carbon neutral electro-fuels which have fallen foul of the same politics.

    It think what we are seeing is an attempt to use the AGW crisis and control roll out of the type of technology as a way of changing and radically altering society. Carbon neutral fuels and HFCV prevent that, they’re seen as a way of continuing as is. Of living in the suburbs and avoiding mass public transport.

    People of my generation regarded affordable personal mobility and freedom of speech and truth speaking as high goods.

    Technology is hard. Public relations is harder still.

    • Issue is that a lot of people deform any good base idea to a religion.
      Instantly things are driven by dogma and not longer by intellect.

    • Lots of ‘true believers’ have invested heavily in Tesla, pushing the price to 10 or 100 times it’s real value. I’ll bet they gave you a hard time!! Also worth remembering in these discussions is that BEVs really came to the fore as a way of combating local pollution in cities. Makers saw their chance to jump on the climate change issue later, but the advantages of BEVs for CO2 reduction are very debatable.

      Another problem which you didn’t add to your list is that BEVs are most economical when charged at home, at night, using fossil fuel electricity, most likely. A bat. airplane would need massive amounts of on demand power to recharge in an hour. If bat. tech. is to avoid using fossil fuels it will need to use more batteries for storage. As battery production is dirty I think it is a vicious cycle which can’t be beaten. Hydrogen can be produced by solar power and stored. Not as efficient, but it works.

      I can’t see battery powered aircraft taking over the world, ever. Required advances needed in battery tech. look to be impossible. Never say never, but I’d say the advances needed are on a par with those needed to produce a thermonuclear aircraft. Hydrogen fuel cells might make it one day. While man made hydrocarbons look good a lot of cities suffer from local polution issues, so something else might be forced upon us the day it becomes practical.

      • China has been pushing for BEV with some force.
        ( and mostly on the smalish vehicle side succeeded.)

        IMU brilliant.

        If people would continue to buy petrol/diesel driven vehicles there is no chance of changing the picture before those citizen investments have run their useful life.
        Push to electric and even with a less than clean source for gird current you have a more central lever to change the greennesss of energy generation.

        Quite a good thing to have a system that is not driven by Zero IQ short term reflexively driven market forces.
        ( Like in the US.. . All the privatize, market will solve everything experiments have an expensive outcome for the full society. )

        • Its obvious that BEV have a future because of their immense energy efficiency, maybe they will be affordable and viable by 10 years time.

          But we have a problem. There isn’t enough renewable energy to charge these, the renewable energy is extremely expensive and it is available only intermittently. Electric cars are not being charged by carbon neutral sources except maybe in Norway or Iceland.

          A Tesla 3 charges at 90% efficiency if charged over 8 hours. If charged over 12 it drops to 80%, if fast charged over 30 minutes it can be as low as 60%. BEV should be charged during the day when sun and wind power is available (wind dies down at night) but the reality is BEV are being charged from fossil fuels, mainly at night. There are people in LA who live in apartments and don’t have a charger who use public fast chargers all the time. All we have is a vehicle that is a little more efficient. About 65%-75% of the electricity gets to the wheels or about 40% to 45% of the fossil fuel energy used to generate it, not much of that power is renewable, that would require smart chargers to which the car is connected all day and which adjust the charge rate to suit renewable power availability. If we do want to charge at night we may have the absurd situation of charging from battery storage. If we fast charge during the day we generate peak surges. They have to be plugged in during the day most of the time.

          An electric aircraft should probably have exchangeable battery packs. Volocopter are now trying to decide because you can’t fast charge these things without reducing battery life and efficiency.

          Of course we wouldn’t be going through this nonsense if we had plenty of ‘carbon neutral’ electricity but we don’t and probably won’t.

          Germany is going to miss its Paris Accord commitments by a wide margin because it shut down it nuclear needlessly. The same people panicking over climate change are often the same ones that prematurely shut down nuclear. This over reaction we call “cutting of ones nose to spite ones own face”

          The CEO of “green” wind turbine electricity producers will tell us that they have the lowest levelized cost of energy production. They’re being deceiving. Their surgy, intermittent power trebles in price when the networks, power factor correction and protection equipment is factored in. Energy storage is going to be even more expensive.

          We have a price problem, a big one.

          We can’t even produce the renewable power to produce the carbon neutral hydrogen needed for ammonia production or steel smelting. Why are we focused on cars and aviation so much?

          So throwing money at electric cars too early can become throwing money away because the technology is not mature and systems not in place. Rich people with brand new $75,000 to $100,000 electric cars subsidised by poor people with $15,000 second hand cars.
          All this does is develop the technology but the subsidies and regulations must not go any further. Investing in an expensive technology prematurely is a way of ensuring the money isn’t available for a technology that does work. So small scale production only in my view.

          In 5 years time it will be different and batteries maybe 70% cheaper. At the moment the drive train of an electric car adds $18,000 and the batteries $12000 according to the SAE.

          My own situation in Australia is indicative. I can buy a small Suzuki Swift hatchback for $19,000 drive away with 5 years warranty. It has autonomous emergency braking, smart cruise control, lane departure warning. For $27,000 I can get a Toyota Prius C Hybrid the same size with 2/3rds the fuel burn. For $50,000 I can get a Nissan Leaf Electric. A nice car and I don’t need to got to a petrol station but it is unaffordable for most and the resale loss is too great. It means I cant jump in my car and drive 600km to Melbourne without serious inconvenience. I cant even drive 300 kilometres to a work site without serious inconvenience. So I have to spend $80,000 on a Tesla Model 3 upgraded to the large battery pack.

          An ordinary person who spends this amount of money wont have money in 5 years time to buy a proper car.

          I don’t think renewables are going to work unless we accept severe austerity and poverty.

          • Some of your assumptions are based on logical fallxy.
            You are too focused on thinking hand in mouth.
            China does it right:
            With a significant amount of vehicles with battery storage : Even if your energy mix at the moment is less than green you are now at leisure able to change the infrastructure to bring renewables more to the front.
            Look into the current German energymix:
            https://www.energy-charts.de/energy_pie.htm

          • @ Dear Uwe, What this chart doesn’t show is
            1 Imports and Exports of Electricity which have made Germany’s rash expansion into wind power possible. Or that Germany’s gird almost collapsed in 2019 and this required emergency imports Germany’s neighbours struggled to provide.
            2 Electricity in Germany is twice the cost of Electricity in France.
            3 This is a chart of energy generated not CO2 emissions.

            Germany has used the wealth its dominance of certain manufacturing export markets to subsidise a wind turbine electricity network whose costs threaten to crush German manufacturing. (I speak German and love the country and people since working there as a young man so don’t take my criticism the wrong way.)

            Rather than argue myself I will provide links to two negative articles on the German energy situation, one by Forbes the other by Reuters.

            https://www.forbes.com/sites/michaelshellenberger/2019/09/05/renewables-threaten-german-economy-energy-supply-mckinsey-warns-in-new-report/#38ad26728e48

            https://www.reuters.com/article/us-germany-energy-retail-idUSKCN1P9233

            I’ll make two more points. This wont provide the affordable energy needed for decarbonisation of industrial processes such as steel, cement, ammonia or ploughing and harvesting a field let alone fuelling an aircraft. It’s painful to make consumers and small businesses suffer from taxes and fees but when these costs start being fed into primary and secondary producers things will get very difficult.

            The poverty induced by such things is not just someone living a poor life with poor food, obesity and poor living circumstances.

            In the Western world and Germany it manifests as people not being able to start a family and a listless frustrated life. We can see that in Germany with fertility rates of 1.38 which imply a decline of 35% every 20 years. Recent increases in Germany are due to immigrants but they too will feel the pressure.

            I’ve never seen a chart of data sceptical or negative from an official government website of anything.

      • In some Power hungry applications they use large flywheels and genertors to give enough Power. One example is the new Ford class Aircraft Carriers where the nuclear powerplans generators do not generate enough electrical Power for the seconds of electrical catapult, hence they added flywheels and generators. Wind Power is progressing pretty fast and now are the GE Haliade 10MW turbines on testing with the competition gearing up to similar Power levels. Not many years ago was 2-3MW the norm. With goverments approval to swap out old less powerful versions to 10MW class ones it will be a massive jump in installed power. The main problem is the powergrid to handle those powers of 1000’s of 10MW turbines hence they might be forced to produce LH2 with the excess Power that the grid cannot swallow and you or compressed H2 pumped into the natural gas grid. Most Western countries only allow these mega turbines off shore.

        • Those GE win turbines are impressive but they don’t fill me with hope. The rotor is 220m in diameter and 3x A380 or B747 wing spans would fit inside. Height to the hub would be over 220m, they are the size of a New York skyscraper. I think they’ll grow bigger. At 12MW Maximum output and 63% capacity factor means they would meet the electrical energy needs of only 7560 people living in an industrial society assuming 24kwhr/day. That doesn’t count the additional needs currently met by oil and natural gas which are each as much again (we are using too much). The electricity Converted to jet fuel at 65% efficiency each wind turbine would produce about 15000L of fuel/day. Enough for one A320 flight. At least 1 million such units would need to be built to just meet current global electrical needs. Granted solar will add to this. The surge prone difficult nature of wind and solar have driven electricity to unprecedented cost increases making it almost a luxury several fold increase due to the enormous network costs.

          I won’t condemn or criticise these monsters but they’re not enough and not cheap enough.

          A SMR Small Modular Reactor such as NuScales 60MW Units planed for factory production now seem the only way to get even remotely close to the Paris accord. Such units are completely passively cooled and are safe due to their size. They’ll be built in groups of 8-10. A 60MW reactor could easily produce 120 tons of jet fuel (1200 in a pack of 10) or produce the electricity needed for 60,000 individuals. It’s getting to late to restart the industry.

          • We will see if they increase the span further and at those radi a small increase of blade length converts to a huge increase in swept area and possible Power increase.
            Eventually wind mills might be flying at altitude in stronger winds, above “normal” birds flightpaths and high enough to aviod noice on ground with the anchor cable also being the Power cord, they are under development and are still small, for now it is easier to increase span on fixed windmills to get more Power than solving the Control system and landing platform to keep these flying Power-kites at the correct positions.

          • Folks are considering windmills as large as 50MW and 100MW. These larger units will likely have blades that fold back or ‘sweep back’ at the hinges so that they can withstand a hurricane. Windmills don’t last long, 20 years max. Many are failing to 7-10. That GE Halliade weighs 2500 tons (more for foundations) will generate an average of 7300kW which is enough for 7300 people so we need 300kg of windmill built for every human being every 20 years. For the planet 1 million would need to be built every 20 years. I’m assuming solar contributes another 50%100% since such energy will be needed to decarbonise industrial processes now reliant on fossil fuels. A 60MW small modular reactor core, convection cooled, would weight 650 tons, maybe 3 times as much again with civils, and last more than 40 years.

  3. Can’t disagree with that prognosis.
    As such I look forward to the next episode – the low hanging fruit.
    Although in truth this should be divided into two parts.What we can do 1.now and what a 2.next gen hydrocarbon powered aircaft could be to lower emissions.
    Adding 10% biofuel to existing kerosene could be done now.Perhaps second gen’blended winglets? Flying 10% slower?
    Further down the line.Full laminar flow wings and second gen’ geared fan engines.
    But if they really want to make a’leap’ it would be interesting if they really got behind contrarotating open rotor engines ( combined with laminar flow wings).
    This is the sort of project I would like to see Boeing embark on for their 737 / mom replacement.

    • The current range of available “bio”fuels is anything but ..

      the basic idea is sound but you need a production path that has much less “fallout, unintended consequences”.

      What about oceanic CO2 accelerated algae bloom?

      • It can easy get “off balance” with massive algee bloom that animal algee cannot consume in enough volumes and that small fish living on animal algee might be too many reducing the animal algee population, the Baltic sea I heard has this off balance with algee bloom, too much small fish and too small population of cod. Can the algee bloom be havested at sea making fuel of it (like JET-A), it can help getting the ocean food system in balance.

  4. If it is obvious that electric or hybrid aircraft don’t work for fundamental reasons that can easily be derived from the basic physics, why are Airbus, Rolls-Royce, Siemens and others putting so much time, effort and money into building an electric / hybrid demonstrator on a BAE 146 platfom? Do they have a different perception from Leeham? Do they know someothing we don’t know? Is it only a PR exercise? Or are they just wrong?

    • Sometimes things are done as PR, other times it is contingency planning, or a combination thereof. Engineers get to test if the combination is really ready for any application while the company gets to tout its green ecodemonstrator. In a sense, tax favored R&D and free PR. I doubt RR has any intentions of it replacing an engine family, but even if pieces of it can be used in a next gen engine or system it’s a win along with the green halo.

    • I can think of a number of reasons.
      1 They have to be seen as trying, else they’ll be hated. It is a publicity exercise.
      2 If build prototypes they can credibly explain why it can’t be forced with credibility.
      3 It employs and trains a bunch of engineers with Government/EU/US money.
      4 Companies like Siemens and Rolls Royce last 100 years by hedging their bets on multiple technologies otherwise they end up like Curtiss-Wright.
      Now the good reasons.
      1 It’s not right to say that electric flight can’t work. There are eVTOL drones with endurances of 2.5 hours doing all sorts of work, mainly photographic, survey but also agricultural spraying and parcel delivery.
      2 The whole area of ‘urban air mobility’ will turn into a monster in the next 10 years and Airbus, Boeing and Rolls-Royce wont to be part of it. Electric aircraft like the Volocopter promise a new kind of operation, a new market with extremely silent flight and the ability to operate safely in urban environments with little landing space requirements or maintenance costs. They may be better than helicopters for ambulance work or shuttles to the airport within cities despite their limited range.
      3 That BAE 146 with the 3MW 3000V siemens motor and the Rolls-Royce fan is probably not really for battery powered flight but fuel cell flight. If in 10 years Airbus is told by regulators that they must emit zero particulates, zero CO2 and zero NOX in the upper atmosphere then fuel cell electric will be the only way to go. They’ll probably be seen as APU that rather than being switched of will drive active laminar flow devices.
      4 There are already turboshaft helicopters flying with electric tail rotors (made up of 9 small electric fans). I can see some interesting stub wing helicopters developing.

      • Last we heard unducted fans were the thing despite the issues.

        Always a few years away, but they never get past the mounting issue adding more weight than it saves (even if you manage the noise and the blade issue)

        And as each approach is unique (no common pylon mounting points) is a one off for the engine.

        Stuck with one engine is not a happy spot for airlines.

        When the Trent 1000/TEN proved to be an unresolved issue and never achieve SPC of the GE, airlines could shift to GE.

        • Outside of a little bit of carbon neutral jet fuels produced from supposed waste cooking oil (thanks McDonalds) we are facing Jet Fuel Costs of about EUR1.20/Litre or USD$4.40/US gallon. The current cost of jet fuel from mineral oil is about 1/5th that. The moment that is mandated those plans for UDF and contra rotating geared ducted turbofans will no longer be shelved and if RR offers say 3% better fuel burn than GE even with less MTBO and risk it’ll still be attractive. The Boeing truss wing with a turboprop looks particularly attractive.

          A B737-8 or A320-neo would burn 2.2L/100km per passenger. Over a 1200mile/2000km flight that would be 44L or 12 US gallons costing about $150. That’s about $110 more than current costs. If we can pull of another 20% with a turboprop or UDF and another 20% from a high aspect ratio truss wing the costs start looking less devastating.

      • Good points William…we all remember the last full scale demonstrator engine made by a number of manufacturers,the prop fan.

        As a concept it had a lot more going for it than a BAe146 with 2.0MW electric fan ‘powered’ by a 2.5MW turbo shaft/generator in the tail cone.
        And no its not Siemens any more , as RR has bought out their ‘electric propulsion branch’

        • Rolls-Royce has long (maybe 20 years from when low temperature superconductivity was discovered) looked at superconductivity. They initially started looking at using superconducting reducers (instead of mechanical gearboxes) to achieve fan speed reductions and at replacing bearings since super-conductivity can generate immense repulsive forces that levitate objects in the middle of the superconducting magnet, its stunning to see this in a university lab experiment as I did in 1989. What know how Rolls Royce intends to obtain is not clear.

          Electric fans can eliminate the notorious lag of jet engines and allow thrust vectoring which can be used to generate sideways crabs and reduce stabilising and control surface size.

          Although electric motors now have power to weight ratios as good or better than turboshafts if one counts the cost of a generator (which will be the same weight) and the cost of conversion power losses (10% in both generator and motor) and the bulk of the High Voltage High Current Cabling its not sensible. However superconductivity can eliminate these losses and dramatically reduce cabling size (mainly due to voltage clearance and insulation issues) and motor and generator size.

          There are now superconductors built into wind turbines in operation and sumitomo who make the stirling based cooling devices for these are pushing ahead with superconducting motors for automobiles and trucks even though they don’t have a known market. In BEV 5% of electricity is lost at transmission and 10% in charging/discharging and 10% at the electric motor.

          Superconductivity makes highly efficient centralised power plants viable.

          So maybe by 2030 the technology will be in place and the investment decisions to make Airbuses flying wing airliner can be built by 2040. I suspect the power plant can be a gas turbine with a supercritical CO2 combined cycle with 75% conversion efficiency. It may be some kind of fuel cell. It may burn colloidal nanometals with oxygen in a heat engine and collect its exhaust to achieve zero emissions it may be some kind of electrochemistry. This may explain Faury’s reticence in investing. Airbus is looking a generation ahead of more practical near term possibilities such as Boeings truss wing.

          Siemens sold its electric flight division to Rolls Royce. I suspect they will be happy to make specialised devices such silicon carbide transistors the way they make hundreds of thousands of fuel injector nozzles.

    • There are alot of Electronic boxes and cables involved that eventually will has to be certified, so doing flight trails with these first generation Aircraft grade boxes will show what problems to solve on the next generation, normally they have to work thru 3 generations of each box to be “on the sunny side”. I assume it will be around 25-55ea of these “Lucas” boxes or a mix of Honeywell & Hamilton Sundstrand black expensive cooled boxes eventually.

  5. Ten times is 1000%, not 10,000%. Looking forward to low hanging fruit.

  6. “… it needs a certifiable battery system that has 10 times (this is 10,000%!) higher energy density than the best research individual cells of today”

    — something wrong or something I don’t understand? How can 10 times be 10,000% ?

    • Regardless of how good your battery is, its never looses weight, so you carry that the whole trip.

      Fuel is used up and you get more efficient.

      I am not sure that overall battery issues will ever overcome and some type of fuel will always be the best for an aircraft.

      • How about mid air refueling with a charging cord from a big A380 electric tanker flying circles over the pacific?

        • Intercontinental Stratospheric Catenary.
          The jet streams need to be homesteaded :-=)

        • With a long power cord down to a farm of floating windmills flying figure 8’s for airlines/fighters and bombers to catch up and do automatic refuel. It will be some years before even the USAF tries it half way between China and Hawaii. Maybe easier re-engine the B52’s so its range doubles for the same fuel load…

          • Tethering is not a completely impractical. Imagine a lift drone like Volocopter’s attached by two winched tethers. One carries positive current the other negative. I would be possible to power an eVTOL drone or passenger aircraft for a few kilometres, perhaps as a crane, crop sprayer, fire fighting device, emergency bridge or rescue device for a fire brigade. Then there is the possibility of transmission of power via microwaves or radio which has been used.

            Floating wind turbines would probably work well for the production of carbon neutral electro-fuels. There is abundant CO2 in sea water and it is rather easy to extract with electricity. The hydrocarbon can be produced on board the wind turbine itself without the need for submarine cables and retrieved by a tender when the tanks are full.

    • Some folks have extrapolated that batteries based around fullerenes can potentially have these sorts of extreme energy densities of over 10000%. It’s extreme but not inconceivable.

        • Why waste it on a plane. A nuke plant in every back yard!

          Then airplanes are miner.

          Just get rid of coal plants (bad in mining, bad in emission and bad in ash waste) and we could not even worry about aircraft.

          Best money would be for Airlines to do the equivalent of planting trees, except its retire a coal plant and replace it with natural gas.

          • You can do it in different ways for these reactors with no moving parts, by generating electricity from heat or have the fuel emit light or beta particles that get converted into electricity thru a “solar cell”. It has been used on satellites that get to far out for solar panels to work but at lower Power levels. Check Oak Ridge Labs pubs on this version of nuclear Power.

  7. “e” stands for environment, not electric, could be what we see.

    Looks like Rolls Royce ultrafan is getting closer. Sam Chui recently (pre-CVD19) visited Derby and has put up this youtube vid. I’ve put the link part way through:

    https://youtu.be/2LZwkdGU0-g?t=750

    Basically, they’re looking at a Trent 1000 with a carbon fibre fan assembly. The RR chap claims that its on a Trent 1000 “because it happens to be the right size”. Yeah right; basically they’ve effectively got a fan swap upgrade for Trent 787s that saves a load of weight but, more importantly, likely has a pretty big fuel burn reduction due to improved aerodynamics in the fan. I’ve read this elsewhere on RR’s website; basically, a CF blade can be made to be any shape desired (i.e. best aerodynamic form), whereas with Ti blades they’re limited to some extent with the shape.

    So, will we see Ultrafan retrofits? It’s got to be an option worth looking at now that they’ve gone and built one.

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