Bjorn’s Corner: New aircraft technologies. Part 8. Propulsion advances

By Bjorn Fehrm

April 14, 2023, ©. Leeham News: This is a summary of the article New aircraft technologies. Part 8P. Propulsion advances. The article discusses how developing the next-generation airliner propulsion system will be the second most important area after we decide on the fuselage type and what to expect from increases in Propulsive efficiency.

Figure 1. The Ultrafan demonstrator readied for tests, with its 140-inch fan giving a bypass ratio of 16:1. Source; Rolls-Royce.

Propulsion efficiency advances

In the last Corner, we explained where the 15% improvement in the total efficiency of the CFM LEAP/Pratt & Whitney GTF engines came from. It was a mixture of increases in engine Propulsive efficiency and core Thermal efficiency.

Could this 15% be gained again for the next generation of heart-of-the-market airliners that we expect by mid-next decade?

We start by examining the advances we can expect in propulsive efficiency. For this, we need to decrease the Overspeed in the equation:

                            Thrust =  Overspeed * Mass flow

The way to decrease the Overspeed is to decrease the fan pressure ratio. At the same time, we need to increase the mass flow to keep the thrust. This we do by increasing the Bypass ratio, either by increasing the fan size (Figure 1) or decreasing the core size, or both.

As we go beyond bypass ratios of 15, we will have problems with the size and weight of the fan, its protective fan casing, and the enclosing nacelle. The alternative way is to skip the nacelle and go for an Open Rotor engine.

These used to be complex, as two rotors were needed to reduce swirl losses, Figure 2.

Figure 2. The SAFRAN open rotor design was tested at the Istres test site in 2018. Source: SAFRAN.

With the development of the CFM RISE, the de-swirling is done by a non-rotating second stage of variable incidence vanes, and the complexity of the engine reduces to close to a turboprop, Figure 3.

Figure 3. The CFM RISE engine gains 20% efficiency compared to the engine it replaces, according to CFM. Source: CFM.

The key question for the aircraft designer for the A320/737 replacement will be if to stick with a high bypass turbofan design or change to an Open Rotor engine.

In the next Corner, we discuss what improvement to expect in the thermal efficiency of the core of the engine.

80 Comments on “Bjorn’s Corner: New aircraft technologies. Part 8. Propulsion advances

  1. Think the RISE 2:nd stage will have movable vanes to optimize the exit flow direction at different speeds/rpms and also work as thrust reversers with unknown efficiency. You don’t want to have variable pitch fan blades at these thrusts.

    • Hi Claes,

      By fixed second stage, I meant non-rotating. I changed that. The fan blades and the second stage vanes are variable pitch. It’s the only way to handle the large speed range from 0 to 500kts. A turbofan uses the nacelle inlet diffuser to fix this problem; here, we don’t have this conditioning of the flow to the fan.

    • Why not variable thrust reverse?

      RR took variable reverse thrust out of their upcoming engine as it was a step to far but stated it would revisit the concept later.

      • What purpose is ‘reverse thrust’ for improving overall efficiency. ?

        Pratt developed but didnt implement variable area exhaust flow for the GTF

        The Me262 Jumo engine had rods along the engine casing which drove gears for moving the tail cone and increased or reduced the exhaust cross section area and that was how they regulated thrust. Its TBO was 20 hrs while the centrifugal Welland which entered service a few weeks later for Meteor was 18o hrs. The reverse flow – but short length- Welland was
        soon replaced by the through flow Derwent ( still centrifugal)

        • I forgot to say the Derwent was the engine for the 2nd to fly ( 2 weeks late) airliner the Avro Canada C-102
          Quite fitting the former Canadian Cseries is the first flight engine for the GTF in 2013
          The Jumo had 8 axial stages to do what the early UK engines ,Welland, Derwent Ghost, had a single impellor

        • Getting rid of the reverse thrust mechanism saved weight, or so RR stated in the past.

          RR also stated integrated reverse thrust saved on MX.

          • The only LCA that I know of that does not have thrust reverse is the KC-46A (agreed its not exactly commercial).

            Tankers may fly few enough hours that the thrust reverse does not pay. Certainly the KC-46A does not have the winglets most use on 767s now (FedEx also does not)

  2. Hallo Bjorn,
    Do you have any info as to whether the RISE engine will be geared?
    I read elsewhere that CFM had challenged a PW patent relating to gearing — so there may be theoretical interest, at least. However, I can imagine that using gearing in this design might represent too many challenges at once.

    • It is geared. The earlier had counter rotation LPT’s and aerodynamically it works as a normal full speed +3600rpm LPT at half the rpm per rotor. Now with one fan stage at this size you gear it down approx 4:1

      • So that PW patent challenge is evidently more than just an academic exercise…

        • Geared turbofans didn’t start with the PW GTF; my jet trainer had a GTF, the Turbomeca Abisque, probably the first GTF but the Garret TFE731 and Lycoming ALF500 were others decades before the PW GTF.

          • Yes, I know that.
            But there’s evidently some key improvement that PW is in the process of patenting — e.g. relating to materials or a specific geometric/aerodynamic design choice.

          • What killed the first P&W GTF – it was proposed as launch engine for the A340 and what a difference that would have made- was the bird
            impact shock loading on the large front fan being passed through to the gearbox. Took a long time to develop a work around and they have patented it.

    • @bjorn @scott

      can we ban this guy and his placeholder comments?

      it contributes nothing to the discussion and is equivalent to “F1rSt P0sT” garbage you get at other sites…

      • I’m guessing so he does it to get notice of comments that are posted.

          • The edit function comes and goes on my system (gone currently).

            Sometimes the post goes right up and other times latter and right now sometimes it does and sometimes it does not.

            Its very difficult to keep all functions working with all browsers. So it goes but the edit function clearly is useful as is the jump to the post.

  3. This topic came up in pontifications, a bit off topic here , but the difference in axial and centrifugal compressors.
    I didnt realise that the pressure rise per stage in small engines is 4-6 for centrifugal where its below 2 for an axial stage. In early engines better airflow handling as well.
    Nowadays used as the last stage where the incoming air is compressed a smaller diameter can be used to reduce the size effects. But the larger size has been transferred to the front fan for turbo fans and that has a big drag effect but other major benefits

    • Centrifugal compressors are often preferred in low thrust/small cores because in an axial flow design, the passages become so small that the blade tip clearance (which doesn’t get proportionally smaller) induces leakage that becomes a dominant term in the efficiency of the compressor.

      • You can design apretty efficient high pressure ratio centrifula compressor, but it is hard to handle all transients on such large unit. Easier on an axial compressor with varibale vanes and bleed ports. Look at the Safran Silvercrests problems. Still will less performance requirements like a car/truck turbocharger (up to screw compressor flows) you use radial compressors.

        • This is an excellent look at the PT-6. It combines axial and centrifugal depending on what works best where in the Turbo Prop (at least PT-6)

          While I have a good general visual of the various turbine engines, this explains the PT-6 in great detail you can understand the comments such as easy to repair. Being a Turbo Prop it only has some aspects in common to a jet engine.

        • yup, in a large/high power core or one where the core is a significant contributor to overall thrust, the mass of the radial compressors becomes an issue, as well as the losses due to flow direction changes.

          • I can follow it but I sure have no background in jet engines other than an very interested observer.

            Game changer the first ride in a DC-8, stunning after the prop jobs.

            I guess you could call me an enthusiast that they keep working!

  4. I don’t get why open rotors are an attraction. They were tried and found wanting already, and I’m not sure that anything will have really changed. Though admittedly, RISE looks very turboprop-ish, and we know how to design for and operate those.

    I understand the weight saving. But it feels like it needs regulatory approval to dispense with containment for blade-off situations. If you lapsed that requirement for an enclosed fan too, you could save a lot of weight there too. If part of the argument for open rotors is slower blade speeds, well that’s also true of an enclosed gear driven fan. We don’t insist on turboprop blades being “contained”, why should geared turbo fan blades have to be contained?

    An open rotor fan blade cannot be as aerodynamically efficient as the same diameter enclosed fan; the open blade wastes energy at the blade tip, no matter how clever one is. It also feels like it’d achieve competitive efficiency only over a narrower operating speed / power setting range. It may end up too optimised, and not operated often enough at this sweet spot.

    Besides, nacelles are useful things; they’re a convenient way to deliver anti-icing heat.

    So far as I can see, open rotor wins only by gaining an advantage in another way, but the advantage would be “artificial” and can only work if certain regulatory requirements are lapsed. Lapse them for a shrouded turbofan too, and the nacelle can suddenly become a lot lighter meaning higher by-pass ratios can be achieved. There should probably be a discussion about whether there is still a blade-off containment requirement, or not.

    I suppose I sense that, really, the idea is being kicked around the park again because of a lack of ideas, and the drive is focused only on whether or not efficiency / performance can be gained. Meanwhile, everyone is probably hoping that all the other problems (noise, safety, accidental damage prevention, etc) can be overcome somehow or other. That’s probably the wrong way round, given that those other problems weren’t solved last time.

    RR’s Ultrafan looks like the only thing on the table with a definite route to use in-service use, with P&W’s now pretty successful GTF to point at as to why it’s a good idea.

    • Matthew:

      I concur but also keep in mind that RISE is nothing more than an idea, its never been proven. There is NO hardware.

      The other aspect is when the assessment of open rotor is driven home in its negatives , they change the design. Now they claim you can hang it on a wing.

      Note the dates for RISE, 2035 (we promise you a complete proven engine by then even though we have not even done a test article let alone a prototype)

      Assume it actually does exactly what it promises in 2035, no one answers the fact people view props as crude and only tolerate them in a limited aspect (Horizon and the Dash 8) , they do not like them.

      I have flown and been flown in a lot of prop jobs. I don’t like the Dash 8, I am fine with it for shorter trips, but its noisy, its small seats and crowding, ungh. Going up to Bellingham after arriving in Seattle the last 2x I elected to go by bus, 2.5 hours but the seats were great and the price was great.

      Alaska is dropping the Dash 8 and going to E175 (and dropping a lot of the frequency to places like Bellingham, twice a day now) – clearly they want better return for the higher pilot salaries.

      Alaska tried to shift the Fairbanks to Anchorage route to Dash 8 and got constant complaints (and that is in Aviation happy Alaska where there are more aircraft per 1,000 people than anywhere in the world)

      What airline mfg is going to take a risk that people refuse to fly a Prop job (which is what the RISE is) let alone Airlines saying, thanks but no thanks.

      CFM is simply trying to stifle development while they come up with a viable new engine. And they get free money to do a new core and gear box from the prop happy EU.

      Its a case that a government has mandated a solution as opposed to a goal.

      They did not do that during the move to Diesel emissions Tiers (levels). They simply said, you will have these levels at this date for Tier 1, 2, 3, 4 and now 5.

      While initially the had to use all the main stratagems , they have also been free to use fewer if they could meet the Tier. So DOCs, Particulate Traps, EGR as well as Urea injection all played into it. And now have been able to get combustion in the cylinder itself to play a major part and drop most if not all of the add ons.

      Of course CFM having no GTF solution on the tool set did not have anything to do with RISE.

      • The P&W GTF use in a larger jet engine was a long gestation and the only real route to a competitive engine that was not rife with materials issues. GE and RR had pursued the materials long and hard.

        P&W has a mixed record on engines. The PW4000 took a long time to mature though its a good engine now.

        The preferred fighter engines where there is a choice is the GE not P&W. The USAF choice for the F-15EX was GE because it had a distinct performance advantage though total thrust is close.

        While none of its been fatal, the F-35 engine continues to see issues crop up (though that engine has been pushed far above what it was designed to do) . The most recent failure (a severe harmonic) was like the GE GenX failure, really fast on a test.

        Nothing I see in the PW x GTF is core, but the odd nickle and dime items have had a major impact (seals). Some have been extremely serious in that they were shutdowns with no lead in (ergo, roll the dice and have two shutdown and you have a crash).

        PW has proven you can move the GTF to large engine and RR has expanded on that to very large engines (at least in prototype form)

        If GE and Safran has some of their own research into a RISE thingy I would be more open (though the drawbacks still are a huge and to me fatal negative).

        Neither one did, the EU mandated that direction and who refuses free money? The core is going to be transferable and gear box experience is a plus (GTF leading the way).

        PW was conservative on the GTF and they have a revamp that pushes things a bit and gets some significant improvement in the same package.

        Revamp the whole engine and you get anohter significant gain.

        And I do not buy that GTF will fail to advance in the next 12 years (and that assume RISE is given all the doubts and exists then)

        • Pratt was the engine choice for F-22, F-35, KC-36, C-17.

          The open rotor systems work and were flight tested decades back. The modern version uses better layout and materials and only one set of rotating blades. There seems to be no doubt it will work

          • Open rotor works as in provides thrust at good efficiency, or ticks all the other boxes too? From what I’ve heard, the latter was a bit of an issue…

          • I’d bet that the new, simplified design with no counter-rotating props has substantially lower efficiency. Couple that with the no-containment issue and likely lower cruise speed, and it may not be worth the bother.
            Matthew’s comment above the other day covered the topic well, I think.

            Yes, the 7E7 (?) demonstrator is in my memory still- it was tested to some degree.

        • The GTF will advance, P&W has been clear given a new engine they would change things that are now clear would be significant improvements.

          So, some architectural changes and use of more advanced materials per the LEAP and I would think a 10% gain is doable, maybe 15% (certainly in 12 years)

          An all new engine to replace the PW1000 series is not likely, P&W need to recover the costs of investment in that engine.

          A new engine for a TBW? That depends on TBW of course as well as what the improvements would be but a new engine looks to be mandatory.

          But there is no new heart of the market aircraft in the offering right now either. The MAX competes equally with the A320 series and NEO and even the -10 meets a lot of the A321NEO performance.

          Hard to make an argument you need to replace something that is equal and how long if ever now it pays off?

      • DHC-8 seats are 17in, same width as in 737. Crowding ?? Alaska Air
        have 31 in pitch which is common to their E175. These arent really valid complaints

        As Ive said before the US scope means regional jets are limited to about the largest TP passenger capacity, which doesnt happen elsewhere.
        Alaska also has weather /mountains issue so being able to climb quickly to a higher altitude than TP makes a better journey. What works in specific instance for Alaska doesnt apply generally in rest of the world regarding TP 70 seaters and short distance flights.

        • Duke:

          I never measured the seats but from personal experience, they sure felt more crowded.

          There really is no area in the Western US that a Turbo Prop does not work. I have flown over that entire area (and yes in Turbo Props), so you might take a personal experience via an opinion.

          So no you do not need a jet to altitude though you might have a smoother trip. Never had a bad one in a Turbo Prop in Western US (never flew one in the MidWest or East).

          The Mountain west in a lot of ways is ideal Dash 8 territory with its better engine out performance and wider allowance for routes you have to avoid.

          The Mountain West certainly has application in Pakistan, Norther India, parts of Africa all being high (and hot at times)

          If there was on Airline Operation that was committed to Turbo Prop it was Alaska, now that is going away as fast as they can manage it.

          Its an assumption but have to guess that they can get better return on jet routes and dropping place like Seattle to Bellingham (and the Bus folks are massively expanding their operation up that way).

          • I havent measured the seats either but there are travel sites that have that information. Its an idea you have thats not valid, we all have those, but its not necessary to continue with that

          • Duke:

            Agreed, but that is what drives us (or not) is impressions. Definitely noisier despite the noise cancelling system. I don’t mind but as noted, I am not most people (for better or worse, figured I better beat Bryce to it)

            That said, Dash 8 does not like it will go back into production, ATR orders and backlog is trending down and Emraer has cancelled their Turbo Prop like I predicted (and they insisted they were going ahead with it)

            Clearly the Turbo prop market does not justify a new one and ATR will struggle due to costs and return, Airbus clearly does not think there is reason to invest in that area.

            China or Indonesia may make an offering as a sacrifice to get aviation industry going.

      • As been stated many times, GE owns the GTF gearbox manufacturer. GE has stated in the past they chose not to go the GTF route due to weight and complexity. LEAP is holding its own with the A320NEO against the vaunted GTF.

        IMO, GE/Safran is working on a GTF as a plan B. But the amount of work into RISE may actually pay off. Get the blade containment in check.

        • GE bought Avio after it worked with Pratt on the gearbox for the GTF.
          All the principal features Pratt has been working on for the engine – maybe over 15 years – are patented by Pratt, not Avio.
          Their tech wasnt the idea of course , but lightweight reliable gears plus the lighter front fans and a better nacelle

          best background Ive seen to the geared turbofan including some forgotten demonstrators and the turboprops converted to turbofan such as the Garrett and Lycoming types.

          The blade count reduction is amazing and also shows side by side the core shrinkage over the decades
          In a power point style so not impenetrable wording

          really worth while to bookmark for the detail in a images and graphical format

          • Thanks, the slides kind of repeated, confirmed what we know, until slide 49, where I had a WTF moment 😉 😀

          • It should be added and understood that if you can make something simpler, its both less expensive, less weight (usually) and the overhaul costs go down.

            RR claim to fame on the 3 spool jet engines was better fuel economy, longer on wing time .

            Both had to occur to make the 2 spool much higher overhaul and maint costs pay back. There is a reason RR was out of the single aisle market, they had no competitive product and the fill in was the V2500 (that was split 7 ways so not much return).

            So longer term, P&W is going to be a less invested cost, has higher SFC than the LEAP (2-3%) and once they get the repairs down then you have an engine that will see more and more pickup.

            GE is a costlier engine as they push materials much harder and those are costly.

            GE beat RR out on the 787 because overall they had the better engine SFC wise and it met or exceeded the Trent 1000/TEN on maint costs and clearly on overhaul.

            With all the issues airlines that liked RR started to drop that engine.

            P&W has an exclusive on the A220 as does GE on the MAX. In time as the A220 production goes up that will offset GE and PW may well have 50% or more of the total single aisle market (they also have Embraer E2 jets though that looks to be low numbers)

            We will never see an MC-21 in service with the GTF nor the Space Jet so both are losses to PW.

      • The EIS date is probably pushed out because the RISE will have a recuperator, which hasn’t been used in a production aircraft engine yet:

        Targeting a 20% reduction in fuel consumption and CO2 emissions compared to current engines, RISE is aimed at a successor to the current Leap 1 turbofan in the 20,000-35,000-lb. thrust class. The RISE open fan will include a new compact high-pressure core to boost thermodynamic efficiency, as well as a recuperating system to preheat combustion air with waste heat from the exhaust.

        • Nice info! P&W is working on some of that tech and I don’t think its ever going to be prime time due to the complexity and failure to return.

          • In the 1960s, PW and Allison tested regenerators (which I believe are similar to recuperators) on some of their small turboprop models. PW said it reduced SFC by 20 percent but doubled the weight of the engine. I don’t know if there have been any major improvements on that tech since then.


            That 1940s TP new design included a recuperator ( as a matrix to remove heat from compressed airflow) But didnt achieve any of the goals which was to match then piston engines fuel consumption.

            Im sure modern design methods and materials could change that but modern turbofans have moved the goal posts for fuel efficiency far quicker and scaling up could be other issues.

        • A high pressure modern turbofan has higher compressor exit temperature than LPT exit temperature so recuperating cycle implementation is not that simple. You also have a higher turbine exit temperature at startup with few LPT stages before they really work and thus lower the LPT exit temperature making matching structures and rotors harder. Having LH2 to cool parts as you please can make life easier.

    • I share your technical analysis: namely that beyond the improvement of the energy performance the RISE project is a mean under cover of sustainable environment to obtain subsidies from the French government in search of legitimacy. Neither Airbus nor Boeing will take the risk of installing a turboprop on a high wing of a new 150-250 seat aircraft, however efficient it may be (TBW for example). An intermediate step is needed .Maybe on a successor of a lower module to replace the ATR72 to see the return of the passengers in term of comfort and acceptability.
      If this were to happen, PW/MTU would launch a project that would be just as efficient and would be flown much faster without taking any marketing risk for the aircraft manufacturer, and GE/Safran would lose a lot. The European Commission has not been mistaken, as it is financing an MTU project in this direction.

      • It is interesting in that we know the Turbo Prop market is declining and fairly rapidly.

        Just reading EU airlines are starting to ask for compensation for the Green Efforts (or future ones) as those cost and other than warm fuzzy no return.

        P&W has said with what they have learned on the current GTF, they would make some significant changes (gears?) and I think some of the propulsion end that was conservative they could stretch.

        It has to be a different market. They have major development costs into the GTF and half the A320 market and the A220 market is years away from serious production.

        That is why the NMA was appealing in that it justified a new engine.

        As that is off the table they will make incremental changes they can insert into existing engines but it won’t be a big jump.

        Reports are that the various maint and parts issues for GTF and the LEAP are costing more than the fuel improvements are paying back.

        The CFM-56 series were rock solid. Not sure how the V2500 was viewed but it did have a following.

        Clearly LEAP and GTF will overcome the issues, both seem to be solid aside from the fiddly bits but no one wants to go through this again.

        That is where RISE is such a laugh, yes they have run open rotor but there never has been more than a test article let alone prototype (or call it both).

        CFM can no more guarantee success than I can guarantee you I will be crowned King in 2035.

        And even success does not mean anyone will buy it. P&W and RR would offer new GTF solutions for a new program.

    • PW’s geared turbofan is designed for a rotational blade tip speed of 1,150 feet/second, compared to a 1,400 ft/sec for the blade tips of a direct-drive turbofan. An open rotor propeller will do no more than 800 ft/sec at the blade tips, though. If you run the numbers for Mach 0.8 cruise at an altitude of 35,000 feet, you get a helical (3-D) tip speed of Mach 1.65 for a direct-drive turbofan, Mach 1.42 for the PW GTF, and Mach 1.15 for an open rotor propeller. Higher speed means the drag is higher for the GTF compared to the open rotor. In addition, the GTF’s blade loading is higher (because an equivalent-thrust GTF will have a smaller diameter than the open rotor), which also increases the amount of drag for the GTF to overcome.

      AFAIK an open rotor aircraft will have to be designed to account for blade-off scenarios. However, Dowty has been producing composite-blade propellers since 1984 without suffering a blade loss. CFAN (another GE/Safran joint venture) has been making composite turbofan blades for the GE90/GE9x/GEnx also without any blade loss incidents, so maybe it’s possible for the blade-out regulations to be loosened.

      • It does not matter what the track record on given TP type blade loss, what is relevant is that when it has occurred its taken down aircraft on more than one occasion, so they have to deal with it.

        Clearly you could have a fuselage solution with some kind of armor in the right location.

        The QF32 flight was an example of how all the best planning and a very good design almost took down that A380, talk about horrific. The failure did not contain and there was far more damage to the aircraft than was ever envisioned/seen/tested (and I don’t dis RR or Airbus, if not for exceeding limits required it would have gone down)

        And you have to ask the question, why do we need to do Mach .8 for a single aisle (or that market)? What is wrong with Mach .75?. Clearly legislation invoking a speed limit would offer huge fuel savings, it levels the playing field.

        • My apologies I did not mean that to be harsh sounding. It is a good point of discussion.

          My work evolved around, the failure is incredibly unlikely, but if it does occur the results are almost certainly to be of guaranteed to be catastrophic

          • No worries.

            I threw out M0.8 because higher speeds appear to be where the MC-21 and future narrowbodies/derivatives seem to be headed. But I agree that we should be applying speed limits, as that’s the easiest way to reduce emissions without forcing the large-scale purchase of new aircraft.

          • Time !
            Cruising speed comes from the aerodynamic design and thrust optimised for the drag and time of flight.
            Enforcing a worthwhile speed limit wont use less fuel for most designs using turbofans ( unless you reduce the wing sweep first or design to fly much higher)

  5. 777X Update:

    Av week has a great article a few issues back on the 777X and the problems.

    While Boeing had its problems (as has GE with the engine) The EU did not like the Triple Boeing redundancy and wanted more.

    Airbus apparently runs with 5 channels of redundancy and as I have brought up in the past, they have 7 computers running (not 3).

    Boeing has a lot of history on its side but the EU is taking advantage of Boeing shooting itself in the foot with the MAX to increase standards.

    The loss of life was horrible, the impact on what Boeing did to itself is stunning.

      • Sorry no. I had to drop my Av Week subscription due to theft of the magazine (the only time in my life I have lost anything in the US Mail, but steal them they did no matter what we tried)

        My main branch library has a subscription (apparently they get theirs!) and I drop in from time to time and get caught up. It was at least two issues back and I think 3 but it might be 4.

        My brother used to feed me his copies but he dropped it. He also was being extracted but that end of town they would feed a whole batch of them back into the system.

        Not exactly grand theft auto and I would have had to make a major effort to deal with it.

        I may get a on line subscription one of these days. I don’t like online for that kind of stuff but I may cave in.

        I have seen some better reporting in Av Week the last year or so, it took a dive previously in my opinion and was not delving into the tech details I am interested in.

        • Thanks for your reply. I’ll try to find that 777X article, as it sounds interesting.

          • You are welcome. I try to list sources and links, getting better on logging them into the save group as time goes on.

            I think I can find them again easily but sometimes I can remember the different search terms I did and I can never find them again.

            I think its extremely important to get factual information out on any forum and Aviation is a fact driven area even if there are various opinions. Some you can prove and some reality only time shows where it went.

            I certainly have had my misses but some are truly speculative and some you can have a pretty good handle from how it worked out in the past.

            Scott wrote up that the 777X will need to up its production, its an area I disagree in. What is the point of upping production and hiring a lot of people on just to lay them off when something changes or you get caught up?

            14 month for the 787 did not work out any better than the high rate for the 777 LR series did (up they went and down they went)

            So a good guess would be rate 5 for the 777X as a long term sustained production. The market will be there or it will not and likely at least 3 ups and downs over the time of the program.

          • Lo many years ago the State Dept I was working with robbed money from a campground to be built account to pay for a failed project.

            We then had too little money for the gravel for the to be built project and with 3 small dumptrucks had to haul our own really bad grade gravel as that was all they could afford. And we had to haul a lot more because they did not walk the ground and it took a lot more gravel than the estimate from an aerial photo (easily reached off a main road). Phew.

            Like the MAX and 777X, the MAX crashes then opened the door to question the 777X setup. I don’t have the expertise to assess how valid the EU position is or is not, but Boeing would not have been there if they had done the MAX correctly.

            You just have to shake your head and then bracket issues pop up and we don’t know how many aircraft6 are impacted but includes P-8 as well.

            I am still trying to get my mind around that its not flight critical but it involved holding the vertical stabilizer on.

            It does look to be a non compliant mfg of a part that several suppliers were in place for. Amazing and drip drip drip.

          • P-8 is based on NG model – including last wing jig to make it the old way and the CFM-56 engines.

    • Ethiopian in this case a fairly large user of Turbo Prop and no regional jets and while smaller, Kenya has gone regional jets.

      I am not sure where you place Egypt Air. To me they are North Africa as discrete from Southern Africa (as would Morocco and Tunisia) .

      I don’t make any claim to know what their route structure looks like and where they fly in total.

      • Kenya seems to have a multitude of smaller carriers with half a dozen or so TP each
        Jambojet, despite the name, is listed as having 7 DHC-8 for example

  6. Thanks for the 777X link above, Bryce- I hadn’t started looking for it yet.

  7. China is playing with its new, sophisticated, supersonic drone.
    However, there’s absolutely no way that the country could develop a successful commercial aircraft program…right? 😉

    “The Chinese military could soon deploy a high-altitude spy drone that travels at least three times the speed of sound, according to a leaked U.S. military assessment, a development that would dramatically strengthen China’s ability to conduct surveillance operations.

    “A secret document from the National Geospatial-Intelligence Agency, which has not previously been reported, shows the Chinese military is making technological advances that could help it target American warships around Taiwan and military bases in the region.”

    • I think you have to take articles like this WaPo one with many grains of salt: it’s actually a suble bid for yet more US MIC spending, which is now over $1,000,000,000,000 (trillion) P.A.,
      including the DoE nuclear weapons budget.

    • That is gone out the end of the limb and breaking it off as far a off topic and Scott will probably step in.

      So the first comparisons is Arianne (sp?) and the failure to build the Ver 6 of their rocket and asking Space X for a ride for the crown jewel of Europe (Galileo nav satellite). Gasp. How are those same people and countries delivering dozens of aircraft a month? I mean really

      Considering the basis of the point is not supported as its a reach in many ways as I am sure the provocateur knows.

      The US has had many aircraft that pushed Mach 3 and one that did Mach 5. We gave them up. Why? They use a lot of fuel and do not have loiter time which is what you need and want from a reconnaissance aircraft. Oh, and they are seriously expensive.

      The only benefit is a Mach 2.5+ aircraft of whatever type is much harder to intercept. Only missiles work and missiles have what is known as engagement envelopes. The U2 was hard to shoot at just because of its altitude, it had no speed to its name (way sub sonic). Still used as its a nice steady long loiter machine that stands off a coast in International Airspace (both China and the Russians have knocked aircraft out of the sky even in that non territorial airspace and by leaps and bounds not even close to on the edge).

      Balloons are ideal but as we saw, if someone sees optically and then changes the coding in the software for Radar systems, well you stand out like a soar (pun intended) balloon.

      And then someone shoots it down (over their territory) and the shootee gets all your Junk (pun also intended).

      Ok, back to Mach 3 drones. The US used them all the time to test ship defense systems as (gasp) many missiles are Mach 3+.

      Going Mach 3 is not an issue for someone sole focusing on that. The question is can you do any reconnaissance from it? Sure you can buzz up and down the Korean Peninsula (West Coast shown) or around Taiwan (well you have to plan for fuel depletion) and can you recover it? Is it one shot?

      And all US Destroyers are equipped with missile system that can shoot down a bird like that. Also a system called Aegis Ashore that does the same.

      Can a Patriot Missile System? I don’t know. Its more an area defense system and I don’t know if its engagement envelope takes in that type of target (its original design was to protect and area with incoming not a skimming the edge of a zone target)

      As always there is a lot of tech background and understanding that does not lend itself to not just building aircraft, or at a high rate, but supporting a system like that and few have managed that. Quite a Plethora have built rockets.

      So maybe Rocket Science is not so hard and a successful commercial aircraft enterprise is? Nah.

      • Far more on-topic than your convoluted story above about gravel.

        No more off-topic than your discussion of computational redundancy in the 777, or the vertical stabilizer fastenings on the 737.

        The point was that there’s a new player in the aviation industry — so, there’s going to be an addition to the list of engine manufacturers. Not something that you can easily grasp, of course, but in the pipeline nevertheless.

        P.s. Webb was launched by an Ariane…remember?

      • You are welcome.

        Getting caught up on Av week and they had an article on it as well.

        That had the mention of how much Raytheon had contract wise in the A220 and the impediment that is as they have no reason to dicker.

        And one that noted that the A320 is not under 50% of sales and declining and the thoughts on an A220-500 for replacing it (fully).

        That breaks into two schools, same range and a lot of mods to the -300 or same wing and live with the range reduction.

        I think they can have both. Simple stretch to start with and a new wing eventfully to extend the range (maybe higher thrust engines).

        They mentioned the 2nd engine source but did not note where in the world they would get it. It has to be a current Gen engine and other than P&W in that size, there are none.

        Embraer faces that 2027 cutoff for the E1 175 as well though I am sure they will dodge it as best they can as will Boeing.

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