back to article Let me X-plane: Boeing R&D unit sheds rudder, ailerons, flaps for DARPA project

DARPA has awarded Boeing research arm Aurora Flight Sciences a contract to build a full-scale demonstration aircraft for the experimental Control of Revolutionary Aircraft with Novel Effectors (CRANE) project. The X-plane relies on active flow control (AFC), or the use of strategically placed actuators and effectors to alter …

  1. Sgt_Oddball

    Stop me if you heard it before..

    Doesn't this sound like an evolution of the way the control surfaces worked on the Harriers?

    Honest question here rather than an invite for flaming.

    1. Anonymous Coward
      Anonymous Coward

      Re: Stop me if you heard it before..

      I believe Harriers use normal control surfaces when in "normal" flight but the puffers come into play for hovering.

      1. LogicGate Silver badge

        Re: Stop me if you heard it before..

        If I read the reports correctly, the technologies involved go beyoond mere puffers.

        Most likely, we are talking about boundary layer and shock wave control.

        Micro jets and microphone arrays can be used to modify or stabilize the boundary layer, delaying or triggering the transition from a laminar to a turbulent boundary layer. sub-skin chambers connected to "gates" in the surface can change the way supersonic shock-waves reflect of a structure.

        Personally, I am intrigued by the way plastma actuators can be used to control airflow. These actuators are electrically inefficient and subject to burning out, but if a way can be found to precisely stabilize instabilities in the laminar boundarylayer, then this may still be a net positive.

        1. LogicGate Silver badge

          Re: Stop me if you heard it before..

          Plastma actuator:

          Stall control through boundarylayer suction:

      2. Clouseau999

        Re: Stop me if you heard it before..

        The Harriers used a system called Vectoring in Flight or Viffing when the nozzles could be rotated independently to provide additional control during normal flight. Remember reading that in a library book about 40-odd years ago....

        1. Sgt_Oddball

          Re: Stop me if you heard it before..

          The nozzle vectoring I'm well aware of, it was more the forced air over control surfaces bit when it's not in normal flight mode. I vaguely remember something about adding air to prevent stalls at low speeds to increase lift over control surfaces and this just sounds like a modern take on that.

    2. Binraider Silver badge

      Re: Stop me if you heard it before..

      Plenty of examples of engine output configured to bleed air over control surfaces to improve low speed performance, not least the Buccaneer.

      Adapting the idea to flight control? Absolutely possible. The obvious disadvantage that you can no longer operate as a glider in an emergency.

      For military applications, this is probably a big deal. The weight savings from getting rid of hydraulics while using a power source that you already have on tap are probably worthwhile, as well as reduced complexity.

    3. SkippyBing

      Re: Stop me if you heard it before..

      Good explanation of how it works here:

      Quite different to the reaction control system on the Harrier which pushes the aircraft around rather than messing with the airflow.

  2. Chris Roberts

    Goo goo, gah gah

    "the next step is to prove out these learnings in flight"

    The word they are looking for is lessons, alternatively "this knowledge" or "this experience". Unless DARPA is run by six year olds.

    Yes, language evolves, but that is not the same as adults adopting baby talk.

    I wouldn't mind what Americans do, but this rubbish keeps migrating into English usage too.

    1. xeroks

      Re: Goo goo, gah gah

      if you haven't worked out that American english and UK english are different things by now, there's no help for you.

      It's a quote from Graham Drozeski, an american with a PhD. he's not stupid, or a child. He simply uses language in a different way from you.

      1. Sceptic Tank Silver badge

        Lekker tekkies

        You'll be appalled to know that here in South Africa a traffic light is often referred to as a "robot". ====>

        What currently makes me want to kick a puppy when I hear it, is if something "caught on fire".

      2. Fr. Ted Crilly Silver badge

        Re: Goo goo, gah gah

        And making himself sound like a child in the process...

      3. notyetanotherid

        Re: Goo goo, gah gah

        ... or maybe Borat (Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan)

        Not enthused about "prove out" either, what is wrong with "demonstrate"?

      4. Chris Roberts

        Re: Goo goo, gah gah

        "It's a quote from Graham Drozeski, an american with a PhD. he's not stupid, or a child. He simply uses language in a different way from you."

        I'll give him the benefit of the doubt that there is a political or corporate requirement to use marketing droid speakings in presentationisationings.

        1. JDX Gold badge

          Re: Goo goo, gah gah

          >>I'll give him the benefit of the doubt that there is a political or corporate requirement to use marketing droid speakings in presentationisationings.

          When someone who is far, FAR more knowledgeable than you and has been deeply immersed in a niche industry with its own terminology for decades uses language you find unusual, we can all agree ONE of you is showing their ignorance.

          Language doesn't just evolve over time, it evolves in weird ways in specialised areas. In IT we refer to a PC as "a box". It's not a box. Often it's not even in a box (it's in a rack). You're just making yourself look silly criticising world-renowned senior experts on their word choice.

          1. notyetanotherid

            Re: Goo goo, gah gah

            What you say might have some validity for expert talking to expert, but this was presumably a press briefing. An attempt to inform the general public across the English-speaking world, and beyond via translation. If you can't do that clearly and concisely in language that avoids unnecessary jargon, neologisms, and local-dialect phrases that will have the average Jo, or a translator, scratching their head trying to work out what you mean, then you have failed.

          2. Chris Roberts

            Re: Goo goo, gah gah

            They are not words from a niche industry or technology, they are marketing neologisms cooked up to try and sound like they are doing something new, exciting or cutting edge. The sad thing is while others have commented that this is not a new idea, they are doing new research and, potentially finding exciting solutions and applications. It could be that English is not the author's first language and so just used words that he knows or has heard or read being used, you would hope however that a press release would have been checked by someone that is.

    2. Joe 59

      Re: Goo goo, gah gah

      That's weird that someone used a word you don't like, no one in England, Scotland, Wales or Northern Ireland uses different words for similar concepts.

      1. Raton que Ruge

        Re: Goo goo, gah gah

        Australia and New Zealand, too.

        1. Anonymous Coward
          Anonymous Coward

          Re: Goo goo, gah gah

          I don't want to be pedantic but is leanings are the acquisition or applications of knowledge doesn't this actually mean that you are going apply the same learning process all over again?

          Think of learning as a derivative of knowledge so now you are applying the process of how you acquired this knowledge (learning) when what you really what to apply is what you have learned, which is the knowledge.

          I think that some people just cannot learn.

  3. Eclectic Man Silver badge

    'Dead stick'

    I'd be interested to see (from a safe distance) its 'dead stick (i.e. engine off) handling capabilities. Even with a turbine in the airflow*, not sure that pure blown air would be adequate for control.

    *Commercial airliners have a turbine which can be lowered if the engines fail and provide power for control surfaces to enable so called 'dead stick' landings.

    1. Martin Gregorie

      Re: 'Dead stick'

      Commercial airliners have a turbine which can be lowered if the engines fail and provide power for control surfaces

      Yes, but that's not in any way an aerodynamic effect. All the turbine does is maintain pressure in the hydraulic system so the control surfaces can still be used to maintain control if the engines fail.

      The classic real-world example of this is Air Transat flight 326, when a fractured fuel line left it over the Atlantic with empty fuel tanks and consequent failed engines. Lowering the ram air turbine provided electric power for instruments and radio as well as the hydraulic pressure needed to operate the flight controls and lower the undercarriage just before it landed at a military airfield on the Azores.

      1. Paul Hovnanian Silver badge

        Re: 'Dead stick'

        "The classic real-world example of this is Air Transat flight 326"

        Also the Gimli Glider.

    2. DS999 Silver badge

      Re: 'Dead stick'

      I would imagine this issue could also be solved with batteries, without the potentially problematic (depending on when engine power is lost) loss of airspeed from a ram air turbine

      1. Eclectic Man Silver badge

        Re: 'Dead stick'

        I would have thought that a batteries would be far too heavy for the required power to control an aircraft by blown air from high altitude to safe landing. The batteries for electric vehicles are very heavy and bulky, and there is considerable commercial incentive to make them more efficient and powerful, but they lack the range of even the most ordinary petrol or diesel equivalent vehicle.

        1. JDX Gold badge

          Re: 'Dead stick'

          Do they need safe landing, or just safe eject?

        2. DS999 Silver badge

          Re: 'Dead stick'

          The batteries are to power the control surfaces and allow maneuverability, not to propel the plane forward like a jet engine. i.e. an alternative to the ram air generator, which provides power for hydraulics but does not propel the plane forward (indeed, it is trading airspeed to generate that power so you're somewhat worse off than you would be with batteries)

  4. Primus Secundus Tertius Silver badge

    Words in wrong order?

    "reducing cost and improving safety"

    Should that have been: "improving cost and reducing safety"? Especially from Boeing.

    1. very angry man

      Re: Words in wrong order?

      In return for using AFC technology, designers can build a lighter aircraft with the hopes of reducing cost and improving safety.

      And they're getting boring to do this?

      Well I never

  5. steelpillow Silver badge

    History lesson

    Blown and/or suction systems for aerodynamic control have been investigated since at least as far back as the mid-twentieth century. One of my mates at Uni tried one in a wind tunnel for his student project. The result has always been the same. Done right, they do work. But the extra complexity, weight, cost and bulk of the whole thing - little things like large ducts passing through key structural components or additional fuel tankage for the blower - render them too much trouble for the benefits they offer.

    Blown flaps for STOL performance briefly made it out into the real world but failed to break the cost-benefit barrier. Even the jump-jet's puffers are just mini-thrusters and not true aerodynamic controls.

    Nevertheless, NASA periodically revisit them to see if the latest wheeze might have spotted a crack in the wall. Who knows, maybe one day...

    but I'm not waiting up.

    1. JDX Gold badge

      Re: History lesson

      Many things were once "too hard" or "theoretically possible but not realistic". Nuclear reactors and microchips for instance.

      Materials science and aerodynamic refinement are both areas which continue to move onward at more than a snail's pace - the latter especially due to the computing revolution (more well known for its impact in areas like F1).

      So maybe they have cracked it this time... or maybe it's like Fusion, always just around the corner (although now even that might happen)

      1. SCP

        Re: History lesson

        Materials science is an interesting research area - I recall reading about the use of adaptable surface texturing to control vortex forming as a means of aerodynamic control (unfortunately I can't recall the project names).

        From the UK side of the pond the work on FLAVIIR and MAGMA are relevant and illustrate some of the work being done at both Cranfield University and University of Manchester.

  6. StrangerHereMyself Silver badge


    Unless this technology enables tailless airplane it's not useful, at least not for the military. Because tail surfaces stick out like a sore thumb on radar and you'd really want to eliminate them if at all possible.

    1. Dr Dan Holdsworth

      Re: Tailless

      The plasma-induced laminar flow looked interesting for that sort of thing. One of the major problems with flying wing designs has been that they could get into an unstable yawing flight mode, which without rudders or other drag-based systems were very hard to damp down. Modern machines like the American B2 and B21 bombers cope with the problem using computer controlled flaps and clam-shells to selectively increase drag.

      Cold plasma generators on the wings would do the same sort of thing, but likely more cheaply since they wouldn't need actual actuators to operate. All of this would be useful on a full size aircraft, but much more useful on a drone since for drones, the name of the game is building the best payload to total weight ratio that you can, to maximise the flight endurance of the drone whilst minimising its cost.

      1. steelpillow Silver badge

        Re: Tailless

        Drag rudders were developed by GTR Hill for his tailless Pterodactyl series back in the 1920s. Control was never the problem, it is pilot awareness. It can be difficult to tell if your plane is yawing badly, and this was the real killer of the Northrop YB-49.

        The problem with plasma systems is that they require two electrodes, and one of those will invariably corrode under the power levels required to affect bulk airflow at high speeds. This is the problem that pretty much killed the rail gun, and it will kill any attempt at aircraft control (or propulsion) too.

        Raise you one geek icon.

      2. John Brown (no body) Silver badge
        Thumb Up

        Re: Tailless

        "since for drones, the name of the game is building the best payload to total weight ratio that you can, to maximise the flight endurance of the drone whilst minimising its cost."

        ...or the entire commercial airline industry :-)

    2. SCP

      Re: Tailless

      "Unless this technology enables tailless airplane it's not useful, at least not for the military."

      Nor will it slice a pineapple - so what! (see Babbage if you want to know).

      The issues of yaw stability and yaw control in rudderless planes are a different area of research and a great deal has been done in that area since the advent of digital flight control (and even before that with analogue stability augmentation systems).

      Vortex generation and boundary layer control can cause profound aerodynamic effects, so it is reasonable to suppose that it could provide yaw control. At some point that will need to be demonstrated with the use of suitably designed aerodynamic structures - but there is no need to do it now. This work is building on previous research by taking it to a full-scale platform, there is no need to address rudderless control (unless it becomes a particular aspect of the research). There are probably many more pressing areas of this technology to research.

      It will be interesting to see how much vectoring of the airflow over the lateral surfaces can be achieved and how well that would support effective yaw control. (It might already have been done - I haven't kept up to date with the research work. Another topic for the 'to do' list).

  7. Anonymous Coward
    Anonymous Coward

    Looks nothing like the X-planes of the past...

    More like a Y plane. Imagine if Skywalker had one of those - no way he'd call that an X-wing

  8. spireite Silver badge

    Can't even get a their rockets up on time or budget....

    So, the likelihood of this getting to see light of day is pretty remote.... IMO

  9. Potemkine! Silver badge

    After the MCAS disaster, should we trust Boeing about designing automated systems controlling a plane's flight and claiming more safety?

    Will those systems be self-certified or does now the FAA take its job seriously?

  10. Antony Shepherd


    I was reminded of the Blackburn Buccaneer, which used boundary layer control to increase aerodynamic performance at low speeds by blowing air from the engine over leading and trailing edges of the wing to give more lift at low speeds such as takeoff and landing.

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