Compound helicors

Why isn't this a thing?
>faster than normal helicopters
>less complex and finicky than tiltrotor
What's the catch? Is it because the US just happen to invest into tiltrotor instead and Russians didn't have the money? Or is there some drawback I'm not seeing?

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  1. 3 weeks ago
    Anonymous

    look up "retreating blade stall"

    • 3 weeks ago
      Anonymous

      That's what the little wings are for. It shouldn't be an issue to make them big enough that the top rotor doesn't even need to spin at all at high speeds (or spin slow enough that it barely makes a difference). It certainly doesn't appear like a dealbreaking technical challenge.

      • 3 weeks ago
        Anonymous

        Might as well go full canard rotor/wing

        • 3 weeks ago
          Anonymous

          Also you could even make it supersonic by stopping the rotor/wing at an angle, thus achieving the same effect as variable-sweep (The asymmetry looks weird, but it turns out that doesn't matter for aerodynamics)

        • 3 weeks ago
          Anonymous

          https://i.imgur.com/9HAzrwk.jpg

          Also you could even make it supersonic by stopping the rotor/wing at an angle, thus achieving the same effect as variable-sweep (The asymmetry looks weird, but it turns out that doesn't matter for aerodynamics)

          The the complexity and finickiness equation would be getting a bit lopsided in the opposite direction at that point.

          In the case of AH56 by the time they got all the kinks worked out the analog controls were dated and the attack helicopter in the follow up program was concerned much more with being a cheaper missile truck for destroying Russian armor in the Fulda Gap than continuing the development of full compound helicopters to achieve quick response CAS/escort/recon. The concept returned in the recent FVL programs but the source selection found the proposal unsatisfactory from Sikorsky mainly in how they would go on to meet the requirements of the entire proposal (not just performance of the airframe).

          This as well. There are ways to mitigate it for helicopters but tiltrotors don't have to worry about it.

          Seems like one of those things where it might be perfectly viable, but there just isn't enough demand and intense war to find out. I dunno how nimble tiltrotors can be, but I would expect them to be more unhappy of the two when there's stuff flying at them.

      • 3 weeks ago
        Anonymous

        https://i.imgur.com/ZhMEayl.jpg

        Might as well go full canard rotor/wing

        https://i.imgur.com/9HAzrwk.jpg

        Also you could even make it supersonic by stopping the rotor/wing at an angle, thus achieving the same effect as variable-sweep (The asymmetry looks weird, but it turns out that doesn't matter for aerodynamics)

        You know what helicopters really need? More complexity and points of failure.

    • 3 weeks ago
      Anonymous

      In the case of AH56 by the time they got all the kinks worked out the analog controls were dated and the attack helicopter in the follow up program was concerned much more with being a cheaper missile truck for destroying Russian armor in the Fulda Gap than continuing the development of full compound helicopters to achieve quick response CAS/escort/recon. The concept returned in the recent FVL programs but the source selection found the proposal unsatisfactory from Sikorsky mainly in how they would go on to meet the requirements of the entire proposal (not just performance of the airframe).

      This as well. There are ways to mitigate it for helicopters but tiltrotors don't have to worry about it.

    • 3 weeks ago
      Anonymous

      >My retreating blade stall ran over my vortex ring state.

  2. 3 weeks ago
    Anonymous

    Can only carry tiny, tiny soldiers so not worth it.

  3. 3 weeks ago
    Anonymous

    They almost were, but bell got the contract. Tbf it was probably the better bird for the military anyway, but sikorsky's design is pretty great

    • 3 weeks ago
      Anonymous

      Sikorsky had problems with rotor flex issues. Advancing Blade Concept designs are not compatible with rotor flex issues. I never heard if they'd fixed them. If Bell wins FARA, then that's a pretty good sign that Sikorsky didn't resolve the issue, because Invictus practically screams "backup plan".

      • 3 weeks ago
        Anonymous

        >FARA
        https://breakingdefense.com/2024/02/army-cancels-fara-helicopter-program-makes-other-cuts-in-major-aviation-shakeup/

        • 3 weeks ago
          Anonymous

          >unmanned vehicles
          >lessons learned from Ukraine and Gaza
          At least they're adjusting quickly to world events.

        • 3 weeks ago
          Anonymous

          Yeah, I saw the other thread. I think that's a pretty good hint that Sikorsky never got it completely fixed. Invictus was just too much of a "look, Ma, here's a backup plan" option.

          There's still a need to haul people around, so FLRAA should be safe. I just hope that they're not killing the legacy Shadow/Raven without an actual replacement (as opposed to "we'll come up with something in a few years"). We need *more* UAVs, and we need the mesh network the Army has been working on for years.

          • 3 weeks ago
            Anonymous

            >backup plan
            They aren't related at all though. One is a high endurance transport and the other is a light armed reconnaissance

      • 3 weeks ago
        Anonymous

        >Advancing Blade Concept designs are not compatible with rotor flex issues.
        Which is exactly why the rotors were designed to be rigid.

        If they don't generate lift with a rotor they aren't helicopters.

        Then the Valor isn't a helicopter either.

        • 3 weeks ago
          Anonymous

          Yes, it's a tilt-rotor.

        • 3 weeks ago
          Anonymous

          There were rumors several years ago that the rotors weren't quite rigid *enough* in all conditions. Hence, the rotor flex problem. I can't point to a smoking gun, but Sikorsky is still without a contract for ABC, and has stated that it doesn't scale up to heavy/ultra-heavy lift, cutting it out of those competitions.

          It's a shame it didn't work out; it was an interesting technology.

  4. 3 weeks ago
    Anonymous

    >faster than normal helicopters
    Normal choppers are speed limited by retreating blade stall and advancing blade compressibility as it goes transonic.

    • 3 weeks ago
      Anonymous

      Yeah, which compounds aren't.

      • 3 weeks ago
        Anonymous

        If they don't generate lift with a rotor they aren't helicopters.

        • 3 weeks ago
          Anonymous

          Yes, they're compound helicopters. That's a separate category.

          >less complex and finicky than tiltrotor

          is this actually true though

          That's what I'm wondering. They basically have two largely separate systems for low speed and high speed flight, both relatively simpler and well proven on their own. So as a layman I would expect that to be the case.

          • 3 weeks ago
            Anonymous

            >Yes, they're compound helicopters. That's a separate category.
            Every compound chopper I have seen uses a rotor for lift.
            I actually know an engineer that worked on the Raider, they had some fun with the landing logic on the flight computer where during a pinnacle landing it would sense weight on wheels and reduce cyclic response to the point they flipped one.

            • 3 weeks ago
              Anonymous

              >Every compound chopper I have seen uses a rotor for lift.
              Ah, yes, of course they do use it during slower speeds. What I meant was that they don't use it for lift during high speeds because

              look up "retreating blade stall"

              • 3 weeks ago
                Anonymous

                Even if you use wings you have to physically stop the rotor to avoid being speed limited by advancing blade compressibility.

              • 3 weeks ago
                Anonymous

                Yes. That or slow the rotor down to a point where it's not an issue. That's exactly what compound helis do.

              • 3 weeks ago
                Anonymous

                Then show one that does that.

              • 3 weeks ago
                Anonymous

                The one in the OP, moron.

              • 3 weeks ago
                Anonymous

                >At high speeds, the amount of lift provided by the wings, along with thrust from the pusher prop, reduced the aerodynamic loading of the rotor. At such speeds, the rotor produced up to 20% of the lift, which could be adjusted by collective pitch control changes
                I'm not seeing about the main rotor RPM being reduced, you got a source?

              • 3 weeks ago
                Anonymous

                https://en.wikipedia.org/wiki/Helicopter#Compound_helicopter

              • 3 weeks ago
                Anonymous

                Can you name one in production that actually does it?

              • 3 weeks ago
                Anonymous

                >in production

        • 3 weeks ago
          Anonymous

          semantics

  5. 3 weeks ago
    Anonymous

    >less complex and finicky than tiltrotor

    is this actually true though

    • 3 weeks ago
      Anonymous

      Tiltrotors definitely scale up way better. For smaller ones it might be close but that drivetrain will grow much more as you go bigger.

      The biggest reason for the complexity of the V-22 was the wing folding mechanism that allows the whole wing assembly, rotors and all, to rotate and align with the body for storage to save carrier deck space.

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