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> The maneuvering thruster system sounds similar to that of the Harrier VTOL. It doesn't really, to me. The big idea here is using blown air to avoid having p

by mlyle 3y ago

> The maneuvering thruster system sounds similar to that of the Harrier VTOL. It doesn't really, to me. The big idea here is using blown air to avoid having physical surfaces deflect-- neither the engine nozzle or any actual control surfaces on the plane. The Harrier uses fairly conventional bending nozzles to vector trust, and uses fairly conventional control surfaces at speed. > That system was very difficult for humans to fly. Anything helicopter-like is difficult to fly, and the Harrier is a pretty mediocre "helicopter" with relatively poor response times. In principle blown-air deflection of thrust could be more responsive for VTOL-type aircraft, but that's not even what this is aiming at. (The deflection attained of thrust is not sufficient for VTOL use at this point-- nor is deflecting thrust in one degree of freedom from one point sufficient for hovering flight.) > Pure-thrust vehicles are unstable. Blowing air to adjust airflow at the trailing edge doesn't necessarily produce anything too hard to control-- it's pretty similar to conventional control schemes. On the other hand, this aircraft will not be controllable at all without the active systems gating the airflow, while aircraft with control surfaces can often fallback completely to dumb control cables.

Animats 3y ago
> The Harrier uses fairly conventional bending nozzles to vector trust, and uses fairly conventional control surfaces at speed. On the Harrier, those are the big rotating lift nozzles. There are also small attitude control nozzles ("puffers") at the nose, tail, and wingtips. The puffers are used in hover and at very low speed. This new drone is pumping out supersonic air through control jets and bending the jets with a fluidic amplifier. That's new. May or may not be useful. [1] https://i.imgur.com/78bVjbC.png https://i.imgur.com/78bVjbC.png
- ianburrell 3y ago
  These aren’t maneuvering thrusters where thrust moves the plane. These are changing the airflow on wing to act like control surfaces. Pilot should fly them the same way as now, with computers making them work and act like normal surfaces. This isn’t replacing aileron with thruster but replacing with inverse aileron. The next generation might use airflow control surfaces.
  - Animats 3y ago
    Right. It's a fluidic amplifier. Steering a fluid jet with a smaller fluid jet is known, but not used much.
- carabiner 3y ago
  It's useful for reducing radar cross section. Moving control surfaces are a headache for RCS management. The F-22 uses "cat eye" slits between its control surfaces to minimize these radar blooms, but it'd better to do away with them altogether. It could also remove the need for those huge aerodynamic fairings on the CS actuators on jetliners, but then add some complexity and remove fuel volume in the wings.
ehnto 3y ago
I am unsure of how the trailing edge tech works, are they blowing the air out of trailing edge for roll control, and is it blowing aft or directionally? Is the blown air itself the force moving the wing or is it just redirecting flow over the wing? I am thinking of diminishing control as speeds lower, which is already a characteristic of regular control surfaces. This is super interesting, I would love to build it in an RC plane.
- Gravityloss 3y ago
  It acts like an aileron. If you blow air up from the right wingtip trailing edge, the right wing will go down. What is key here is that it affects the airflow and the effect is bigger than just the momentum of the blown air itself.
- carabiner 3y ago
  The key concept is Coanda effect: https://en.wikipedia.org/wiki/Coand%C4%83_effect https://en.wikipedia.org/wiki/Coand%C4%83_effect There's a diagram of how this is implemented in the aircraft: https://www.baesystems.com/en/article/magma-the-future-of-flight https://www.baesystems.com/en/article/magma-the-future-of-fl... For roll, air is blown out of the TE aftward. Per Coanda and the lift equation (lift is proportional to square of flow speed), this blowing will generate higher lift on one wing, imparting a roll moment on the aircraft. For pitch, air is blown up at the engine's exhaust surface to point the flow up/down. It is shaped so that with 0 blowing, it's pointing down.
- flapless_anon 3y ago
  The air is blown out aft, but the jet is blown adjacent to a curved surface and tends to stick to it. This entrains the flow over the wing and creates a change in lift distribution just like a normal aileron. The thrust vectoring is similar but slightly different, again the blown air is used to change an existing airflow.

by mlyle 3y ago

Animats 3y ago

> The Harrier uses fairly conventional bending nozzles to vector trust, and uses fairly conventional control surfaces at speed. On the Harrier, those are the big rotating lift nozzles. There are also small attitude control nozzles ("puffers") at the nose, tail, and wingtips. The puffers are used in hover and at very low speed. This new drone is pumping out supersonic air through control jets and bending the jets with a fluidic amplifier. That's new. May or may not be useful. [1] https://i.imgur.com/78bVjbC.png https://i.imgur.com/78bVjbC.png

ianburrell 3y ago
These aren’t maneuvering thrusters where thrust moves the plane. These are changing the airflow on wing to act like control surfaces. Pilot should fly them the same way as now, with computers making them work and act like normal surfaces. This isn’t replacing aileron with thruster but replacing with inverse aileron. The next generation might use airflow control surfaces.
- Animats 3y ago
  Right. It's a fluidic amplifier. Steering a fluid jet with a smaller fluid jet is known, but not used much.
carabiner 3y ago
It's useful for reducing radar cross section. Moving control surfaces are a headache for RCS management. The F-22 uses "cat eye" slits between its control surfaces to minimize these radar blooms, but it'd better to do away with them altogether. It could also remove the need for those huge aerodynamic fairings on the CS actuators on jetliners, but then add some complexity and remove fuel volume in the wings.

ehnto 3y ago

I am unsure of how the trailing edge tech works, are they blowing the air out of trailing edge for roll control, and is it blowing aft or directionally? Is the blown air itself the force moving the wing or is it just redirecting flow over the wing? I am thinking of diminishing control as speeds lower, which is already a characteristic of regular control surfaces. This is super interesting, I would love to build it in an RC plane.

Gravityloss 3y ago
It acts like an aileron. If you blow air up from the right wingtip trailing edge, the right wing will go down. What is key here is that it affects the airflow and the effect is bigger than just the momentum of the blown air itself.
carabiner 3y ago
The key concept is Coanda effect: https://en.wikipedia.org/wiki/Coand%C4%83_effect https://en.wikipedia.org/wiki/Coand%C4%83_effect There's a diagram of how this is implemented in the aircraft: https://www.baesystems.com/en/article/magma-the-future-of-flight https://www.baesystems.com/en/article/magma-the-future-of-fl... For roll, air is blown out of the TE aftward. Per Coanda and the lift equation (lift is proportional to square of flow speed), this blowing will generate higher lift on one wing, imparting a roll moment on the aircraft. For pitch, air is blown up at the engine's exhaust surface to point the flow up/down. It is shaped so that with 0 blowing, it's pointing down.
flapless_anon 3y ago
The air is blown out aft, but the jet is blown adjacent to a curved surface and tends to stick to it. This entrains the flow over the wing and creates a change in lift distribution just like a normal aileron. The thrust vectoring is similar but slightly different, again the blown air is used to change an existing airflow.