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Sikorsky Defiant-X make yaw

That picture I took from here. To understand my question I suggest you to watch it just 10s, just very short, but it will show you very closely when that Sikorsky make yaw. As it is no tail rotor like commonly has in every helicopter, it has propeller to push only (called pusher compound rotor), then how does it make yaw? In that video (just simply click it, it will take you the part I want to show), it make yaw when it being hover and the propeller is not even rotating. Hence, it is clear that the propeller is not involved to make yaw.

Then, how does it make yaw?

AirCraft Lover
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  • I am pretty sure that the Yaw-control is used in this Sikorsky Defiant-X is not the same as it does with other coaxial rotor helicopter. If we see very carefully the main rotor by play it only 25% speed on YouTube, we will se that there is no changing with the rotor pitch, either the upper or the lower. I suspect, its Yaw-control is performed using bleed air like it does with VTOL F-35C. – AirCraft Lover Dec 22 '22 at 17:22
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    https://www.boeing.com/features/2022/07/defiant-pilots-talk-future-long-range-assault-aircraft.page Yaw control is managed by the flight controls using differential main rotor torque. – Jim Dec 22 '22 at 17:33
  • @Jim, as I said, that is probably true for another, but for this Sikorsky Defiant-X, it seems like not really. Have you watch it closely? – AirCraft Lover Dec 22 '22 at 17:36
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    @AirCraftLover Jim is right. In the link he provided, the test pilot explicitly states that differential torque is used. The video you linked only has very little yaw rotation, plus it is a sustained yaw rotation, which would require only very little to no input, hence you might not see it. Additionally, a bleed air system like you proposed would be heavier, than just using the existing control. Using differential torque or differential cyclic input to the main rotors is state of the art and established for coaxial (and flettner) rotors. – U_flow Dec 22 '22 at 17:44
  • "… tail rotor like commonly has in every helicopter …" to my knowledge neither all the Kamovs nor many of the Kamans have a tail rotor. – Peter Kämpf Dec 22 '22 at 20:56
  • @PeterKämpf, single rotor helicopter I meant, not the coaxial one. – AirCraft Lover Dec 23 '22 at 04:50
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    "If we see very carefully the main rotor by play it only 25% speed on YouTube, we will se that there is no changing with the rotor pitch": do you really think to be able to see a half degree pitch variation from a video on YouTube? "its Yaw-control is performed using bleed air": from where and toward where? – sophit Dec 23 '22 at 07:26

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