Kasama has been working on a UAV drone for a while. It looks like they went with a turbine. Here are a few photos, including a early model with water floats. Click the photos for a larger version. See more photos here: Kasama UAV Drone
They are pointing opposite directions (see the last photo over the water) which implies they may be working as one. I'm guessing that a normal tail wasn't giving them the tail authority they were looking for.
I think you're on the right track John. I'm thinking the "tail" boom is shortened enough to require two. Notice how the main blades extend well beyond the "tail" blades.
Good eye Bill. I didn't notice that the tail booms were short. Maybe not enough leverage if they used only one. I think the design is interesting, but I don't think I'd buy one.
What comes to my mind (IMO) or to expand upon all your previous thoughts: Another advantage to having a shorter boom with two opposing tails, think about what happens with one tail ... Due the side thrust produced by the tail the helicopter drifts sideways! Therefor the two opposing tails would cancel out the drift we see with one tail. Next by keeping the rotational diameter small the shorter booms with double the tail authority or thrust would in effect allow for faster pirouettes. Last but not least the counter rotating tails would negate the torque produced by the main rotor much more efficiently than given by one All in all it would be something I'm sure the military would find very attractive. It's a given the military would need all the speed, maneuverability and stability they can get from a drone of this caliber. The two tail rotors is indeed an interesting concept born out a simple idea, in this case "more is better" ... and the 'military' do luv their equip w/ the benefits of 'double' redundancy built in ... A thought that just come to mind, although I think this might be stretching the concept. Survivability, I'm thinking battle damage and what happens if the tail is hit on a bird with only one tail, it goes down! Maybe having two tails would be an advantage only if one tail is damaged the other might get the bird home thereby keeping their expensive TOY out of the hands of the 'enemy' !?! [acronym=EYE See! To w00d's Photo Musings, my pages][shadow=grey,left][size=1em]w[/size][size=1.25em]00[/size][size=1em]d[/size][/shadow][/acronym]
Good point W00D, translating would not end up in a crooked hover with tails like that. And I bet you could make it back with only one tail rotor, just at the minimun authority though.
I hadn't thought about that as I was only thinking of the side drift but yes, I agree, it makes sense As for 'survivability' I was thinking of the one thing or the most common failure that was certain to bring a 1:1 helicopter down and tail damage was first to come to mind. Again I agree, would have "minimum authority" and yes, this might be enough !?!
