Anyone ever flown a NOTAR?

[Frank N. O.]

I don't think I've asked this before but I just remembered that there was this so-called revolutionary safety invention for helicopters but what ever became of that, I haven't really seen any new helicopters with this system. I think I read some years ago that the NOTAR system was different to maneuver with, or maybe that was from this forum?

Frank

[AirScorp]

Found an explanation on Wiki.. So, what it basically does is deflect a portion of the downgoing flow from the main rotor to create a vortice in the tail which counteracts the torque? Looks familiar to one of the reasons we have to apply rudder on takeoff on fixed wings (the airflow spins round the fuselage and hits the tail fin, specially on slow speeds - what is this particular one called again?). Guess someone found a way to use this as an advantage.

Great concept! Thanks for sharing Frank!

[G-man]

I flew one back in the early 90's--in terms of flying technique--there is no difference to a regular helicopter. In terms of how it looks is different--there is no tail rotor--hence "NOTAR". You can put the tail of a Notar into the trees. It works on the coanda effect--go to your kitchen sink right now and grab a curved spoon. Turn on the water in the faucet and hold the spoon with the curved side, (convex), towards the flow of water and gradually let the water flow over the curve of the spoon---the spoon will be sucked into the flow.

Basically, coanda effect is using bernoulli's principle by forcing air out of horizontal slats along the tail-boom. The increased velocity of the air on the right side of the boom lowers the pressure and hence the boom is drawn one way.

Better yet--check this out:

http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/the-aerodynamics-of-a-ping-pong-ball/

I never really noticed a difference in performance, however Phoenix PD, who were the launch customer, found they lacked tail authority at hot and high conditions.
Having just done my own description--I found these:

[AirScorp]

Wow great! I had the part with the coanda effect down from wiki. The word "hug" just didn't occure to me 

Still, (and this comes from much debate with fellow pilots) it would be a misconception to think that the coanda actually produces the lift. It just makes the air hug the boom and creates a vortice that is responsible for the lift. Just as in the engineering point of view, the wing shape itself doesn't produce lift, but creates the vortice that produces the lift.. Arghhhh, and imagine that I never passed the exam for fluid dynamics no matter how interested I was in it 

I realized from the picture you posted that the actual mechanism is even more exciting than I thought at first. The flow is inside the boom and only exits from slots, yet it's still sufficient to create the effect. Guess the tail fins don't contribute to much after all. Just one question.. What does the rudder controls do in such a helicopter? Do the control the little fan inside the boom, change the pitch of it's blades or there are actual rudder surfaces on the tail fins??

Thanks G!

[G-man]

The pedals control the amount of airflow in the tail-boom, which ultimately control the amount of "lateral lift" on the boom thereby controlling yaw.