Helicopters with no tail rotors..?

[erdnase]

I was watching some air ambulance program the other night, and noticed the helicopter had no tail rotor. How can that work? Surely there needs to be something to counteract the torque from the main rotors - or is it just well hidden inside the fuselage?

I'm trying to find a photo of the copter I mean, but can't find one as I don't even know the name of it. Can anyone help?

[erdnase]

Zad said:

McDonnell Douglas "NOTAR" Explorer



There is a high speed fan in the tail boom, and a rotating slot at the end of the tail that controls the direction of the air, to counteract the torque.

NOTAR was originally developed by Hughes http://en.wikipedia.org/wiki/NOTAR

That's the one!

I've read up a little on Wiki about these, and it's pretty fascinating. If I understood it correctly, as well as having a "fan" pushing air out the tail, the actual boom/shaft is like a wing on its side? This way, the downwash from the main rotor flows over the wing design and creates "lift", albeit at 90 degrees to how a normal wing would work, creating a force in the opposite direction to counter the torque?

I'd never heard about this, and spent a good hour on Wiki reading about helicopter designs today. Awesome

[erdnase]

So I assume the shaft/wing creates the majority of the counter-torque, and the fan is used for minor adjustments, etc? I'm just wondering why you'd need both.

If there was no wing shaped boom (excuse my awful terminology!), would all that downwash from the main rotor be going to waste - or is there a trade off between vertical lift when using the NOTAR design?

Helicopters are amazing things. I've had a few radio controlled ones. Just the cheap little electric designs with 2 coutner rotating blades, but they never cease to amaze me. You can understand a bit of the science behind them.. but when you see them just hovering - it's not science, it's voodoo!