NOTAR

[Lawyerboy]

How does this work, then?

"Made by US manufacturer MD Helicopters, based in Mesa, Arizona, the gadget-stuffed chopper with its innovative NOTAR (No Tail Rotor) system will be used almost exclusively to transport and treat the most severely injured patients."

[WhoNeedsRunways]

Lawyerboy :

Instead of a traditional tail rotor, NOTAR uses a combination of a nozzle at the end of the tailboom to provide heading control, and a slot in the tailboom through which air is pumped which interacts with the main rotor downwash to provide anti-torque.

That's it is a ( very brief ) nutshell. For more info from the horse's mouth, have a look at
http://www.mdhelicopters.com/Rotorcraft/pdfs/md600_Tech/600techd_Overview.pdf

[Lawyerboy]

Thanks for that, WNR. Clever little system, but it does make you wonder why no one's thought of it before.