Waaaaaay back in the "good ole days" when Nieuports and Camels and Fokkers had rotary engines, they would tend to climb when turned to the left and tend to dive when turned to the right. I'm assuming that the prop turned clockwise when viewed from the cockpit, just like american planes do. This is all due to the huge precessional force from that rotating engine.
Can't blame Bell entirely, as much as I would like to. Between DOD trying to kill it multiple times (Osprey is THE Congressional Pet Rock) and the services adding ridiculous requirements, this thing was bound to take forever.
FWIW, I am on the AFOTEC IOT&E test team as the lead for SIRFC (RF ECM package).
"It's time to get medieval, I'm goin' in for guns" - Dos Gringos
To finish habu2's sentence,
so the local precessional torques are still there to affect bearings, engine mounts and such, but the left rotor and right rotor precessional torques cancel each other. Therefore the airplane does not experience the unwanted effects mentioned in previous posts.