Delta 3 - fabulous diagrams which show a basic problem with flying a helicopter - as you increase forward speed the lift on the advancing and retreating sides of the rotor disc are different and therefore the aircraft will try to roll towards the advancing side. We (brits) call it Inflow Roll, others (Americans) call it Transverse Flow. All that stops it happening is the interference of the pilot who moves the stick towards the retreating side to keep the'wings' level. IIRC the R22 has a little spring/weight combination that reduces the lateral stick force required in cruise flight to ease pilot workload.