how the hell does a heli fly inverted?

[Lynx.1677]

i understand what negative & positive pitch is, but when the heli is filpped upside down y dosnt it just plough straight in the ground,

Hey buddy, I don't think you are grasping what pitch generates. Pitch + rpm = lift so if you have negative pitch you then have negative lift as long as the blades are spinning at least! Lol. Remember, each blade is basically a wing.