Browsing through the newly-available past columns, I happened upon an article about how helicopters work. Although I loathe to suggest that Maestro Cecil may have made a boo-boo, I must suggest a slightly different answer.
Cecil says that when a helicopter moves into forward flight, the pitch of the individual rotor blade is maximum in the rear of the rotor, which provides maximum lift at that point, tilting the rotor disk forward.
What actually happens is this: the point of maximum cyclic pitch on the rotor is 90 degrees before the point at which the maximum lift is applied to the rotor disk.
In a clockwise-rotating rotor (viewed from above), the pitch is maximum on the right side of the helicopter, but the lift generated by this pitch is applied 90 degrees later in its rotation due to a principle of physics known as gyroscopic precession. It is this pitch on the right side of the disk which lifts the rear of the disk, and propels the helicopter forward.