Vertical Flight

Hovering is actually an element of vertical flight. Increasing the angle of incidence of the rotor blades (pitch) while keeping their rotation speed constant generates additional lift and the helicopter ascends. Decreasing the pitch causes the helicopter to descend. In a no-wind condition in which lift and thrust are less than weight and drag, the helicopter descends vertically. If lift and thrust are greater than weight and drag, the helicopter ascends vertically. [Figure 1]

Helicopter vertical flight
Figure 1. Balanced forces: hovering in a no-wind condition

Forces Acting on the Aircraft
Airfoil Terminology, Definitions and Types
Airflow and Reactions in the Rotor System
Hovering Flight
Forward Flight
Sideward, Rearward and Turning Flight