What must a helicopter be doing to create wingtip vortices?

A helicopter creates wingtip vortices primarily during forward flight. This phenomenon occurs because, like fixed-wing aircraft, helicopters generate lift through the rotational motion of their blades. When the helicopter moves forward, the airflow around the rotor blades causes a pressure differential, leading to the formation of vortices at the wingtips. These vortices can be particularly strong behind the helicopter and may pose a hazard to other aircraft, especially in close proximity.

In contrast, hovering does not produce the same forward movement necessary for the creation of distinct wingtip vortices, which is why it is not a correct choice. While a helicopter can experience some turbulence during ascending and sideways movement, these actions do not typically produce the notable wingtip vortices associated with forward flight. Therefore, forward flight is crucial for the generation of these swirling air patterns.