Description

In forward flight, the downwash from the main rotor of a helicopter is transformed into a pair of trailing vortices comparable to the wing tip vortices generated by a fixed wing aircraft and there is some evidence that these vortices are more intense than those from a similar-weight fixed-wing aircraft. It is therefore recommended that helicopters should be operated well clear of light aircraft when hovering or whilst air taxiing.

Two blade main rotor systems, typical of lighter helicopters, produce stronger wake than rotor systems with more blades.

The strength of the vortex depends not only on the blade geometry and loading, but also on the aircraft's operational state (i.e., hovering, climbing, descending, or manoeuvring) but is more pronounced in forward flight, especially when pitch is being applied, such as at take off or landing