What is the preferred landing formation for helicopters in adverse conditions?

In adverse conditions, the preferred landing formation for helicopters is the trail formation. This formation allows helicopters to approach the landing zone one after the other in a staggered manner, which minimizes the risk of rotor wash affecting the aircraft behind. By flying in trail, each helicopter can maintain a safe distance and avoid turbulent air created by the rotor blades of the helicopter ahead. This spacing is crucial in maintaining stability and control during the landing maneuver, especially in situations where visibility may be limited or wind conditions are uncertain. The trail formation also provides a clear line of sight for pilots to monitor the landing zone and enables effective coordination among the helicopters, enhancing the overall safety of the operation.