Accident Details
The pilot reported that he was performing aerial agricultural spraying from a helicopter. He landed on the bed of a service truck to reload insecticide and fuel. As he began to lift off and transition to forward flight, he pitched the helicopter forward to gain airspeed. However, the helicopter continued to descend. The pilot stated that he "never gained lift from the ground effect" and subsequently struck the terrain.
Damage and Mechanical Status
The helicopter sustained substantial damage to its tail boom and fuselage. The pilot indicated that there were no preimpact mechanical malfunctions or failures with the airframe or engine that would have prevented normal operation.
Ground Effect Definition
The FAA Helicopter Flying Handbook, Chapter 2 "Aerodynamics," defines "In Ground Effect (IGE)" as the increased efficiency of the rotor system caused by airflow interference when near the ground. This results in increased air pressure or density, which reduces the downward velocity of air. Ground effect allows the relative wind to be more horizontal, the lift vector to be more vertical, and induced drag to be reduced, making the rotor system more efficient. Maximum ground effect is achieved when hovering over smooth hard surfaces. Over surfaces such as tall grass, trees, bushes, rough terrain, and water, maximum ground effect is reduced. Rotor efficiency is increased by ground effect up to a height of about one rotor diameter from the ground to the rotor disk for most helicopters.