Robinson R44 crash near Okawville, IL, United States

The helicopter pilot reported that, before starting aerial application flights for the day, he calculated that about 490 pounds of chemical would bring the helicopter's weight near the manufacturer's maximum gross weight limitation. After an aerial application flight, he landed on a platform located on top of a chemical reloading truck and reloaded the chemical tank with the pre-calculated amount. Once reloaded, he maintained a stabilized hover over the truck and transitioned to forward flight. When the helicopter cleared the truck, the "engine [made] a lower sound" and the main rotor low revolutions per minute (RPM) horn activated and the caution light illuminated. He immediately added power, lowered the collective to restore main rotor RPM, and pitched forward to gain airspeed but the helicopter would not climb. He then decided to perform a roll-on landing on the adjacent field, but the helicopter landed hard. The helicopter sustained substantial damage to the tail cone, tail rotor blades, and fuselage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation. The pilot added that after the accident, he recalculated the helicopter's weight and balance. He determined that during the reloading operation, the chemical tank was not empty with about 80 pounds of chemical remaining and the added precalculated amount of chemical exceeded the maximum gross weight limitation.