According to the helicopter pilot, after an agricultural flight, he landed on the platform located on top of the truck to refuel the helicopter. The ground crew connected the fuel hose and the chemical hose to the helicopter. The pilot was taking notes and his focus was inside the helicopter during the connection of the hoses. The pilot reported that he did not expect for the chemical hose to be connected to the helicopter. Once the helicopter had taken on the required amount of fuel, the pilot motioned to the ground crew using hand and arm signals, that more fuel would be required after the next flight. The driver removed the fuel hose from the helicopter, then stepped back and made eye contact with the pilot. The pilot asserted that the ground crew then gave a "thumbs up" signal to the pilot. The pilot understood the signal to mean that the helicopter, "was clear and safe for departure." The pilot returned the "thumbs up" signal and advanced the throttle. The helicopter ascended, and the pilot noticed the ground crew motioning that the helicopter remained connected to the chemical hose. The pilot observed that the chemical hose was indeed still connected to the helicopter, and he applied aft cyclic. The tail rotor struck the truck, followed by the main rotor striking the truck also. Per the National Transportation Safety Board Pilot Aircraft Accident Report, the pilot noted that the accident could have been prevented if he had visually confirmed, "with his own eyes, that all possible connecting hoses were in fact, not connected and the departure could be safely executed." The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.