Robinson R44 II N442RN accident near Pomeroy, Washington

Probable cause

The pilot's failure to ensure that the helicopter was properly loaded, which resulted in the helicopter being in excess of its maximum allowable gross weight and led to a loss of main rotor rpm on takeoff. Contributing to the accident were the ground crewman's inadvertent overloading of the helicopter and the design of the spray tank's visual sight glass, which did not allow the pilot to visually verify the amount of the spray tank load without exiting the helicopter.

NTSB analysis

Before the agricultural application flight, the pilot asked the ground crewman to refill the spray tank with 50 gallons of chemical solution; 10 gallons of aviation fuel was also added. Subsequently, the ground crewman signaled to the pilot that the helicopter was ready to depart. During the departure and while transitioning to forward flight, the low-rotor rpm horn activated, and the pilot immediately pushed the emergency dump button to lighten the load; however, the rpm continued to decrease, and the pilot initiated a run-on landing to a field. During the landing, the pilot was unable to maintain control as the left skid dug into the dirt, which resulted in the helicopter nosing over and coming to rest on its left side.

The pilot reported that he believed the amount of solution added to the tank was more than 50 gallons, which placed the helicopter outside of weight and balance and performance limitations. The pilot added that the spray tank sight glass is long and very shallow, and that, unless the helicopter is level, the sight glass reading is inaccurate. Additionally, when seated in the helicopter, it was not possible for the pilot to see the spray tank sight glass or know how much spray solution had been loaded into the tank. Therefore, the pilot had to rely either on the ground crewman or exit the helicopter after each load and visually check the load to ensure that the helicopter was loaded with the proper amount of chemical solution. The pilot reported no mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for WPR13LA217 for the full record.