HISTORY OF FLIGHTOn May 2, 2013, about 1550 Pacific daylight time, a Robinson R44 II helicopter, N442RN, was substantially damaged following a loss of control during takeoff near Pomeroy, Washington. The certified commercial pilot, who was the sole occupant of the helicopter, was not injured. The helicopter was operated by Leading Edge Aviation of Clarkston, Idaho. The aerial application flight was being operated in accordance with 14 Code of Federal Regulations (CFR) Part 137, and a flight plan was not filed. Visual meteorological conditions prevailed for the flight, which was originating at the time of the accident. In a statement submitted to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that about 1400, the ground crewman prepared 800 gallons of spray solution for the 165 acres to be sprayed. Subsequently, 11 loads were taken from the loading spot, which was directly adjacent to the field being sprayed. The pilot stated that he was hauling 50 gallon loads and refueling as necessary, and that after he had sprayed about 150 acres, he landed on top of the loading platform for another load. The pilot reported that the helicopter was then loaded with chemical and about 10 gallons of fuel was added, after which the ground crewman gave him the thumbs up sign, which indicated that he was ready to depart. The pilot revealed that as he initiated forward flight the LOW ROTOR revolutions per minute (RPM) horn began to sound, at which time he activated the emergency dump button. However, as the low rotor rpm continued to decay the pilot attempted a run on landing to a stubble field, during which the left skid dug into the soil. This resulted in the helicopter nosing over and coming to rest on its left side. A postaccident examination of the helicopter revealed that it had sustained substantial damage to the forward fuselage structure, main cabin, and tail section. The pilot reported that there were no known mechanical anomalies with either the helicopter's airframe or engine that would have precluded normal operation. PERSONNEL INFORMATIONThe pilot, age 33, possessed a commercial pilot certificate with ratings for rotorcraft-helicopter, helicopter instructor, and airplane single-engine land. The pilot reported a total time of 1,911 hours in all aircraft; 1,572 hours in helicopters, and 1,262 hours in the same make and model as the accident helicopter. The pilot's most recent flight review was completed on December 5, 2012, in a Robinson R44 II helicopter. The pilot also reported having flown 270 hours, 83 hours, and 4 hours, in the past 90 day, 30 days, and 24 hours respectively. The pilot received his most recent Federal Aviation Administration (FAA) second-class medical certificate on January 22, 2013, with no waivers or limitations. AIRCRAFT INFORMATIONThe accident helicopter, N442RN, was a 2006 Robinson R44 II Raven, serial number (s/n) 11047. The helicopter was a four-seat, single-engine helicopter that was equipped with a skid type landing gear. It was powered by a 245-horsepower Lycoming IO-540-AE1A5, s/n L-30772-48A, reciprocating engine. The helicopter's maximum gross weight was 2,500 pounds. The helicopter was issued a Standard Airworthiness Certificate on January 19, 2006. A review of the maintenance records showed that the helicopter had undergone an annual inspection on April 18, 2013. At the time of the accident, the airframe and engine had accumulated 1,615 hours in service. The helicopter had accumulated 30 hours since the last maintenance inspection. METEOROLOGICAL INFORMATIONThe pilot reported the following weather conditions existed at the time of the accident: Wind calm and not gusting, sky clear, visibility 10 miles, temperature 66 degrees Fahrenheit (18.8 degrees Celsius), and an altimeter setting of 30.48 inches of mercury. The pilot computed a density altitude of 4,008 feet. AIRPORT INFORMATIONThe accident helicopter, N442RN, was a 2006 Robinson R44 II Raven, serial number (s/n) 11047. The helicopter was a four-seat, single-engine helicopter that was equipped with a skid type landing gear. It was powered by a 245-horsepower Lycoming IO-540-AE1A5, s/n L-30772-48A, reciprocating engine. The helicopter's maximum gross weight was 2,500 pounds. The helicopter was issued a Standard Airworthiness Certificate on January 19, 2006. A review of the maintenance records showed that the helicopter had undergone an annual inspection on April 18, 2013. At the time of the accident, the airframe and engine had accumulated 1,615 hours in service. The helicopter had accumulated 30 hours since the last maintenance inspection. WRECKAGE AND IMPACT INFORMATIONOnsite documentation of the wreckage by a FAA airworthiness inspector assigned to the FAA's Flight Standards District Office (FSD0), Spokane, Washington, revealed that the main wreckage came to rest on its left side in a stubble field about 450 feet west-northwest of the departure point. The helicopter's at rest position was oriented in a northwesterly direction, with the tail rotor blades and associated tail rotor assembly located about 5 feet forward of the main wreckage. The main rotor blades were observed at the main wreckage site, with both having sustained substantial damage as a result of impact forces. The helicopter's spray booms and SIMPLEX spray system was both located partially attached to the fuselage. Both had sustained impact damage. The two-place cockpit was intact, with minimal impact damage observed. ADDITIONAL INFORMATIONIn the accident report submitted to the NTSB IIC under RECOMMENDATION, the pilot commented that the amount of chemical spray solution that was loaded into the onboard spray tank was in excess of the 50 gallons that he had requested. As noted by the pilot, this put the helicopter outside of the weight and balance [envelope] and performance limitations. Additionally, the pilot stated that the spray tank's sight glass is long and very shallow, and unless the helicopter is in a level attitude [when loading], the sight glass reading is inaccurate. He added, in general the pilot has no visual ability to see the spray tank or know how much spray solution has been loaded into the tank. TESTS AND RESEARCHDuring the initial stages of the investigation, the pilot of the accident helicopter revealed to the IIC that during loading operations, as well as during inflight operations, the amount of chemical on board the helicopter is not visible. Additionally, the pilot stated that while in the process of loading the helicopter, the pilot must either rely solely on the ground crewman to advise him of the amount of chemical solution on board prior to departing, or the pilot must physically deplane the helicopter to view the sight gauge, one located on both sides of the spray tank, in order to definitively know how much chemical is on board. The pilot reiterated that neither sight gauge is visible from either the left or right R44 II pilot seat positions. On May 16, 2013, the IIC traveled to the facilities of SIMPLEX AEROSPACE, which is located in Portland, Oregon. SIMPLEX AEROSPACE is the manufacturer of the Robinson R44 Simplex Model 244 spray system, the same spray system that was installed on the accident helicopter at the time of the event. SIMPLEX personnel had previously agreed to meet with the IIC in order to provide an orientation relative to the spray system in question. The IIC was not permitted to photograph the equipment during the orientation. Information provided by SIMPLEX AEROSPACE relative to the Simplex Model 244 spray system revealed that the spray tank is a lightweight (186 pounds), chemical resistant tank, with a capacity of 130 gallons. Features include a jettison door, a dual spray valve, single and dual spray boom depressurization, as well as a self-contained system with attached spray boom. During the visual orientation of the spray tank and accompanying components, the IIC observed both of the sight gauges, one located on each side of the spray tank. However, as there was no helicopter present for the tank to be attached to, the IIC could not determine the visual limitation of the system from either pilot position as reported by the accident pilot.