HISTORY OF FLIGHTOn April 9, 2024, at 1444 Pacific daylight time, an Ayres Corporation S2R-G10 airplane, N40261, was substantially damaged when it was involved in an accident near Derner, California. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. According to the pilot’s co-workers, about 0830 on the day of the accident, the pilot flew the airplane from the operator’s facility in Williams, California, to an airstrip near a rice farm about 174 miles northeast. The airplane departed with full fuel tanks, and the co-workers stated the flight normally takes about 70 to 90 minutes. After the pilot departed the operator’s facility, he texted the mechanic, stating the airplane’s fuel gauge was inoperative. The mechanic explained that the gauge did not read fuel quantities greater than 82 gallons per tank. The pilot also told the mechanic that the airplane’s fuel gauge was slower to respond to fuel quantity changes than other airplanes. About 0930, the pilot landed at the airstrip where workers loaded the airplane’s hopper with wild rice, and the pilot subsequently seeded eight hopper loads of rice on the paddies. About 1230, the pilot returned to the airstrip, requested another load of rice, and asked the fuel truck operators to fuel the airplane to 3/4 of its capacity. The pilot then applied another seven or eight loads of rice to the fields. About 1400, the pilot returned to the airstrip and informed his co-workers that he was feeling unwell and was going to conclude the workday early after applying one more load of rice to the field. The pilot was asked if more fuel was needed for the airplane, but the pilot declined to refuel and returned to the aircraft. A witness saw the pilot don his helmet and safety harness before departing. A witness who was in a building about 2.5 miles from the airstrip stated he heard a crash and looked out the building’s door to see the airplane inverted in the rice paddy. The witness reached the accident site and attempted to open the airplane’s cabin door without success. A shovel was then used to pry the door open. The witness stated that the pilot was unresponsive and that the pilot’s safety harness was unbuckled. AIRCRAFT INFORMATIONAccording to a mechanic who worked for the operator, the airplane had been purchased recently, and the pilot had not flown it before the day of the accident. The accident airplane, which was equipped with an AlliedSignal TPE-331-10 engine, differed from other aircraft in the fleet, which were equipped with different engines. The mechanic stated the airplane burned about 80 gallons per hour during takeoff, and about 60 to 65 gallons of fuel per hour during other phases of flight. The airplane’s Type Certificate Data Sheet indicated that the airplane had a usable fuel quantity of 228 gallons, stored in two wing tanks, each with a capacity of 115 gallons. The airplane’s fuel gauge in the cockpit was labeled, “USEABLE FUEL 114 U.S. GAL. FUEL ABOVE 82 GAL IS UNGAGEABLE.” AIRPORT INFORMATIONAccording to a mechanic who worked for the operator, the airplane had been purchased recently, and the pilot had not flown it before the day of the accident. The accident airplane, which was equipped with an AlliedSignal TPE-331-10 engine, differed from other aircraft in the fleet, which were equipped with different engines. The mechanic stated the airplane burned about 80 gallons per hour during takeoff, and about 60 to 65 gallons of fuel per hour during other phases of flight. The airplane’s Type Certificate Data Sheet indicated that the airplane had a usable fuel quantity of 228 gallons, stored in two wing tanks, each with a capacity of 115 gallons. The airplane’s fuel gauge in the cockpit was labeled, “USEABLE FUEL 114 U.S. GAL. FUEL ABOVE 82 GAL IS UNGAGEABLE.” WRECKAGE AND IMPACT INFORMATIONThe airplane came to rest inverted on the western edge of a rice paddy about 2.3 miles southwest of the departure airstrip. The rice paddy was filled with about 2 ft of standing water, and the upper portion of the airframe was submerged. The outboard right wing, vertical stabilizer, and rudder were crushed and deformed. All flight control surfaces remained attached, and flight control continuity was confirmed between the cabin controls and control surfaces. The flaps were partially extended. The cabin was generally intact. The windscreens were shattered, with portions missing from the frames. The instrument panel was intact. The engine power lever was in the mid-travel position, and the engine speed lever was near the fully forward position. The fuel selector valve was On. The emergency fuel cutoff lever was Off (open). No obvious fuel sheen was observed on the surface of the water, and both wing tanks were empty. The header tank, which had a capacity of 5 gallons, contained about 1 gallon of fuel. The fuel shutoff valve and emergency shutoff valve cabin controls were in the open position, and their corresponding valves were in the open positions. All fuel lines from the fuel controller to the auxiliary fuel pump and header tank were clear of obstruction and contained no fuel. All fuel line fittings and hoses were tight throughout the entire system, and all fuel vent lines were clear. There was no evidence of fuel leak at any fitting, nor were any fuel streaks observed on any airframe skin. The fuel senders remained attached at their respective fittings on the inboard side of each tank. Both senders could be moved freely by hand and did not appear to be hung up on any part of the tank structure. The electrical resistance for both senders varied appropriately between each limit stop, and both were repeatable throughout their range. The engine remained mounted to the airframe. The exterior of the engine was unremarkable, with no obvious damage to the case. The oil filter bypass was not actuated. Engine control continuity was established from the control levers to the engine fuel control and governor. The emergency shutoff was not actuated and remained connected to the feather valve. A trace amount of fuel was observed at the forward fuel plenum drain, and no fuel was observed at the aft fuel plenum drain. The fuel filter element was free of debris. A trace amount of fuel was found at the secondary fuel nozzle. The tailpipe was removed to inspect aft turbine 3rd stage rotor. All blades were intact and displayed full geometry with normal dark coloration with a small amount of debris present. The propeller hub was intact, and all blades remained mounted in the hub. The propeller hub could be rotated freely by hand, and continuity was established through to the 3rd stage turbine. With the debris shield removed, the first stage compressor blade geometry appeared consistent with no blade damage. Debris was present at the debris shield and on hub of the impeller blades and outer flow path. Fuel was present in the line between the Fuel Shutoff Valve (FSOV) and flow divider, and between fuel control and FSOV. The lines to the FSOV were removed, and air flowed through valve when low pressure air was supplied to inlet. Three of the four propeller blades were bent uniformly aft, and the fourth blade was bent forward. All blades exhibited smooth abrasion to the leading edges and tips with almost no material loss. ADDITIONAL INFORMATIONThe fuel truck that had been used to fuel the airplane did not have any recording capabilities, so the timing and quantities of fuel dispensed to the airplane could not be confirmed. Additionally, the airplane was not equipped to transmit ADS-B, and so its flight time on the day of the accident and the timing of its fuel stop could not be confirmed. A performance chart contained in the airplane’s Pilot’s Operating Handbook (POH) indicates that, based on the weather conditions reported at the nearest airport 39 miles away, the engine consumed about 70 gallons of fuel per hour at 100% rpm. Given this rate of fuel consumption and a fuel load of 171 gallons (3/4 capacity), the airplane would have had an endurance of about 2.4 hours. The POH does not provide fuel consumption figures for other engine power settings. Given the operator’s report of the airplane consuming between 60 and 80 gallons per hour, the airplane would have had an endurance ranging between 2.1 hours and 2.9 hours. FLIGHT RECORDERSA Satloc M3 Bantam GPS spray management system was recovered from the airplane and shipped to the NTSB Vehicle Recorder Laboratory. Data from the accident flight was recovered from the device’s memory but was unable to be read. The data was then sent to the manufacturer, who determined that the data was corrupt, and that only a limited and sporadic amount of data would be extracted. The cleaned file contained 74 data points that began at 0940:25 PDT and ended at 1441:47 PDT, when the airplane was at an altitude of 4,317 ft and at a groundspeed of 43 mph. MEDICAL AND PATHOLOGICAL INFORMATIONThe pilot’s autopsy identified hypertensive and atherosclerotic cardiovascular disease as the cause of death, and his manner of death was natural. Morbid obesity and pulmonary emphysema were listed as significant conditions contributing to death. The pilot’s heart was described as enlarged and had a thickened left ventricle. Slight coronary artery disease was present in multiple coronary arteries, with maximum narrowing of 40%. No recent coronary artery clot was identified, and no old heart muscle scarring was visible. The only traumatic injuries identified during autopsy were three rib fractures. Review of the pilot’s medical records revealed a medical history that included obesity, high blood pressure, high cholesterol, as well as chronic obstructive pulmonary disease (COPD) with components of both bronchitis and emphysema. During visits to his primary care provider in October and December 2023, the pilot reported increasing shortness of breath over the previous year. Four days before the accident, the pilot underwent a cardiac stress test. The pilot did not report chest pain during this examination. The interpreting cardiologist noted below-average functional capacity, with an exaggerated blood pressure response, frequent premature atrial and ventricular contractions. Postmortem toxicological testing detected acetaminophen and salicylic acid in peripheral blood and urine. Desmethylsildenafil, albuterol, and lisinopril were detected in urine and were not detected in peripheral blood. Desmethylsildenafil is a metabolite of sildenafil. Sildenafil (which was not detected in this case) is a prescription medication commonly used to treat erectile dysfunction, as a sexual enhancement aid, or in the treatment of certain other conditions, including pulmonary hypertension. Sildenafil is not typically impairing, although the FAA states that pilots should wait 8 hours after using it before flying, to monitor for side effects. Albuterol is a prescription medication commonly used as needed to relax tight lungs and improve wheezing and cough in conditions such as asthma and COPD. The pilot’s documented home medication levalbuterol is a form of albuterol. Albuterol is not typically impairing. According to the FAA medical case review for this accident, pilot use of albuterol as needed up to twice weekly is acceptable, but pilot medical certification on albuterol depends on the underlying condition. Lisinopril is a prescription medication commonly used to treat high blood pressure, and was documented as one of the pilot’s home medications in reviewed personal medical records. Acetaminophen is a pain- and fever-reducing medication widely available over the counter, including cold and flu products. Salicylic acid is the primary active metabolite of aspirin, a widely available over-the-counter medication that can be used to control pain and fever and to reduce cardiovascular risk. Salicylic acid also is a metabolite of some other drugs and is used as a topical skin exfoliant in a variety of retail products. Lisinopril, acetaminophen, and salicylic acid/aspirin, are not generally considered impairing. TESTS AND RESEARCHThe fuel level senders and fuel quantity gauge were removed and sent to an instrument calibration laboratory. Inspection and testing of the gauge and senders revealed they operated within manufacturer specifications.