N5450Grumman Acft Eng Cor-Schweizer G-164A

On August 06, 2023, about 0927 Pacific daylight time, a Grumman G164A, N5450, sustained substantial damage when it was involved in an accident near Davis, California. The pilot sustained fatal injuries. The airplane was operated as Title 14 Code of Federal Regulations Part 137 aerial application flight.

The purpose of the flight was for the pilot to conduct an aerial application of pesticide on a local tomato crop. According to the operator, the airplane was topped off with fuel and 1,700 lbs of pesticide the night before the accident. The morning of the accident, the pilot departed from Medlock Field Airport (69CL), Woodland, California, and conducted aerial applications while flying from west to east about 68 ft agl. An employee responsible for refueling the airplane and loading the hopper reported that the airplane was fueled to about ¾ of a full tank and he added 1,500 lbs of pesticide before the accident. The employee reported that he continued with their daily tasks and did not witness the accident. There were no witnesses to the accident.

Postaccident examination of the ground scars and the resting position of the airplane revealed that the airplane landed on the soft-field and nosed over. A fire consumed the airplane wreckage; the operator reported that the pilot self-extricated and was transported to a nearby medical facility.

No pilot logbooks were recovered or provided during this investigation.

The operator identified the insecticide used in the aerial application as Wilbur-Ellis BEN-SUL 85. According to the United States Environmental Protection Agency, Pesticide Product Label, the pesticide contained 85 percent Sulfur and is marked with a label stating, “CAUTION: Harmful if absorbed through the skin. Causes eye irritation. Avoid contact with skin, eyes or clothing.” Additionally, the operator reported that the accident airplane was solely used to conduct aerial applications of Wilbur-Ellis BEN-SUL 85.

The operator provided airframe, engine, and propeller logbooks from the last annual inspection, which was less than one month before the accident, on July 31, 2023. No additional logbook entries were provided.

The weather reported at an airport about 12 nautical miles from the accident site included a temperature of 82°F and a dew point 59°F. The calculated relative humidity at this temperature and dewpoint was 46 percent. Review of the icing probability chart contained within Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35 revealed the atmospheric conditions at the time of the accident were conducive to serious icing at glide power.

The operator identified the insecticide used in the aerial application as Wilbur-Ellis BEN-SUL 85. According to the United States Environmental Protection Agency, Pesticide Product Label, the pesticide contained 85 percent Sulfur and is marked with a label stating, “CAUTION: Harmful if absorbed through the skin. Causes eye irritation. Avoid contact with skin, eyes or clothing.” Additionally, the operator reported that the accident airplane was solely used to conduct aerial applications of Wilbur-Ellis BEN-SUL 85.

The operator provided airframe, engine, and propeller logbooks from the last annual inspection, which was less than one month before the accident, on July 31, 2023. No additional logbook entries were provided.

Review of photographic evidence revealed that ground scars, consistent with the landing, were about 93 ft east of the main wreckage. The wreckage came to rest, inverted in the field where the pilot was applying pesticide. A fire consumed the engine compartment, fuselage, and empennage. Examination of the airplane revealed substantial impact and thermal damage; due to the damage the investigation was not able to identify the source of the fire or determine if it began in flight. The left and right upper and lower wings sustained impact damage to the leading edges, with thermal damage signatures emanating from the wing roots. The engine was separated from the engine mount and came to rest about 4 ft from the main wreckage.

Examination of the recovered wreckage revealed that the cockpit was mostly consumed by fire except for the steel tube frame, which was thermally damaged, but remained intact. Flight control continuity was observed. The fuel system was completely consumed by fire.

Examination of the airplane’s engine showed that it was separated from the airframe; however, it remained attached to engine mount structure. No holes were observed in the engine cases. All nine cylinders remained attached and secured to the intermediate case. The rear case and engine accessories exhibited thermal damage. Damage to the magneto prevented a functional test. The carburetor, generator, and remains of the magneto were removed from the rear case and the front spark plugs were removed from each cylinder. The propeller was rotated by hand throughout 360°. Rotational continuity was established throughout the engine and valvetrain, with movement observed on all the rear accessory case gears.

Thumb compression was obtained on all cylinders except for cylinder Nos. 5 and 9. Each cylinder was examined internally using a lighted borescope. Varying degrees of corrosion, water, oil, and dirt were observed in each cylinder. All intake and exhaust valves, pistons, and internal areas of each cylinder were unremarkable except for cylinder Nos. 5 and 9, in which the intake and exhaust seats exhibited an abundance of dirt debris. All front spark plugs exhibited normal operation signatures. The oil screen contained a small amount of melted metallic debris.

A visual examination of the carburetor revealed impact and thermal damage. The throttle and mixture control ends remained attached to their respective controls on the carburetor. The jet covers were removed and both metering jets were found secure. The carburetor could not be disassembled due to impact damage.

An autopsy of the pilot was performed by the Sacramento County Department of the Coroner. According to the pilot’s autopsy report, the cause of death was complications associated with thermal injuries.

The pilot succumbed to his injuries 25 days after the accident.