History of Flight
On May 15, 2019, at 1151 Pacific daylight time, a Grumman Aircraft Corporation-Schweizer G-164C (N6787K) and a Gulfstream-Schweizer Aircraft Corporation Gulfstream AM G-164D (N6929K) collided midair near Pleasant Grove, California. Both airplanes were substantially damaged and the two pilots were fatally injured. The airplanes were operating as Title 14 Code of Federal Regulations Part 137 aerial application flights.
The pilot of N6787K (the white airplane) departed on his first flight to apply rice seed to a field about 3 nautical miles southeast of the departure point. The pilot of N6929K (the yellow airplane) departed from a different airstrip to spread rice seed on another field. The white airplane was flying south toward the field to be treated, while the yellow airplane had completed its application and was flying north/northwesterly returning to the departure airstrip when the collision occurred.
A witness near the accident site reported seeing the yellow airplane fly south and spray a field, then bank east, turn around, and fly north to spray another field. Seconds after looking away, he heard an impact. When he looked back, he saw the white airplane in a nosedive toward a field and the yellow airplane crash into a rice field.
No Federal Aviation Administration (FAA) air traffic control radar data was associated with either airplane. A SATLOC agricultural GPS unit recovered from the yellow airplane revealed its flight track on the day of the accident. A similar unit from the white airplane contained no recorded data from the accident day.
Wreckage and Impact Information
The wreckage and debris path was distributed over about ¼ mile of rural agricultural terrain. The yellow airplane impacted a flooded rice field, while the white airplane came to rest in a dry field south of the yellow airplane. Various debris from both airplanes was located between the two main wreckage sites.
The white airplane came to rest on its left side adjacent to an unpaved road. The airplane was mostly intact; the engine remained attached and the propeller remained attached to the engine. The left lower wing was located about 140 ft from the main wreckage. A yellow aileron and a portion of a yellow wing strut were found near the white airplane’s left lower wing. Flight control continuity was established with no anomalies noted.
The yellow airplane was not accessible at the accident site due to its location in a flooded rice field. The majority of the airplane was within the confines of the main wreckage. The engine separated and was forward of the main wreckage; the propeller assembly separated from the crankshaft.
Medical and Pathological Information
An autopsy of the pilot of the white airplane determined the cause of death as multiple blunt force injuries. No significant natural disease was identified. Toxicology testing identified the non-sedating antacid medication ranitidine in the pilot’s urine.
An autopsy of the pilot of the yellow airplane determined the cause of death as multiple injuries. The autopsy identified an enlarged heart (470 grams) and severe atherosclerosis with 70 to 90% narrowing in several coronary arteries and branches. Toxicology testing identified delta-9-tetrahydrocannabinol (THC) at 1.7 ng/mL in femoral blood; 11-hydroxy-delta-9-THC and carboxy-delta-9-THC were identified in urine at 9.9 ng/mL and 15.8 ng/mL, respectively. The non-impairing high blood pressure medications amlodipine and valsartan were detected in blood and urine.
The cannabis plant (Cannabis sativa) contains cannabinoids; THC is the primary psychoactive cannabinoid compound. THC's mood-altering effects include euphoria and relaxation and can cause alterations in motor behavior, perception, and cognition. Significant performance impairments are usually observed for at least 1-2 hours following cannabis use, with residual effects reported up to 24 hours. THC is rapidly metabolized, but the rate depends on ingestion method, potency, frequency of use, and user characteristics. Peak THC concentrations of 100-200 ng/mL commonly occur soon after smoking cannabis and are generally below 5 ng/mL after 3 hours. Both blood and urine test results do not necessarily reflect recent use and cannot be used to prove impairment at the time of testing.