Accident Overview
On July 10, 2020, about 1102 mountain daylight time, a Schweizer Grumman G-164B airplane, registration N6917K, was destroyed in an accident near Springfield, Colorado. The commercial pilot sustained serious injuries and succumbed to those injuries on July 14, 2020. The airplane was operating under 14 Code of Federal Regulations Part 137 as an aerial application flight.
Flight History
The pilot, also the company owner, was en route to Two Buttes, Colorado, for a high-elevation low-level aerial application flight after departing from Springfield Municipal Airport (8V7). An employee who performed ground loading operations reported that the airplane was loaded with 48.85 gallons of AgSaver Glyphosate herbicide, 15.62 gallons of Atarrus fertilizer, 125 gallons of Kugler KQ-XRN fertilizer, and about 85 gallons of fuel. The pilot had previously experienced foam on the windshield and had returned to add more defoaming agent and activate the circulating pump. It is unknown if the spray pump fan was activated during the takeoff roll.
A witness observed white smoke from the cockpit before impact, describing it as "granular in nature" and "looked solid." The airplane impacted a remote flat field at an elevation of about 4,370 feet mean sea level while traveling southeast, followed by a postimpact fire. The wreckage came to rest about 0.65 miles southeast of the departure end of runway 17.
After the accident, the pilot told his wife that a chemical reaction in the hopper caused severe foaming during flight, which covered the windshield and impaired his vision. The employee noted that foam emerged from the hopper overflow located in front of the cockpit. No jar test of the chemical mixture was performed that day, and the pilot's wife stated it was the pilot's first time using that specific mixture.
Personnel and Aircraft Information
The pilot's most recent flight review was completed on March 1, 2018. Title 14 CFR Part 61.56 requires a flight review within the preceding 24 calendar months.
The airplane was equipped with a Herr 335-gallon fiberglass hopper installed on January 1, 1995; the specific model and serial number could not be determined. The aircraft lacked windshield washer and wiper systems and an emergency locator transmitter; these were not required.
Wreckage Examination
The airplane was fragmented by impact and destroyed by postimpact fire. All major structural components and flight control surfaces were present at the site. Flight control and engine continuity were established. Propeller damage was consistent with high rotational speed at impact. No mechanical anomalies were found in the airframe or engine.
The hopper was destroyed by fire. Its top and door were separated; the door was bent and broken, and the door seal was charred and consumed. Vent tubes and spray applicator lines were traced from the hopper to beneath the fuselage. Due to extensive fire damage, the identification of the overflow venting system could not be confirmed. No chemical residue from foam was observed on the windshield or fuselage.
Additional Information
Postaccident testing conducted by the Colorado Agricultural Aviation Association used a mixture of glyphosate and low-salt nitrogen fertilizer. Agitation produced foam that rapidly filled a container to the 30-ounce level within seconds. The Kugler KQ-XRN technical sheet warns that a chemical foaming reaction may occur when mixed with products containing glyphosate.
The U.S. Department of Agriculture publication "Aerial Application of Agricultural Chemicals" discusses hopper vent design to prevent cockpit contamination. The National Agricultural Aviation Association's Fly Safe Campaign message of August 10, 2020, emphasizes jar testing for chemical compatibility.
Reid Aviation & Aerial Spraying, LLC, a Part 137 operator based in Springfield, Colorado, solely used the accident airplane. FAA Advisory Circular 137-1B does not address chemical mixture reactions or windshield contamination. Part 137 does not require operators to have a Safety Management System.