Springfield, CO, USA
N6917K
GRUMMAN G164
The pilot had just departed the airport to perform an aerial application flight utilizing a combination of a herbicide and fertilizers. An employee of the operator reported that the pilot was having issues with foam exiting from the hopper, which was located in front of the cockpit. The pilot had returned to the airport prior to the accident to add more de-foaming agent to the hopper and had activated the circulating pump to correct the problem. The pilot took off and a witness reported observing white smoke coming from the cockpit prior to impact; however, the smoke was "granular in nature" and "looked solid." The airplane impacted a remote flat field, a postimpact fire ensued, and the airplane was destroyed. After the accident, the pilot reported to his wife, that there was a reaction of the chemicals in the hopper, and it was foaming “really bad” while in flight. The foam was coming out of the hopper, and it covered the windshield. The pilot reported he couldn’t see while flying. A postaccident examination of the airplane did not reveal any mechanical anomalies. The airplane hopper had been loaded with a glyphosate herbicide, Atarrus fertilizer, and Kugler KQ-XRN fertilizer. The Kugler fertilizer technical sheet contained a caution stating that when mixing KQ-XRN with phosphate, sulfur, humic acid, and products containing glyphosate, a chemical foaming reaction may occur. Kugler also recommended performing a jar test when mixing KQ-XRN with any pesticides and fertilizers. Postaccident testing of the chemicals used by the pilot produced significant foam when they were combined and agitated. Neither the pilot nor the ground crew performed the recommended jar test. It is likely the pilot was unable to maintain control during flight due his view from the cockpit being obscured from foam originating from the hopper, which resulted in an impact with terrain. The foam was the result of the mix of chemicals used in the hopper, which was a combination known to produce foam, and the pilot did not perform a jar test prior to flying with the chemicals as recommended. Had a jar test been performed the pilot likely would have recognized the foaming problem and adjusted the chemical mixture appropriately.
HISTORY OF FLIGHTOn July 10, 2020, about 1102 mountain daylight time, a Schweizer Grumman G-164B airplane, N6917K, was destroyed when it was involved in an accident near Springfield, Colorado. The commercial pilot sustained serious injuries and succumbed to his injuries on July 14, 2020. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 137 aerial application flight. The pilot, who was also the owner of the company, was enroute to Two Buttes, Colorado to perform a high elevation low-level aerial application flight in a rural area after departing from the Springfield Municipal Airport (8V7), Springfield, Colorado. An employee who worked for the operator doing ground loading operations, reported the airplane was loaded with 48.85 gallons of AgSaver Glyphosate herbicide, 15.62 gallons of Atarrus fertilizer, and 125 gallons of Kugler KQ-XRN fertilizer. The airplane had about 85 gallons of fuel onboard. He reported the pilot was having trouble with foam coming onto the windshield of the airplane. The pilot had returned prior to the accident to add more de-foaming agent to the hopper and had activated the circulating pump to correct the problem. It was undetermined how much de-foaming agent was added at the time. During the takeoff roll for the accident flight, it was unknown if the pilot had the spray pump fan activated, thereby causing agitation to the chemical mixture. A witness reported observing white smoke coming from the cockpit prior to impact, however the smoke was "granular in nature" and "looked solid." The airplane impacted a remote flat field at an elevation of about 4,370 ft above mean sea level (msl), while traveling to the southeast, and a postimpact fire ensued. The airplane came to rest about 0.65 miles southeast of the departure end of runway 17 at 8V7. After the accident, the pilot reported to his wife, that there was a reaction of the chemical in the hopper, and it was foaming “really bad” while in flight. The foam was coming out of the hopper, the foam covered the windshield, and the pilot reported he was couldn’t see while flying. The pilot did not report where exactly the foam was coming out of the hopper. The employee who performed ground loading operations reported that the foam came out of the “hopper overflow,” which is in front of the cockpit. He additionally reported that the hopper would get washed by the pilot after every flight and on the day of the accident, a test jar of the chemical mixture used in the hopper was not performed by him or the pilot. The pilot’s wife reported that this was the pilot’s first time using that specific chemical mixture in the hopper. PERSONNEL INFORMATIONThe pilot’s last flight review occurred on March 1, 2018. 14 CFR Part 61.56 discusses flight review requirements and states that no person may act as pilot in command of an aircraft unless, since the beginning of the 24th calendar month before the month in which that pilot acts as pilot in command, that person has: (1) Accomplished a flight review given in an aircraft for which that pilot is rated by an authorized instructor and (2) A logbook endorsed from an authorized instructor who gave the review certifying that the person has satisfactorily completed the review. AIRCRAFT INFORMATIONAirplane’s maintenance records revealed that a Herr 335-gallon fiberglass hopper was installed in the airplane on January 1, 1995. The investigation was not able to determine the specific model and serial number for the hopper or the date of manufacture. The airplane was not equipped with a windshield washer system, a windshield wiper system, or an emergency locator transmitter, nor was it required to be. AIRPORT INFORMATIONAirplane’s maintenance records revealed that a Herr 335-gallon fiberglass hopper was installed in the airplane on January 1, 1995. The investigation was not able to determine the specific model and serial number for the hopper or the date of manufacture. The airplane was not equipped with a windshield washer system, a windshield wiper system, or an emergency locator transmitter, nor was it required to be. WRECKAGE AND IMPACT INFORMATIONThe airplane was fragmented from impacting terrain and was destroyed from a postimpact fire. All major structural components and flight control surfaces were located at the accident site. A postaccident examination of the wreckage was conducted. Flight control and engine continuity was established. The damage sustained to the propeller was consistent with the propeller turning at a high revolutions per minute when it impacted terrain. The postaccident examination did not reveal any mechanical anomalies with the airframe and the engine. The hopper was destroyed from the postimpact fire. The top of the hopper and hopper door was separated. The door was bent and broken and the seal around the door was charred and consumed. Vent tubes and lines to the spray applicator tubes were traced from the hopper to an area beneath the airplane’s fuselage. Due to extensive fire damage, the identification of the overflow venting system could not be confirmed. Chemical residue from foam on the windshield or on the fuselage was not observed. ADDITIONAL INFORMATIONThe U.S. Department of Agriculture has published Aerial Application of Agricultural Chemicals. This document discusses recommended aerial application equipment, particularly about hopper features, and states in part: A large air vent is required to assure uniform flow during spraying and to prevent tank collapse or reduced flow when jettisoning a load. A large spring-loaded flapper valve is satisfactory, but a preferred vent is a tube in the top of the tank, projecting upward a few inches, then curving downward, and out through the bottom of the fuselage. This type of vent confines accidental overflow during loading, so chemicals fall free of the aircraft, without contaminating the cockpit or loading crew. It also keeps the chemicals away from the pilot during application maneuvers. The National Agricultural Aviation Association has a Fly Safe Campaign that publishes safety messages for the aerial application community on a recurring basis. The Fly Safe Campaign message for August 10, 2020, discusses chemical mixtures in hoppers and states in part: Many crop consultants like to recommend complex tank mixtures of various pesticides, fertilizers, and adjuvants. You may have sprayed some of the individual products before, but not the exact combination being requested. If you’re unsure of how the mixture will react, do a jar test to verify compatibility. Foaming, toxic fumes, exothermic reactions, physical and other chemical incompatibilities may result. Tank cleaning agents that have not been thoroughly rinsed from the hopper may also contribute to dangerous chemical reactions. Labels should provide warnings for any known issues when using the product. Manufacturers, however, may not be aware of every combination in which their product might be used. Read the labels, and if you have any questions, reach out to your local company representatives to get those questions answered before you fly. Don’t let spray mixtures lead to an accident. The Kugler KQ-XRN Technical Sheet discusses precautions when using the chemical and states: Use caution when mixing KQ-XRN with phosphate, sulfur, humic acid, and products containing glyphosate, a chemical foaming reaction may occur. Kugler recommends always performing a simple jar test when mixing KQ-XRN with any pesticides and fertilizers. TESTS AND RESEARCHMembers from the Colorado Agricultural Aviation Association conducted postaccident testing with a plastic container containing a chemical mixture, similar to what was carried in the accident airplane’s hopper. The chemical mixture was comprised of two ounces of glyphosate and eight ounces of low-salt nitrogen fertilizer. The initial response of combining the two chemicals was a thin, white layer that formed over the top of the mixture. The mixture was then agitated with a pole, like chemicals being agitated inside a hopper. The result was foam forming immediately and filling the container to about the 30-ounce level within a few seconds. An internet hyperlink to a video of the test is in the public docket. ORGANIZATIONAL AND MANAGEMENT INFORMATIONReid Aviation & Aerial Spraying, LLC is a 14 CFR Part 137 aerial application operator based in Springfield, Colorado, that solely utilized the accident airplane for aerial application in eastern Colorado. The 14 CFR Part 137 operating certificate for Reid Aviation & Aerial Spraying, LLC was managed by the FAA Denver Flight Standards District Office, Denver, Colorado. FAA Advisory Circular 137-1B Certification Process for Agricultural Aircraft Operators contains information on the certification process for 14 CFR Part 137 operations. The document does not contain guidance on chemical mixture reactions or the potential for windshield contamination due to chemicals. 14 CFR Part 137 does not require operators to have a Safety Management System.
The pilot’s loss of visibility in the cockpit due to foam created by the chemicals loaded in the hopper, which resulted in collision with terrain. Contributing to the accident was the combining of chemicals known to produce foam and the pilot’s failure to perform a jar test prior to flight as recommended.
Source: NTSB Aviation Accident Database
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