NTSB Factual Report

On September 3, 1997, at 1130 central daylight time, a Schweizer 164B, N8326K, piloted by a commercial pilot, was destroyed during a collision with high tension electrical wires, the ground and post-impact fire. The 14 CFR Part 137 flight was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot was seriously injured, but succumbed to chemical poisoning 8-days after the accident. The flight departed Larimore, North Dakota, exact time unknown.

The accident flight was the pilot's third aerial application flight of the day. The pilot was spraying a herbicide known as Gromoxone Extra on a field of pinto beans. According to the operator, the pilot had been spraying this chemical compound on his previous flights. He said the pilot's flying routine was to make swath runs parallel to the bean rows. As the pilot neared the field's edge, he would begin a 180-degree climbing turn and make another swath run parallel to the previous one. The swath runs could overlap each other at times, according to the operator.

The airplane flew about 200-yards beyond the field's end before starting its climb. As the airplane flew under the electrical power lines, it began a climb. Its top wing and engine collided with a 2-inch diameter electrical line. The airplane went out of control and fell to the ground. The airplane burned upon ground impact. The pilot removed himself from the burning wreckage and was subsequently taken to the hospital.

According to an eye witness, the airplane began a climb and it "...suddenly started to spin end for end in a circular motion. This plane then went north and appeared to be upside down and going backwards. An explosion happened in midair... ." The Grand Forks County Sheriff's Department report stated, "The plane was northbound when it hit the wire, it was spinning around and going straight up when it tipped over upside down and appeared to move backwards and then flipped over, right-side up, before it struck the ground and spun around, facing south. There was a cloud of gray smoke before the airplane struck the ground and then there was a lot of black smoke."

The operator of the airplane said he did not understand why the pilot did not begin his climbing turn when he neared the field's edge as was his habit. He said the pilot acted as though he was preoccupied with something or not aware of where he was.

The on-scene investigation revealed control continuity for all 3-axis' of N8326K. A 6 to 8-foot section of electrical power line was imbedded in the leading edge of N8326K's lower left wing The airplane's top wing had separated near the fuselage centerline. The left wing was forward of, and parallel to, the fuselage. The engine had separated from the fuselage and was at the front of the fuselage, nose down. The propeller had separated from the engine. Its blades had chord-wise scratching on their top surfaces. The fuselage and inner half of the wings had all the covering burnt away from their framework.

The manufacturer of Gramoxone Extra said it is a herbicide. The manufacturer provided the Material Safety Data Sheet (MSDS) concerning the chemical compound. Its active ingredient is paraquat dichloride, a highly toxic substance according to the MSDS. According to the MSDS section entitled "Health Hazard Assessment," this compound can cause "...progressive kidney failure, liver complications, and pulmonary insufficiency may follow. Death is usually due too respiratory failure secondary to pulmonary fibrosis." The health assessment section continues, "Skin absorbsion [of paraquat] ... is faster through injured or damaged skin. Death ensues after respiratory failure." The MSDS health section continues, "Effects of overexposure: These circumstances can result in systemic poisoning which is severe, progressive, and frequently terminates in irreversible lung damage and death." The irreversible lung damage results in suffocation.

The manufacturer's specimen label said that Gramoxone Extra is, "Fatal to Humans... fatal if swallowed, inhaled or absorbed through the skin... ." A review of the specimen label information and the MSDS did not reveal the amount of this chemical compound that would cause a fatal reaction.

A representative of the manufacturer was asked how small amounts of Gromoxone, if ingested, would have affected the pilot's performance. The representative's replied that they do not know what affects low level ingestion would have had on a pilot's flight performance.

The autopsy on the accident pilot was conducted by Dr. Solem at the Regions Hospital, St. Paul, Minnesota, on September 11, 1997. The report stated the pilot's death was caused by: "Diffuse alveolar damage." Webster's Collegiate Dictionary, Ninth New Edition define's Alveolar as "...the air cells of the lungs."

The Federal Aviation Administration's Civil Aeromedical Institute (CAMI) toxicology examination said that carbon monoxide and cyanide analysis "...was not performed due to a lack of suitable specimen." The CAMI report continues by stating there was not ethanol detected in the blood. Their examination did identify 0.20 (ug/ml, ug/g) morphine in the blood sample. According to the medical records, the pilot was administered morphine while at the hospital. The blood sample used for the CAMI toxicological examination were taken after the pilot had been administered the morphine. Tests for other chemical substances was not performed because the sample received from the Regions Hospital was not large enough to complete CAMI's required tests, according to a CAMI representative.

NTSB Probable Cause

the pilot delaying the swath run turnaround maneuver at the end of the field boundary, and his failure to maintain clearance between the airplane and the high tension wires. A factor was the pilot's inattentiveness regarding the time to begin the swath run turnaround maneuver.