NTSB Factual Report

On August 1, 2000, about 1147 Pacific daylight time, a Grumman G-164B, N6737K, collided with an electrical tower approximately 5 miles north of Tracy, California. The airplane was destroyed in the collision sequence. The certificated commercial pilot, the sole occupant, received fatal injuries. Haley Flying Service, Inc., operated the airplane during the agricultural flight under the provisions of 14 CFR Part 137. The flight departed the Haley Flying Service private agricultural strip about 1143. Visual meteorological conditions prevailed and no flight plan had been filed.

Witnesses stated that the airplane was making a turn when it appeared to stall, roll to the right, and collide with the top of a 300-foot-tall electrical transmission tower. The airplane's right wing was partially severed. Thereafter, they observed the airplane continue traveling about 130 yards before finally impacting the ground in an inverted attitude in an adjacent agricultural field. A fire erupted about 10 seconds after the airplane came to rest, and it partially consumed the wreckage.

According to Federal Aviation Administration (FAA) personnel, when the pilot initiated the flight the airplane was carrying 60 gallons of fuel and 300 gallons of nonflammable pesticide. The FAA reported that according to the pilot's ground-based "flagger" (who was also a pilot), the spray application flight profile called for the pilot to execute his first pass on the east side of the crop. After commencing the flight in this direction, the pilot made an abrupt midcourse directional change, as though he had elected to spray from another direction first. According to the flagger, following the abrupt course change, the airplane was headed toward the transmission tower. The flagger additionally reported that the pilot then raised the nose of the airplane to clear the tower. The airplane appeared to stall just before the collision.

During the subsequent wreckage examination, a portion of the airframe was found lodged in the top of the electrical tower at the point of initial impact. A wing segment was found severed and lay near the tower's base. Two transmission lines were downed and lay strewn about the main wreckage area. Pacific Gas and Electric Company personnel reported that, at the time of the accident, the lines were energized with 230,000 volts of electricity.

The manager of the FAA's Toxicology and Accident Research Laboratory reported finding evidence of tetrahydrocannabinol carboxylic acid (marihuana) in the pilot's blood at a level of 0.018 ug/ml. It was also found in his urine.

NTSB Probable Cause

The pilot's failure to maintain adequate clearance from obstacles while maneuvering during an aerial application flight.