NTSB Factual Report

On August 23, 2007, at 0815, an Air Tractor AT-301, N3163T, was substantially damaged during a forced landing in Vandemere, North Carolina. The airline transport pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local aerial application flight conducted under 14 Code of Federal Regulations Part 137.

The pilot reported to a Federal Aviation Administration (FAA) inspector, that he departed from a private grass strip in Fort Barnwell, North Carolina, about 0740, with 40 gallons of fuel. He flew to a location 37 miles away, and then sprayed 84 acres in a "race track pattern." While the airplane was in a turn, the pilot heard a “loud squeal,” the engine lost power, and the pilot prepared for a forced landing to a cornfield. During the landing, the airplane nosed-over and sustained substantial damage to the wings.

The pilot additionally stated that during the flight he leaned the mixture to 42 to 45 gallons per hour.

Examination of the airplane by the FAA inspector revealed the airplane came to rest inverted. A small amount of fuel was observed on the ground, emanating from the right wing vent. An approximate 7-inch diameter area of the ground near the vent was moist with fuel.

Once the airplane was positioned upright, the inspector rocked the wings of the airplane and did not hear any fuel in the tanks. He also removed the fuel caps and did not observe any fuel in the intact tanks. The inspector also did not observe any leaks in the fuel system.

The propeller rotated freely, and no mechanical noises were heard during the rotation. Examination of the exhaust manifold and fuselage revealed no indication oil leaks.

The throttle control was observed in the "mid-range" position, the mixture control was in the "leaned" position, and the propeller control was in the "full forward" position.

The radial engine was sent to an engine repair station for complete teardown. The results of the examination revealed the supercharger bearings failed and were ingested into the engine case. According to the Chief Inspector at the teardown facility, the exact cause of the supercharger failure could not be determined. He also stated the recommended time to overhaul this model engine was 1,200 hours.

Examination of the airframe and engine logbook revealed a “pre-certification inspection” on January 30, 2007, and the airplane had accumulated 23 hours since that date. The most recent annual inspection was completed on March 2, 2007, at a tach time (and time since overhaul) of 765 hours. No anomalies were noted during the inspection, and no additional maintenance was logged after the inspection.

A review of the type certificate for the airplane revealed it had a capacity of 76 gallons of fuel, 38 in each tank, 6 of which were unusable.

The property owner who requested the pilot’s aerial application services submitted a statement to the Safety Board, through the pilot’s attorney, 10 months after the accident. In the statement he reported that the pilot had applied “several loads” to his field, and prior to his last load, the property owner put fuel into the accident airplane. He stated that he added fuel to the left wing “within two to three inches from the top.”

The property owner watched the airplane depart, and heard the airplane spraying the field about 2 miles away. About 20 minutes later, he heard the sound of the airplane cease, and shortly after received a call from the pilot stating he had an engine failure and impacted the bean field.

Upon arrival to the field, the property owner observed the “lowest wing to the ground” leaking fuel, and he reported that 10 months after the accident there has been no growth in the area of the fuel leakage.

Weather reported at an airport 10 miles to the southwest of the accident site, at 0754, included wind from 060 degrees at 6 knots, 9 miles visibility, scattered clouds at 2,100 feet, temperature 24 degrees Celsius, dew point 22 degrees Celsius, and an altimeter setting of 30.14 inches of mercury.

NTSB Probable Cause

The loss of engine power due to the failure of the supercharger bearings.