Primary finding
Probable cause
The pilot's inadequate in-flight planning that resulted in settling with power during an aerial application turn-to-reverse direction and collision with the ground. Factors were high density altitude and a wind shift.
Investigator assessment
Analysis narrative
During the aerial application turn-to-reverse direction to continue spraying chemicals, the helicopter began settling with power and collided with the ground. According to the pilot, "near triple digit" temperatures, a wind shift, and a steep 180-degree turn resulted in the power settling that could not be arrested prior to ground impact. The pilot also reported that the temperature over the unplanted field where he was executing the reverse turn was higher than over the corn field he had been spraying.
Source record
Factual narrative
On May 31, 2001, at 1136 hours Pacific daylight time, a Bell 47G-4A, N110DT, collided with the ground during an aerial application turn to reverse direction near Buttonwillow, California. The helicopter sustained substantial damage; however, the certificated commercial pilot was not injured. The helicopter was being operated by Inland Crop Dusters, Inc., as an aerial application flight under 14 CFR Part 137 when the accident occurred. The flight had originated in the Bakersfield area earlier that morning. Visual meteorological conditions prevailed at the time and no flight plan had been filed. The pilot was reported by Kern County Sheriff's Deputies to have been performing an aerial application flight when the helicopter crashed. According to the pilot, he was making a series of steep 180-degree turns between aerial application passes. He reported that on the last turn the helicopter began to "settle with power" and there was not enough time to recover. By his account, wind direction was a contributing factor. Wind speeds recorded at Bakersfield weather station were variable at 3 knots.