Primary finding
Probable cause
The pilot's failure to maintain adequate altitude while maneuvering. Contributing factors were the failure of the helicopter's lights during the night flight and the effect of that failure on the pilot's visual perception.
Investigator assessment
Analysis narrative
The pilot reported that a few minutes after taking off for a nighttime agricultural spray flight over an alfalfa field, the ground illumination lights in his helicopter went out. At the time, he was descending and maneuvering close to the ground on a spray run. The pilot reported that he did not see the field before impacting it with the spray boom. The helicopter rolled over and was substantially damaged.
Source record
Factual narrative
The pilot reported that a few minutes after taking off for a nighttime agricultural spray flight over an alfalfa field, the ground illumination lights in his helicopter went out. At the time, he was descending and maneuvering close to the ground. The pilot reported that he did not see the field before impacting it with the spray boom. The helicopter rolled over and was substantially damaged.