On May 13, 1989, a Hiller UH-12E (registration N5594N) was involved in an aviation accident near Mack, CO. Investigators recorded the probable cause as: The pilot's failure to maintain adequate altitude during the agricultural application, which resulted in the helicopter contacting the crop and rolling over. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter descended too low during an agricultural application pass, causing its skids and spray equipment to strike alfalfa before rolling over in the field.
What happened
The pilot was conducting a swath run for agricultural purposes when he allowed the helicopter to descend below a safe altitude. The aircraft's skids made initial contact with an alfalfa crop, followed immediately by the spray apparatus striking the vegetation. Unable to regain sufficient lift, the helicopter continued its descent into the ground and subsequently rolled over.
The investigation
An eyewitness observed the incident and confirmed the pilot's account of the sequence of events. However, this witness declined to provide a formal written statement for the record.
Probable cause
The pilot's failure to maintain adequate altitude during the agricultural application, which resulted in the helicopter contacting the crop and rolling over.