Incident Overview
A helicopter experienced a loss of rotor RPM shortly after takeoff during an agricultural operation. The incident occurred after the pilot had dispensed eight loads, refueled, and taken off with a ninth load. The pilot suspected a vapor lock issue, noting that he had turned off the fuel pump during refueling and could not recall reactivating it before departure.
Sequence of Events
About 4 to 6 seconds into the flight, while approaching transitional lift at approximately 6 feet above ground level, the helicopter began to vibrate and immediately lost rotor RPM. The pilot initiated a landing straight ahead, but the helicopter yawed to the left and touched down level in a crabbed-to-the-left attitude. The right skid collapsed, and the helicopter rolled to the right. The main rotor struck the ground, severing the tail boom and a 5-inch drive line.
Examination Findings
Post-incident examination revealed no preimpact part failure or malfunction. The pilot's suspicion of vapor lock, stemming from the fuel pump being switched off, was noted but not confirmed as a cause. The aircraft sustained substantial damage, including the collapsed right skid and separated tail boom.