Primary finding
Probable cause
The student pilot's improper flare while performing an autorotation and the flight instructor's delayed remedial action to correct the high sink rate, which resulted in a hard landing.
Investigator assessment
Analysis narrative
The flight instructor was providing primary helicopter instruction to a fixed-wing pilot on how to conduct 180-degree autorotations. The instructor said the pilot entered the flare lower to the ground than usual and began to descend. By the time the instructor noticed the high descent rate, it was too late for him to recover and he was only able to apply full-up collective to cushion the impact. The helicopter landed hard spreading the skids. During the landing and the main rotor blades flexed downward and severed the tailboom.
Source record
Factual narrative
The flight instructor was providing primary helicopter instruction to a fixed-wing pilot on how to conduct 180-degree autorotations. The instructor said the pilot entered the flare lower to the ground than usual and began to descend. By the time the instructor noticed the high descent rate, it was too late for him to recover and he was only able to apply full-up collective to cushion the impact. The helicopter landed hard spreading the skids. During the landing and the main rotor blades flexed downward and severed the tailboom.