Incident Overview
A helicopter pilot was performing a practice autorotation when he noticed an abnormal sensation during the maneuver. According to the pilot's report, he began the practice autorotation by lowering the collective fully and reducing the throttle setting to a point where the engine RPM and rotor RPM needles split. He verified the needle split but stated that "something didn't feel normal."
Decision to Abort
Upon sensing the abnormality, the pilot decided to abandon the maneuver and added power to recover. He recalled that at the time of recovery, the engine and rotor RPM needles had synchronized and were at approximately the right clock position on the tachometer face. However, he then became aware of an extremely high descent rate.
Aircraft Manual Procedure
The pilot flight manual for the aircraft describes the practice autorotation procedure: "Split the needles by lowering the collective while maintaining throttle setting. The throttle correlation will establish a high idle rpm (approximately 2000 rpm) which will aid in preventing the engine from loading up or stalling during recovery."
No Mechanical Issues Found
No apparent preexisting anomalies were detected with respect to the aircraft or systems. The pilot's written report did not list any mechanical malfunction. The incident occurred during a routine training flight, but specific aircraft details, location, and date were not provided in the report.