Incident Overview
A helicopter sustained a hard landing during a training flight focused on low-altitude engine failure and autorotation maneuvers. The Certified Flight Instructor (CFI) reported that the student pilot had rolled the throttle to flight idle in preparation for the maneuver. As the helicopter descended, the CFI heard the engine spool down but did not observe any split between the rotor and engine tachometer needles.
Sequence of Events
The CFI realized that the student had not completely lowered the collective and immediately took over the flight controls. He attempted to regain decayed rotor rpm by rolling the throttle to full flight rpm, lowering the collective, and raising the nose to build inertia in the blades. However, he determined that the engine did not have enough time to spool up. He then reduced the throttle to flight idle, leveled the skids, and used the pedals to control yaw in preparation for touchdown.
Outcome
The helicopter landed hard with forward speed and came to rest upright. The maneuver had been initiated at 100 feet above ground level (AGL) with a targeted recovery at 20 feet AGL. The CFI stated that there were no mechanical anomalies with the helicopter.