Sikorsky 269C N2091E accident near Lumberton, New Jersey

Probable cause

The pilot's movement of the throttle to the idle detent at the beginning of a practice autorotation, which was contrary to procedures and resulted in the engine hesitating during the power recovery and a subsequent hard landing.

NTSB analysis

The pilot initiated a practice autorotation about 951 feet above ground level (agl), rolled off the throttle to the idle detent, and maintained 60 knots during the descent until 50 feet agl, at which time, he flared the helicopter. At the end of the flare, when the helicopter was about 20 to 30 feet agl, the pilot lowered the nose to level the helicopter, began to increase the collective, and rolled on the throttle for a power recovery. The pilot reported that, subsequently, the engine sounded like it was "bogging down" and that the engine rpm was not increasing enough for the helicopter to continue to come to a hover. The helicopter continued to descend and contacted the runway hard, which resulted in substantial damage to the vertical firewall. A postaccident engine run revealed no evidence of a preimpact failure or malfunction that would have precluded normal operation. According to the pilot's flight manual, when performing practice autorotations, the pilot should lower the collective while maintaining the throttle setting to prevent the engine from "loading up or stalling" during recovery. Therefore, it is likely that the pilot rolling the throttle to the idle detent at the beginning of the maneuver, which was contrary to procedures, resulted in the engine hesitating when power was applied for the recovery.

Text from the NTSB. Open the NTSB docket for ERA13LA300 for the full record.