Hughes TH-55 N74914 accident near Pittsfield, Pennsylvania

Probable cause

The student pilot's failure to maintain helicopter control during an encounter with loss of tail rotor effectiveness.

NTSB analysis

According to the student pilot, who had about 36 hours total flight time, he had completed a solo flight earlier in the day that included seven takeoffs and landings. After refueling, he completed a local flight and returned to the departure airport, where he initiated an approach that terminated "perfectly" in a normal hover. However, the helicopter then "started spinning to the right," and the spin could not be arrested with full application of left pedal. The pilot stated that he then increased collective pitch and the corresponding increase in engine power aggravated the spin. He then attempted a hovering autorotation, but the helicopter landed hard, rolled over on to its side, and was substantially damaged. A witness described the helicopter as it approached "flying somewhat erratically" about 40 feet above the runway. The helicopter was "twisting" to the left and right as it hovered "shakily" closer to the runway. The helicopter noise increased, the nose pitched up, the main rotors struck the ground, and the helicopter came to rest on its side. A detailed examination of the wreckage revealed no preimpact mechanical malfunctions or anomalies that would have precluded normal operation. A Federal Aviation Administration advisory circular stated that loss of tail rotor effectiveness (LTE) is a critical, low-speed aerodynamic flight characteristic which could result in an uncommanded rapid yaw rate which does not subside of its own accord and, if not corrected, could result in the loss of aircraft control. Further, any maneuver that required the pilot to operate in a high-power, low-airspeed environment with a left crosswind or tailwind would create an environment where unanticipated right yaw may occur. The nearest weather reporting station, which was located about 19 nautical miles from the accident site, recorded a 7-knot, left quartering tailwind for the landing on runway 9.

Text from the NTSB. Open the NTSB docket for ERA12CA357 for the full record.