Aviation Accident Summaries

Aviation Accident Summary MIA02LA029

Hernando, MS, USA

Aircraft #1

N129BC

Hughes OH-6A

Analysis

The flight instructor stated that he and the dual student were performing autorotations, and the student flared the helicopter at an altitude of about 65 feet, and applied initial collective pitch control input at about 10 feet, leveling the helicopter. The instructor said that the aircraft was about 2 feet high, and still moving forward, and at that point the student did not let the helicopter settle to the ground, but continued to apply collective pitch control input. He said he stopped the student from applying collective pitch control input and the aircraft descended, but during the descent the student applied aft cyclic control input, causing the aircraft to hit on the heels of the skids, while rotor rpms were low. The instructor said, that as a result, the main rotor blades contacted the tail boom, severing the tail just forward of the tail rotor gear box.

Factual Information

On November 25, 2001, about 1600 central standard time, a Hughes OH-6A helicopter, N129BC, registered to, and operated by the Desoto County Sheriff's Office, as Title 14 CFR Part 91 instructional flight, made a hard landing at a private field in Hernando, Mississippi. Visual meteorological conditions prevailed, and no flight plan was filed. The student pilot, and the airline transport-rated flight instructor were not injured, and the helicopter incurred substantial damage. The flight originated from Hernando, Mississippi, the same day, about 1610. The flight instructor stated that they had been practicing autorotations and during the last autorotation the student was flying the helicopter. The instructor said that the airspeed on final was 70 knots, and that the student flared the helicopter at an altitude of about 65 feet, and applied initial collective pitch control input at about 10 feet, leveling the helicopter. He said that the helicopter was about 2 feet high, and still moving forward, and at that point the student did not let the helicopter settle to the ground, but continued to apply collective pitch control input. The instructor said he stopped the student from applying collective pitch control input, and the helicopter started to descend, but the student applied aft cyclic control input, and the helicopter contacted the ground on the heels of the skids, while main rotor rpms were low. He said the main rotor blades contacted the tail boom, severing the tail just forward of the tail rotor gear box. According to the flight instructor, prior to the accident, there were no failures or malfunctions to the helicopter, or any of its systems.

Probable Cause and Findings

The flight instructor's improper supervision of the dual student during a practice autorotation landing by allowing an excessive aft pitch attitude and low main rotor rpm conditions to develop during the landing/flare touchdown, which resulted in the helicopter making a hard landing on the heels of the skids, and the main rotor severing the tail boom.

 

Source: NTSB Aviation Accident Database

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