Benson, AZ, USA
N6641D
HUGHES OH-6A
The instructor pilot reported that they were practicing autorotations to the runway. During a straight-in autorotation at approximately 200 feet above ground level, the instructor called for an increase in throttle to bring rotor rpm into the normal operating range in preparation for landing. Between 200 feet and 100 feet agl, the instructor assisted the flying pilot with the throttle increase when he realized that the pilot had delayed throttle application. The flying pilot then initiated the flare at approximately 50 feet agl. The flying pilot leveled the helicopter and applied collective to slow the descent rate. Upon realizing that the descent rate had not been checked prior to beginning the flare, the instructor joined the flying pilot on the controls. The helicopter landed hard on the runway and bounced, rotated to the left of runway heading as it touched down a second time, resulting in the collapse of the right landing skid. The pilot reported that were no mechanical anomalies with the flight control systems.
On June 4, 2009, at 0850 mountain standard time (MST), a Hughes OH-6A, N6641D, experienced a hard landing at Benson Municipal Airport, Benson, Arizona. The public-use flight was operated by U.S. Customs and Border Protection as a pilot training flight under the provisions of Title 14 of the Code of Federal Regulations, Part 91. Neither commercial pilot was injured, and the helicopter was substantially damaged. Visual conditions prevailed, and no flight plan had been filed. The flight originated at Tucson International Airport, Tucson, Arizona, at 0715. The instructor pilot reported that they were practicing autorotations to the runway. During a straight in autorotation at approximately 200 feet agl, the instructor called for an increase in throttle to bring rotor rpm into the normal operating range in preparation for landing. Between 200 feet and 100 feet agl the instructor assisted the flying pilot with the throttle increase when he realized that the pilot had delayed throttle application. The flying pilot initiated the flare at approximately 50 feet agl. The flying pilot leveled the helicopter and applied collective to slow the descent rate. Upon realizing that the descent rate had not been checked prior to beginning the flare, the instructor joined the flying pilot on the controls. The helicopter landed hard on the runway and bounced, rotated to the left of runway heading as it touched down a second time, resulting in the collapse of the right landing skid. The helicopter came to rest on the runway heading 150 degrees to the left of runway heading. Examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed structural damage to the right landing skid and the fuselage of the helicopter. The pilot indicated that there were no mechanical anomalies with the flight control systems prior to the flight. Weather conditions reported at Fort Huachuca, Arizona, at 0755 MST, 24 miles to south of the accident location, indicated that the wind was variable at 1 knot, and visibility was 50 miles with a ceiling of 20,000 feet.
The pilot under instruction's inadequate autorotation technique and the instructor pilot’s delayed remedial action to arrest the rate of descent of the helicopter while in an autorotation flare.
Source: NTSB Aviation Accident Database
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