What happened
On June 4, 2009, at 0850 mountain standard time, a Hughes OH-6A, registration N6641D, performed a hard landing at Benson Municipal Airport in Benson, Arizona. The flight, operated by U.S. Customs and Border Protection, was a pilot training flight under Part 91 regulations. The flight had departed from Tucson International Airport earlier that morning.
The crew was practicing autorotations to the runway. During a straight-in autorotation, the instructor pilot called for an increase in throttle at approximately 200 feet above ground level (agl) to bring rotor RPM into the normal operating range. The instructor assisted with the throttle increase between 200 feet and 100 feet agl after noticing the flying pilot had delayed the application.
The flying pilot initiated the flare at approximately 50 feet agl, leveling the helicopter and applying collective to reduce the descent rate. After realizing the descent rate had not been checked before the flare, the instructor also took control. The helicopter struck the runway with significant force and bounced. Upon the second touchdown, the aircraft rotated left of the runway heading, causing the right landing skid to collapse. The aircraft came to rest 150 degrees left of the runway heading. There were no injuries to the two pilots, but the helicopter sustained substantial damage.
The investigation
An FAA inspector examined the aircraft and found structural damage to the fuselage and the right landing skid. The pilot reported that the flight control systems showed no mechanical anomalies prior to the accident. Weather at the time was visual meteorological conditions (VMC) with 50 miles of visibility and winds of approximately 1 knot.