NTSB Identification: SEA05CA168.
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Accident occurred Thursday, August 11, 2005 in Ashland, OR
Probable Cause Approval Date: 10/27/2005
Aircraft: Hughes 269A, registration: N488MC
Injuries: 2 Uninjured.
NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.
After arriving at Ashland Airport, the dual-student and the instructor performed hovering exercises, hovering autorotations, and hovering loss of tail rotor effectiveness (LTE) maneuvers. They next performed some stuck-pedal exercises on a parallel taxiway, and then performed a series of run-on landings to runway 30. The last maneuver was a full-down autorotation to runway 30. The maneuver was initiated about 300 feet above ground level (agl), and the flare was started about 50 feet agl. According to both the student and the instructor, the flare and touchdown were performed correctly, and were uneventful. The helicopter then slid directly down the runway for about 150 feet, but just prior to coming to a normal stop (at about five knots), the left skid sank into some soft tar on the runway surface. The helicopter then veered abruptly to the left, and rolled over onto its right side. When the occupants got out of the helicopter, they found that the tar in the area where the aircraft rolled over was thick, soft, and sticky. In a post accident interview, both the student and the instructor said that when they departed Medford for Ashland, they were not aware that the Ashland Airport runway surface was made of chip-seal (a combination of tar and crushed rock). According to the instructor, although the runway surface did not seem to present any problem during the run-on landings, he did notice that when they came around the pattern for subsequent maneuvers that he could see imprints in the surface from the previous skid contacts. The instructor further noted that the temperature at the time of the accident was just over 90 degrees, and that on the previous two days the temperature had reached about 100 degrees. He also stated that the runway surface was inconsistent, in that some areas contained more rock in the composite, and some areas contained more tar in the composite.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The inability of the dual student to maintain directional control of the helicopter during the landing roll when the left skid sank into an area of thick, soft, sticky tar, and the instructor pilot's improper decision to perform a full-down autorotational landing to a surface which had already shown itself to be soft. Factors include a soft, sticky landing surface, and high temperature that contributed to the softening of the landing surface. Full narrative available
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