NTSB Factual Report

On August 11, 2005, approximately 1800, Pacific daylight time, a Hughes 269A helicopter, N488MC, impacted the runway surface during a practice full-down autorotation at Ashland Municipal Airport, Ashland, Oregon. Neither the flight instructor nor his dual student were injured, but the aircraft, which is owned and operated by Crater Aviation, of Medford, Oregon, sustained substantial damage. The 14 CFR Part 91 instructional flight, which was being conducted in visual meteorological conditions, was practicing proficiency maneuvers in the pattern at Ashland Municipal at the time of the accident. No flight plan had been filed. There was no report of an ELT activation.

According to the instructor pilot, who had not conducted training at Ashland Municipal before, after initially departing Medford, Oregon, he and his student flew directly to Ashland to practice a series of proficiency maneuvers. After arriving at Ashland, they 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.

NTSB Probable Cause

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.