HISTORY OF FLIGHT On September 8, 1995, about 1145 hours Hawaii standard time, a McDonnell Douglas 369D, N58388, operated by the Honolulu Fire Department (HFD) as a public-use aircraft, was substantially damaged during an emergency landing near Pearl City, on the island of Oahu, Hawaii. The pilot, the sole occupant, received serious injuries. Visual meteorological conditions prevailed for the local flight which originated at Honolulu International Airport at 1035 on the morning of the accident. The pilot was returning after completing an aerial survey of a brushfire. After crossing a ridgeline of the Koolau Mountains, the pilot reported feeling a bump, and then a vibration feedback through the antitorque pedals. The helicopter rotated about the vertical axis several times as the pilot attempted to land with power. The helicopter landed hard on the side of a ridgeline. The helicopter was being operated with the doors off. The pilot reported that his jacket was missing and that he had put it in the bench seat box in the aft compartment of the helicopter. The box was secured with hook-type latches, with a locking safety pin in one latch. The jacket was not found in the box. PERSONNEL INFORMATION The commercial instrument rated helicopter pilot reported a total flight time of 2,188 total flight hours, with 1,052 hours in the accident helicopter's make and model. The pilot's last biennial flight review was conducted on January 11, 1992. His last second-class flight physical was dated December 6, 1994. AIRCRAFT INFORMATION Postaccident examination of the helicopter revealed that the tail rotor boom had sheared off at the same area where the tail rotor driveshaft had sheared. The tail rotor blades exhibited minor damage. There was leading edge imprinting, paint loss, and abrasion strip disturbance noted on one of the tail rotor blades. TESTING AND RESEARCH Tests were conducted by the Honolulu Police Department (HPD) Scientific Lab of the material and fibers found on the leading edge of a tail rotor blade. There was a scuff mark on the same rotor blade that revealed a series of striations that are consistent with fabric impression damage. The material found on the leading edge of the blade was found to be a component consistent with polyester. Fibers found under the mylar tape abrasion strip were very similar to fibers from jackets worn by the HFD pilots. According to their report: "The microscopic examination of the scuff area of the rotor blade revealed a series of striations which are consistent with fabric impression damage. The instrumental analysis of this grey transfer material was identified to be a component consistent with polyester. Although no fibers could be identified in this area, based on the transfer pattern and type of substance present, this type of damage could be consistent with fabric transfers."