19990607023849A

(.19) On June 7, 1999, at 0900 hours local time, a Hughes 369HS, N4278M, crashed into the pacific ocean following separation of the tail rotor gear box approximately 300 miles southwest of majuro in the marshall islands. The helicopter, owned and operated by hoffman helicopters, yona, guam, was destroyed. Both the commercial pilot/mechanic and the observer suffered minor injuries. The local flight was conducted under the provisions of 14 CFR part 91 as a tuna spotting operation, and had originated from a fishing vessel about 0845. Visual meteorological conditions prevailed and no flight plan was filed. According to the operator, the pilot reported that he was flying at 600 feet above the water. He felt a vibration and decided to decrease his speed in order to assess the problem. The vibration increased and the tail rotor gearbox broke away from the airframe. The helicopter started spinning, nosed down, and impacted the water on the pilot's side (left side). The ship was approx 1 hour away from the accident site. The pilot and observer had life jackets on, and they employed the use of a life raft while waiting for rescue. The helicopter was recovered, except for the tail r otor system rotating components and gearbox, and taken aboard the ship. The operator reported that the helicopter had received an annual inspection approximately 35 days (75 flight hours) before the accident. He reported that during the annual inspection he removed the tail rotor blade abrasion strips because he felt that the strips had a history of problems on this series of helicopter and he felt it was better to remove the strips all together. He stated that he knew that this ation made the aircraft noncompliant with the current airworthiness directives (ad's) regarding the abrasion strips. The operator further reported that about 2 days before the accident, the pilot/mechanic had reported two discrepancies to him. The pilot noted that the paint was cracked in the area where the tip cap of the tail rotor blade joins the blade skin and stateed that it looked as if the cap had shifted. He applied structural glue to mend the crack. The pilot also noted that the exhaust stack had a crack in the center area, inside toward the back. He applied glue and a patch. Following recovery of the helicopter, the oerator reported that all four studs, which secure the tail rotor gearbox, were found sheared off. He also reported that "chunks" were missing from the exhaust stack. This accident was reported to the safety board by the san francisco international field office (ifo) on July 14, 1999.