On February 14, 2000, at 1700 local meridian time, a Hughes 369HS, N717ST, made a precautionary landing due to engine problems in international waters on the Pacific Ocean about 500 miles north of Papua, New Guinea. The helicopter, operated by O'Hara Helicopters, Inc., under 14 CFR Part 91 as a fish spotting operation, subsequently sank in deep water after rolling over in a large ocean swell. The pilot, who held an Australian commercial pilot certificate, and one passenger were not injured. Visual meteorological conditions prevailed for the aerial observation flight. The flight originated from a fishing vessel at an unknown time. In the pilot's written statement to the Safety Board, he reported that this was the third flight of the day. After takeoff, at 100 feet, he felt a metal-on-metal grinding sensation through the cyclic and then a loud noise. The pilot noted that prior to the precautionary landing the helicopter responded "abnormally" to control inputs. He elected to land immediately on the water instead of attempting to return to the vessel due to safety precautions. The pilot stated that the ocean conditions were rough and after exiting the helicopter it was overturned by a large swell and sank. The pilot and observer were rescued from the water by the fishing vessel. According to an inspector from the Federal Aviation Administration (FAA) International Flight Operations (IFO) division, who reviewed the FAA pilot certification database, the pilot did not possess a U.S. flight certificate.