On March 2, 2013, about 1500 Atlantic standard time, a Robinson R44 II helicopter, N834RC, operated by a private individual, was destroyed when it collided with powerlines and terrain while making an autorotation following a reported loss of main rotor RPM near Ciales, Puerto Rico. P. R. The private pilot received minor injuries. The flight departed from a field, near Yauco, PR, about 1420, and was destined for Fernando Luis Ribas Dominicci Airport (TJIG), San Juan, PR. Visual meteorological conditions prevailed, and no flight plan was filed for the flight. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. While enroute at about 700 feet above ground level, the pilot observed the rotor rpm decaying and immediately entered a 180 degree autorotation. The helicopter subsequently collided with high tension wires and then impacted terrain. A post crash fire consumed a significant portion of the helicopter. According to Federal Aviation Administration (FAA) records, the pilot held a private pilot certificate, with a rating for a rotorcraft-helicopter. The pilot’s most recent FAA third-class medical certificate was issued on February 19, 2013. The pilot reported 239 total hours of flight experience with 73 hours in the R44. The single-engine, single-rotor helicopter, serial number 11616, was powered by a Lycoming IO-540, 260-horsepower engine. An annual inspection was completed on October 1, 2012 at 743 total aircraft hours. Witnesses reported they saw a low flying helicopter making exploding noises and saw black smoke coming from it. The helicopter then collided with power lines, caught fire and crashed underneath the power lines. Examination of the engine by a FAA inspector revealed no external impact or fire damage to the cylinders or manifolds. The engine was free to move when examined by a FAA Inspector. Compression was confirmed on all six cylinders using a compression tester. The magnetos were not tested due to fire damage. Examination of the lower spark plugs revealed normal wear on all six plugs. The fuel injection servo was removed, and examined by an NTSB investigator in Ashburn, Virginia on April 15, 2013, and no anomalies were noted. At 1550, the weather observation at Mercedita Airport (TJPS), Ponce, Puerto Rico, 20 miles south of the accident site included wind from 150 degrees at 10 knots, 10 miles visibility, and a few clouds at 3,000 feet. The temperature was 29 degrees C, the dew point was 21 degrees C, and the altimeter setting was 29.99 inches of mercury.