On February 12, 2005, about 1540 eastern standard time, an experimental amateur built Johnson Revolution Mini 500 helicopter, N38DJ, sustained substantial damage when it collided with terrain following a loss of engine power, and subsequent emergency descent and landing at Isabela, Puerto Rico. The helicopter was being operated by the pilot as a local visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. The solo private pilot received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on February 13, the FAA aviation safety inspector who interviewed the pilot said the pilot told him the helicopter had a loss of engine power for an unknown reason. The pilot reported he attempted an autorotation to a building construction site, but had to maneuver hard to miss power lines. The pilot said that during the maneuver, the rotor rpm dropped, and he was unable to stop the descent prior to the collision with terrain. He said the helicopter sustained structural damage to the fuselage and rotor system. In a written statement to the NTSB dated May 19, the pilot said due to the extensive damage to the helicopter, he was unable to determine why the engine lost power.