On August 21, 2012, approximately 1740 central daylight time, a Thorp T-18 experimental amateur-built airplane, N2443, sustained substantial damage when it impacted terrain during an attempted takeoff from Gilmer Municipal Airport (JXI), Gilmer, Texas. The airline transport pilot sustained minor injuries, and the pilot-rated passenger sustained serious injuries. The airplane was registered to McClendon Associates and operated by the pilot under the provisions of the 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight was destined for Denton, Texas. According to the pilot, the fuel tanks were 3/4 full. Prior to takeoff, the pilot completed an engine run up with no problems noted. Shortly after takeoff, the engine rpm rolled back from 2,300 to 1,500 rpm. The pilot attempted to restore engine power; however, he was unsuccessful. The pilot executed a forced landing to tree-covered terrain. The airplane impacted several trees and came to rest upright. A review of the engine maintenance records showed the engine underwent a conditional inspection on September 1, 2011, at a tachometer time of 930.9 hours. The engine was overhauled on March 23, 2003, at a tachometer time of 593.4 hours. On September 21, 2012, at the facilities of Air Salvage of Dallas, Lancaster, Texas, the engine was examined under the supervision of a Federal Aviation Administration inspector. Examination of the engine revealed that the fuel line from the fuel pump to the metering unit was disconnected at the metering unit. No other anomalies were noted with the engine during the examination.