On April 22, 2005, approximately 1130 mountain daylight time, a Ross/Stonecipher Vans RV-6 single-engine homebuilt airplane, N345JE, sustained substantial damage during a forced landing following a loss of engine power while descending near Longmont, Colorado. The airline-transport pilot, who was the sole occupant, was not injured. The airplane was registered to a private individual and operated by the pilot. Visual meteorological conditions prevailed, and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 91 personal flight. The flight departed Skypark Airport, Bountiful, Utah, at 0920, and was destined for Longmont. In a telephone interview conducted by the NTSB investigator-in-charge (IIC), the pilot reported he purchased the airplane from a private individual in Utah. A day prior to the accident flight, the pilot test flew the airplane for approximately 40 minutes. Upon completion of the test flight, the pilot noted the engine oil had decreased approximately 1/2 quart. On the day of the accident, the pilot was flying the airplane to Kansas, with a planned intermediate fuel stop in Longmont. Prior to departure from Bountiful, the fuel tanks were topped off, and the pilot completed a preflight of the airplane. During the preflight, the pilot noted 6 quarts of oil in the engine. While descending from 12,500 feet to the Vance Brand Airport (2V2) near Longmont, the engine started to vibrate and subsequently, lost total power. The pilot reported no anomalies during the flight prior to the engine vibration. The pilot initiated a forced landing, and the airplane came to rest upright in a field approximately 3 miles from 2V2. After the forced landing, the pilot checked the oil and noted the oil "barely" measured on the dipstick. No evidence of oil was noted in the engine cowling or along the bottom of the fuselage. The right wing sustained substantial damage to the spar, and the main landing gear were bent. The airplane was recovered to the facilities of Beegles Aircraft, Greeley, Colorado, for further examination by the NTSB. On May 4, 2005, at the Beegles Aircraft facility, the Lycoming IO-360-A1A engine was examined by the NTSB IIC. Examination of the engine revealed approximately 3 quarts of oil in the engine. A crack in the crankcase was noted below the number 2 cylinder, and no evidence of residual oil around the crack was noted. The two crankcase halves were separated, and all four connecting rod journals and connecting rod caps and straps displayed discoloration and heat signatures consistent with oil starvation. The number 2 and 3 connecting rod assemblies were fragmented and destroyed. No debris or contamination was noted within the crankshaft oil passages. The crankshaft main bearings were secure and the main journals were undamaged. No discoloration was noted in the cylinder bores and the piston rings were intact. According to the Champion Spark Check-A-Plug Chart, the electrodes displayed signatures consistent with normal operation. The airplane was equipped with a Christen inverted oil system. Examination of the inverted oil system's separator revealed a black residue in the unit which also partially blocked the separator ports. According to Lycoming Service Instruction No. 1397, "Overflow Oil From Breather Fitting of Inverted Oil System," reports had been received from the field of oil being exhausted overboard through the breather fitting. The loss of oil in that manner could cause the engine to become inoperative in a short period. The loss of oil from the breather fitting could be caused by an excessive amount of residue in the oil separator and oil line. The instruction states, "As a means of forestalling any problems that may arise from residue in the inverted oil system, it is recommended that the oil system be disconnected from the engine and flushed with a petroleum solvent...every 300 hours of operation, or at anytime there is evidence of oil being discharged from the breather fitting." A review of the maintenance records revealed the engine had accumulated 829 hours since major overhaul. The most recent conditional inspection was completed on October 7, 2004, at a tachometer time of 790 hours. The tachometer time at the time of the accident was 797 hours. According to a mechanic, the engine oil and filter had been changed prior to the pilot's test flight. In addition, the mechanic completed a compression check and noted "normal" compression on all cylinders. No logbooks entries were noted for compliance with Lycoming Service Instruction No. 1397; however, no entry was required by Federal Aviation Regulations.