WPR09LA254

Prior to departure, the pilot performed an engine run-up and noted that the performance appeared to be normal. During the takeoff ground roll, the pilot reported that the airplane seemed sluggish. Shortly after the airplane lifted off the runway surface, the engine experienced a partial loss of power. The airplane began to buffet and the pilot lowered the nose to prevent a stall. The airplane was losing altitude and he maneuvered it for an off airport landing. After clearing power lines, he made the forced landing in a vineyard adjacent to the airport. During the post accident engine inspection no mechanical anomalies were noted that would have precluded normal operation.

On May 21, 2009, about 1655 Pacific daylight time, a Mooney M20J, N4718H, experienced a loss of engine power after takeoff from runway 13, and made an off airport landing in a vineyard at the Healdsburg Airport (O31), Healdsburg, California. The pilot/owner operated the airplane under the provisions of 14 Code of Federal Regulations Part 91, as a personal flight. The airplane sustained structural damage during the forced landing. Visual meteorological conditions prevailed for the local area flight, and no flight plan had been filed. The flight was destined for Charles M. Schulz – Sonoma County Airport (STS), Santa Rosa, California. According to the pilot, the previous weekend he had noticed that the number two cylinder had been running hotter than normal. He flew the airplane to Healdsburg Airport to have his mechanic inspect the airplane. The pilot reported that the mechanic noted that the fuel injector for the number two cylinder was partially clogged. The pilot stated that he had been finding bits of debris in the fuel sump during fuel checks; the mechanic told him that he would check all the screens and fuel injectors at the next annual inspection in July. The pilot and mechanic performed a ground run up, and noted that the number three cylinder was now running "somewhat warmer [than] the rest, but it came more in line during warm up." The airplane was shut down, and they exited the airplane. The pilot refueled the airplane and then prepared the airplane for takeoff. He started the engine, and performed a run up and magneto check with no discrepancies noted; and no popping noises heard. He powered up for takeoff, and noted that on the takeoff roll the gauges were in the green, but the airplane seemed "sluggish," which the pilot attributed to the full fuel tanks. The pilot stated that the airplane finally achieved rotation speed, but he was past the point of making a successful aborted takeoff. Seconds after the airplane lifted off, he knew something was not right. The airplane was "shaking slightly," and he had almost no power for the climb out. He lowered the airplane's angle of attack, and started to look for places to land. He did not feel that he would be able to make it to Santa Rosa due to the instability of the airplane and lack of power, so he made a gradual right turn back toward the runway. At that point, he looked at the engine analyzer, and saw that the number three cylinder was at the "bottom of the graph." He turned on the boost pump, but there was no effect on the engine. The airplane was losing altitude, and he maneuvered the airplane for an off airport landing. After clearing power lines, he made the forced landing in a vineyard adjacent to the airport. The responding deputy from Sonoma County Sheriff's Department interviewed the mechanic. The mechanic reported that he had performed maintenance on the number two cylinder. He found debris in the cylinder and cleaned it out. He returned the airplane to service; while taxiingto get fuel, he heard a "popping sound," but did not mention it to the pilot. The airplane was fueled, and the pilot dropped the mechanic at his shop. The flight departed shortly thereafter. An inspection of the engine by the National Transportation Safety Board investigator revealed no additional mechanical problems. During the inspection, manual rotation of the crankshaft produced thumb compression in all the cylinders in proper firing order and the accessory gears rotated. The fuel injectors were removed and were clear of debris.