Incident Overview
On May 21, 2009, at approximately 1655 Pacific daylight time, a Mooney M20J, registration N4718H, experienced a loss of engine power after takeoff from runway 13 at Healdsburg Airport (O31) in Healdsburg, California. The pilot/owner was operating the airplane under 14 Code of Federal Regulations Part 91 as a personal flight. The airplane sustained structural damage during the subsequent forced landing in a vineyard adjacent to the airport. Visual meteorological conditions prevailed, and no flight plan had been filed. The intended destination was Charles M. Schulz – Sonoma County Airport (STS) in Santa Rosa, California.
Pilot Account
According to the pilot, the previous weekend he had noticed the number two cylinder running hotter than normal. He flew the airplane to Healdsburg Airport to have his mechanic inspect it. The mechanic found that the fuel injector for the number two cylinder was partially clogged. The pilot reported finding bits of debris in the fuel sump during checks; the mechanic stated he would inspect all screens and fuel injectors at the next annual inspection in July. A ground run-up showed the number three cylinder running somewhat warmer, but it normalized during warm-up. The airplane was shut down, and both exited. The pilot refueled and prepared for takeoff. The engine start, run-up, and magneto check revealed no discrepancies, and no popping noises were heard. During the takeoff roll, gauges were in the green, but the airplane seemed sluggish, which the pilot attributed to full fuel tanks.
Loss of Power and Forced Landing
The pilot reported that the airplane finally achieved rotation speed, but he was past the point of a successful aborted takeoff. Seconds after liftoff, he noticed the airplane shaking slightly and had almost no climb power. He lowered the angle of attack and began looking for landing sites. He felt unable to reach Santa Rosa due to instability and lack of power, so he made a gradual right turn back toward the runway. At that point, the engine analyzer indicated the number three cylinder at the bottom of the graph. He turned on the boost pump with no effect. The airplane continued losing altitude, and he maneuvered for an off-airport landing. After clearing power lines, he landed in a vineyard near the airport.
Mechanic Interview
The responding deputy from the Sonoma County Sheriff's Department interviewed the mechanic, who reported performing maintenance on the number two cylinder. He found debris in the cylinder and cleaned it. While taxiing to get fuel, he heard a popping sound but did not mention it to the pilot. The airplane was fueled, and the mechanic was dropped at his shop before the flight departed.
Post-Incident Inspection
An inspection by the National Transportation Safety Board investigator revealed no additional mechanical problems. Manual rotation of the crankshaft produced thumb compression in all cylinders in proper firing order, and accessory gears rotated. The fuel injectors were removed and found clear of debris.