Cessna R182 N3138C accident near Mccall, Idaho

Probable cause

Maintenance personnel's failure to properly torque and inspect the magneto hardware, which resulted in a partial loss of engine power.

NTSB analysis

The passenger recalled that on the morning of the accident, the pilot had performed a preflight inspection and did not point out any mechanical issues with the airplane. The start-up and run-up were normal. As the airplane rotated for takeoff, the pilot reported that they had a power problem. The passenger stated that the pilot wanted to return to the airport, but the airplane had not gained enough altitude to clear the obstacles near the departure end of the runway.

Witnesses near the accident site reported that the departure roll appeared to be unusually long and the engine did not seem to be developing full power. From their vantage point they saw the airplane's nose pitch up and begin to climb, but it did not gain enough altitude to clear the trees near the departure end of the runway where the airplane impacted the top of a pine tree.

Postaccident examination of the engine revealed that the single-drive dual magneto remained attached to the engine accessory case, but not secured to the mounting pad. Both the upper and lower retaining hardware were loose, which allowed the magneto to be rotated with minimal resistance. The engine manufacturer issued a service instruction letter that cautioned that the magneto and/or its attaching hardware can become loose or unfastened following maintenance work. A review of the airplane’s maintenance records revealed that the magneto had been replaced about 15 hours before the accident flight. It is likely that the magneto’s hardware was not properly installed, torqued, or inspected, resulting in loose hardware and a subsequent loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR23FA225 for the full record.