What happened
On January 3ly, 2021, at approximately 11:44 Pacific standard time, a Cessna T182T, registration N291FR, was involved in an accident near Crescent City, California. The aircraft was being operated as a Part 91 instructional flight.
During the flight, the flight instructor observed a flashing red turbine inlet temperature (TIT) warning light. After enriching the fuel mixture, the TIT indication returned to normal, but the engine subsequently began running rough. The instructor attempted to troubleshoot by switching between the left and right magnetos, but the engine continued to run poorly or lost power. Despite adjusting the mixture and activating the auxiliary fuel pump, the instructor could not maintain altitude. The instructor identified an open field and performed a forced landing into marshland, during which the aircraft nosed over. The flight instructor and the student pilot sustained two minor injuries; there were no fatalities.
The investigation
Post-accident examination of the engine revealed that all sparkplugs had excessive gaps and two electrodes were fouled. The magnetos failed to produce a spark and showed evidence of internal corrosion. Investigators noted that the pressurized magnetos were missing a moisture trap or filter.
Further examination of the magnetos revealed that the internal components contained corrosion and rust. The magneto points showed deterioration and buildup on the contact surfaces. Bench testing of the magneto capacitors showed that both had failed under normal testing. Additionally, an ohmmeter test of the four point assemblies revealed inconsistent resistance on the surface areas. When a used set of points and capacitors was installed, the magnetos produced a normal amount of spark.
Maintenance records indicated that the magnetos had been replaced with overhauled units on February 1, 2019, at 1,248.8 hours of total aircraft time. The most recent annual inspection occurred on November 10, 2020, at 1,704.5 hours. At the time of the accident, the magnetos had 537 hours of operation since installation.