Robinson Helicopter R22 BETA N393LE accident near Mendon, Utah

Probable cause

A loss of engine power due to a failure of the magnetos as a result of inadequate maintenance.

NTSB analysis

The certified flight instructor (CFI) and student pilot departed on a local area training flight and found a suitable area to perform practice autorotations. During the first autorotation, the engine experienced a loss of power. The CFI assumed control of the helicopter and the student attempted to restart the engine. During the touchdown, the right skid caught on the terrain, and the helicopter rolled to the right. The CFI indicated that it appeared the grass-covered terrain was flat and would make a good emergency landing spot; however, upon touchdown he realized that the terrain was rough. A post accident examination and test run of the engine by a Federal Aviation Administration (FAA) inspector did not reveal any operational anomalies with the helicopter. Disassembly of the magnetos revealed evidence of internal arcing. The magneto manufacturer and engine manufacturer had issued service bulletins related to the inspection of the magnetos every 100 hours and 500 hours. The 500-hour inspection required that the magnetos be removed from the engine, disassembled, inspected, and serviced. According to the FAA inspector, review of the maintenance records for the helicopter showed that neither service bulletin had been complied with.

Text from the NTSB. Open the NTSB docket for WPR10LA232 for the full record.