Accident Details
On May 7, 2010, at 1732 mountain daylight time, a Robinson R22 Beta, registration N393LE, collided with terrain following a loss of engine power near Mendon, Utah. The helicopter was operated by Mountain Ridge Helicopters under Title 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed, and no flight plan was filed.
Flight Sequence
The certified flight instructor (CFI) reported that he and the student were practicing autorotations. They entered the first autorotation, rolled the throttle to idle, and the engine lost power. The CFI force-landed the helicopter in a field, and it rolled onto its right side. The CFI indicated that the grass-covered terrain appeared flat and would make a good emergency landing spot; however, upon touchdown he realized the terrain was rough. Neither the CFI nor the student was injured; the helicopter sustained substantial damage.
Examination
A Federal Aviation Administration (FAA) inspector examined the helicopter. The engine was test run, and no anomalies were identified. During the examination and testing, the magneto internal timing and the magneto timing to engine was not verified prior to the removal and disassembly of the magnetos. Disassembly of the magnetos showed evidence of internal arcing.
The engine was equipped with TCM S4LSC-200 (left) and S4LSC-204T (right) magnetos. According to TCM Service Bulletin No. 515 and Textron Lycoming Service Bulletin No. 515, magnetos must be inspected at each 100-hour and 500-hour interval. The 500-hour inspection requires removal, disassembly, inspection, and servicing in accordance with the TCM Service Support Manual.
Maintenance
The last annual/100-hour inspection was on April 22, 2010, at a total time of 999.8 hours. According to the FAA inspector, review of the maintenance documentation for the helicopter showed that neither TCM SB 515 nor Textron Lycoming SB 515 was complied with.