Incident Overview
During a cross-country flight, a student pilot encountered rain and decided to descend to confirm their position. While descending, the engine experienced a loss of RPM. The pilot attempted to restore power multiple times but was unsuccessful. An emergency landing was then performed in a plowed field. During the landing, the nose gear collapsed, and the aircraft nosed over.
Post-Incident Examination
Following the incident, an examination of the engine revealed low compression on the number 2 cylinder. This was attributed to lead deposits found between the exhaust valve and the valve seat. Additional testing of the magnetos showed high activation speeds and erratic spark throughout their operating ranges. Upon disassembly, carbon deposits and tracking were found on the distributor gear support plate. The brush in the magnetos was slightly misaligned and worn.
Magneto Specifications
The magnetos in question were Slick Electro models 4150 and 4181. These are sealed units that require no field maintenance. Piper Aircraft recommends that these magnetos be exchanged after 900 hours of service. The total time in service for the subject magnetos was 714 hours.