Piper PA-31, VH-FML

Approaching the top of the climb, the pilot of the Navajo observed that the cylinder head temperature (CHT) for the left engine was higher than normal. When the CHT started to exceed the accepted company maximum of 400 degrees Fahrenheit, the pilot enriched the mixture to attempt to control it. After reaching the desired cruise altitude and speed, a vibration was felt through the airframe. After confirming that the vibration was from the left engine, the pilot decided that further troubleshooting was not possible. He elected to shut down the left engine and feathered the propeller. With concern for last light, a diversion to an alternate aerodrome and successful single engine landing was carried out.

Maintenance investigation found that the left engine No. 6 cylinder fuel injection nozzle had become blocked. That cylinder assembly had recently been changed and the engineer thought that a small piece of ceramic might have been dislodged when the nozzle and supply line was disturbed. The cylinder also had the single cylinder head temperature probe for the left engine fitted to it and would have registered the high temperature in this cylinder due to the leaning effect of the blockage. The nozzle was cleaned and the aircraft returned to service.