The FAA has adopted a new airworthiness directive (AD) for Teledyne Continental Motors (TCM) GTSIO-520-series engines. The AD requires initial and repetitive visual inspections of the starter adapter assemblies and crankshaft gears and the installation of a certain TCM service kit at the next engine overhaul or starter adapter replacement, whichever occurs first. The AD resulted from six service difficulty reports and one fatal accident report related to failed starter adapter assemblies. The FAA estimates that 4,240 engines installed on airplanes in the U.S. registry are affected, including the Twin Commander 685 and Cessna 404, 411, and 421 series. The AD becomes effective November 1. Download the AD.