Textron Aviation issued a service letter on November 14 regarding reduced service life of magnetos installed on several Cessna models. Aircraft on the list that have Champion SLICK 4200, 4300, or 4700 series magnetos installed may experience an issue with the distributor gear assembly of the magnetos leading to the reduction in service life.
The letter, SEL-74-05, states that symptoms of this issue include an unusual drop in rpm during a mag check, starting issues, and rough running engine. The Textron letter came in response to an earlier service bulletin, SB15-4A, issued by Champion Aerospace in 2015 and revised in December 2018.
Owners and operators of the models and serial numbers listed in the service letter are advised to complete the instructions listed in service bulletins Continental Motors SB15-4A, Lycoming SB 622A, or Champion Aerospace SB1-15 at their next 100-hour or annual inspection.