2011-25-51: Starter adapter shaft gears

Emergency order 2011-25-51 is an airworthiness directive. The FAA's subject line: Starter adapter shaft gears. It names the Continental IO-550-N, Continental TSIO-520-AE, Continental TSIO-520-AF, Continental TSIO-520-B, Continental TSIO-520-BB, Continental TSIO-520-BE, Continental TSIO-520-C, Continental TSIO-520-CE, Continental TSIO-520-D, Continental TSIO-520-E, Continental TSIO-520-EB, Continental TSIO-520-G, Continental TSIO-520-H, Continental TSIO-520-J, Continental TSIO-520-JB, Continental TSIO-520-K, Continental TSIO-520-L, Continental TSIO-520-M, Continental TSIO-520-N, Continental TSIO-520-NB, Continental TSIO-520-P, Continental TSIO-520-R, Continental TSIO-520 series, Continental TSIO-520-T, Continental TSIO-520-U, Continental TSIO-520-UB, Continental TSIO-520-VB, Continental TSIO-520-WB, Continental TSIO-550-K, Continental TSIOF550-D engines: about 9,975 aircraft on the U.S. register today across them, though an order usually covers particular versions or serial numbers rather than every one. System: engine.