Airworthiness Directives; Lycoming Engines Reciprocating Engines

We are superseding an existing airworthiness directive (AD) for certain Lycoming Engines (L)O-360, (L)IO-360, AEIO-360, O-540, IO- 540, AEIO-540, (L)TIO-540, IO-580, and IO-720 series reciprocating engines. That AD currently requires replacing certain crankshafts in the affected engines. This AD continues to require replacing certain crankshafts, corrects the start date of affected engine models in Lycoming Mandatory Service Bulletin (MSB) No. 569A to the start date in Supplement No. 1 to Lycoming MSB No. 569A, dated May 27, 2009, and includes additional (formerly experimental) IO-390, AEIO-390, and AEIO- 580 series engine models having affected crankshafts. This AD was prompted by Lycoming Engines discovering that the start date of affected engine models in MSB No. 569A is incorrect and the need to include additional engine models having the affected crankshafts. We are issuing this AD to prevent failure of the crankshaft, which will result in total engine power loss, in-flight engine failure, and possible loss of the aircraft.