Airworthiness Directives; Cessna Aircraft Company 300 and 400 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 75-23- 08 R5, which currently requires repetitively inspecting and replacing or repairing the exhaust system on certain Cessna Aircraft Company (Cessna) 300 and 400 series airplanes. The requirements of this AD replace the inspections and replacements that are required by AD 75-23- 08 R5 with inspections and replacements containing new simplified procedures for all 300 and 400 series airplanes (models affected by the current AD plus additional models). This AD also revises the inspection intervals and requires replacing certain unserviceable parts and removing the exhaust system for a detailed inspection. This AD is the result of numerous incidents and accidents relating to the exhaust systems on Cessna 300 and 400 series airplanes dating from the middle 1970's to the present, including six incidents since issuance of AD 75- 23-08 R5 where exhaust problems were cited. The actions specified by this AD are intended to detect and correct cracks and corrosion in the exhaust system, which could result in exhaust system failure and a possible uncontrollable in-flight fire with pilot and/or passenger injury.