Summary
This document proposes to supersede 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 proposed AD would 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). The proposed AD would also revise the inspection intervals and would require replacing certain unserviceable parts and removing the exhaust system for detailed inspections at regular intervals. The proposed 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 the proposed 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.