Study on Continuing Airworthiness of Reciprocating Aeroengine about Valve Sticking and Valve Breakage

Recently, a certain type of aviation reciprocating engine encountered some valve sticking and valve breakage problems in succession because of lead built-up and bad compression performance of cylinders in China, which has serious impact on the safety and continuing airworthiness of this reciprocating engine and equipped aircraft. This article has undertaken an in-depth study on this valve sticking and breakage issue, analysis has been done on Chinese aviation gasoline chemical ingredient as well as differences of avgas between China and America. Binding the characteristics of this aero-engine, compression test and borescope inspection have been done on the affected cylinders, also an in-depth microscopic analysis on the deposit which has been accumulated on the cylinder, valve, spark plug and valve guide. Finally, solutions and recommendations are proposed to ensure the continuing safe operation of the engine and aircraft based on the analysis on obtained engine operation data. The reasons of valve sticking and valve breakage because of the lead built-up issue of reciprocation engine are not only the Tetraethyl lead content in Chinese avgas, but also engine operation conditions and levels of maintenances on engine.