Airworthiness Directives; Austro Engine GmbH Engines

The FAA is superseding Airworthiness Directive (AD) 2021-22-20 which applied to certain Austro Engine GmbH E4 and E4P model diesel piston engines. AD 2021-22-20 required, for engines with an affected cylinder head, inspection of the high pressure pump (HPP) driving gear and, depending on the results of the inspection, replacement of the HPP driving gear with a part eligible for installation. AD 2021-22-20 also required, for engines with an affected HPP driving gear, replacement of the HPP driving gear before further flight or within a certain number of flight hours, depending on the engine configuration and number of affected engines installed. This AD requires, for engines equipped with a certain cylinder head and HPP driving gear combination, removal, inspection, and replacement of the HPP driving gear before further flight and, depending on the inspection findings, replacement of the HPP shaft, cylinder head, camshaft gear, or inlet/outlet camshaft bushing. This AD also requires, for engines with an affected HPP driving gear, replacement of the HPP driving gear before further flight or within a certain number of flight hours, depending on the engine configuration and number of affected engines installed. This AD was prompted by reports of failure of the HPP driving gear and a subsequent determination that a batch of HPP driving gears may have been damaged during assembly. This AD was also prompted by an investigation which found that certain cylinder heads installed in combination with certain HPP driving gear on the same engine may cause damage to the HPP driving gear. The FAA is issuing this AD to address the unsafe condition on these products.