AD 2021-22-20 Prompted By Reports Of Failure Of The High-Pressure Pump (HPP) Driving Gear

The FAA is adopting a new airworthiness directive (AD) for certain Austro Engine GmbH E4 and E4P model diesel piston engines.

This AD was prompted by reports of failure of the high-pressure pump (HPP) driving gear and a subsequent determination that a batch of HPP driving gears may have been damaged during assembly. This AD requires, for engines with an affected cylinder head, inspection of the HPP driving gear and, depending on the results of the inspection, replacement of the HPP driving gear with a part eligible for installation. This AD also requires, for engines with an affected HPP driving gear, replacement of the HPP driving gear either before further flight or within a certain number of flight hours after the effective date of this AD. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective November 16, 2021.

Supplementary Information: The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, issued EASA AD 2021-0203R1, dated September 24, 2021 (referred to after this as “the MCAI”), for Austro Engine GmbH E4 and E4P model diesel piston engines, to address the unsafe condition on these products.

The MCAI states:

• Occurrences were reported of HPP driving gear failure. Subsequent investigation determined that a certain batch of HPP driving gears was produced with a worn out assembly tool P/N AE300T012-1. Those HPP driving gears may have been damaged during assembly. Concurrently, it was determined that, for engines equipped with a certain cylinder head, a stack up of tolerances exists between the cylinder head, cylinder head cover, camshaft gear and HPP gear. Both scenarios could result in premature HPP gear failure.
• This condition, if not corrected, could lead to engine in-flight shut-down with consequent forced landing, possibly resulting in damage to the aeroplane and injury to occupants. To address this potential unsafe condition, Austro Engine published the inspection SB, as defined in this [EASA] AD, to provide instructions for HPP gear inspection on engines equipped with an affected cylinder head, as defined in this [EASA] AD. Austro Engine also published the replacement SB, as defined in this [EASA] AD, to provide instructions for replacement of affected HPP gears, as defined in this [EASA] AD. For the reason described above, EASA issued Emergency AD 2021-0203-E to require inspection and/or replacement of HPP gears.

You may obtain further information by examining the MCAI in the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA-2021-0946.

FMI: www.regulations.gov