AD 2020-25-12 Prompted By Three Crankshaft Assembly Failures That Resulted In The Loss Of Engine Power

The FAA is adopting a new airworthiness directive (AD) for all Superior Air Parts, Inc. (SAP) Model IO-360-series and O-360-series reciprocating engines and certain Lycoming Engines (Lycoming) Model AEIO-360-, IO-360-, and O-360-series reciprocating engines with a certain SAP crankshaft assembly installed.

This SAP crankshaft assembly is installed as original equipment on the affected SAP engines and as a replacement part under parts manufacturer approval (PMA) on the affected Lycoming engines. This AD was prompted by three crankshaft assembly failures that resulted in the loss of engine power and immediate or emergency landings. This AD requires the removal from service of all affected crankshaft assemblies. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective January 15, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all SAP Model IO-360-series and O-360-series reciprocating engines and certain Lycoming Model AEIO-360-, IO-360-, and O-360-series reciprocating engines with a certain SAP crankshaft assembly installed. The NPRM published in the Federal Register on January 29, 2020 (85 FR 5173). The NPRM was prompted by three crankshaft assembly failures that resulted in the loss of engine power and immediate or emergency landings. The FAA determined that the crankshaft assembly failures resulted from the manufacturing process at SAP's crankshaft vendor during 2012 and 2014 causing excessive residual white layer of iron nitride forming on the assemblies. This white layer is brittle and can lead to spalling or fatigue cracking of the crankshaft assembly as a result of the normal mechanical loads during engine operation. The FAA's analysis concluded that all three SAP crankshaft assembly failures were the result of this fatigue cracking. In the NPRM, the FAA proposed to require the removal from service of all affected crankshaft assemblies. The unsafe condition, if not addressed, could result in failure of the engine, in-flight shutdown, and loss of the airplane.

FMI: www.regulations.gov