AD 2020-15-05 Requires Amendment Of Certain Existing Afms To Limit The Use Of Windmill Restarts

The FAA is superseding Airworthiness Directive (AD) 2018-18-02 for certain Austro Engine GmbH model E4 engines and all Austro Engine GmbH model E4P engines. AD 2018-18-02 required replacement of the timing chain and amending certain airplane flight manuals (AFMs) to limit the use of windmill restarts.

This AD requires amendment of certain existing AFMs to limit the use of windmill restarts and removes the timing chain replacement requirement in AD 2018-18-02. This AD was prompted by reports of considerable wear of the timing chain on the affected engines. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective August 31, 2020.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2018-18-02, Amendment 39-19381 (83 FR 53802, October 25, 2018), (“AD 2018-18-02”). AD 2018-18-02 applied to certain Austro Engine GmbH model E4 engines and all Austro Engine GmbH model E4P engines. The NPRM published in the Federal Register on March 17, 2020 (85 FR 15079). The NPRM was prompted by reports of considerable wear of the timing chain on the affected engines. The NPRM proposed to retain the requirements of AD 2018-18-02 for amending certain AFMs to limit the use of windmill restarts to emergency procedures. The NPRM also proposed to remove the requirement in AD 2018-18-02 for replacing the timing chain. The FAA is issuing this AD to address the unsafe condition on these products.

The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA AD 2017-0103R1, dated February 25, 2019 (referred to after this as “the MCAI”), to address the unsafe condition on these products. The MCAI states:
Considerable wear of the timing chain has been detected on some engines. This may have been caused by windmilling restarts, which are known to cause high stress to the timing chain. This condition, if not detected and corrected, could lead to failure of the timing chain and consequent engine power loss, possibly resulting in reduced control of the aeroplane.

To address this potential unsafe condition, AE included instructions in the engine maintenance manual to periodically inspect the condition of the timing chain and, depending on findings, to replace the timing chain and the chain wheel. The operation manual was updated to allow windmilling restart only as an emergency procedure. AE also published Mandatory Service Bulletin (MSB) MSB-E4-017/2, providing instructions to replace the timing chain for engines with known windmilling restarts, and EASA issued AD 2017-0103, requiring replacement of the timing chain for engines with known windmilling restarts, and amendment of the applicable Aircraft Flight Manual (AFM). Since that [EASA] AD was issued, AE revised the applicable Airworthiness Limitation Section (ALS) including, among others, the limitation required by that AD. Consequently, EASA published AD 2019-0041, requiring accomplishment of the actions specified in the ALS.

For the reason described above, this [EASA] AD is revised accordingly, removing the requirement of timing chain replacement. This action remain required through EASA AD 2019-0041.

FMI: www.regulations.gov