AD 2021-23-07 Requires Replacing A Certain Circuit Breaker With A Part Having A Higher Rating

The FAA is adopting a new airworthiness directive (AD) for certain Saab AB, Support and Services Model SAAB 340B airplanes.

This AD was prompted by a report that the circuit breaker for the emergency cabin lighting tripped without fault in the system. This AD requires replacing a certain circuit breaker with a part having a higher rating, as specified in a European Union Aviation Safety Agency (EASA) AD, which is incorporated by reference. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective January 5, 2022.

Supplementary Information: EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2021-0058, dated March 1, 2021 (EASA AD 2021-0058) (also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI), to correct an unsafe condition for certain Saab AB, Support and Services Model SAAB 340B airplanes.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Saab AB, Support and Services Model SAAB 340B airplanes. The NPRM published in the Federal Register on August 9, 2021 (86 FR 43451). The NPRM was prompted by report that the circuit breaker for the emergency cabin lighting tripped without fault in the system. The NPRM proposed to require replacing a certain circuit breaker with a part having a higher rating, as specified in EASA AD 2021-0058.

The FAA is issuing this AD to address the low rating of the 2LN circuit breaker during maximum charging conditions. This condition, if not corrected, could lead to an insufficiently charged emergency battery, with consequent loss of cabin emergency lighting, possibly resulting in injury to occupants during an evacuation. See the MCAI for additional background information.

FMI: www.regulations.gov