2023-26636

Document Headings Document headings vary by document type but may contain the following: • the agency or agencies that issued and signed a document • the number of the CFR title and the number of each part the document amends, proposes to amend, or is directly related to • the agency docket number / agency internal file number • the RIN which identifies each regulatory action listed in the Unified Agenda of Federal Regulatory and Deregulatory Actions See the Document Drafting Handbook for more details. Department of Transportation Federal Aviation Administration • 14 CFR Part 39 • [Docket No. FAA-2023-1050; Project Identifier AD-2022-00602-E; Amendment 39-22620; AD 2023-24-04] • RIN 2120-AA64 AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all Honeywell International Inc. (Honeywell) Model AS907-1-1A and AS907-2-1G engines. This AD was prompted by reports of compressor surge, including a dual engine compressor surge, during takeoff climb out through a steep temperature inversion, causing a loss of engine thrust control. This AD requires either the replacement of a certain electronic control unit (ECU) software version installed on AS907-1-1A engines with updated software or the replacement of certain ECUs installed on AS907-1-1A engines with ECUs eligible for installation. This AD also requires the replacement of certain ECUs installed on AS907-2-1G engines. The FAA is issuing this AD to address the unsafe condition on these products. DATES: This AD is effective January 10, 2024. ADDRESSES: AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2023-1050; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. FOR FURTHER INFORMATION CONTACT: Joseph Costa, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: (562) 627-5246; email: joseph.costa@faa.gov. SUPPLEMENTARY INFORMATION: Background The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Honeywell Model AS907-1-1A and AS907-2-1G engines. The NPRM published in the Federal Register on May 23, 2023 (88 FR 32980). The NPRM was prompted by several reports that Honeywell Model AS907-1-1A and AS907-2-1G engines experienced compressor surge, including an AS907-1-1A dual engine compressor surge, during takeoff climb out through a steep temperature inversion, which resulted in loss of engine thrust control. The FAA determined that the installed ECU software version logic locked the engine inlet total temperature (Tt2) at 60 knots on a takeoff roll and that reference Tt2 remained locked until the aircraft reached 400 feet above ground level (AGL) or the pilot moved the throttle before reaching 400 AGL. The locked Tt2 is mathematically adjusted by the ECU software for altitude and Mach number changes as the takeoff progresses. During a climb to 400 feet AGL with a thermal inversion, the actual engine Tt2 can increase above the Tt2 that is being calculated by the ECU, which causes the compressor guide vanes' (CGVs) and surge bleed valves' (SBVs) positions to be off-schedule for the actual ambient conditions. Significant off-scheduling of the CGVs and the SBVs can lead to a compressor surge event. The compressor surge margin is decreased when scheduling is based on a colder Tt2 temperature than what the engine is actually running. Engine deterioration impacts compressor surge margin and can increase the likelihood of a du…

Fonte: Federal Register (federalregister.gov). Texto original em inglês. Conteúdo sanitizado por segurança.