{"abstract":"We propose to supersede an existing airworthiness directive (AD) that applies to all PW PW4074 and PW4077 turbofan engines. The existing AD currently requires removing the 15th stage high pressure compressor (HPC) disk within 12,000 cycles since new (CSN) or using a drawdown removal plan for disks that exceed 12,000 CSN. Since we issued that AD, we received a request from an operator that we clarify our inspection schedule for 15th stage HPC disks. This proposed AD would clarify that 15th stage HPC disks that have accumulated more than 9,685 CSN require a borescope inspection (BSI) or eddy current inspection (ECI) of the disk outer rim front rail for cracks prior to accumulating 12,000 CSN. We are proposing this AD to prevent cracks from propagating into the disk bolt holes, which could result in a failure of the 15th stage HPC disk, uncontained engine failure, and damage to the airplane.","action":"Notice of proposed rulemaking (NPRM).","agencies":[{"raw_name":"DEPARTMENT OF TRANSPORTATION","name":"Transportation Department","id":492,"url":"https://www.federalregister.gov/agencies/transportation-department","json_url":"https://www.federalregister.gov/api/v1/agencies/492","parent_id":null,"slug":"transportation-department"},{"raw_name":"Federal Aviation Administration","name":"Federal Aviation Administration","id":159,"url":"https://www.federalregister.gov/agencies/federal-aviation-administration","json_url":"https://www.federalregister.gov/api/v1/agencies/159","parent_id":492,"slug":"federal-aviation-administration"}],"body_html_url":"https://www.federalregister.gov/documents/full_text/html/2012/02/24/2012-4286.html","cfr_references":[{"chapter":null,"citation_url":null,"part":39,"title":14}],"citation":"77 FR 11017","comment_url":"http://www.regulations.gov/commenton/FAA-2010-1095-0005","comments_close_on":"2012-04-24","correction_of":null,"corrections":[],"dates":"We must receive comments on this proposed AD by April 24, 2012.","disposition_notes":null,"docket_ids":["Docket No. FAA-2010-1095","Directorate Identifier 2009-NE-40-AD"],"dockets":[],"document_number":"2012-4286","effective_on":null,"end_page":11019,"executive_order_notes":null,"executive_order_number":null,"explanation":null,"full_text_xml_url":"https://www.federalregister.gov/documents/full_text/xml/2012/02/24/2012-4286.xml","html_url":"https://www.federalregister.gov/documents/2012/02/24/2012-4286/airworthiness-directives-pratt-and-whitney-pw-models-pw4074-and-pw4077-turbofan-engines","images":{},"images_metadata":{},"json_url":"https://www.federalregister.gov/api/v1/documents/2012-4286?publication_date=2012-02-24","mods_url":"https://www.govinfo.gov/metadata/granule/FR-2012-02-24/2012-4286/mods.xml","not_received_for_publication":null,"page_length":3,"page_views":{"count":106,"last_updated":"2026-04-04 18:15:03 -0400"},"pdf_url":"https://www.govinfo.gov/content/pkg/FR-2012-02-24/pdf/2012-4286.pdf","presidential_document_number":null,"proclamation_number":null,"public_inspection_pdf_url":"https://public-inspection.federalregister.gov/2012-04286.pdf?1330005332","publication_date":"2012-02-24","raw_text_url":"https://www.federalregister.gov/documents/full_text/text/2012/02/24/2012-4286.txt","regulation_id_number_info":{"2120-AA64":{"issue":"202410","html_url":"https://www.federalregister.gov/regulations/2120-AA64/airworthiness-directives","title":"Airworthiness Directives","xml_url":"http://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202410&RIN=2120-AA64&operation=OPERATION_EXPORT_XML","priority_category":"Routine and Frequent"}},"regulation_id_numbers":["2120-AA64"],"regulations_dot_gov_info":{"supporting_documents":[{"title":"U.S. DOT/FAA - See Attachments","document_id":"FAA-2010-1095-0006"},{"title":"U.S. DOT/FAA  - See Attachments","document_id":"FAA-2010-1095-0004"}],"regulatory_plan":{"html_url":"https://www.federalregister.gov/regulations/2120-AA64/airworthiness-directives","title":"Airworthiness Directives"},"comments_url":"https://www.regulations.gov/docketBrowser?rpp=50&so=DESC&sb=postedDate&po=0&dct=PS&D=FAA-2010-1095","supporting_documents_count":2,"docket_id":"FAA-2010-1095","regulation_id_number":"2120-AA64","title":"2009-NE-40-AD","checked_regulationsdotgov_at":"2023-03-01T18:08:44Z"},"regulations_dot_gov_url":"http://www.regulations.gov/commenton/FAA-2010-1095-0005","significant":false,"signing_date":null,"start_page":11017,"subtype":null,"title":"Airworthiness Directives; Pratt & Whitney (PW) Models PW4074 and PW4077 Turbofan Engines","toc_doc":"Pratt and Whitney (PW) Models PW4074 and PW4077 Turbofan Engines","toc_subject":"Airworthiness Directives:","topics":["Air transportation","Aircraft","Aviation safety","Incorporation by reference","Safety"],"type":"Proposed Rule","volume":77}