{"abstract":"The FAA is adopting a new airworthiness directive (AD) for all helicopters equipped with a radio (also known as radar) altimeter. This AD was prompted by a determination that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band (5G C-Band). This AD requires revising the limitations section of the existing rotorcraft flight manual (RFM) for your helicopter to incorporate limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C-Band interference in areas as identified by Notices to Air Missions (NOTAMs). The FAA is issuing this AD to address the unsafe condition on these products.","action":"Final rule; request for comments.","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/2021/12/09/2021-26779.html","cfr_references":[{"chapter":null,"citation_url":null,"part":"39","title":14}],"citation":"86 FR 69992","comment_url":null,"comments_close_on":null,"correction_of":null,"corrections":[],"dates":"This AD is effective December 9, 2021.","disposition_notes":null,"docket_ids":["Docket No. FAA-2021-0954","Project Identifier AD-2021-01170-R","Amendment 39-21811","AD 2021-23-13"],"dockets":[],"document_number":"2021-26779","effective_on":"2021-12-09","end_page":69996,"executive_order_notes":null,"executive_order_number":null,"full_text_xml_url":"https://www.federalregister.gov/documents/full_text/xml/2021/12/09/2021-26779.xml","html_url":"https://www.federalregister.gov/documents/2021/12/09/2021-26779/airworthiness-directives-various-helicopters","images":{"ER09DE21.008":{"large":"https://img.federalregister.gov/ER09DE21.008/ER09DE21.008_large.png","original_size":"https://img.federalregister.gov/ER09DE21.008/ER09DE21.008_original_size.png"}},"images_metadata":{"ER09DE21.008":{"large":{"identifier":"ER09DE21.008","content_type":"image/png","size":48742,"width":822,"sha":"140f5e7f71577bd4dd24a3e36952613a","url":"https://img.federalregister.gov/ER09DE21.008/ER09DE21.008_large.png","height":472},"original_size":{"identifier":"ER09DE21.008","content_type":"image/png","size":85506,"width":3601,"sha":"99ea8397ff73a8faead9271e460ab2df","url":"https://img.federalregister.gov/ER09DE21.008/ER09DE21.008_original_size.png","height":2067}}},"json_url":"https://www.federalregister.gov/api/v1/documents/2021-26779?publication_date=2021-12-09","mods_url":"https://www.govinfo.gov/metadata/granule/FR-2021-12-09/2021-26779/mods.xml","not_received_for_publication":null,"page_length":5,"page_views":{"count":863,"last_updated":"2026-08-23 20:15:04 -0400"},"pdf_url":"https://www.govinfo.gov/content/pkg/FR-2021-12-09/pdf/2021-26779.pdf","presidential_document_number":null,"proclamation_number":null,"public_inspection_pdf_url":"https://public-inspection.federalregister.gov/2021-26779.pdf?1638903625","publication_date":"2021-12-09","raw_text_url":"https://www.federalregister.gov/documents/full_text/text/2021/12/09/2021-26779.txt","regulation_id_number_info":{"2120-AA64":{"issue":"202504","html_url":"https://www.federalregister.gov/regulations/2120-AA64/airworthiness-directives","title":"Airworthiness Directives","xml_url":"http://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202504&RIN=2120-AA64&operation=OPERATION_EXPORT_XML","priority_category":"Routine and Frequent"}},"regulation_id_numbers":["2120-AA64"],"regulations_dot_gov_info":{"supporting_documents":[{"title":"Supporting AD Documents","document_id":"FAA-2021-0954-0002"}],"regulatory_plan":{"html_url":"https://www.federalregister.gov/regulations/2120-AA64/airworthiness-directives","title":"Airworthiness Directives"},"comments_count":2,"agency_id":"FAA","comments_url":"https://www.regulations.gov/docketBrowser?rpp=50&so=DESC&sb=postedDate&po=0&dct=PS&D=FAA-2021-0954","supporting_documents_count":1,"docket_id":"FAA-2021-0954","document_id":"FAA-2021-0954-0001","regulation_id_number":"2120-AA64","title":"AD-2021-00170-R  All helicopters equipped with a radio/radar altimeter; radio/radar altimeter","checked_regulationsdotgov_at":"2022-01-27T04:30:05Z"},"regulations_dot_gov_url":null,"significant":false,"signing_date":null,"start_page":69992,"subtype":null,"title":"Airworthiness Directives; Various Helicopters","toc_doc":"Various Helicopters","toc_subject":"Airworthiness Directives:\n","topics":["Air transportation","Aircraft","Aviation safety","Incorporation by reference","Safety"],"type":"Rule","volume":86}