{"id":"F2014L01683","name":"AD/B737/224 Amdt 4 - Horizontal Stabiliser Attachment Pins and Bolts - Inspection","slug":"ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":92353,"registerId":"commonwealth-F2014L01683-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/224 Amdt 4 | Horizontal Stabiliser AttachmentPins and Bolts - Inspection | 25/2014 |\n| ------------------ | ----------------------------------------------------------- | ------- |\n\n| Applicability: | This AD applies to all Boeing model 737-600, 737-700, 737-700C, 737-800 and737-900 series aircraft. |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | Subject to the exceptions mentioned below, action must be taken in accordance with the technical requirements of AD 2004-05-19 Amdt 39-13514, as corrected in the Federal Register of 13 April 2004, (the FAA AD) issued by the Federal Aviation Administration of the United States of America (FAA).Note: Boeing Service Bulletin (SB) 737-55-1086 Original Issue, dated11 December 2003, relates to the FAA AD.Compliance with Boeing SB 737-55-1086 Revision 1, dated 16 December 2004, or a later revision of that SB approved by the FAA, is taken to be compliance with Boeing SB 737-55-1086 Original Issue as required by paragraphs (a), (b), (c), (d) and (e) of the FAA AD in relation to the inspection, repair or replacement of the rear spar attach pins and front spar attach bolts.Compliance with Boeing SB 737-55-1093, Original Issue, dated 9 April 2012, is taken to be compliance with paragraphs (a), (b), (c), (d) and (e) of the FAA AD in relation to the inspection, repair or replacement of the rear spar attach pins.For an aircraft with a line number from 1725 to 3534 inclusive that is fitted with front spar attach bolts part number (P/N) 180A1611-3 or 180A1611-5, the inspection, repair or replacement of the front spar attach bolts required by paragraphs (a), (b), (c), (d) and (e) of the FAA AD is not required.For an aircraft with a line number of 3535 or higher, the inspection, repair or replacement required by paragraphs (a), (b), (c), (d) and (e) of the FAA AD is not required. |\n| Compliance: | The required action must be taken at the time specified for the action in the FAA AD, as if it had an effective date of 13 May 2004. |\n| | The effective date of this AD is 11 December 2014. |\n| Background: | Reports were received of a significant number of aircraft with damaged bolts and pins that attach the horizontal stabiliser to the aircraft. The bolts and pins were replaced due to wear, pits or corrosion damage. If not detected and corrected, damage to the bolts and pins could lead to failure, and consequent loss of the horizontal stabiliser. |\n| | AD/B737/224 was issued to address this unsafe condition and became effective on 13 May 2004.AD/B737/224 Amdt 1 was issued in response to a correction issue of the FAA AD, which included the phrase “whichever occurs first” in the grace period for the initial compliance time. The phrase was inadvertently omitted from the original FAA AD issue. AD/B737/224 Amdt 1 became effective on 25 November 2004.AD/B737/224 Amdt 2 allowed the use of Revision 1 of the referenced SB or a later revision approved by the FAA as an alternative method of compliance.AD/B737/224 Amdt 2 became effective on 9 June 2005.AD/B737/224 Amdt 3 reflected CASA’s acceptance of FAA approved alternative methods of compliance with the equivalent requirements of this AD, including the exclusion of aircraft with line number 3535 and higher from the requirement to conduct the inspections required by paragraphs (a) and (b) of the FAA AD in relation to horizontal stabiliser rear spar attach pins and front spar attach bolts.AD/B737/224 Amdt 4 reflects CASA’s acceptance of FAA approved alternative methods of compliance with the equivalent requirements of this AD, including the exclusion of aircraft with line numbers from 1725 to 3534 inclusive from the requirement to conduct the inspections, repair or replacement required by paragraphs (a), (b), (c), (d) and (e) of the FAA AD in relation to horizontal stabiliser front spar attach bolts if they are fitted with front spar attach bolts with P/N 180A1611-3 or 180A1611-5. |\n\n![](image.001.png)\n\nDavid Punshon \nDelegate of the Civil Aviation Safety Authority\n\n9 December 2014","sortOrder":0},{"sectionNumber":"AD/B737/224 Amdt 4","sectionType":"part","heading":"AD/B737/224 Amdt 4","content":"## AD/B737/224 Amdt 4","sortOrder":1},{"sectionNumber":"Horizontal Stabiliser AttachmentPins and","sectionType":"part","heading":"Horizontal Stabiliser AttachmentPins and Bolts - Inspection","content":"## Horizontal Stabiliser Attachment \nPins and Bolts - Inspection","sortOrder":2},{"sectionNumber":"25/2014","sectionType":"part","heading":"25/2014","content":"## 25/2014","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Scope has been narrowed compared with the original AD by adding specific exemptions. The amendment accepts FAA‑approved alternative methods and excludes aircraft with line numbers 3535 and higher from the inspection requirement, and further excludes aircraft with line numbers 1725–3534 from the front-spar bolt inspection/repair requirement when fitted with P/N 180A1611-3 or -5. This reduces inspection obligations for those subsets of aircraft while maintaining full requirements for others (Requirement; Background)."},"complexity_factors":["Cross-reference to an external FAA AD (2004-05-19) as the operative technical requirement increases interpretive complexity and dependence on FAA documents and effective dates (Requirement; Compliance).","Multiple acceptable compliance paths: original Boeing SB, Revision 1, SB 737-55-1093, or later FAA-approved revisions — operators must track which revision is FAA‑approved (Requirement).","Conditional exemptions based on airframe line numbers and specific part numbers (P/N 180A1611-3 or -5) create case-by-case applicability and record‑checking burdens (Requirement; Background).","Several prior amendments and corrections are incorporated (Amdt 1–3 history), so understanding current obligations requires reconciling prior changes (Background).","Timing linkage: compliance timing is tied to the FAA AD’s effective date (treated as 13 May 2004) while this AD’s effective date is later (11 Dec 2014), producing potential retroactivity/record issues (Compliance).","Operational cost and logistics: inspections, repairs or replacements impose maintenance, downtime and parts costs on operators (Background; Requirement).","Regulatory discretion: CASA’s acceptance of FAA-approved alternative methods of compliance (AMOCs) transfers some decision-making to FAA-approved processes, requiring operators to obtain/verify approvals (Background).","Technical complexity: inspections target wear, pits and corrosion on critical fittings, requiring qualified maintenance personnel and potential structural repair actions (Background)."],"plain_english_summary":"This amendment requires operators of Boeing 737-600/700/700C/800/900 series aeroplanes to carry out the FAA’s inspection, repair or replacement regime for horizontal stabiliser rear-spar pins and front-spar bolts, using the specified Boeing service bulletins or FAA‑approved alternatives. CASA accepts FAA-approved alternative methods and exempts certain line-number ranges and specific front-spar bolt part numbers from some inspection requirements. It matters because undetected wear, pits or corrosion could lead to bolt/pin failure and loss of the horizontal stabiliser; operators bear inspection, repair and compliance costs."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"The original AD (2004) applied broadly to all affected Boeing 737 aircraft. Over four amendments, the scope has progressively narrowed through exemptions: Amendment 3 excluded newer aircraft (line 3535+), and Amendment 4 further excluded mid-range aircraft (1725–3534) with specific bolt part numbers. The directive has evolved from a blanket safety requirement to a more targeted rule that exempts approximately half the fleet based on manufacturing data and component specifications."},"complexity_factors":["Multiple nested exceptions based on aircraft line numbers and specific part numbers","Incorporation by reference of foreign legislation (FAA AD 2004-05-19) requiring cross-referencing to US Federal Register","Multiple amendments (4 versions) with cumulative changes to scope and compliance methods","Technical aviation terminology requiring specialised knowledge (line numbers, part numbers, service bulletins, spar attach pins)","Conditional compliance pathways: original Boeing SB, Revision 1, or later FAA-approved revisions treated as equivalent for different paragraphs"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspection, repair or replacement of worn, pitted or corroded bolts and pins that attach the horizontal stabiliser on Boeing 737-600/700/700C/800/900 series to prevent potential detachment and loss of control. \n\nIt affects operators of those models but exempts newer line numbers (≥3535) and some mid-range line numbers (1725–3534) for certain front-spar bolt part numbers; compliance may follow FAA guidance and Boeing service bulletins."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection","history":"/api/acts/ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection/history","analysis":"/api/acts/ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection/analysis","conflicts":"/api/acts/ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection/conflicts","importantCases":"/api/acts/ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection/important-cases","documents":"/api/acts/ad-b737-224-amdt-4-horizontal-stabiliser-attachment-pins-and-bolts-inspection/documents"}}