{"id":"F2006B09698","name":"AD/F27/131 Amdt 1 - AN - Bolts","slug":"ad-f27-131-amdt-1-an-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115858,"registerId":"commonwealth-F2006B09698-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F27/131 Amdt 1 - AN - Bolts","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nFokker F27 Series Aeroplanes\n\nAD/F27/131\n\nAmdt 1\n\n  \nAN \\- Bolts 2/94\n\nApplicability: Model F27 aircraft (except Mk 050), with serial numbers listed in Fokker Service Bulletin F27/51-10 Revision 2.\n\nRequirement: Accomplish the following:\n\n    Replace the affected eight (8) AN-bolts part number AN178-13A and four (4) AN- bolts part number AN178-26A in the nacelle brace installation (IPC Chapter 2B14300, items 15, 23, and 24) with bolts part number NAS1308-11D and part number NAS1308-34D, respectively; and replace the eight (8) AN-bolts part number AN178-26A that attach the engine mount to the nacelle firewall with bolts part number NAS1308-34D, in accordance with Engineering Modification Instruction (EMI) No. 171, as detailed in Fokker Service Bulletin F27/51-10 Revision 2.\n\n    b. In the connection between the nose landing gear bracket and the forward pressure bulkhead, replace AN-bolt part number AN7-14A with bolt part number NAS1307-15D, replace AN-bolt part number AN7-16A with bolt part number NAS1307-19D, replace three AN-bolts part number AN8-16A with bolts part number NAS1308-17D, and replace AN-bolt part number AN8-17A with bolt part number NAS1308-19D, in accordance with Figure No. 7 in Fokker Service Bulletin F27/51-10 Revision 2.\n\nNote: RLD AD 91-111/2 (A) refers.\n\nCompliance: Prior to 1 January 1995.\n\nBackground: A number of AN-bolts are located in places which are critical to the safety of flight. This Directive requires replacement of such bolts with bolts which are manufactured to a superior specification.\n\nAmendment 1 is issued to align with a revision of the related RLD AD which now requires the replacement of a limited number of specific AN-bolts.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"Amendment 1 narrows the scope compared to the original directive. The background note states the amendment was issued to 'align with a revision of the related RLD AD which now requires the replacement of a limited number of specific AN-bolts' — indicating the original AD likely covered more bolts, and this amendment restricts the requirement to fewer, specifically identified bolts."},"complexity_factors":["Single, specific technical requirement with no conditional logic or exceptions","Only 4 defined part numbers referenced (AN178-13A, AN178-26A, AN7-14A, AN7-16A, AN8-16A, AN8-17A and their replacements)","Clear applicability section limiting scope to specific aircraft models and serial numbers","Single compliance deadline with no phased or alternative compliance options","Straightforward amendment note explaining the change from original directive","No cross-references to other legislation beyond a single related airworthiness directive"],"plain_english_summary":"This is a **safety directive for aircraft maintenance** that applies to specific Fokker F27 model aeroplanes (a type of regional turboprop aircraft). It **mandates the replacement of certain bolts** in two critical areas of the aircraft:\n\n- **Engine mounting area**: Bolts in the nacelle brace installation and engine mount-to-firewall connections\n- **Landing gear area**: Bolts connecting the nose landing gear bracket to the forward pressure bulkhead\n\nThe old **AN-bolts** (a standard military specification fastener) must be replaced with stronger **NAS-bolts** (National Aerospace Standard, a higher-grade specification) by **1 January 1995**.\n\n**Why this matters**: The original bolts are located in flight-critical structural areas. The replacement bolts meet superior manufacturing specifications, reducing the risk of mechanical failure that could endanger the aircraft and passengers.\n\n**Who must comply**: Operators of affected Fokker F27 aircraft (excluding the Mk 050 variant) with specific serial numbers listed in the referenced Fokker Service Bulletin."},"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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 aligns this AD with a revised related RLD AD and narrows the work required to the replacement of a limited number of specific AN-bolts. In other words, the amendment adjusts the set of bolts required for replacement compared with the prior version of the directive (Amendment 1; Background)."},"complexity_factors":["Technical specificity of parts and locations: multiple part-number substitutions (AN178-13A, AN178-26A, AN7-14A, AN7-16A, AN8-16A, AN8-17A → various NAS/NAS1307/NAS1308 parts) (Requirement).","Dependency on external documents and precise procedures: work must follow Fokker Service Bulletin F27/51-10 Rev 2 and EMI No.171 (Requirement).","Limited applicability by serial number: only aircraft listed in the service bulletin are affected, requiring traceability of fleet records (Applicability).","Fixed compliance deadline imposes scheduling and potential rush maintenance costs for operators (Compliance).","Cross-reference to a related RLD AD and an amendment that altered the list of required replacements introduces regulatory coordination and interpretation needs (Amendment 1; Note).","Installation locations include structurally critical interfaces (nacelle brace, engine mount, nose-gear bracket/forward pressure bulkhead), requiring competent maintenance and possible inspection access work (Requirement; IPC references)."],"plain_english_summary":"The AD mandates replacement of specified AN-bolts with defined NAS bolts on listed Fokker F27 serial numbers, following Fokker Service Bulletin F27/51‑10 Rev 2 and EMI No.171, to be completed before 1 January 1995 (Requirement; Compliance; Applicability). Aircraft owners/operators must carry out and pay for the work using the prescribed parts and procedures. The directive states the replacements fit bolts made to a superior specification for locations deemed critical to flight safety (Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f27-131-amdt-1-an-bolts","history":"/api/acts/ad-f27-131-amdt-1-an-bolts/history","analysis":"/api/acts/ad-f27-131-amdt-1-an-bolts/analysis","conflicts":"/api/acts/ad-f27-131-amdt-1-an-bolts/conflicts","importantCases":"/api/acts/ad-f27-131-amdt-1-an-bolts/important-cases","documents":"/api/acts/ad-f27-131-amdt-1-an-bolts/documents"}}