{"id":"F2006B06176","name":"AD/PFP/18 - Hoffman Propeller Bolt Replacement","slug":"ad-pfp-18-hoffman-propeller-bolt-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47021,"registerId":"commonwealth-F2006B06176-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PFP/18 - Hoffman Propeller Bolt Replacement","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nPropellers \\- Fixed Pitch\n\nAD/PFP/18 Hoffman Propeller Bolt Replacement 11/98\n\nApplicability: All Hoffman HO 27 ( ) and HO4 27 ( ) model propellers using propeller mounting bolts P/N FP20-147.\n\nIf the part number of the installed bolts cannot be positively established, assume they are P/N FP20-147 and are, therefore, subject to the requirements of this Directive.\n\nRequirement: 1. Inspect propeller installation in accordance with Hoffman Propeller Service Bulletin SB 61-11-03 E10 Revision A dated 28/7/98.\n\n2. Replace the propeller mounting bolts, P/N FP20-147 with serviceable bolts that feature a “V” marking in accordance with Hoffman Propeller Service Bulletin SB 61-11-03 E10 Revision A dated 28/7/98.\n\nNote 1: LBA AD 1998-322 also refers.\n\nNote 2: Refer to AD/PFP/1 Amdt3 (or later amendment) for ongoing torque requirements for fixed pitch wooden propellers.\n\nCompliance: 1. Within 30 days of the effective date of this Directive.\n\n2. At the next occasion the propeller is removed from the aircraft, but no later than 1 April 1999.\n\nThis Airworthiness Directive becomes effective on 8 October 1998.\n\nBackground: After an accident investigation it was found that the strength values of the propeller mounting bolts were below design specifications. The lower design specifications of the bolts could lead to premature failure of the bolts and subsequent separation of the propeller in flight.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific manufacturing defect in a specific aircraft component. The scope remains precisely limited to the identified safety risk and does not extend beyond the original purpose of ensuring airworthiness of the affected propeller bolts."},"complexity_factors":["Single, specific technical subject matter (one bolt part number on two propeller models)","Only two substantive requirements (inspect and replace)","Minimal defined terms (only standard aviation abbreviations like P/N for 'part number')","Simple compliance timeline with clear deadlines","No cross-references to other legislation or complex conditional logic","Short document (approximately 200 words)"],"plain_english_summary":"This Airworthiness Directive orders operators of aircraft fitted with certain Hoffman propellers (HO 27 / HO4 27 using FP20-147 mounting bolts) to inspect the installation and replace suspect bolts with correctly marked, higher‑strength bolts. It applies to anyone with these propellers — or who cannot verify bolt type — because deficient bolts were found that risk bolt failure and propeller separation in flight."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The Directive's scope follows its stated safety purpose: it targets bolts P/N FP20‑147 on specified Hoffman propellers and treats unidentified bolts as subject. It does not expand to other parts, models, or broader maintenance regimes beyond referencing ongoing torque requirements (Notes, Requirement)."},"complexity_factors":["Applicability scope: Covers all Hoffman HO 27 and HO4 27 propellers using bolts P/N FP20‑147; if PN cannot be positively established, the bolts are assumed to be FP20‑147 (Applicability).","Two-tier timing: Immediate inspection required within 30 days; physical replacement deferred until next propeller removal but with an absolute backstop date (Compliance).","External-document dependency: Inspection and replacement procedures are defined by Hoffman Propeller Service Bulletin SB 61-11-03 E10 Revision A — operator must obtain and follow that SB (Requirement).","Part identification and verification burden: Operators must positively identify part numbers or apply the conservative assumption, increasing record‑check and inspection workload (Applicability).","Parts/availability constraint: Replacement requires serviceable bolts marked with a “V”; sourcing correct marked parts may involve supply-chain delays or certification checks (Requirement).","Operational disruption and scheduling cost: Replacement at removal or by deadline imposes maintenance scheduling and possible downtime for aircraft owners (Compliance).","Technical specificity vs. enforcement: The Directive prescribes a specific PN and marking but relies on external SB for detailed methods, creating potential ambiguity in acceptable evidence of compliance (Requirement, Note 2).","Safety rationale tied to accident findings: Background links action to understrength bolts causing risk of propeller separation; this focuses the measure narrowly but imposes immediate compliance costs on affected parties (Background)."],"plain_english_summary":"This Directive requires owners/operators of Hoffman fixed‑pitch propellers (HO 27 and HO4 27 models) to inspect installations and replace any propeller mounting bolts part number FP20‑147 with serviceable bolts marked with a “V”, following a Hoffman Service Bulletin. Inspections must occur within 30 days and replacements at next propeller removal or by 1 April 1999.\n\nIt affects aircraft operators, maintenance providers and parts suppliers because an accident found these bolts may be understrength and could lead to in‑flight propeller separation if not replaced."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pfp-18-hoffman-propeller-bolt-replacement","history":"/api/acts/ad-pfp-18-hoffman-propeller-bolt-replacement/history","analysis":"/api/acts/ad-pfp-18-hoffman-propeller-bolt-replacement/analysis","conflicts":"/api/acts/ad-pfp-18-hoffman-propeller-bolt-replacement/conflicts","importantCases":"/api/acts/ad-pfp-18-hoffman-propeller-bolt-replacement/important-cases","documents":"/api/acts/ad-pfp-18-hoffman-propeller-bolt-replacement/documents"}}