{"id":"F2006B06185","name":"AD/PHOF/1 - Blade Pitch Change Fork - Replacement","slug":"ad-phof-1-blade-pitch-change-fork-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47041,"registerId":"commonwealth-F2006B06185-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PHOF/1 - Blade Pitch Change Fork - 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 \\- Variable Pitch \\- Hoffman\n\nAD/PHOF/1 Blade Pitch Change Fork \\- Replacement 5/83\n\nApplicability: All Hoffman variable pitch Model HO-V123 series propellers fitted to Lycoming Model 0-540 and IO-540 series engines.\n\nRequirement: Required action:\n\n    (a) The forks and the pitch change blocks are to be exchanged in accordance with instructions given in overhaul manual E 105 by an appropriately approved organisation.\n\n| Part                                       | Old P/No. | New P/No. |\n| ------------------------------------------ | --------- | --------- |\n| Pitch change fork                          | VP 20-747 | VP 20-909 |\n| Pitch change block, symetric alternatively | VP 20-554 | VP 20-912 |\n| Pitch change block, unsymmetrical          | VP-20-550 | VP 20-908 |\n\n    (b) Mark modified propellers with 4 mm high letters \"SB 3\" above the manufacturing year.\n\nNote: German A.D. Luftfahrt-Bundesamt 63-303-61-83-29 refers.\n\nCompliance: Part 1: All models fitted to aerobatic certificated aircraft, by 31st July, 1983.\n\nPart 2: All other models by the next reconditioning inspection or 30th November, 1983 whichever is the sooner.\n\nBackground: The manufacturer advises that reports have been received of cracked pitch change forks particularly on aerobatic certificated aircraft, consequently a stronger designed pitch change fork has been introduced.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive does not expand or narrow the originally targeted hardware or fleet. It remains focused on Hoffman HO‑V123 propellers on Lycoming O‑540/IO‑540 engines, mandating specified part replacements, a marking, and staged compliance deadlines to address reported cracked pitch change forks."},"complexity_factors":["Technical specificity: precise part numbers listed for old and replacement parts (Requirement (a) table).","Limited applicability: applies only to Hoffman HO‑V123 series propellers on Lycoming O‑540/IO‑540 engines (Applicability).","Work must be done by an appropriately approved organisation and per overhaul manual E 105 (Requirement (a)), adding regulatory/compliance steps.","Staged compliance deadlines differentiate aerobatic certificated aircraft and others (Compliance: Part 1 and Part 2).","Marking requirement for modified propellers (“SB 3”, 4 mm high letters) adds an inspection/verifiability step (Requirement (b)).","Cross-reference to a foreign airworthiness directive (German A.D.) and manufacturer reports creates reliance on external technical findings (Note; Background).","Operational cost and scheduling burden on aircraft owners/operators (Compliance); potential logistical lead times for approved organisations to perform replacements."],"plain_english_summary":"This airworthiness directive requires replacing the blade pitch change forks and associated pitch-change blocks on Hoffman HO‑V123 variable‑pitch propellers fitted to Lycoming O‑540 and IO‑540 engines, and marking modified propellers “SB 3”. An appropriately approved overhaul organisation must perform the change per overhaul manual E 105. The manufacturer reports cracked forks; the rule is intended to reduce failure risk. Aircraft owners/operators pay for the work and must meet staged compliance dates, with aerobatic‑certificated aircraft required to comply sooner."},"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":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical defect in specific propeller models. It has not expanded beyond its original purpose of mandating replacement of defective pitch change forks."},"complexity_factors":["Single, specific technical requirement with clear part number substitutions","Only two compliance deadlines based on aircraft type (aerobatic vs non-aerobatic)","Minimal cross-referencing (one German aviation authority reference, one overhaul manual)","No nested exceptions or conditional logic — straightforward applicability rule","Short document (approximately 200 words) with simple tabular data"],"plain_english_summary":"This mandatory CASA Airworthiness Directive requires owners/operators of Hoffman HO‑V123 variable‑pitch propellers on Lycoming O‑540/IO‑540 engines to replace cracked or lower‑strength pitch‑change forks with redesigned parts, have the propeller stamped \"SB 3,\" and have work done by an approved maintenance organisation. Aerobatic aircraft must comply by 31 July 1983; all others by 30 November 1983 or at next reconditioning. Compliance prevents in‑flight propeller failure and loss of legal airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-phof-1-blade-pitch-change-fork-replacement","history":"/api/acts/ad-phof-1-blade-pitch-change-fork-replacement/history","analysis":"/api/acts/ad-phof-1-blade-pitch-change-fork-replacement/analysis","conflicts":"/api/acts/ad-phof-1-blade-pitch-change-fork-replacement/conflicts","importantCases":"/api/acts/ad-phof-1-blade-pitch-change-fork-replacement/important-cases","documents":"/api/acts/ad-phof-1-blade-pitch-change-fork-replacement/documents"}}