{"id":"F2006B09012","name":"AD/DHC-1/31 Amdt 1 - Fin Rear Spar","slug":"ad-dhc-1-31-amdt-1-fin-rear-spar","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52676,"registerId":"commonwealth-F2006B09012-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-1/31 Amdt 1 - Fin Rear Spar","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)  \nDe Havilland DHC-1 (Chipmunk) Series Aeroplanes\n\nAD/DHC-1/31\n\nAmdt 1\n\n  \nFin Rear Spar 1/96\n\nApplicability: All English production aircraft.\n\nRequirement: Inspect the fin structure for cracks and corrosion in accordance with paragraphs 2, 3 and 5 of British Aerospace Technical News Sheet (TNS) CT (C1) No. 156 Issue 4. Conduct the dye penetrant inspections in accordance with CAO 108.10.\n\nModifications H283 and H360 performed in accordance with paragraphs 3 and 5 respectively of TNS No. 156 Issue 4, cancel the re-inspection requirements of paragraphs 3 and 5 respectively.\n\nCompliance: Inspect in accordance with paragraphs 2, 3, and 5 within 3 years or 600 hours, whichever occurs first, since the last inspection.\n\nThereafter perform all the Requirement inspections at intervals not to exceed 3 years or 600 hours, whichever occurs first.\n\nThis Amendment is effective from 4 May 1996.\n\nBackground: British Aerospace has reported that cracks have been found in the fin rear spar at three critical locations, and that corrosion has been found in the internal fin structure. Amendment 1 incorporates Issue 4 of TNS No. 156, which revises paragraph 5 inspection interval from 6 years or 600 hours, to 3 years or 600 hours.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1838},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"Amendment 1 tightens the inspection interval from 6 years to 3 years but does not alter the fundamental scope covering fin rear spar inspections of DHC-1 aircraft. The change reflects increased safety vigilance rather than expansion of regulatory coverage."},"complexity_factors":["References to external technical standards (British Aerospace Technical News Sheet TNS No. 156 Issue 4 and CAO 108.10)","Dual measurement compliance periods (calendar years vs flight hours)","Conditional exemptions based on specific modification status (H283 and H360)","Technical aviation terminology requiring specialist knowledge"],"plain_english_summary":"This airworthiness directive requires owners/operators of English-built De Havilland DHC-1 Chipmunks to perform regular inspections of the fin rear spar for cracks and corrosion using dye‑penetrant methods per CAO 108.10 and British Aerospace guidance. \n\nThe first check must be done within 3 years or 600 flight hours (whichever first) and repeated at the same interval; aircraft modified with kits H283 or H360 per instructions are exempt from continued re‑inspections for those areas."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-1-31-amdt-1-fin-rear-spar","history":"/api/acts/ad-dhc-1-31-amdt-1-fin-rear-spar/history","analysis":"/api/acts/ad-dhc-1-31-amdt-1-fin-rear-spar/analysis","conflicts":"/api/acts/ad-dhc-1-31-amdt-1-fin-rear-spar/conflicts","importantCases":"/api/acts/ad-dhc-1-31-amdt-1-fin-rear-spar/important-cases","documents":"/api/acts/ad-dhc-1-31-amdt-1-fin-rear-spar/documents"}}