{"id":"F2006B09270","name":"AD/DHE/20 Amdt 1 - Propeller Shaft - Inspection and Modification","slug":"ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53295,"registerId":"commonwealth-F2006B09270-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHE/20 Amdt 1 - Propeller Shaft - Inspection and Modification","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nDe Havilland Piston Engines\n\nAD/DHE/20\n\nAmdt 1\n\n  \nPropeller Shaft \\- Inspection and Modification 3/68\n\nApplicability: All GQ 70 series which have been repaired in accordance with one or more of the following modifications and repair schemes. Mod. 1399 (R155), Mod. 1609 (R259), Mod. 2289 (R155 and R259, with introduction of 70 Mk. 2). Mod. 2931 (R563 and R564) Repair scheme R155 and R259 (70 Mk. 3).\n\nDocument: Inspection \\- Bristol Siddeley TNS GQ70 No. 105 Modification \\- Mod. No. 2925.\n\nCompliance: Inspection \\- within 100 hours time in service after 21 March 1968 and thereafter at intervals not exceeding 400 hours time in service until Mod. 2925 is incorporated. Modification - Before installation is an aircraft following next overhaul completed after 21 March 1968.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive (AD/DHE/20). The scope remains tightly focused on the original purpose: ensuring airworthiness of De Havilland GQ 70 series propeller shafts. The amendment appears to update compliance timeframes or applicability details without expanding beyond the specific engine model and defect originally targeted."},"complexity_factors":["Single, specific technical subject matter (propeller shaft inspection)","Limited applicability — only affects GQ 70 series engines with specific historical repair schemes (5 specific mods/repairs listed)","Clear binary compliance structure: inspection schedule OR modification deadline","No nested definitions or extensive cross-referencing to other legislation","Specific numeric thresholds (100 hours, 400 hours, date 21 March 1968) provide concrete compliance criteria","Document references are external technical standards (Bristol Siddeley TNS GQ70 No. 105) rather than legislative cross-references"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's aviation regulator (CASA) that requires specific maintenance actions on aircraft engines.\n\n**What it does:**\n- Requires owners/operators of certain **De Havilland GQ 70 series piston engines** to inspect and modify the propeller shaft.\n- **Inspection requirement:** Must check the propeller shaft within 100 hours of flying time after 21 March 1968, then re-check every 400 hours until a specific modification is done.\n- **Modification requirement:** Must install a specific engineering fix (Modification No. 2925) before putting the engine back into an aircraft after its next major overhaul following 21 March 1968.\n\n**Who it affects:**\n- Owners and operators of aircraft with GQ 70 series engines that were previously repaired using specific modification schemes (Mods 1399, 1609, 2289, 2931, or repair schemes R155, R259, R563, R564).\n\n**Why it matters:**\n- This is a **safety-critical mandate**. Propeller shaft failures can cause catastrophic engine failure and loss of aircraft control. The directive addresses a known defect or wear pattern discovered in engines that underwent certain historical repairs.\n- Non-compliance is illegal — aircraft cannot fly legally without meeting these requirements.\n\n**Key technical terms explained:**\n- **Time in service:** Actual flying hours (not just calendar time or engine running time).\n- **Overhaul:** A major rebuild where the engine is completely disassembled, inspected, and rebuilt to factory specifications.\n- **Modification (Mod.):** An approved engineering change to the original design."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This entry is an amendment (Amdt 1) to AD/DHE/20. The amended text prescribes inspection intervals (initial 100 hours after 21 March 1968, then at intervals not exceeding 400 hours) and requires incorporation of Mod. 2925 before installation after the next overhaul; it applies specifically to GQ 70 series engines repaired under the listed modifications and repair schemes. Those elements (applicability, inspection timing, and mandatory incorporation of Mod. 2925) reflect a defined scope change implemented by this amendment."},"complexity_factors":["Multiple specific prior modification and repair-scheme references make applicability dependent on historical records (Applicability).","Two-step compliance regime: interim recurring inspections with a defined interval until a permanent modification is fitted (Compliance).","Requirement to acquire and follow a named inspection document and to install a specific modification number (Document).","Timing linkage to overhauls (modification must be fitted before installation following the next overhaul after a fixed date) creates scheduling constraints (Compliance)."],"plain_english_summary":"This instrument mandates recurring inspections of the propeller shaft on specified De Havilland GQ 70 series engines using Bristol Siddeley TNS GQ70 No.105 and requires incorporation of Mod. 2925. It applies to engines repaired under the listed mods/repair schemes and makes operators/owners responsible for inspection costs and modification work.\n\nInspections are due within 100 hours TIS after 21 March 1968 and every 400 hours until Mod. 2925 is fitted; the modification must be installed before reinstalling the engine after the next overhaul."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification","history":"/api/acts/ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification/history","analysis":"/api/acts/ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification/analysis","conflicts":"/api/acts/ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification/important-cases","documents":"/api/acts/ad-dhe-20-amdt-1-propeller-shaft-inspection-and-modification/documents"}}