{"id":"F2006B10352","name":"AD/HILLER 12/24 Amdt 4 - Main Rotor Blade Doubler & Honeycomb Areas","slug":"ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115959,"registerId":"commonwealth-F2006B10352-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HILLER 12/24 Amdt 4 - Main Rotor Blade Doubler & Honeycomb Areas","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)  \nHiller UH-12 Series Helicopters\n\nAD/HILLER 12/24\n\nAmdt 4\n\n  \n\nMain Rotor Blade Doubler & Honeycomb Areas\n\n  \n3/87\n\nApplicability: All models UH-12D, UH-12E, UH-12E4, OH-23F and OH-23G.\n\nAll models converted by STC 178WE and STC 177WE fitted with main rotor blades assembly P/N 53200-03.\n\nRequirement: 1. (a) Visually inspect the main rotor blades root doubler area for evidence of delamination. This includes all doublers on the leading and trailing edge surface, upper and lower, from the fork attachment plate to the tip of the outboard doubler.\n\n(b) Visually inspect the main rotor blades for bond separation and voids along the entire length of the blade as shown in Hiller Aviation SB UH-12-51-7 Fig 1 and 2.\n\n2. Inspect and test the main rotor blades for delamination and bond separation, (Tap test), IAW Hiller Aviation SB UH- 12-51-7 and SL 51-3A.\n\nCompliance: 1.(a) & (b) before each flight.\n\nNote: This Directive shall be entered on the Maintenance Release as maintenance required. These inspections may be performed by the pilot in command, in which case certification is not required. A copy of this AD shall be carried in the aircraft.\n\n2. At each scheduled inspection for Maintenance Release issue.\n\nBackground: Bond separation has been detected in main rotor blades at the root doubler area and at the tip extending inboard for 24 inches and separation growth has been found to be very rapid on some blades. Amendment 4 to this Directive consolidates the inspections to a visual at each pre-flight inspection and aligns the additional checks with the Maintenance Release issue.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"This is Amendment 4 to an original directive from 1987 (indicated by '3/87' reference). The background explicitly states this amendment 'consolidates the inspections to a visual at each pre-flight inspection and aligns the additional checks with the Maintenance Release issue.' This represents a scope refinement — streamlining and simplifying the inspection regime from earlier versions, rather than expanding regulatory burden. The original likely had more complex or frequent inspection requirements."},"complexity_factors":["Short, single-purpose directive focused on one aircraft type and specific part","Only 2 main requirements with clear compliance timing (pre-flight vs scheduled maintenance)","References external technical documents (Hiller SB UH-12-51-7 and SL 51-3A) without reproducing their content","Minimal defined terms — relies on standard aviation terminology","Simple conditional logic: applicability determined by model number or STC conversion","No nested exceptions or complex cross-referencing within the instrument itself"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of Hiller UH‑12 series helicopters (including UH‑12D/E/E4, OH‑23F/G and certain STC‑modified aircraft using blade assembly 53200‑03) to inspect main rotor blades for delamination and bond separation. It mandates pilot pre‑flight visual checks of blade roots/length and scheduled maintenance \"tap tests\" per Hiller service bulletins; pilots may perform the pre‑flight checks but must carry the AD and record it on the Maintenance Release. It prevents rapid blade failure that could cause catastrophic loss."},"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 4 consolidated inspection requirements by specifying a visual inspection at each pre‑flight and aligning additional tap‑test checks with Maintenance Release issue. In other words, it reorganised when inspections occur (pre‑flight visual vs. scheduled maintenance tap tests) rather than changing the affected parts or models (Background)."},"complexity_factors":["Multiple affected airframes and STC conversions listed (Applicability).","Two inspection regimes with different frequencies: pre‑flight visual (before each flight) and tap/tap‑test at scheduled Maintenance Release (Requirement 1(a),(b); Compliance).","References to external technical procedures (Hiller Aviation SB UH‑12‑51‑7 and SL 51‑3A) for how to inspect and test (Requirement 2).","Operational flexibility but practical burden: pilots may perform pre‑flight inspections without certification, but they must judge delamination visually (Compliance note).","Administrative obligations: enter AD on the Maintenance Release and carry a copy in the aircraft (Compliance note).","Safety urgency and potential operational impact due to reported rapid growth of bond separation, creating possible grounding, replacement or repair actions once defects are found (Background)."],"plain_english_summary":"Requires operators of specified Hiller UH‑12 series helicopters (including certain STC conversions fitted with P/N 53200‑03 blades) to perform a visual inspection for delamination of the main rotor blade doubler and the full blade before each flight, and to perform tap‑test inspections at scheduled Maintenance Release checks per Hiller service documents. The AD must be recorded on the Maintenance Release and a copy carried in the aircraft. It responds to detected rapid bond separation and shifts recurring inspection and recordkeeping duties to pilots and maintenance personnel."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas","history":"/api/acts/ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas/history","analysis":"/api/acts/ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas/analysis","conflicts":"/api/acts/ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas/conflicts","importantCases":"/api/acts/ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas/important-cases","documents":"/api/acts/ad-hiller-12-24-amdt-4-main-rotor-blade-doubler-honeycomb-areas/documents"}}