{"id":"F2006B09570","name":"AD/ENST 28/15 Amdt 2 - Tail Rotor Spindle and Drive Shaft - Inspection and Retirement","slug":"ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54242,"registerId":"commonwealth-F2006B09570-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/15 Amdt 2 - Tail Rotor Spindle and Drive Shaft - Inspection and Retirement","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)  \nEnstrom F-28 Series Helicopters\n\nAD/ENST 28/15\n\nAmdt 2\n\n  \n\nTail Rotor Spindle and Drive Shaft \\- Inspection and Retirement\n\n  \n8/77\n\nApplicability: All models F-28 and 280.\n\nRequirement: 1. Remove tail rotor spindles P/N 28-15202 from service and replace with a new spindle P/N 28-15202-13 or a re- worked spindle which may be identified by an 8- character serial number acid etched on the outside of the spindle centre section.\n\n    2. Install tail rotor strike tabs in accordance with Enstrom Service Directive Bulletin No. 0037 Revision A or FAA AD 77-04-04 Amendment 39-2839.\n\n    3. Inspect the tail rotor spindle in accordance with the above Bulletin or FAA AD.\n\n    4. Inspect the tail rotor drive shaft in accordance with Enstrom ServiceDirective Bulletin No. 0039.\n\nCompliance: For Para. 1 \\- Within 10 hours time in service after 17 August 1977.\n\nFor Para. 2 \\- Forthwith.\n\nFor Para. 3 and 4 \\- Before further flight following any tail rotor strike.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 2 to an existing Airworthiness Directive, but the scope remains tightly focused on tail rotor spindle and drive shaft safety for Enstrom F-28/280 helicopters. The amendments appear to refine or update the original safety requirements without expanding beyond the original safety purpose."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined compliance actions with clear, numbered requirements","Single cross-reference to external documents (Enstrom Service Directive Bulletins and FAA AD)","Simple conditional logic: inspections triggered only by a specific event (tail rotor strike)","No nested exceptions or complex definitions section","Clear applicability statement (all F-28 and 280 models)"],"plain_english_summary":"This CASA Airworthiness Directive applies to all Enstrom F‑28 and 280 helicopters and mandates safety fixes to prevent catastrophic tail‑rotor failure. It requires replacing old tail‑rotor spindles with improved or reworked units (10 flight‑hour compliance window from 17 Aug 1977), immediate installation of tail‑rotor strike tabs, and inspections of the spindle and drive shaft after any tail‑rotor strike before further flight."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"As an amendment (Amdt 2), the directive replaces earlier wording by mandating retirement of original tail rotor spindles P/N 28‑15202 and specifying acceptable replacements (new P/N 28‑15202‑13 or reworked units with an 8‑character acid‑etched serial number). It also adds a mandatory installation of tail‑rotor strike tabs and explicit inspection requirements for spindles and drive shafts, with defined short compliance timelines (10 hours for replacement, immediate for tabs, inspection before further flight after a strike)."},"complexity_factors":["Part‑number specific mandate (replace P/N 28‑15202 with P/N 28‑15202‑13 or an approved reworked spindle identified by an 8‑character acid‑etched serial number)","Cross‑reference to manufacturer Service Directive Bulletin No. 0037 Revision A, Service Directive Bulletin No. 0039, and FAA AD 77‑04‑04 for procedural detail","Short compliance windows (10 hours for replacement; immediate for strike tabs; inspections before further flight after any strike)","Multiple required actions (replacement, installation of strike tabs, two distinct inspections)","Applicability to all F‑28 and 280 models creates broad operational coverage","Operational disruption risk: grounding until inspections/repairs completed after a tail‑rotor strike","Logistical burden on operators to source new or certified reworked spindles and to perform/record inspections","Limited technical discretion for operators — specific part numbers and identification methods prescribed","Enforcement and certification depend on regulator oversight and compliance records"],"plain_english_summary":"This airworthiness directive forces owners/operators of Enstrom F‑28 and 280 helicopters to replace tail rotor spindles P/N 28‑15202 with a new P/N 28‑15202‑13 or an approved reworked spindle, fit tail‑rotor strike tabs, and carry out inspections of the spindle and drive shaft (including after any tail‑rotor strike). Replacement must occur within 10 flight hours of 17 August 1977; tabs immediately; inspections before further flight after a strike. Costs and compliance duties fall on aircraft owners/operators; the regulator enforces the AD."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement","history":"/api/acts/ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement/history","analysis":"/api/acts/ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement/analysis","conflicts":"/api/acts/ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement/conflicts","importantCases":"/api/acts/ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement/important-cases","documents":"/api/acts/ad-enst-28-15-amdt-2-tail-rotor-spindle-and-drive-shaft-inspection-and-retirement/documents"}}