{"id":"F2006B09575","name":"AD/ENST 28/2 Amdt 2 - Stabilizer Spar Attachment","slug":"ad-enst-28-2-amdt-2-stabilizer-spar-attachment","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54260,"registerId":"commonwealth-F2006B09575-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/2 Amdt 2 - Stabilizer Spar Attachment","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 28/2\n\nAmdt 2\n\n  \n\nStabilizer Spar Attachment 5/88 DM\n\nApplicability: All models F28, F28A, F28C and F28C-2 helicopters, and all model F28F up to and including S/N 743.\n\nRequirement: 1. Check the security of the attachment of both left and right stabilizers as detailed in section 5.1 of Enstrom Helicopter Corporation Service Directive Bulletin (SDB) 0076 of 15 December 1987.\n\n    2. Inspect and measure the stabilizer spars and attachments as detailed in section 5.2 of SDB 0076.\n\n    3. Remove from service any stabilizer spar having a nominal wall thickness of .035 inch.\n\nCompliance: For para 1 of the Requirement:\n\nBefore each flight.\n\nNote: This inspection may be performed by the pilot in command in which case certification is not required.\n\nFor para 2 of the Requirement:\n\n    (a) if never previously inspected in accordance with previous issues of this Directive; within the next 10 hours time in service after 22 January 1988.\n\n    (b) If previously inspected in accordance with previous issues of this Directive; within 50 hours time in service after the last such inspection or within 10 hours time in service after 22 January 1988, whichever is the later.\n\n    (c) Thereafter, repeat the inspections at intervals not exceeding 100 hours component time in service.\n\nFor para 3 of the Requirement:\n\nPrior to further flight after detection.\n\nBackground: These Requirements follow the November 1987 in-flight failure (overseas) of a spar with .049 inch wall thickness. Amendment 1 which was issued by telex, extended the inspection to additional helicopter models and made the inspection more explicit and more intensive, and effectively placed a 500 hour life on the .039 inch wall thickness spars. Further review has shown this to be unconservative, this amendment therefore requires the thin wall spars, once identified, to be removed before further flight in accordance with SDB 0076.","sortOrder":0}],"analysis":{"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":3,"scope_assessment":{"changed":true,"description":"The original directive (implied by Amendment 1) allowed 0.039 inch wall thickness spars to remain in service for up to 500 hours. This Amendment 2 significantly tightens the scope by requiring immediate removal of the thinnest spars (0.035 inch) before further flight, removing the 500-hour grace period. The scope shifted from 'inspect and monitor' to 'inspect and immediately ground if defective'."},"complexity_factors":["Single technical subject matter (stabilizer spar inspection) with clear sequential requirements","Three distinct compliance timelines with conditional logic (never inspected vs. previously inspected vs. recurring intervals)","Cross-reference to external technical document (Enstrom SDB 0076) for detailed procedures","Specific applicability criteria (model numbers and serial number cutoff)","One nested condition: pilot-performed inspection exempts certification requirement","No defined terms section — uses plain technical language","Short document (approximately 250 words) with clear paragraph numbering"],"plain_english_summary":"Owners and operators of certain Enstrom F‑28 series helicopters must perform preflight checks and regular thickness inspections of tail stabilizer spars, and remove any spar found with a 0.035‑inch wall before further flight. This CASA Airworthiness Directive tightens earlier rules after a spar failure overseas, imposing short-term inspection windows and recurring checks to prevent catastrophic stabilizer failure. It affects pilots, owners and maintenance personnel of the listed F‑28 helicopters."},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"Yes. Amendment 1 had extended inspections to additional models and effectively imposed a 500‑hour life on .039‑inch spars; this amendment replaces that approach by requiring identified thin‑wall spars to be removed before further flight (Background; Requirement para 3), thereby tightening retirement/removal rules and altering the prior service life treatment."},"complexity_factors":["Applicability spans multiple airframe models and a serial‑number cut‑off for F28F (Applicability) — increases tracking and parts/records complexity.","Tiered inspection timing and conditional windows: before each flight (Requirement para 1); initial detailed inspections with different deadlines depending on prior inspections (Requirement para 2(a),(b)); recurring 100‑hour component intervals (Requirement para 2(c)).","Mandatory removal threshold tied to a measured nominal wall thickness of 0.035 inch (Requirement para 3) — requires precise measurement and judgment.","Procedural reliance on an external technical document (Enstrom SDB 0076, sections 5.1 and 5.2 referenced in Requirement) — adds dependency on vendor procedures for compliance.","Option for pilot to perform the before‑flight inspection without certification (Note under Requirement para 1) — shifts some compliance responsibility to flight crew and affects training/documentation.","Immediate grounding consequence: removal prior to further flight after detection (Requirement para 3 compliance) — operational disruption and logistical replacement/repair burden.","Regulatory history / amendment interaction (Background) — reconciling prior Amendment 1 measures (500‑hour life on .039\" spars) with the current removal mandate adds interpretive complexity for operators and maintainers."],"plain_english_summary":"Requires operators of Enstrom F‑28 series (all F28, F28A, F28C, F28C‑2 and F28F up to S/N 743) to perform pre‑flight checks of stabilizer attachments before each flight, carry out detailed inspections and measurements per Enstrom Service Directive Bulletin 0076 on a defined schedule, and remove any stabilizer spar with nominal wall thickness 0.035 inch before further flight. Pilots may perform the pre‑flight check without certification. The directive follows an in‑flight spar failure and tightens inspection and retirement rules."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-2-amdt-2-stabilizer-spar-attachment","history":"/api/acts/ad-enst-28-2-amdt-2-stabilizer-spar-attachment/history","analysis":"/api/acts/ad-enst-28-2-amdt-2-stabilizer-spar-attachment/analysis","conflicts":"/api/acts/ad-enst-28-2-amdt-2-stabilizer-spar-attachment/conflicts","importantCases":"/api/acts/ad-enst-28-2-amdt-2-stabilizer-spar-attachment/important-cases","documents":"/api/acts/ad-enst-28-2-amdt-2-stabilizer-spar-attachment/documents"}}