{"id":"F2006B09798","name":"AD/F28/63 Amdt 1 - Horizontal Stabiliser Attach Fitting","slug":"ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54719,"registerId":"commonwealth-F2006B09798-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F28/63 Amdt 1 - Horizontal Stabiliser Attach Fitting","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)  \nFokker F28 Series Aeroplanes\n\nAD/F28/63\n\nAmdt 1\n\n  \nHorizontal Stabiliser Attach Fitting 5/93\n\nApplicability: Model F28 series with serial numbers 11003 through 11151, and 11991 and 11992\\. Requirement: Action in accordance with the technical requirements of RLD AD 92-119.\n\nNote: Fokker SB F28/55-29 refers.\n\nCompliance: Prior to 1 November 1995.\n\nBackground: A report was received of a major crack in the RH upper lug of the horizontal stabilizer attach fitting. Investigation revealed that it was caused by stress corrosion, to which aluminium AL7079 is known to be sensitive. A crack could cause lug fracture and hazardous movement of the horizontal stabiliser.\n\nAmendment 1 is issued to align this Directive with a new RLD AD which requires replacement of all aluminium AL7079 fittings with units made from AL7075-T73, which is less sensitive to stress corrosion.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment stays tightly within the original safety purpose — preventing catastrophic failure of the horizontal stabiliser attach fitting. The change from 'inspect/repair as needed' to 'replace all' is a strengthening of the same safety measure, not an expansion into new regulatory territory."},"complexity_factors":["Very short document (under 200 words)","Only 2 defined terms implicitly referenced (RLD AD 92-119, Fokker SB F28/55-29)","Single, unambiguous compliance requirement (replace fittings)","Clear applicability criteria (specific serial number ranges)","No nested exceptions or conditional logic","Straightforward deadline (single date, no phased compliance)"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs or inspections on certain aircraft.\n\n**What it does:** It orders owners and operators of specific Fokker F28 series aeroplanes to replace a critical part — the **horizontal stabiliser attach fitting** (the metal bracket that connects the tail's horizontal wing to the fuselage). The original aluminium fittings (made from AL7079) must be swapped for new ones made from a different, more corrosion-resistant aluminium alloy (AL7075-T73).\n\n**Why it matters:** The old fittings can develop **stress corrosion cracks** due to a known weakness in the AL7079 material. A cracked fitting could break, causing the horizontal stabiliser (the tail wing that controls the aircraft's pitch) to move dangerously or detach — potentially leading to loss of control and a crash. One major crack had already been reported before this directive was issued.\n\n**Who must comply:** Anyone operating Fokker F28 aircraft with serial numbers 11003 through 11151, or 11991 and 11992.\n\n**When:** The replacement had to be completed before 1 November 1995.\n\n**Key change in this version (Amendment 1):** Originally, the directive may have only required inspection or partial replacement. This amendment makes it mandatory to replace **all** the old AL7079 fittings with the improved AL7075-T73 version, following updated requirements from the Dutch aviation authority (RLD)."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 changes the operational requirement by aligning this AD with a revised RLD AD that requires replacement of all aluminium AL7079 horizontal stabiliser attach fittings with AL7075-T73 fittings (Amendment 1). The original AD text directs operators to act in accordance with RLD AD 92-119 (Requirement); the amendment updates the substantive technical remedy in that referenced RLD AD to mandatory replacement rather than the prior measures. The applicability (listed serial numbers) and the compliance date remain specified in this AD (Applicability; Compliance), while the technical remedy now explicitly requires material replacement (Amendment 1)."},"complexity_factors":["Cross-reference to an external technical document (RLD AD 92-119) for the substantive technical requirements increases dependency on another instrument.","Technical specificity of materials (AL7079 vs AL7075-T73) requires material-identification and correct parts procurement.","Safety-critical engineering work and airworthiness certification impose specialised maintenance and documentation processes.","Serial-number-limited applicability requires operators to identify whether individual airframes are in scope.","Compliance deadline creates scheduling and supply-chain timing pressures for parts and labour."],"plain_english_summary":"This AD requires owners/operators of specified Fokker F28 serials to replace aluminium AL7079 horizontal‑stabiliser attach fittings with AL7075‑T73 fittings per RLD AD 92‑119 by the compliance date. It responds to stress‑corrosion cracking that could cause lug fracture and hazardous stabiliser movement.\n\nAffected parties (operators, maintenance organisations and parts suppliers) bear replacement costs and scheduling burdens; the rule shifts risk mitigation from inspection to mandated material replacement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting","history":"/api/acts/ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting/history","analysis":"/api/acts/ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting/analysis","conflicts":"/api/acts/ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting/conflicts","importantCases":"/api/acts/ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting/important-cases","documents":"/api/acts/ad-f28-63-amdt-1-horizontal-stabiliser-attach-fitting/documents"}}