{"id":"F2006B09893","name":"AD/F50/64 - Seat Rails Tapered Shims","slug":"ad-f50-64-seat-rails-tapered-shims","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55043,"registerId":"commonwealth-F2006B09893-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/64 - Seat Rails Tapered Shims","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n \n\nAD/F50/64 Seat Rails Tapered Shims 5/94\n\nApplicability: Model F27 Mk 050 Series aircraft, serial numbers 20103 through 20258. Requirement:               Action in accordance with Fokker Service Bulletin F50-25-045.\n\nNote: RLD AD 94-033 (A) refers.\n\n \n\nCompliance: Prior to 1 November 1994.\n\n \n\nBackground:  The ageing of the tapered nylon shims that are installed under the seat rails from fuselage STA.14025 aft, may result in a reduction in strength of the seat rail attachments. This Directive requires the removal of the shims and the replacement of the current seat rail attachment bolts with shorter ones.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical ageing issue in a defined aircraft population. It has not expanded beyond its original purpose of ensuring seat rail structural integrity."},"complexity_factors":["Single, specific aircraft model and narrow serial number range (20103-20258)","One clear mechanical action required (remove shims, replace bolts)","No nested exceptions or conditional logic","Only one defined reference (Fokker Service Bulletin F50-25-045)","Straightforward compliance deadline with no alternative methods","Background explanation provided in plain language"],"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) for specific aircraft.\n\n**What it does:** It requires owners/operators of certain Fokker F50 aeroplanes to remove old nylon shims (thin wedge-shaped spacers) from under the seat rails and replace the attachment bolts with shorter ones.\n\n**Who it affects:** Operators of Fokker F50 aircraft with serial numbers 20103 through 20258.\n\n**Why it matters:** The nylon shims age and weaken over time. If they fail, the seat rails (which anchor passenger and crew seats to the aircraft floor) could lose strength. In turbulence or an accident, seats could detach — endangering occupants. This directive prevents that failure mode.\n\n**Key deadline:** The work had to be completed before 1 November 1994.\n\n**What triggered it:** Fokker (the manufacturer) issued Service Bulletin F50-25-045 identifying the problem, and CASA made compliance mandatory through this Directive."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive, as presented, defines a targeted corrective action for a specific set of serial-numbered aircraft: removal of tapered nylon shims under seat rails from fuselage STA.14025 aft and replacement of seat-rail attachment bolts with shorter bolts per Fokker SB F50-25-045 (Requirement; Background). There is no textual indication within the source that the scope has been altered from its original stated intent."},"complexity_factors":["Narrow applicability limited to a specific model and serial-number range (Applicability)","Single, clearly described corrective action (remove shims and install shorter bolts) (Background; Requirement)","Mandated method delegated to an external Fokker Service Bulletin (Requirement) which operators must obtain and follow","Fixed compliance deadline reduces scheduling flexibility (Compliance)","Operational risks limited to parts availability, installation accuracy and aircraft downtime (Background; Requirement)"],"plain_english_summary":"This directive requires operators of Fokker F27 Mk 50 aircraft serials 20103–20258 to follow Fokker Service Bulletin F50-25-045: remove ageing tapered nylon shims under seat rails from fuselage STA.14025 aft and fit shorter seat‑rail attachment bolts to restore attachment strength. The Civil Aviation Safety Authority mandates compliance (by 1 Nov 1994); costs and downtime fall to owners/operators and their maintenance providers."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-64-seat-rails-tapered-shims","history":"/api/acts/ad-f50-64-seat-rails-tapered-shims/history","analysis":"/api/acts/ad-f50-64-seat-rails-tapered-shims/analysis","conflicts":"/api/acts/ad-f50-64-seat-rails-tapered-shims/conflicts","importantCases":"/api/acts/ad-f50-64-seat-rails-tapered-shims/important-cases","documents":"/api/acts/ad-f50-64-seat-rails-tapered-shims/documents"}}