{"id":"F2006B09901","name":"AD/F50/71 - Wings - Bottom Skin Access Covers","slug":"ad-f50-71-wings-bottom-skin-access-covers","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55079,"registerId":"commonwealth-F2006B09901-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/71 - Wings - Bottom Skin Access Covers","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/F50/71 Wings - Bottom Skin Access Covers 8/96\n\nApplicability: Model F.27 Mk 050 Serial numbers 20103 to 20263. Requirement:  Action in accordance with Fokker SB F50-57-015.\n\nNote: RLD BLA 1996-042(A) refers.\n\n \n\nCompliance: Prior to the accumulation of 24,000 flight cycles since new.\n\n \n\nThis Directive has effect from 18 July 1996.\n\n \n\nBackground: The heads of some countersunk screws used to attach access panels P/N 923AB and 924AB have been found not to be seating properly. This condition may result in unequal loads and cause fatigue cracking in the rabbets of the centre wing bottom skin.\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":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies to a defined set of aeroplanes (F.27 Mk 050 serial numbers 20103–20263) and requires action in accordance with a named Fokker service bulletin prior to a specified flight-cycle threshold. The text does not expand the affected fleet, the types of actions required, or the compliance window beyond those specified terms, so the scope as stated remains targeted to those aircraft and that remedial action. (See: \"Applicability\", \"Requirement\", \"Compliance\".)"},"complexity_factors":["Narrow applicability limited to a specific model and serial-number range (reduces administrative complexity). (Applicability)","Mandates action by direct reference to an external manufacturer service bulletin, requiring access to that document for technical detail (adds procedural dependency). (Requirement)","Compliance tied to an aircraft usage metric (flight cycles), requiring operators to track cycles accurately. (Compliance)","Potential for follow-on technical work if inspection finds damage (introduces variable downstream repair complexity). (Background)","Clear effective date fixes timing but provides no staged or phased compliance options in the text (administrative rigidity). (Effect date)"],"plain_english_summary":"### What this directive does (mechanical change)\n\nThis Airworthiness Directive requires operators of specific Fokker F.27 Mk 050 (F50) aeroplanes (serial numbers 20103 to 20263) to carry out the work set out in Fokker Service Bulletin F50-57-015 before each affected aeroplane accumulates 24,000 flight cycles since new. (See: \"Applicability\", \"Requirement\", \"Compliance\").\n\nThe directive took legal effect on 18 July 1996. (See: \"This Directive has effect from 18 July 1996.\")\n\n### Official reason given\n\nThe directive states that some countersunk screw heads used to attach bottom access panels P/N 923AB and 924AB were not seating properly. The stated concern is that this may cause unequal loads and lead to fatigue cracking in the rabbets of the centre wing bottom skin. (See: \"Background\" and \"Requirement\").\n\n### Who it affects and who pays\n\n- Affected parties: operators (owners/airlines/maintenance organisations) of Fokker F.27 Mk 050 aeroplanes with serial numbers 20103–20263. (See: \"Applicability\".)\n- Who pays: the directive requires the operator to perform the work specified in the Fokker service bulletin. That implies the operator bears direct costs for inspection, labour, parts and any consequential repairs or downtime needed to comply. (See: \"Requirement\" and \"Compliance\".)\n\n### What decisions and behaviour change\n\n- Operators must arrange for inspection and any follow-up corrective action described in Fokker SB F50-57-015 by the specified flight-cycle milestone (prior to 24,000 flight cycles since new). (See: \"Requirement\" and \"Compliance\".)\n- The directive is prescriptive rather than discretionary: it points to a specific service bulletin as the required action. (See: \"Requirement: Action in accordance with Fokker SB F50-57-015.\")\n\n### Costs, incentives, trade-offs and implementation points\n\n- Compliance burden: operators must schedule maintenance/inspections for the affected serial-numbered fleet, allocate labour and parts, and accept aircraft downtime while work is carried out. The service bulletin will contain the technical steps; accessing countersunk screws and panels can require removal of coverings and time in the maintenance schedule. (See: \"Requirement\" and \"Background\".)\n- Measurement: compliance is tied to flight cycles. Operators must know each aircraft's accumulated cycles to determine the compliance window (prior to 24,000 flight cycles since new). (See: \"Compliance\".)\n- Implementation risk and consequential repairs: if inspections find improperly seated screw heads or fatigue cracking, additional repairs beyond the initial inspection may be required. That increases cost and aircraft downtime relative to a simple inspection. (See: \"Background\".)\n- Incentives: operators are required to follow the specified actions; the directive creates an incentive to perform the mandated work by the cycle threshold. The text points operators to the manufacturer service bulletin for the technical remedy. (See: \"Requirement\".)\n\n### Concentration of benefits and costs\n\n- Benefits are concentrated on maintaining structural integrity for the specific aircraft at risk (those serial numbers cited). Costs are concentrated on operators of those aircraft, who must fund and schedule the work. (See: \"Applicability\", \"Requirement\", \"Compliance\".)\n\n### Administrative discretion and source of authority\n\n- The directive is framed as a mandatory action tied to a named service bulletin; it leaves little operational discretion about what action must be taken, but the exact technical method is delegated to the manufacturer's service bulletin referenced. (See: \"Requirement: Action in accordance with Fokker SB F50-57-015.\")\n- The document states the date the Directive has effect, which fixes when compliance obligations apply. (See: \"This Directive has effect from 18 July 1996.\")\n\nSummary of key citations from the directive: Applicability (serial numbers 20103–20263); Requirement (do work per Fokker SB F50-57-015); Compliance (prior to 24,000 flight cycles since new); Background (countersunk screw heads not seating properly could lead to fatigue cracking); Effect date (18 July 1996)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating inspection/repair of wing access cover screws."},"complexity_factors":["Very short document (under 200 words)","Only 2 defined applicability criteria (model and serial number range)","Single compliance trigger (24,000 flight cycles)","No cross-references to other legislation or complex conditional logic","Refers to external technical document (Fokker SB) for actual procedure rather than embedding it","Straightforward cause-and-effect explanation in background section"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **Fokker F50 aircraft**.\n\n**What it does:**\n- Requires owners/operators of specific Fokker F50 planes (serial numbers 20103 to 20263) to inspect and fix a problem with screws on wing access panels.\n- The problem: Some screws on bottom skin access covers aren't sitting flush properly, which can cause uneven pressure and eventually lead to **fatigue cracking** (tiny cracks that grow over time due to repeated stress) in the wing structure.\n\n**Who must act:**\n- Operators of affected Fokker F50 aircraft before they reach 24,000 flight cycles (roughly takeoffs and landings) since the plane was new.\n\n**Why it matters:**\n- Fatigue cracking in wing structures can compromise aircraft safety. This directive prevents potential structural failure by catching the screw problem early.\n\n**What to do:**\n- Follow the instructions in **Fokker Service Bulletin F50-57-015** (the manufacturer's official repair notice)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-71-wings-bottom-skin-access-covers","history":"/api/acts/ad-f50-71-wings-bottom-skin-access-covers/history","analysis":"/api/acts/ad-f50-71-wings-bottom-skin-access-covers/analysis","conflicts":"/api/acts/ad-f50-71-wings-bottom-skin-access-covers/conflicts","importantCases":"/api/acts/ad-f50-71-wings-bottom-skin-access-covers/important-cases","documents":"/api/acts/ad-f50-71-wings-bottom-skin-access-covers/documents"}}