{"id":"F2006B09722","name":"AD/F27/155 - Aileron Spring Tab Balance Unit","slug":"ad-f27-155-aileron-spring-tab-balance-unit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115905,"registerId":"commonwealth-F2006B09722-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nFokker F27 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/F27/155 Aileron Spring Tab Balance Un","sectionType":"part","heading":"AD/F27/155 Aileron Spring Tab Balance Unit 7/2003","content":"# AD/F27/155 Aileron Spring Tab Balance Unit 7/2003\n\nApplicability: All Model F.27 Mk.100 through Mk. 700 series aircraft.\n\nRequirement: Inspect, and if necessary, replace the aileron spring tab balance units in accordance with Part 2, Accomplishment Instructions of Fokker Service Bulletin F27/27-137, dated 19 March 2003.\n\nNote: Netherlands CAA AD 2003-037 refers.\n\nCompliance: Before 1 May 2005, unless already accomplished.\n\nThis Airworthiness Directive becomes effective on 10 July 2003.\n\nBackground: The CAA-NL received a report of an in- flight incident where the flight crew had to apply aileron trim during heavy turbulence. After landing, inspection revealed that the left hand aileron was hanging down approximately 25 mm. A subsequent detailed inspection uncovered damage to the stop of the aileron spring tab; and the skin was damaged due to overtravel of the push-pull rod. After removal from the aircraft, the affected aileron was inspected and a crack was found in the upper inboard attachment lug of the aileron spring tab balance unit housing. Failure of all four attachment lugs could result in total loss of roll control for the affected wing.\n\n![Signature of David Villiers, Delegate of the Civil Aviation Safety Authority.](image.002.jpeg)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 29 May 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 18 June 2003.","sortOrder":1}],"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD reproduces the Netherlands CAA concern and applies to all listed Fokker F.27 Mk.100–Mk.700 aircraft, requiring inspections per the manufacturer service bulletin. It does not broaden applicability beyond those models or extend requirements beyond the specified inspection/replacement instruction and compliance date."},"complexity_factors":["Narrow technical scope: single component (aileron spring tab balance unit) and a single manufacturer service bulletin specified.","Clear applicability: limited to F.27 Mk.100–Mk.700 models.","Fixed compliance deadline (before 1 May 2005) reduces scheduling ambiguity.","Safety-critical failure mode (possible total loss of roll control) raises urgency and inspection scrutiny.","Operational cost and logistics concentrated on aircraft operators (inspection and replacement costs).","Dependence on external document (Fokker Service Bulletin) for accomplishment instructions may require access and interpretive judgment by maintenance organisations.","Regulatory basis cited (CASR subreg 39.1(1)) is straightforward; minimal discretionary enforcement described in source text."],"plain_english_summary":"This directive requires operators of all Fokker F.27 Mk.100–Mk.700 aircraft to inspect — and if necessary replace — the aileron spring tab balance units following Fokker Service Bulletin F27/27-137. The action must be done by 1 May 2005 (Requirement; Compliance). Operators pay for inspections and any replacements; CASA issued the AD under CASR subreg 39.1(1). The background notes that failure of the attachment lugs could lead to total loss of roll control for one wing, so the inspection targets a specific safety risk."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific mechanical failure mode discovered through incident reporting. The scope remains precisely limited to the identified unsafe condition on the specified aircraft type."},"complexity_factors":["Single, specific mechanical component targeted (aileron spring tab balance unit)","Clear, single requirement: inspect and replace per referenced service bulletin","Simple binary applicability (all F.27 Mk.100-Mk.700 series)","Single compliance deadline with one exception clause (\"unless already accomplished\")","No nested definitions, cross-references limited to one external service bulletin and one foreign aviation directive","Background narrative is descriptive rather than legalistic"],"plain_english_summary":"This CASA safety order requires owners/operators of Fokker F27 Mk.100–Mk.700 to inspect the aileron spring tab balance unit and replace it if defective, with work completed by 1 May 2005. \n\nIt follows discovery of a cracked attachment lug after turbulence-induced control difficulty; failure of all four lugs could cause total loss of roll control, so the directive prevents a potentially catastrophic loss of ability to bank the aircraft."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f27-155-aileron-spring-tab-balance-unit","history":"/api/acts/ad-f27-155-aileron-spring-tab-balance-unit/history","analysis":"/api/acts/ad-f27-155-aileron-spring-tab-balance-unit/analysis","conflicts":"/api/acts/ad-f27-155-aileron-spring-tab-balance-unit/conflicts","importantCases":"/api/acts/ad-f27-155-aileron-spring-tab-balance-unit/important-cases","documents":"/api/acts/ad-f27-155-aileron-spring-tab-balance-unit/documents"}}