{"id":"F2006B09089","name":"AD/DHC-3/39 - Elevator Servo Tab","slug":"ad-dhc-3-39-elevator-servo-tab","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115642,"registerId":"commonwealth-F2006B09089-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\n![](image.001.png)  \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 CAR 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\nDHC-3 (Otter) Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/DHC-3/39 Elevator Servo Tab 3/2003","sectionType":"part","heading":"AD/DHC-3/39 Elevator Servo Tab 3/2003","content":"# AD/DHC-3/39 Elevator Servo Tab 3/2003\n\nApplicability: All Model DHC-3 aircraft incorporating 524085 BC Ltd (Viking Air Ltd) Supplemental Type Certificate (STC) No. SA99-219, Issue 1 or 2.\n\nRequirement: Incorporate the Redesigned Elevator Tab, introduced by Viking Air Ltd. Retro Kit No. V3MK1151, in accordance with Viking Air Service Bulletin No. V3/01 dated 6 March 2002.\n\nNote: Transport Canada AD CF-2002-48 refers.\n\nCompliance: Within 300 hours time in service after 20 March 2003 or before 31 July 2003, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 20 March 2003.\n\nBackground: There has been one reported incident of structural failure of the right hand Elevator Servo Tab Balance Assembly (Viking part number VALTOC1136-2) approximately 120 hours after installation of the Flutter Prevention Modification Kit STC SA99-219. This resulted in vibration and flutter of the elevator servo tab.\n\n![Signature: David Alan Villiers](image.002.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 30 January 2003\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD targets a clearly identified subset of DHC-3 aircraft (those with STC SA99-219 Issue 1 or 2) and requires a specific retrofit. The text does not expand applicability beyond that population or add further obligations, so there is no change in scope from the action described."},"complexity_factors":["Narrow technical applicability limited to DHC-3 aircraft that incorporate Viking STC SA99-219 Issue 1 or 2 (Applicability) — reduces scope but concentrates affected parties.","Mandates a specific retrofit kit and compliance with a named service bulletin (Retro Kit No. V3MK1151; Viking Service Bulletin V3/01) (Requirement) — creates procurement and technical-standards dependence.","Fixed, short compliance window framed as either flight hours or a calendar date (300 hours after 20 March 2003 or before 31 July 2003) (Compliance) — schedules maintenance workload and may force out-of-cycle shop visits.","Technical cause stated as a structural failure of a particular balance assembly leading to vibration/flutter (Background) — remedy requires hands-on structural/flight-control work and qualified maintenance personnel.","Cross-reference to a foreign regulator's AD (Transport Canada AD CF-2002-48) (Note) — introduces cross-jurisdictional alignment and reliance on external certification/documentation.","Costs and action are borne by aircraft owners/operators (Requirement/Compliance) — the operator pays for the kit and installation, and must organise compliance.","Administrative issuance and enforceability via CASA delegate signature — standard regulatory discretion/administration point but no unusual delegations in the text."],"plain_english_summary":"Requires installation of a redesigned elevator servo tab (Viking Retro Kit No. V3MK1151) on DHC-3 (Otter) aircraft that carry Viking Air Ltd STC SA99‑219, Issue 1 or 2. CASA says the retrofit corrects a reported structural failure of the elevator servo tab balance assembly that produced vibration and flutter. Owners/operators must fit the kit per Viking Service Bulletin V3/01 within 300 flight hours after 20 March 2003 or by 31 July 2003, whichever is earlier."},"summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This instrument imposes a new airworthiness directive requirement; it does not amend another legislative instrument."},"complexity_factors":["Requires cross-referencing a specific Supplemental Type Certificate and Viking Air service bulletin to determine applicability and compliance.","Compliance deadline has passed, but the AD imposes an ongoing airworthiness obligation for any affected aircraft entering or remaining in service.","The directive applies to a narrow subset of DHC-3 aircraft, making applicability checks dependent on modification records."],"plain_english_summary":"This AD applies to De Havilland DHC‑3 (Otter) aircraft fitted with STC SA99‑219 (Viking Air). It was issued after a right‑hand elevator servo tab balance assembly failed ~120 hours post‑STC, causing vibration/flutter that could lead to loss of control.\n\nThe AD mandates installing Viking Air Retrofit Kit V3MK1151 per Service Bulletin V3/01 (6 Mar 2002); compliance was required by the earlier of 300 hours TIS after 20 Mar 2003 or 31 Jul 2003. Compliance is mandatory for Australian airworthiness; CASA may approve alternatives under the Regulations."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope: addressing a specific structural failure in a specific modification kit on a specific aircraft type. There is no evidence of scope creep; it targets exactly the unsafe condition described in the background."},"complexity_factors":["Single, clearly defined applicability (specific aircraft model + specific STC numbers)","Single mandatory action with explicit reference to manufacturer documentation","Simple compliance deadline (whichever-comes-first formula with two clear dates)","Only 1 defined term implicitly used (STC — Supplemental Type Certificate)","No nested exceptions or conditional logic","Short document (approximately 250 words)","Clear causal chain in background section (failure → vibration/flutter → mandatory fix)"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's aviation regulator (CASA) requiring specific repairs or modifications to aircraft.\n\n**What it does:** It orders owners/operators of certain De Havilland Canada DHC-3 \"Otter\" aircraft to replace a faulty elevator servo tab (a small control surface on the tail that helps pilots move the main elevator) with a redesigned, safer version.\n\n**Who it affects:** All DHC-3 aircraft that have been modified with a specific Supplemental Type Certificate (STC) — basically an approved aftermarket modification kit — issued by Viking Air Ltd (numbers SA99-219, Issue 1 or 2).\n\n**Why it matters:** One aircraft already suffered structural failure of this part about 120 hours after the modification was installed. The failure caused dangerous vibration and \"flutter\" (rapid, uncontrolled oscillation that can destroy control surfaces). This AD prevents potential crashes by forcing replacement of the defective design before it fails again.\n\n**What must be done:** Install Viking Air's redesigned elevator tab using Retro Kit V3MK1151, following their Service Bulletin V3/01 dated 6 March 2002.\n\n**When:** Within 300 flight hours after 20 March 2003, or before 31 July 2003 — whichever comes first. The AD takes effect on 20 March 2003."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-3-39-elevator-servo-tab","history":"/api/acts/ad-dhc-3-39-elevator-servo-tab/history","analysis":"/api/acts/ad-dhc-3-39-elevator-servo-tab/analysis","conflicts":"/api/acts/ad-dhc-3-39-elevator-servo-tab/conflicts","importantCases":"/api/acts/ad-dhc-3-39-elevator-servo-tab/important-cases","documents":"/api/acts/ad-dhc-3-39-elevator-servo-tab/documents"}}