{"id":"F2008L04386","name":"AD/AT/30 - Rudder and Vertical Fin","slug":"ad-at-30-rudder-and-vertical-fin","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":76343,"registerId":"commonwealth-F2008L04386-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Airtractor AT-300, 400 and 500 Series Ae","sectionType":"division","heading":"Airtractor AT-300, 400 and 500 Series Aeroplanes","content":"### Airtractor AT-300, 400 and 500 Series Aeroplanes\n\n| AD/AT/30 | Rudder and Vertical Fin | 13/2008 |\n| -------- | ----------------------- | ------- |\n\n| Applicability: | Model AT-402, AT-402A, and AT-402B aircraft, serial numbers 0694 through 1176.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Visually inspect the rudder and vertical fin hinge attachment for loose fasteners, and inspect the rudder or vertical fin skins, spars, hinges, and brackets for cracks and/or corrosion in accordance with Snow Engineering Co. Service LetterNo. 247, Revised 2 June 2008, or later FAA approved revision.If any damage is detected during any Requirement 1 inspection, before further flight, replace any damaged parts with new parts, and accomplish the installation of the external doubler at the upper rudder hinge as specified in Requirement 2.2. Accomplish the installation of the external doubler at the upper rudder hinge in accordance with Snow Engineering Co. Service Letter No. 247, Revised 2 June 2008, or later FAA approved revision, and Snow Engineering Co. Process Specification Number 145, dated 6 December 1991.The installation of the external doubler at the upper rudder hinge terminates the Requirement 1 repetitive inspections.As of 18 December 2008, do not install any rudder that does not have the external doubler at the upper rudder hinge incorporated.Note: FAA AD 2008-21-08 Amdt 39-15692 refers. |\n| Compliance:    | 1. Initially inspect when the aircraft accumulates a total of 3,500 hours time in service or within 100 hours time in service after 18 December 2008, whichever occurs later. Thereafter, repetitively inspect at intervals not to exceed 100 hours time in service until the external doubler at the upper rudder hinge is incorporated.2. When the aircraft accumulates a total of 5,000 hours time in service, or within 100 hours time in service after 18 December 2008, whichever occurs later, unless already accomplished.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |\n|                | This Airworthiness Directive becomes effective on 18 December 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n\n| Background: | The FAA received a report of a loose upper rudder hinge on a Model AT-402 aircraft that was caused by fatigue. This Directive requires inspections to detect and correct loose fasteners; cracks in the rudder or vertical fin skins, spars, hinges, or brackets; or corrosion of the rudder and vertical fin hinge attachment structure. Hinge failure adversely affects ability to control yaw and has led to the rudder folding over during flight. This condition could allow the rudder to contact the elevator and affect ability to control pitch with consequent loss of control. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n28 October 2008","sortOrder":0},{"sectionNumber":"AD/AT/30","sectionType":"part","heading":"AD/AT/30","content":"## AD/AT/30","sortOrder":1},{"sectionNumber":"Rudder and Vertical Fin","sectionType":"part","heading":"Rudder and Vertical Fin","content":"## Rudder and Vertical Fin","sortOrder":2},{"sectionNumber":"13/2008","sectionType":"part","heading":"13/2008","content":"## 13/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"This Directive targets the same rudder/vertical‑fin hinge fatigue issue described in the background and the referenced FAA AD and confines measures to specified AT‑402 series serial numbers. It prescribes inspections, immediate repairs, and a specific terminating modification (external doubler) without expanding to other aircraft models or unrelated systems."},"complexity_factors":["Narrow applicability by serial numbers 0694–1176 (Applicability).","Specified initial and repetitive inspection timing: initial at 3,500 hours TIS or within 100 hours after 18 December 2008, then every 100 hours until doubler installation (Compliance).","Mandatory replacement of any damaged parts before further flight (Requirement).","Terminating modification: installation of an external doubler at the upper rudder hinge per Snow Engineering Service Letter No.247 and Process Specification No.145 (Requirement).","Prohibition on installing rudders without the external doubler as of 18 December 2008 (Requirement).","Dependence on external technical documents and an FAA AD reference (Snow Engineering service documents; FAA AD 2008-21-08), creating administrative coordination and potential approval steps (Requirement/Note).","Operational impact on owners/operators through inspection, repair and modification workload and associated aircraft downtime (implied by Requirement/Compliance)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Airtractor AT-402, AT-402A and AT-402B aircraft (serial numbers 0694–1176) to inspect the rudder and vertical‑fin hinge attachments for loose fasteners, cracks and corrosion, repair any damage before further flight, and install an external doubler at the upper rudder hinge. It sets initial and repeat inspection intervals and forbids installing rudders that lack the external doubler after 18 December 2008. Costs and downtime for inspections, repairs and the doubler installation are borne by the aircraft owner/operator."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with a focused, narrow scope addressing a specific airworthiness concern (rudder hinge fatigue) on specific aircraft models. The scope remains tightly constrained to the identified safety issue without expansion into unrelated operational or maintenance areas."},"complexity_factors":["Single technical subject matter (rudder hinge fatigue) with clear, sequential requirements","Two distinct compliance paths (inspection vs. modification) with specific flight hour thresholds","Cross-reference to external technical documents (Snow Engineering Service Letter No. 247 and Process Specification 145) without reproducing their content","Conditional logic based on aircraft serial numbers and accumulated flight hours","Reference to corresponding FAA AD 2008-21-08 for context","Limited defined terms (only 'time in service' requires implicit understanding)","No nested exceptions or complex definitional sections"],"plain_english_summary":"This AD mandates inspections and a required reinforcement of the upper rudder hinge on specified Airtractor AT-402/402A/402B (S/N 0694–1176) after reports of fatigue loosening the hinge. Owners/operators must inspect for loose fasteners, cracks and corrosion at set intervals and fit an external doubler by the compliance hour limit; it prevents rudder failure that could cause loss of control."},"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-at-30-rudder-and-vertical-fin","history":"/api/acts/ad-at-30-rudder-and-vertical-fin/history","analysis":"/api/acts/ad-at-30-rudder-and-vertical-fin/analysis","conflicts":"/api/acts/ad-at-30-rudder-and-vertical-fin/conflicts","importantCases":"/api/acts/ad-at-30-rudder-and-vertical-fin/important-cases","documents":"/api/acts/ad-at-30-rudder-and-vertical-fin/documents"}}