{"id":"F2006B02547","name":"AD/AT/19 Amdt 1 - Flap System Overrun Prevention","slug":"ad-at-19-amdt-1-flap-system-overrun-prevention","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41803,"registerId":"commonwealth-F2006B02547-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AT/19 Amdt 1 - Flap System Overrun Prevention","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nAirtractor AT-300, 400 and 500 Series Aeroplanes\n\nAD/AT/19\n\nAmdt 1\n\n  \nFlap System Overrun Prevention 3/99\n\nApplicability: Models AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-401B,\n\nAT-402, AT-402A, and AT-402B aircraft, serial numbers 300-0001 through 401B- 1063; and, models AT-501, AT-502, AT-502A, AT-502B, and AT-503A aircraft, serial numbers 502-0001 through 502B-0500; that do not have a part number (P/N) 70975-1 flap actuator overtravel stop installed in accordance with the Rework Instructions section of Snow Engineering Co. Service Letter 165, dated May 15, 1998.\n\nRequirement: Replace the existing flap actuator overtravel stop with a new one of improved design, P/N 70975-1. Accomplish this replacement in accordance with the Rework Instructions section of Snow Engineering Co. Service Letter 165.\n\nNote: FAA AD 98-25-01 Amdt 39-10922 refers.\n\nCompliance: Unless already accomplished, within 50 hours time in service after 25 March 1999.\n\nThis Amendment becomes effective on 25 March 1999.\n\nBackground: Investigations have shown that it is possible for the flap control system to overrun through disengagement of the flap actuator overtravel nut. As a result of this overrun it is possible for the flap control pushrod to interfere with the aileron control pushrod to the extent that aileron control is lost. A modification introduced a new overtravel stop with improved security to prevent flap actuator overrun.\n\nAmendment 1 is issued in response to a new FAA AD which was prompted by reports of the flap actuator jackscrew breaking through the roll pin hole on three of the affected aircraft that were already in compliance with Snow Service Letter 140, Revised (FAA AD 96-23-19). This Directive requires installation of a new improved overtravel stop that is secured to the jackscrew by a welding method.\n\nThe original issue of this Airworthiness Directive became effective on 27 March 1997.","sortOrder":0}],"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive (effective March 1997) required compliance with Snow Service Letter 140. This Amendment 1 expands the scope by mandating a different, more robust modification (Service Letter 165 with welded overtravel stop) after the original fix proved insufficient. Three aircraft experienced jackscrew failures despite compliance with the original directive, prompting this more stringent requirement. The scope has tightened to exclude aircraft with the old modification and mandate the new welded design."},"complexity_factors":["Limited conditional logic: single applicability test (serial number ranges plus exclusion for already-modified aircraft)","Moderate cross-referencing: references to FAA AD 98-25-01, Snow Engineering Service Letter 165, and predecessor directive AD/AT/19 original issue","Technical aviation terminology requires domain knowledge (flap actuator, overtravel stop, jackscrew, time in service)","Precise part number and serial number ranges create parsing complexity","Brief document (approximately 250 words) with straightforward single requirement"],"plain_english_summary":"Australia’s regulator requires owners/operators of specified Air Tractor AT‑300/400/500 aircraft to fit an improved welded overtravel stop (PN 70975‑1) to the flap jackscrew to prevent flap overtravel that can jam the ailerons and cause loss of control. \n\nThis urgent amendment — for aircraft without the part already installed — must be done within 50 flight hours after 25 March 1999 due to recurring jackscrew failures."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 1 tightens the original directive by requiring an improved overtravel stop that is secured to the jackscrew by a welding method. The change responds to reports of jackscrew failure even after earlier compliance with Snow Service Letter 140, and thus expands the required installation method and security standard beyond the original AD (Amendment 1; Background)."},"complexity_factors":["Narrow applicability by specific models and serial number ranges (Applicability) increases tracking and verification burden for operators.","Mandatory replacement with a specific part number (P/N 70975-1) creates a single-design compliance path and potential supply dependency (Requirement).","Installation must follow external Rework Instructions in Snow Engineering Co. Service Letter 165, creating reliance on that document's availability and clarity (Requirement).","Short compliance window — 50 hours time in service from 25 March 1999 — raises operational scheduling pressure for affected aircraft (Compliance).","Amendment requires the new overtravel stop to be secured by welding to the jackscrew, adding a maintenance method that may require qualified personnel or shop capability (Amendment 1 / Background).","Cross-reference to FAA ADs and prior Snow service letters means compliance requires checking multiple regulatory and manufacturer documents (Note / Background).","Safety-critical consequence (possible aileron control loss) increases enforcement priority and may accelerate compliance expectations (Background)."],"plain_english_summary":"**What it does:** Requires owners/operators of specified Airtractor AT-300/400/500 series aeroplanes (by model and serial number) to replace the flap actuator overtravel stop with an improved part (P/N 70975-1) installed per Snow Engineering Co. Service Letter 165. The amendment requires the new stop to be secured to the jackscrew by welding to prevent the flap actuator overrunning and possible loss of aileron control. Compliance is mandatory within 50 hours time in service after 25 March 1999."}},"importantCases":[],"_links":{"self":"/api/acts/ad-at-19-amdt-1-flap-system-overrun-prevention","history":"/api/acts/ad-at-19-amdt-1-flap-system-overrun-prevention/history","analysis":"/api/acts/ad-at-19-amdt-1-flap-system-overrun-prevention/analysis","conflicts":"/api/acts/ad-at-19-amdt-1-flap-system-overrun-prevention/conflicts","importantCases":"/api/acts/ad-at-19-amdt-1-flap-system-overrun-prevention/important-cases","documents":"/api/acts/ad-at-19-amdt-1-flap-system-overrun-prevention/documents"}}