{"id":"F2009L00438","name":"AD/AT/24 Amdt 2 - Overturn Skid Plate","slug":"ad-at-24-amdt-2-overturn-skid-plate","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":76914,"registerId":"commonwealth-F2009L00438-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/24 Amdt 2 | Overturn Skid Plate | 3/2009 |\n| --------------- | ------------------- | ------ |\n\n| Applicability: | Group 1 aircraft Models AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401,AT-401A, AT-402, AT-402A, and AT-402B, with serial numbers -0001 through-1196, and; Models AT-501, AT-502, AT-502A, and AT-502B with Serial Numbers-0001 through -2620.Group 2 aircraft Model AT-401B, with serial numbers -0952 through -1196.                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | For Group 1 aircraft:If overturn skid plate kit part number (P/N) 11411-1-500 or an FAA-approved equivalent part number is already installed, then install P/N 11411-1-501 modification kit; in accordance with Snow Engineering Co. Service Letter (SL) No. 97, revised 7 November 2007, or SL No. 97, revised 19 September 2008.If there is no overturn skid plate installed, then install overturn skid plate modification kit P/N 11411-1-502 or an FAA-approved equivalent part number; in accordance with SL No. 97, revised 7 November 2007, or SL No. 97, revised 19 September 2008.For Group 2 aircraft:Install P/N 11411-1-501 modification kit in accordance with SL No. 97, revised 19 September 2008.Note: FAA AD 2008-26-01 Amdt 39-15767 refers. |\n| Compliance:    | For Group 1 aircraft:Within 180 days after 31 July 2008.For Group 2 aircraft:Within 180 days after 12 March 2009, unless already accomplished.The compliance time for Requirement 1 remains unchanged by this issue of the Directive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n\n|             | This Amendment becomes effective on 12 March 2009.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Background: | The FAA received accident reports on Model AT-301 and AT-401 aircraft which indicate that the aircraft skids tail first during an overturn. As a result, the windshield and curved overturn tube act as a scoop, foreign material enters the cockpit if the canopy is damaged; and this foreign material then enters into the cabin area and possibly contributes to pilot deaths. The actions required by this Directive are intended to minimise the possibility of dirt or mud penetrating the cockpit during an overturn skid and causing pilot asphyxia or injury.Since the original issue of this Airworthiness Directive, there have been reports of the bolts that attach the forward end of the original design overturn skid plate breaking in an overturn accident. This allowed the skid plate to rotate around the rear attach point and the forward end of the plate to enter the cockpit area.Amendment 1 was issued in order to prevent the front and rear connections of the overturn skid plate to the airframe from breaking.Amendment 2 is issued in response to a new FAA AD, which retains the current actions required by this Directive but adds the requirement to modify the overturn skid plate installed Model AT-401B aircraft. |\n\n![](image.001.png)  \nDavid Punshon  \nDelegate of the Civil Aviation Safety Authority\n\n7 January 2009","sortOrder":0},{"sectionNumber":"AD/AT/24 Amdt 2","sectionType":"part","heading":"AD/AT/24 Amdt 2","content":"## AD/AT/24 Amdt 2","sortOrder":1},{"sectionNumber":"Overturn Skid Plate","sectionType":"part","heading":"Overturn Skid Plate","content":"## Overturn Skid Plate","sortOrder":2},{"sectionNumber":"3/2009","sectionType":"part","heading":"3/2009","content":"## 3/2009","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive addressed the basic overturn skid plate installation to prevent cockpit scooping. Amendment 1 added requirements to prevent bolt failures. Amendment 2 expands scope to include Model AT-401B aircraft (Group 2) which were not previously covered, and updates compliance dates. The directive has evolved from a simple installation requirement to a multi-stage, multi-group retrofit program spanning several years."},"complexity_factors":["Multiple aircraft groups with different serial number ranges requiring different actions","Specific part numbers (P/N 11411-1-500, 501, 502) and FAA-approved equivalents must be tracked","References external documents (Snow Engineering Service Letters) for installation procedures","Two different compliance deadlines based on aircraft group (180 days from 31 July 2008 vs 180 days from 12 March 2009)","Conditional logic: different requirements depending on whether skid plate already installed"],"plain_english_summary":"CASA's AD requires owners/operators of Air Tractor crop-dusters to install or upgrade an overturn skid plate to stop windshield/frame intrusion and mud/dirt from entering the cockpit during tail-first rollovers — a known cause of asphyxia and serious injury. It affects roughly 3,800 aircraft (mirroring an FAA action) and is a mandatory life‑safety measure; aircraft cannot legally fly until compliant."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 2 expands the Directive's scope by adding Model AT‑401B aircraft (serials -0952 through -1196) to the list of aircraft required to receive the P/N 11411-1-501 modification kit. It retains prior actions for the other models and serial ranges. In other words, the Directive's original safety objective (preventing cockpit contamination and skid plate failures during overturns) is unchanged, but the covered fleet has been increased to include additional serial numbers/models."},"complexity_factors":["Two distinct compliance groups (Group 1 and Group 2) with different model/serial applicability","Multiple model names and overlapping serial number ranges to check against (several AT-300/400/500 variants and AT-501/502 families)","Conditional requirement for Group 1: different action depending on whether P/N 11411-1-500 is already installed versus no skid plate","Multiple part numbers to manage (P/N 11411-1-500, 11411-1-501, 11411-1-502) and allowance for FAA‑approved equivalents","Dependency on external technical documents: Snow Engineering Service Letter No. 97 (two revision dates cited) and cross‑reference to FAA AD 2008‑26‑01","Two separate compliance deadlines (180 days after two different trigger dates) and a note preserving an earlier compliance timing for Requirement 1"],"plain_english_summary":"**What this directive does (mechanically)\n\n- **Who must act:** Owners/operators of Airtractor AT-300/400/500 series aeroplanes listed under \"Applicability\" (see serial number ranges and models). (Applicability)\n- **What to install:**\n  - For Group 1 aircraft: if an overturn skid plate with part number P/N 11411-1-500 (or an FAA‑approved equivalent) is already fitted, replace/modify it by installing kit P/N 11411-1-501 in accordance with Snow Engineering Co. Service Letter (SL) No. 97 (revised 7 Nov 2007 or 19 Sep 2008). If no overturn skid plate is installed, install kit P/N 11411-1-502 (or FAA‑equivalent) following the same SL. (Requirement)\n  - For Group 2 aircraft (Model AT-401B, serials -0952 to -1196): install kit P/N 11411-1-501 in accordance with SL No. 97, revised 19 Sep 2008. (Requirement)\n- **When to comply:**\n  - Group 1: within 180 days after 31 July 2008. (Compliance)\n  - Group 2: within 180 days after 12 March 2009, unless already done. (Compliance)\n- **Reference:** The Directive notes the related FAA Airworthiness Directive (FAA AD 2008-26-01). (Requirement / Note)\n\n**Why it matters (stated purpose and background)\n\n- The FAA investigated overturn accidents where the aeroplane skids tail‑first. In those events the windshield and overturn tube can act like a scoop, allowing dirt, mud or other debris to enter the cockpit if the canopy is damaged. Such foreign material entering the cabin has been linked to pilot asphyxia or injury. (Background)\n- There have also been reports that bolts attaching the forward end of the original skid plate design can break in an overturn, allowing the plate to rotate and penetrate the cockpit. Earlier amendment addressed these bolt failures; the current amendment adds Model AT-401B aircraft to the required modifications. (Background / Amendment note)\n\n**Practical effects and who pays / decides / changes behaviour**\n\n- Owners/operators of the affected Airtractor models must source and fit the specified modification kits (P/N 11411-1-501 or 11411-1-502, or FAA‑approved equivalents) and have the work done in accordance with the Snow Engineering Service Letter. (Requirement)\n- Costs fall on aircraft owners/operators: purchase of kit(s), labour to install per the service letter, and any downtime while the work is done. The kit supplier (Snow Engineering or an FAA‑approved equivalent maker) is likely to receive concentrated demand. (Requirement / Applicability)\n- The regulator (Civil Aviation Safety Authority via this Airworthiness Directive) sets the action and compliance dates; there is no discretionary compliance timetable for individual operators beyond the stated deadlines. (Compliance)\n\n**Implementation, compliance and operational trade-offs**\n\n- Implementation requires checking aircraft serial numbers against the Applicability list, confirming which kit applies (existing P/N 11411-1-500 versus no skid plate), procuring the correct kit, and completing the installation per the specified Snow Engineering Service Letter. (Applicability / Requirement)\n- Risk and friction points: kit availability, scheduling maintenance within the 180‑day windows, and ensuring the installer follows the correct revision of the Service Letter. The Directive also cross‑references FAA material (FAA AD), so operators may need to reconcile documentation between regulators. (Requirement / Note)\n- Benefits as stated: reduced chance of cockpit contamination during an overturn and reduced likelihood of the skid plate breaking forward into the cockpit. These are safety benefits concentrated to affected aircraft and their crews. The operator bears the cost; the benefit accrues chiefly to the same operators and their occupants. (Background)\n\n**Compliance and legal effect**\n\n- This is an Airworthiness Directive. Non‑compliance can affect an aircraft's legal airworthiness and its ability to operate legally until the mandated modification is done. (Compliance)\n\n**Source‑grounded assessment of incentives and costs**\n\n- Incentives: operators have a safety and regulatory incentive to carry out the modification to keep aircraft airworthy and avoid grounding or enforcement. Snow Engineering (and any FAA‑approved suppliers) have an incentive to supply kits. (Requirement)\n- Costs/opportunity: the directive imposes a one‑off hardware and labour cost and some operational disruption (downtime), with limited ongoing recurring costs beyond standard maintenance. There is no direct subsidy or compensation mechanism in the Directive. (Requirement / Compliance)\n- Market effects: small, concentrated demand for specific aftermarket parts; limited effect on broader competition, prices or ownership structures outside the affected operator base. (Applicability)\n\n**Mechanics cited:** Applicability, Requirement, Compliance, Background, and Note referencing FAA AD 2008‑26‑01."},"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-24-amdt-2-overturn-skid-plate","history":"/api/acts/ad-at-24-amdt-2-overturn-skid-plate/history","analysis":"/api/acts/ad-at-24-amdt-2-overturn-skid-plate/analysis","conflicts":"/api/acts/ad-at-24-amdt-2-overturn-skid-plate/conflicts","importantCases":"/api/acts/ad-at-24-amdt-2-overturn-skid-plate/important-cases","documents":"/api/acts/ad-at-24-amdt-2-overturn-skid-plate/documents"}}