{"id":"F2006B08365","name":"AD/CESSNA 400/81 Amdt 4 - Engine Mount Beams","slug":"ad-cessna-400-81-amdt-4-engine-mount-beams","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115776,"registerId":"commonwealth-F2006B08365-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 400/81 Amdt 4 - Engine Mount Beams","content":"![](image.001.png)  \nCessna 400 Series Aeroplanes\n\nAD/CESSNA 400/81\n\nAmdt 4\n\n  \nEngine Mount Beams 5/98\n\nApplicability: All models 402C aircraft with serial numbers 402C0001 through 402C0808, and all models 414A aircraft with serial numbers 414A0001 through 414A1206.\n\nRequirement: 1\\. For aircraft with Cessna Kit SK414-17 incorporated, incorporate Cessna Kit SK414-19-1, and one of the following, as applicable, in accordance with the instructions to Service Kit SK414-19B, Revised 4 March 1986:\n\n    (a) Cessna Kit SK414-19-2: All of the affected Models 402C and 414A aircraft that are equipped with propeller unfeathering accumulators;\n\n    (b) Cessna Kit SK414-19-3: Model 402C aircraft, serial numbers 402C0001 through 402C0468; and Model 414A aircraft, serial numbers 414A0001 through 414A0646;\n\n    (c) Cessna Kit SK414-19-5: Model 402C aircraft, serial numbers 402C0469 through 402C0808; and Model 414A aircraft, serial numbers 414A0647 through 414A1206.\n\n    2. For aircraft without Cessna Kit SK414-17 incorporated, incorporate Cessna Kit SK414-19-1, and one of the following, as applicable, in accordance with the instructions to Service Kit SK414-19B, Revised 4 March 1986:\n\n    (a) Cessna Kit SK414-19-2: All of the affected Models 402C and 414A aircraft that are equipped with propeller unfeathering accumulators;\n\n    (b) Cessna Kit SK414-19-4: Model 402C, serial numbers 402C0001 through 402C0468; and Model 414A aircraft, serial numbers 414A0001 through 414A0646;\n\n    (c) Cessna Kit SK414-19-5: Model 402C aircraft, serial numbers 402C0469 through 402C0808; and Model 414A aircraft, serial numbers 414A0647 through 414A1206.\n\n    3. Inspect, using radiographic methods, the engine mount beam for cracks in accordance with the Accomplishment Instructions section of Attachment to Service Bulletin MEB85-3, Revised 23 August 1985, as referenced in Cessna Service Bulletin MEB85-3, Revision 2, dated 23 October 1987.\n\n    (a) If any crack is found in the left side (vertical portion) of the left engine beam of either nacelle, obtain a repair scheme from the manufacturer, and then incorporate this repair scheme.\n\n    (b) If cracks are found in the top (horizontal portion) of the engine beam and the total length of the cracks is less than 1.75 inches (44.5 mm), stop drill each end of each crack using a 0.098 inch drill bit.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n    (c) If cracks are found in the top (horizontal portion) of the engine beam and the total length of the cracks is equal to or greater than 1.75 inches, but less than\n\n2.75 inches (70 mm), obtain a repair scheme from the manufacturer, and then incorporate this repair scheme.\n\n    (d) If cracks are found in the top (horizontal portion) of the engine beam and the total length of the cracks is equal to or greater than 2.75 inches, replace the engine beam with a part number specified in the instructions to Service Kit SK414-19B, Revised 4 March 1986.\n\n    4. If parts for any of the engine beam modifications required by Requirements 1 and 2 of this Directive have been ordered from the manufacturer but are not available, accomplish the following in accordance with the Accomplishment Instructions section of Attachment to Service Bulletin MEB85-3, Revised 23 August 1985; as referenced in Cessna Service Bulletin MEB85-3, Revision 2, dated 23 October 1987:\n\n    (a) For aircraft with Cessna Kit SK414-17 incorporated, inspect the engine mount beams using radiographic methods.\n\n    (b) For aircraft without Cessna Kit SK414-17 incorporated, fluorescent penetrant inspect the engine mount beams.\n\n    5. If any of the following occurs during any of the inspections required by Requirement 4 of this Directive, accomplish the following specified actions:\n\n    (a) If parts become available, terminate the repetitive inspections specified in Requirement 4 of this Directive, incorporate the modification kits required by Requirement 1 or 2 of this Directive, and inspect the engine mount beams as specified in Requirement 3 of this Directive;\n\n    (b) If any crack is found in the left side (vertical portion) of the left engine beam of either nacelle, obtain a repair scheme from the manufacturer, incorporate this repair scheme, and continue the repetitive inspections required by Requirement 4 of this Directive.\n\n    (c) If cracks are found in the top (horizontal portion) of the engine beam and the total length of the cracks is less than 1.75 inches, stop drill each end of each crack using a 0.098 inch drill bit, and continue the repetitive inspections required by Requirement 4 of this Directive;\n\n    (d) If cracks are found in the top (horizontal portion) of the engine beam and the total length of the cracks is equal to or greater than 1.75 inches, but less than\n\n2.75 inches, obtain a repair scheme from the manufacturer, incorporate this repair scheme, and continue the repetitive inspections required by Requirement 4 of this Directive; or,\n\n    (e) If cracks are found in the top (horizontal portion) of the engine beam and the total length of the cracks is equal to or greater than 2.75 inches, replace the engine beam with a part number specified in the instructions to Service Kit SK414-19B, Revised 4 March 1986, and inspect the engine mount beams as specified in Requirement 3 of this Directive.\n\nNote: FAA AD 97-26-16 Amdt 39-10259 refers.\n\nCompliance: 1. Within 1,600 hours time in service after 23 April 1998 or at the next engine overhaul, whichever occurs first.\n\n    2. Within 200 hours time in service after 23 April 1998.\n\n    3. Within 9,600 hours time in service after the modification required by Requirement 1 or 2 of this Directive, as applicable, and thereafter at intervals not to exceed 9,600 hours time in service.\n\n    4. (a) Within 1,600 hours time in service after 23 April 1998, and thereafter at intervals not to exceed 1,600 hours time in service; provided that no provision specified in Requirement 5 of this Directive occurs.\n\n4. (b) Within 200 hours time in service after 23 April 1998, and thereafter at intervals not to exceed 200 hours time in service; provided that no provision specified in Requirement 5 of this Directive occurs.\n\nThis airworthiness directive becomes effective on 23 April 1998.\n\nBackground: Cracking of the engine mount beams has been experienced in service. Failure of the engine mount beam caused by fatigue cracks could result in loss of the engine with consequent loss of the aircraft.\n\nAmendment 3 introduced Revision 1 of the Requirement document and noted the related FAA AD.\n\nAmendment 4 is issued in response to a new FAA AD which requires incorporating engine mount kits that will eliminate the need for the on-going repetitive inspection requirement. The FAA has determined that reliance on critical repetitive inspections on aircraft utilised in commuter service carries an unnecessary safety risk when a design change exists that could eliminate or, in certain circumstances, reduce the number of those critical inspections.\n\nAmendment 3 of this airworthiness directive became effective on 31 December 1985\\. Amendment 2 of this airworthiness directive became effective on 30 June 1985.\n\nThe original issue of this airworthiness directive became effective on 23 June 1981.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":7,"scope_assessment":{"changed":true,"description":"The original 1981 directive required repetitive inspections to detect cracks. Amendment 4 (1998) significantly expanded the scope by introducing permanent design modifications (engine mount kits) that eliminate the need for ongoing inspections. This shifted the regulatory approach from 'detect and manage' to 'permanently fix' — a substantial expansion beyond the original inspection-only mandate, driven by FAA determination that repetitive inspections posed 'unnecessary safety risk' for commuter aircraft."},"complexity_factors":["Multiple branching requirement paths based on three variables: aircraft model (402C vs 414A), serial number ranges, and whether previous modification kit SK414-17 was installed","Five different Cessna modification kits (SK414-19-1 through SK414-19-5) with specific applicability matrices","Nested conditional logic for crack findings: location (vertical vs horizontal) × length thresholds (1.75 inches vs 2.75 inches) × five different prescribed actions","Cross-references to four external documents: Service Kit SK414-19B (Revised 4 March 1986), Service Bulletin MEB85-3 (Revised 23 August 1985), and Revision 2 of same bulletin (23 October 1987), plus FAA AD 97-26-16","Four separate compliance timelines with conditional triggers and interval-based repetitive requirements","Requirement 5 creates a complex state machine where findings during temporary inspections trigger different paths (termination, continuation, or modification of inspection intervals)","Mixed measurement systems (imperial inches and metric millimetres) requiring conversion precision"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain Cessna 400-series aircraft (specific 402C and 414A serials) to address fatigue cracking of engine mount beams—via mandated inspections (radiographic or dye-penetrant) and installation of Cessna modification kits or repairs—to prevent engine separation in flight. Amendment 4 permits newer kit installations that remove the need for repetitive inspections. Actions are time-limited (e.g., within 1,600 or 200 flight hours or at next overhaul)."},"flash_summary":{"complexity_score":8,"scope_assessment":{"changed":true,"description":"Yes. The Directive started as inspection‑focused measures (original AD) and has been amended to mandate incorporation of engine‑mount modification kits that, where installed, remove or reduce the need for ongoing repetitive inspections (Amendment 4; Requirements 1–2). It also formalises temporary inspection procedures and staged compliance while parts are unavailable (Requirements 4–5), altering operator obligations from inspection‑only to modification plus inspection/remedy rules."},"complexity_factors":["Serial‑numbered applicability covering two models with multiple ranges (Applicability).","Different modification paths depending on whether earlier Kit SK414‑17 was incorporated (Requirements 1–2).","Multiple kit variants to choose from (SK414‑19‑1, ‑2, ‑3, ‑4, ‑5) tied to equipment fit (e.g. propeller unfeathering accumulators) and serial ranges (Requirements 1–2).","Tiered inspection regimes: radiographic vs fluorescent penetrant depending on kit status, with temporary repetitive inspections while parts unavailable (Requirements 3–5).","Explicit crack‑length decision thresholds (less than 1.75 in; ≥1.75 in and <2.75 in; ≥2.75 in) that mandate different remedies including stop‑drilling, manufacturer repair schemes, or replacement (Requirements 3(b)–(d), 5(c)–(e)).","A specific stop‑drill size is prescribed (0.098 inch) for small cracks (Requirement 3(b), 5(c)).","Multiple compliance timeframes (within 200 or 1,600 hours; repetitive intervals at 200, 1,600 or 9,600 hours) creating staging and scheduling complexity (Compliance).","Dependency on manufacturer‑supplied repair schemes and service bulletins (Service Kit SK414‑19B instructions; Service Bulletin MEB85‑3 references), which limits operator discretion and requires coordination with the manufacturer (Requirements 3(a), 4, 5).","Provisions for terminating repetitive inspections only upon parts availability and kit incorporation, creating conditional and transitional obligations (Requirement 5(a))."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of specified Cessna 402C and 414A aeroplanes to install defined engine‑mount modification kits or, if parts are unavailable, perform recurring inspections and repairs for mounting‑beam cracks. It sets specific crack‑length thresholds that trigger stop‑drilling, manufacturer repair schemes, or full beam replacement. The stated aim is to address fatigue cracking that can lead to engine loss. Compliance shifts costs and downtime to aircraft owners and changes inspection frequency and methods depending on configuration and parts availability."},"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-cessna-400-81-amdt-4-engine-mount-beams","history":"/api/acts/ad-cessna-400-81-amdt-4-engine-mount-beams/history","analysis":"/api/acts/ad-cessna-400-81-amdt-4-engine-mount-beams/analysis","conflicts":"/api/acts/ad-cessna-400-81-amdt-4-engine-mount-beams/conflicts","importantCases":"/api/acts/ad-cessna-400-81-amdt-4-engine-mount-beams/important-cases","documents":"/api/acts/ad-cessna-400-81-amdt-4-engine-mount-beams/documents"}}