{"id":"F2006B09176","name":"AD/DHC-8/21 Amdt 1 - Engine Rear Mount Strut","slug":"ad-dhc-8-21-amdt-1-engine-rear-mount-strut","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52934,"registerId":"commonwealth-F2006B09176-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-8/21 Amdt 1 - Engine Rear Mount Strut","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)  \n![](image.002.png)  \nBombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\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\n![](image.003.png)AD/DHC-8/21\n\nAmdt 1\n\n  \nEngine Rear Mount Strut 10/2001\n\nApplicability: DHC-8 aircraft, Models 102, 103, 106, 201, 202, 301, 311, 314, and 315, with serial numbers 003 through 517; equipped with engine rear mount struts, part numbers 87110016-003, -005, -007, -009, -011, or 8DK1763-001.\n\nRequirement: Perform a detailed visual inspection for cracks in the affected engine rear mount strut assemblies listed in the Applicability part of this Directive, on both the left and right engine nacelles.\n\nReplace cracked struts before further flight.\n\nReplacement of both engine rear mount struts in a nacelle with the new machined struts, part number 87110047-001, terminates the repetitive inspection requirements of this Directive for that nacelle only.\n\nNote 1: Termination of the repetitive inspections as specified in this Directive does not alter the operator’s approved maintenance program for these rear mount struts.\n\nNote 2: Transport Canada AD CF-2001-20 refers.\n\nCompliance: Initially, within 1,000 hours time in service since new or within 250 hours time in service after 4 October 2001, whichever occurs later, unless already accomplished.\n\nSubsequently, repeat at intervals not to exceed 250 hours time in service.\n\nThe installation of one new machined strut, part number 87110047-001, in a nacelle, increases the repeat inspection interval to 500 hours time in service for that nacelle only.\n\nThis Amendment becomes effective on 4 October 2001.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBackground: There have been five reported failures of the engine rear mount strut. Investigation has determined that the fracture initiated at one of the rosette welds on the shank of the strut just above the bearing where full weld penetration was not achieved.\n\nAmendment 1 is issued in response to a new Transport Canada AD which was prompted by reports that new and reworked struts required by the previous issue of this Directive, continued to fail. Failure of the engine rear mount strut would result in a degradation of the integrity of the engine/nacelle installation.\n\n![](image.004.png)The original issue of this Airworthiness Directive became effective on 23 July 1992.\n\n![](image.005.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 20 August 2001\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 12 September 2001.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Amendment 1 remains tightly scoped to the original purpose: addressing engine rear mount strut failures in specific DHC-8 aircraft. While it responds to continued failures after the original 1992 AD, it does not expand beyond the original safety concern or aircraft population. The amendment refines the technical solution (introducing new machined struts as a terminating action) but stays within the original safety intent."},"complexity_factors":["Single discrete safety issue with clear mechanical trigger (specific part numbers and aircraft serial numbers)","Straightforward conditional logic: IF cracked THEN replace; IF both new struts installed THEN inspection requirement terminates for that nacelle only","Limited cross-referencing (one reference to Transport Canada AD CF-2001-20 and Civil Aviation Regulations 1998 Part 39)","Precise but narrow applicability section (9 aircraft models, specific serial number range, 6 specific part numbers)","Clear compliance timeline with simple alternative triggers (hours since new OR hours after effective date)","Two explanatory notes clarifying that termination of AD inspections doesn't override general maintenance programs"],"plain_english_summary":"This CASA safety order requires urgent inspections and repairs on Bombardier DHC‑8 (Dash 8) series 100/200/300 aircraft with certain engine rear mount strut part numbers and serials 003–517 after repeated weld failures. Operators must inspect both engine struts for cracking, remove any cracked parts before flight, and carry out recurring inspections (250‑hour intervals unless upgraded). Installing redesigned struts on an engine nacelle reduces or ends the repetitive inspections for that nacelle. This is a life‑safety measure responding to recurring mount failures."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 1 modifies the original 1992 Directive in response to reports that new and reworked struts continued to fail. It tightens and clarifies inspection and replacement requirements, introduces a specific new machined strut (part 87110047‑001) as the means to extend or terminate repetitive inspections for a nacelle, and restates that operator maintenance programs remain operative (Background; Requirement; Note 1)."},"complexity_factors":["Applicability limited by specific aircraft models, serial numbers, and multiple affected part numbers (Applicability)","Multiple and conditional inspection intervals: initial timing, 250‑hour repeats, 500‑hour extension when one new strut is installed, and termination when both new struts are fitted (Compliance/Requirement)","Per‑nacelle treatment and asymmetric effects when one versus both struts are replaced (Requirement/Compliance)","Interaction with existing operator-approved maintenance programs — termination of AD inspections does not alter those programs (Note 1)","Reference to and alignment with an external regulator's AD (Transport Canada AD CF‑2001‑20) and prior AD history (Background/Note 2)","Technical specificity of the failure mode (rosette weld fracture) directing inspection focus (Background)","Timing choices (hours-in-service thresholds) tied to new/used status create tracking and recordkeeping burdens (Compliance)"],"plain_english_summary":"This Airworthiness Directive requires operators of specified Bombardier (De Havilland) DHC‑8 models and serial numbers fitted with certain engine rear‑mount struts to carry out detailed visual inspections for cracks and to replace any cracked struts before further flight. Installing the new machined strut part (87110047‑001) changes inspection intervals or, if both struts in a nacelle are replaced, ends the repetitive inspections for that nacelle. It matters because fractures were reported originating at rosette welds, so operators must change inspection and maintenance practices and bear inspection/repair costs."},"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-8-21-amdt-1-engine-rear-mount-strut","history":"/api/acts/ad-dhc-8-21-amdt-1-engine-rear-mount-strut/history","analysis":"/api/acts/ad-dhc-8-21-amdt-1-engine-rear-mount-strut/analysis","conflicts":"/api/acts/ad-dhc-8-21-amdt-1-engine-rear-mount-strut/conflicts","importantCases":"/api/acts/ad-dhc-8-21-amdt-1-engine-rear-mount-strut/important-cases","documents":"/api/acts/ad-dhc-8-21-amdt-1-engine-rear-mount-strut/documents"}}