{"id":"F2006B03259","name":"AD/B747/81 Amdt 1 - Wing Landing Gear Trunnion","slug":"ad-b747-81-amdt-1-wing-landing-gear-trunnion","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42683,"registerId":"commonwealth-F2006B03259-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/81 Amdt 1 - Wing Landing Gear Trunnion","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\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B747/81 and issues the following 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\nBoeing 747 Series Aeroplanes\n\nAD/B747/81\n\nAmdt 1\n\n  \nWing Landing Gear Trunnion 12/2001\n\nApplicability: All Model 747 series aircraft.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 2001-17-25 Amdt 39-12416.\n\nIf any corrosion or cracking is found during any inspection required by this Directive, before further flight, repair per data meeting the type certification basis of the aircraft approved by a Boeing Company Designated Engineering Representative (DER) authorised to make such findings.\n\nNote: Boeing Service Bulletins 747-32-2190 Revision 4 and 747-32A2465 Revision 1 refer.\n\nCompliance: As specified in the Requirement document with a revised effective date of 29 November 2001.\n\nBackground: The FAA received reports of landing incidents in which the landing gear collapsed. Investigation revealed corrosion and fatigue cracking as the cause. The Australian operator found cracking during routine overhaul. If not corrected this could lead to inability to safely control the aircraft during landing.\n\nAmendment 1 is issued in response to a new FAA AD which requires new repetitive inspections for cracks or corrosion of the aft trunnion outer cylinders of the wing landing gear, follow-on actions, and repetitive overhaul of the wing landing gear.\n\nApplicability is expanded to include all aircraft subsequent to line number 779.\n\n![Signature of Eugene Paul Holzapfel, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 19 October 2001\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 7 November 2001.\n\n  \nPage 1 of 1","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the AD’s scope beyond the original AD by adopting a new FAA AD that adds repetitive inspections, follow-on actions and repetitive overhaul requirements for the aft trunnion outer cylinders, and by explicitly extending applicability to include all Model 747 aircraft subsequent to line number 779. Mechanically, the instrument moves from a narrower inspection/repair instruction set to a broader, recurrent inspection/overhaul regime and covers additional airframes that were not in the earlier applicability."},"complexity_factors":["Cross-reference to an external FAA AD (FAA AD 2001-17-25) rather than reproducing technical steps","Reference to Boeing Service Bulletins (747-32-2190 Rev 4 and 747-32A2465 Rev 1) as related documents","Conditional requirement: if corrosion/cracking found then repair before further flight using DER‑approved data","Requirement that repairs meet the aircraft’s type certification basis and require Boeing DER approval (third‑party approval dependency)","Expanded applicability (now includes aircraft subsequent to line number 779) introducing a fleet segmentation condition","Repetitive inspections and periodic overhaul obligations referenced but not fully specified in this text (operator must consult the FAA AD for timing and procedures)","Single-page AD with compact sections but several external dependencies increases operational complexity"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- This is an Airworthiness Directive (AD) applying to Boeing Model 747 series aeroplanes (see Applicability). It replaces an earlier AD and requires operators to carry out the inspections, follow-on actions, and overhauls specified in the FAA AD 2001-17-25 (see Requirement).\n- Inspections target the aft trunnion outer cylinders of the wing landing gear (the attachment components that take landing loads). If corrosion or cracking is found during an inspection, the aircraft must not fly until repaired using data that meets the aircraft’s type certification basis and that is approved by a Boeing Designated Engineering Representative (DER) authorised to make such findings (see Requirement).\n- Compliance must follow the FAA AD’s technical requirements and timing, with a revised effective date of 29 November 2001 (see Compliance). The AD’s Note cross-references Boeing Service Bulletins 747-32-2190 Rev 4 and 747-32A2465 Rev 1 as related documents (see Note).\n\n**Why the regulator issued it (claimed purpose)**\n\n- The Background says the FAA investigated landing-gear collapses and found corrosion and fatigue cracking in these trunnions. The AD’s stated purpose is to detect and correct corrosion or cracking so the landing gear does not fail during landing (see Background).\n\n**Who this affects and who pays/decides**\n\n- Affected: operators and owners of Boeing 747s described in the Applicability. The Amendment expands applicability to include aircraft subsequent to line number 779 (see Applicability).\n- Who pays: aircraft operators (airlines, lessors) bear inspection, repair, overhaul, parts and downtime costs. Maintenance organisations perform the work and charge operators.\n- Who decides/approves: the Civil Aviation Safety Authority (CASA) delegate issued the AD; repairs must be approved by a Boeing Company Designated Engineering Representative (DER) authorised to make such findings (see Requirement).\n\n**How it changes operator behaviour**\n\n- Operators must schedule and perform the specified repetitive inspections, carry out required repairs or overhauls when defects are found, and keep affected aircraft out of service until repairs are approved and completed.\n- Where cracking or corrosion is found, operators must obtain DER-approved repair data meeting the aircraft type certification basis before returning the aircraft to service.\n\n**Costs, incentives, trade-offs, and implementation risks**\n\n- Direct costs: labour, parts, inspection tooling, DER approval fees, and aircraft downtime. If repetitive overhauls are required, those costs and downtime are recurring.\n- Incentives: Operators have a strong incentive to inspect and repair promptly to restore aircraft to service; they also have an incentive to manage inspection timing to minimise schedule disruption. Maintenance providers have an incentive to supply compliant inspections, repairs and DER-approved data.\n- Trade-offs: increased maintenance and possible temporary loss of aircraft availability versus reduced risk of landing-gear collapse and associated loss/events. Those trade-offs can affect route schedules, aircraft utilisation and operating costs.\n- Implementation risks: availability of DERs and approved repair data; spare parts or overhaul capacity constraints; potential for disagreement over whether proposed repair data meets the type certification basis; and scheduling bottlenecks causing prolonged ground time.\n- Compliance burden: the AD references external FAA requirements and Boeing service bulletins rather than reproducing all technical steps, so operators must consult and follow those documents exactly.\n\n**Concentrated benefits and diffuse costs**\n\n- Concentrated benefits: operators, crew and passengers of affected aircraft are the primary beneficiaries through reduced risk of landing-gear collapse (Background). Aviation insurers and lessors also benefit from lower technical risk.\n- Diffuse costs: while the safety benefit accrues to flight stakeholders, costs fall clearly and directly on the operators of the specified aircraft (maintenance, downtime, possible accelerated retirement of older airframes).\n\n**Potential unintended consequences**\n\n- Operators may choose to retire or ground older 747s if repeated overhauls and inspections make continued operation uneconomic, accelerating fleet changes or lease/secondary-market effects.\n- Short-term capacity loss on affected routes if multiple aircraft require overhaul at the same time.\n\n**Where to look in the document**\n\n- Applicability: which aircraft are covered.\n- Requirement and Note: which FAA AD and Boeing service bulletins to follow and the repair-approval requirement.\n- Compliance: timing (revised effective date 29 November 2001).\n- Background: factual reason (corrosion/fatigue cracking leading to past landing gear collapses).\n\n(References in parentheses above point to the document sections titled Applicability, Requirement, Note, Compliance and Background.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original AD has expanded in scope through this amendment. The applicability section explicitly states it now includes 'all aircraft subsequent to line number 779' — meaning the directive now covers more aircraft than the original version. The amendment also adds new requirements: 'new repetitive inspections', 'follow-on actions', and 'repetitive overhaul' that were not in the original directive."},"complexity_factors":["Short, single-page document with straightforward structure","Only 4 defined elements: Applicability, Requirement, Compliance, and Background","Minimal conditional logic — essentially 'inspect and repair if found'","Heavy reliance on external technical document (FAA AD 2001-17-25) for actual implementation details","Single cross-reference to Boeing Service Bulletins","No nested exceptions or complex definitional sections"],"plain_english_summary":"This safety order revokes the earlier AD/B747/81 and requires Australian operators and maintenance organisations of all Boeing 747 series (including later-line aircraft) to follow FAA AD 2001-17-25: mandatory, repetitive inspections of the wing landing gear trunnion and immediate grounding and repair if cracks or corrosion are found.  \n\nIt matters because corrosion and metal fatigue have caused actual landing-gear collapses on landing; the inspections prevent potentially catastrophic 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-b747-81-amdt-1-wing-landing-gear-trunnion","history":"/api/acts/ad-b747-81-amdt-1-wing-landing-gear-trunnion/history","analysis":"/api/acts/ad-b747-81-amdt-1-wing-landing-gear-trunnion/analysis","conflicts":"/api/acts/ad-b747-81-amdt-1-wing-landing-gear-trunnion/conflicts","importantCases":"/api/acts/ad-b747-81-amdt-1-wing-landing-gear-trunnion/important-cases","documents":"/api/acts/ad-b747-81-amdt-1-wing-landing-gear-trunnion/documents"}}