{"id":"F2006B03038","name":"AD/B747/136 Amdt 1 - Fuselage - Nose Wheel Well","slug":"ad-b747-136-amdt-1-fuselage-nose-wheel-well","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42397,"registerId":"commonwealth-F2006B03038-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/136 Amdt 1 - Fuselage - Nose Wheel Well","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)  \nBoeing 747 Series Aeroplanes\n\nAD/B747/136\n\nAmdt 1\n\n  \nFuselage \\- Nose Wheel Well 7/99\n\nApplicability: B747 Line No 001 to 685 inclusive.\n\nRequirement: 1. Externally inspect for cracks in the nose wheel well top panel and intercostals. Inspect in accordance with Boeing SB 747-53-2293 Rev 6 using either detailed close visual (Option 1) or a combination of detailed close visual and high frequency eddy current (Option 2) methods.\n\n    2. Perform a detailed close visual inspection, internally and externally, for cracks in the nose wheel well vertical beam clips and the adjacent side wall panel web. If cracks are found, extend the inspection area and inspect using high frequency eddy current methods. Inspect in accordance with Boeing SB 747-53-2293 Rev 6.\n\n    3. Inspect, internally and externally, for cracks in the nose wheel well vertical beam webs. Inspect in accordance with Boeing SB 747-53-2293 Rev 6 using either a detailed close visual (Option 1) or a combination of detailed close visual and high frequency eddy current (Option 2) methods.\n\nNote: FAA AD 90-06-14R1 refers.\n\nCompliance: 1. Initially inspect the nose wheel well top panel and intercostals before 4000 flights or within 1500 flights from 27 April 1995, whichever is the later. Reinspect at intervals not exceeding 1500 flights (Option 1) or intervals not exceeding 3000 flights (Option 2).\n\n    2. Initially inspect the vertical beam clips and side wall panels before 10000 flights or within 1500 flights from 27 April 1995, whichever is the later. Reinspect at intervals not exceeding 3000 flights.\n\n    3. Inspect the vertical beam webs before 10000 flights or before 1500 flights from 27 April 1995, whichever is the later. Reinspect at intervals not exceeding 1500 flights (Option 1) or intervals not exceeding 3000 flights (Option 2).\n\n    4. For the purposes of this AD a flight may be taken as a ground-air-ground cycle where the pressure differential exceeds 2.0 psi.\n\n    5. Modification in accordance with Boeing SB 747-53-2293 Rev 6 constitutes terminating action for the inspection requirements of this AD for those areas so modified.\n\nThe compliance times of the original issue of this Directive remains unchanged except for the Requirement 2 repetitive inspection.\n\nThis Amendment becomes effective on 15 July 1999.\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 approximately 70 reported instances of cracking in the nose wheel well structure. Cracks up to 11\" long have been reported. Continued operation with undetected cracks could lead to rapid cabin depressurisation. Inspections in accordance with this AD will ensure timely detection of critical cracks.\n\nAmendment 1 is issued to align the Requirement 2 repetitive inspection interval with the related FAA AD requirement.\n\nThe original issue of this Airworthiness Directive became effective on 27 April 1995.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"Amendment 1 does not expand the AD beyond its original safety goal. It adjusts the repetitive inspection interval for Requirement 2 to align with the FAA requirement; all other compliance times remain as in the original AD. The AD therefore retains the same target areas, inspection methods, and terminating modification option, without a substantive scope expansion beyond the original purpose of detecting and managing nose wheel well cracking."},"complexity_factors":["Applicability limited to Boeing 747 Line No 001–685 (narrow, well-defined scope)","Three distinct inspection requirements targeting different structural areas (top panel/intercostals; vertical beam clips and adjacent side wall panel web; vertical beam webs)","Two inspection method options (Option 1: detailed close visual; Option 2: detailed close visual + high-frequency eddy current) with different repeat intervals","Different initial compliance thresholds by area (4,000 flights; 10,000 flights) plus a uniform fallback of 1,500 flights from 27 April 1995 (whichever is later)","Repeat-interval variation tied to inspection Option selected (1,500 v. 3,000 flights), and Requirement 2 has a specific 3,000-flight repeat","Reference to an external technical document (Boeing SB 747-53-2293 Rev 6) for inspection procedures and for a terminating modification","Cross-reference to FAA AD 90-06-14R1 and an amendment aligning one interval with FAA","Special definition of a \"flight\" for counting purposes (ground–air–ground cycle where pressure differential > 2.0 psi)","Termination provision (modification that removes inspection requirement for modified areas)"],"plain_english_summary":"**What this directive does**\n\n- This Airworthiness Directive (AD) requires regular inspections of the nose wheel well structure on Boeing 747 aeroplanes (Line Nos. 001–685). It targets specific locations where cracking has been reported: the nose wheel well top panel and intercostals, the vertical beam clips and adjacent side wall panel web, and the vertical beam webs. (Requirements 1–3)\n\n- Inspections must follow Boeing Service Bulletin SB 747-53-2293 Rev 6 and may be done either as detailed close visual checks (Option 1) or by combining detailed visual and high-frequency eddy-current non‑destructive testing (Option 2), depending on the area and option chosen. (Requirements 1–3)\n\n- The AD sets initial compliance deadlines (based on flight counts) and recurring inspection intervals. For example: the top panel/intercostals must be inspected before 4,000 flights or within 1,500 flights measured from 27 April 1995, whichever is later; thereafter at intervals of no more than 1,500 flights (Option 1) or 3,000 flights (Option 2). Other areas have their own initial and repeat intervals. (Compliance 1–3)\n\n- For the AD, a \"flight\" may be taken as a ground–air–ground cycle where the cabin pressure differential exceeds 2.0 psi. (Compliance 4)\n\n- Carrying out a modification described in Boeing SB 747-53-2293 Rev 6 removes (terminates) the inspection requirements of this AD for the areas that have been modified. (Compliance 5)\n\n**Who is affected**\n\n- Aircraft operators, owners and maintenance organisations responsible for Boeing 747 aircraft within the specified Line Number range (001 to 685). Maintenance personnel and engineers must perform or supervise the inspections per the Boeing service bulletin. Airlines pay for the inspections, any required repairs, and any downtime while inspections or modifications are done.\n\n**Why it matters (stated purpose and mechanical effect)**\n\n- The AD responds to about 70 reported instances of cracking in the nose wheel well structure (some cracks reported up to 11 inches long). The stated safety concern is that undetected cracks could grow and threaten structural integrity with a risk of rapid cabin depressurisation. The AD’s mechanical effect is to mandate inspection frequency, method, and corrective action to detect and remove that risk in time. (Background)\n\n**How the directive changes operator behaviour and incentives**\n\n- Operators must schedule and budget for repetitive inspections and any follow-up repairs. They must decide whether to adopt the less-frequent but more technically intensive Option 2 (which uses eddy‑current NDT) or to continue with more frequent visual inspections. Choosing the Boeing SB modification removes the need for ongoing inspections in the modified areas and therefore creates an incentive to invest up front in modification work to reduce recurring inspection cost and downtime. (Requirement 1–3; Compliance 1–5)\n\n**Costs, trade-offs and implementation risks**\n\n- Direct costs: labour for detailed inspection access, possible use or procurement of eddy‑current testing equipment/qualified technicians, parts and repairs if cracks are found, and aircraft downtime. \n\n- Trade-off: Option 2 reduces inspection frequency (longer intervals) but demands equipment/skill and may still require repairs; the terminating modification requires capital expenditure and downtime initially but removes recurring inspection costs for the modified areas. \n\n- Implementation risk: inspection quality depends on access, the skill of personnel and the chosen inspection method; inadequate inspections or missed intervals increase the chance that cracks go undetected. The AD relies on compliance with the Boeing service bulletin—if the bulletin’s procedures are incomplete or misapplied, detection effectiveness may vary. (Requirements and Compliance sections)\n\n**Administrative and cross‑jurisdiction notes**\n\n- The AD references the related FAA AD (FAA AD 90-06-14R1) and aligns one inspection interval (Requirement 2) with that FAA requirement (Amendment 1). The AD requires following Boeing SB 747-53-2293 Rev 6 for inspection technique and reporting. (Note; Background; Amendment 1)\n\n**Where to look in the AD text**\n\n- Specific inspection locations and methods: Requirements 1–3.\n- Timing and intervals: Compliance paragraphs 1–3; definition of flight counting: Compliance 4.\n- Terminating modification: Compliance 5.\n- Rationale (reported cracking and depressurisation risk): Background and Amendment 1.\n\nOverall, the AD compels a mix of recurring inspections and an optional terminating modification to manage a known structural cracking risk in specific nose wheel well areas on early-model B747 aircraft. Operators bear the costs and must choose inspection method or modification based on cost, capability and operational disruption."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope of inspecting Boeing 747 nose wheel well structures for cracks. The only change is aligning one repetitive inspection interval (Requirement 2) with the related FAA directive. The core safety purpose and applicability remain unchanged from the original 1995 directive."},"complexity_factors":["Multiple inspection methods (Option 1 vs Option 2) with different compliance intervals","Three distinct inspection requirements with different initial deadlines and repetitive intervals","Cross-reference to external Boeing Service Bulletin (SB 747-53-2293 Rev 6) and FAA AD 90-06-14R1","Specific technical terminology requiring aviation engineering knowledge (intercostals, eddy current, ground-air-ground cycle)","Conditional logic for compliance dates ('whichever is the later')","Definition of 'flight' as a technical term (ground-air-ground cycle with pressure differential >2.0 psi)"],"plain_english_summary":"This safety order requires operators of Boeing 747s (line numbers 001–685) to perform mandatory, recurring inspections of three areas in the nose wheel well using Boeing procedures to detect cracking. It updates one inspection interval to align with U.S. standards.\n\nThe action responds to ~70 reported cracks (some up to 28 cm) that could lead to rapid cabin depressurisation. Inspections begin by specified flight-count thresholds, repeat at set intervals, and may be halted if the aircraft is permanently modified per Boeing."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-136-amdt-1-fuselage-nose-wheel-well","history":"/api/acts/ad-b747-136-amdt-1-fuselage-nose-wheel-well/history","analysis":"/api/acts/ad-b747-136-amdt-1-fuselage-nose-wheel-well/analysis","conflicts":"/api/acts/ad-b747-136-amdt-1-fuselage-nose-wheel-well/conflicts","importantCases":"/api/acts/ad-b747-136-amdt-1-fuselage-nose-wheel-well/important-cases","documents":"/api/acts/ad-b747-136-amdt-1-fuselage-nose-wheel-well/documents"}}