{"id":"F2007L00121","name":"AD/B747/143 Amdt 1 - Fuselage Section 41 Skin Stringer Joints","slug":"ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":68220,"registerId":"commonwealth-F2007L00121-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 747 Series Aeroplanes","sectionType":"division","heading":"Boeing 747 Series Aeroplanes","content":"### Boeing 747 Series Aeroplanes\n\n| AD/B747/143 Amdt 1 | Fuselage Section 41 Skin Stringer Joints | 2/2007 |\n| ------------------ | ---------------------------------------- | ------ |\n\n| Applicability: | Model 747-100, -100B, -200B, -200C, -200F, 747SR, and 747SP series aircraft; line numbers 001 through 430.                                                                                                                                                                                                                                                                                                                                                                           |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Action in accordance with the technical requirements of FAA AD 2006-24-02 Amdt 39-14831.                                                                                                                                                                                                                                                                                                                                                                                             |\n| Compliance:    | As specified in the Requirement document, with a revised effective date of15 February 2007.                                                                                                                                                                                                                                                                                                                                                                                          |\n|                | This Amendment becomes effective on 15 February 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                |\n| Background:    | A number of operators reported skin cracks at skin-stringer fastener locations. Some cracks were up to 0.5\" long. Skin cracks that reach critical length can cause an in flight de-pressurization.Amendment 1 is issued in response to a new FAA AD, which requires an additional inspection of areas that may have Alodine-coated rivets installed. The FAA received a report of cracking that was detected in a skin lap joint previously inspected using the eddy current method. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n3 January 2007","sortOrder":0},{"sectionNumber":"AD/B747/143 Amdt 1","sectionType":"part","heading":"AD/B747/143 Amdt 1","content":"## AD/B747/143 Amdt 1","sortOrder":1},{"sectionNumber":"Fuselage Section 41 Skin Stringer Joints","sectionType":"part","heading":"Fuselage Section 41 Skin Stringer Joints","content":"## Fuselage Section 41 Skin Stringer Joints","sortOrder":2},{"sectionNumber":"2/2007","sectionType":"part","heading":"2/2007","content":"## 2/2007","sortOrder":3}],"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":2,"scope_assessment":{"changed":true,"description":"This Amendment expands the inspection scope relative to the original AD by adopting the FAA’s additional inspection requirements for areas that may have Alodine‑coated rivets. The stated background notes that the FAA AD was prompted by cracking detected in a lap joint that earlier eddy‑current inspection missed — so Amendment 1 broadens the inspections required (an increase in scope) rather than merely restating previous obligations. The Amendment also sets a revised effective date (15 February 2007)."},"complexity_factors":["Single cross-reference to one external FAA AD (FAA AD 2006‑24‑02 Amendment 39‑14831).","Short applicability list: seven Boeing 747 variants limited to line numbers 001–430.","Single compliance requirement (follow FAA AD) with one revised effective date (15 February 2007).","No nested exceptions or multiple compliance paths in the instrument text provided.","Limited technical detail in the instrument itself — technical procedures reside in the external FAA AD."],"plain_english_summary":"**What this instrument does (mechanical effect)**\n\n- This Airworthiness Directive (AD) applies to Boeing 747‑100, ‑100B, ‑200B, ‑200C, ‑200F, 747SR and 747SP aeroplanes with line numbers 001–430. (See \"Applicability\".)\n- It requires operators to carry out the inspections and corrective actions stated in FAA AD 2006‑24‑02 (Amendment 39‑14831). In short: inspect the fuselage Section 41 skin‑to‑stringer joints and any related lap joints and repair any cracking found. (See \"Requirement\".)\n- The compliance regime and any required corrective work follow the technical instructions in the FAA AD. CASA has adopted that FAA AD as the required method of compliance, with this Amendment coming into force on 15 February 2007. (See \"Compliance\".)\n\n**Who this affects**\n\n- Owners and operators of the specified Boeing 747 models (line numbers 001–430). They must schedule and pay for the inspections and any repairs.\n- Maintenance organisations, aircraft engineers and inspectors who perform the mandated inspections and repairs must follow the FAA AD procedures.\n- The regulator (CASA) enforces compliance by making the FAA AD mandatory under Australian rules.\n\n**Why it matters (stated safety concern and response)**\n\n- Operators reported skin cracks around skin‑to‑stringer fasteners; some cracks approached 0.5 inch. If left to grow to “critical length”, such cracks can lead to in‑flight depressurisation. The FAA AD — and therefore this AD — adds an inspection of areas that may have Alodine‑coated rivets, because cracking was reported in a lap joint that had previously passed eddy‑current inspection.\n\n**Practical consequences and implementation mechanics**\n\n- Who pays: aircraft operators pay for the inspections, any non‑routine access (e.g. removal of structure or paint), and repairs. Maintenance providers bill for labour and parts.\n- Who decides what to do: the FAA AD provides the mandated inspection methods, intervals and repair instructions; CASA enforces those instructions in Australia by reference. Operators must follow the FAA AD’s technical steps unless CASA issues an alternative approved method.\n- Behaviour change required: operators must add the specified Section 41 inspections into their maintenance schedule and act on findings per the FAA AD.\n\n**Costs, incentives, trade‑offs and implementation risks**\n\n- Direct costs are inspection labour, possible nondestructive testing (e.g. eddy‑current), parts and repairs. The instrument does not fund those costs; they fall to operators.\n- Incentives: operators are incentivised to find and fix cracks early to avoid larger structural repairs or aircraft grounding. There is also an incentive to document and justify any deviations to obtain CASA approval.\n- Trade‑offs: more frequent or wider inspections increase maintenance cost and downtime but reduce risk of in‑flight depressurisation and potentially costly structural failure.\n- Opportunity cost: resources spent on these inspections/repairs cannot be used for other maintenance or commercial activity.\n- Implementation risk: effectiveness depends on inspection thoroughness and correct identification of Alodine‑coated rivets. The FAA AD was issued after a crack was missed by an eddy‑current inspection, so there is a non‑zero risk of false negatives depending on inspection method and workmanship.\n- Compliance burden and discretion: the AD delegates no new discretionary powers to the regulator; it makes a foreign regulator’s (FAA) technical requirements mandatory locally. Any variation requires formal approval.\n\n**Market effects and distribution of benefits/costs**\n\n- Concentrated benefits: passengers and operators benefit from reduced risk of depressurisation and structural failure; aircraft longevity may improve if cracks are found and repaired early.\n- Diffuse costs: all affected operators (a relatively small group given the aircraft types and line numbers) bear inspection and repair costs.\n- Effects on competition and private choice: the AD imposes a regulatory compliance cost but does not change ownership, market entry, or pricing mechanisms directly. Smaller operators with fewer resources may experience proportionally larger operational impacts when an aircraft is out of service for inspection or repair.\n\n**Summary statement**\n\nMechanically, CASA requires the inspections and repairs set out in FAA AD 2006‑24‑02 for certain Boeing 747 models (line numbers 001–430), effective 15 February 2007, because of reports of skin cracking at Section 41 stringer joints (including instances missed by earlier eddy‑current checks). Operators must perform and pay for the mandated inspections and remedial work; effectiveness depends on inspection quality and adherence to the FAA AD’s technical instructions."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is an amendment to an existing Airworthiness Directive (AD/B747/143). The original AD addressed fuselage skin cracks; Amendment 1 simply expands the inspection requirements to cover additional areas with Alodine-coated rivets based on new safety data. The scope remains tightly focused on the original safety issue (Section 41 skin integrity) and has not expanded beyond this specific airworthiness concern."},"complexity_factors":["Short, single-purpose instrument (approximately 250 words)","Only 1 defined term implied ('line numbers' referring to manufacturing sequence)","Heavy reliance on external technical document (FAA AD 2006-24-02) — the actual requirements are not reproduced in the text","No nested conditional logic or exceptions within the instrument itself","Simple structure: Applicability → Requirement → Compliance → Background","Technical aviation terminology requires domain knowledge but is standard for the field"],"plain_english_summary":"This Airworthiness Directive mandates additional inspections and repairs of Section 41 fuselage skin—focusing on skin‑stringer joints—on early Boeing 747s (‑100, ‑100B, ‑200B/C/F, 747SR, 747SP) with line numbers 001–430. It responds to cracks missed by prior checks (including in Alodine‑coated rivet areas) that risk rapid decompression. Operators must follow FAA AD 2006‑24‑02 and comply by 15 February 2007."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints","history":"/api/acts/ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints/history","analysis":"/api/acts/ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints/analysis","conflicts":"/api/acts/ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints/conflicts","importantCases":"/api/acts/ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints/important-cases","documents":"/api/acts/ad-b747-143-amdt-1-fuselage-section-41-skin-stringer-joints/documents"}}