{"id":"F2006B02687","name":"AD/B727/164 - NLG Wheel Well Pressure Web","slug":"ad-b727-164-nlg-wheel-well-pressure-web","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42003,"registerId":"commonwealth-F2006B02687-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B727/164 - NLG Wheel Well Pressure Web","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 727 Series Aeroplanes\n\nAD/B727/164 NLG Wheel Well Pressure Web 1/2000\n\nApplicability: Model 727 series aircraft; line numbers 124, 126, 130, 146, 221, 287, 331, 339, 345,\n\n355, 416, 439, 516, 532, 540, 608, 631, 650, 717, 777, 788, 791, 837, and 1087.\n\nRequirement: Install reinforcement straps and stiffeners on the sidewall, top and forward bulkhead panels of the pressure web of the nose landing gear wheel well, in accordance with Part II of the Accomplishment Instructions of Boeing Service Bulletin 727-53-0145, Revision 1, dated December 7 1989.\n\nNote: FAA AD 99-20-10 Amdt 39-11340 refers.\n\nCompliance: Before the accumulation of 60,000 total flight cycles, or before 8 November 2003, whichever occurs later.\n\nThis Airworthiness Directive becomes effective on 31 December 1999.\n\nBackground: The FAA received reports of fatigue cracks in the pressure web of the nose landing gear (NLG) wheel well. The actions required by this Directive are intended to prevent cracking of the pressure web of the NLG wheel well, which could result in loss of aircraft pressurisation.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted airworthiness directive addressing a specific structural fatigue issue in a defined aircraft population. It has not expanded beyond its original purpose of mandating repairs to prevent pressure web cracking."},"complexity_factors":["Single, clearly defined applicability (24 specific aircraft by line number)","One specific technical requirement referencing a single external document (Boeing Service Bulletin)","Simple binary compliance condition (60,000 flight cycles OR fixed date, whichever is later)","No defined terms section, no cross-references to other legislation beyond a note about the related FAA directive","Straightforward background explanation with clear safety rationale","Total length is approximately 200 words"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of 24 specified Boeing 727s to repair and reinforce the nose landing-gear wheel-well \"pressure web\" by installing metal straps and stiffeners per Boeing Service Bulletin 727-53-0145 Rev 1.  \n\nThe work addresses fatigue cracks that could lead to loss of cabin pressurisation; compliance is required before 60,000 flight cycles or by 8 November 2003 (whichever is later). Effective 31 December 1999."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The Directive's scope aligns with the stated intent in the Background: to prevent fatigue cracking of the NLG wheel-well pressure web by requiring specified reinforcements. It does not broaden obligations beyond the installation specified in Boeing Service Bulletin 727-53-0145 or extend applicability beyond the listed line numbers (Requirement; Background; Applicability)."},"complexity_factors":["Targeted applicability by specific line numbers increases administrative tracking and fleet sorting (Applicability).","Requires structural modification work per Boeing Service Bulletin 727-53-0145 Revision 1, Part II — technical and maintenance complexity (Requirement).","Compliance threshold tied to flight-cycle accumulation or a calendar date forces operators to monitor cycles and plan retrofit windows (Compliance).","Reference to FAA AD 99-20-10 creates regulatory cross-reliance and potential coordination of records (Note).","Safety-critical outcome (prevention of pressurisation loss) raises certification and oversight obligations after modification (Background).","Mandated installation may cause aircraft downtime, parts procurement and certified maintenance labour costs (implied by Requirement).","Limited regulatory discretion: instruction is prescriptive (install specified reinforcements) rather than optional, reducing interpretative flexibility (Requirement)."],"plain_english_summary":"This Airworthiness Directive orders operators of specified Boeing 727 airframes to fit reinforcement straps and stiffeners to the nose-landing-gear wheel-well pressure web, following Boeing Service Bulletin 727-53-0145 (Part II). It applies to listed line numbers and must be done before 60,000 total flight cycles or by 8 November 2003 (whichever is later). The stated purpose is to prevent fatigue cracking of the pressure web and the possible loss of aircraft pressurisation."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-164-nlg-wheel-well-pressure-web","history":"/api/acts/ad-b727-164-nlg-wheel-well-pressure-web/history","analysis":"/api/acts/ad-b727-164-nlg-wheel-well-pressure-web/analysis","conflicts":"/api/acts/ad-b727-164-nlg-wheel-well-pressure-web/conflicts","importantCases":"/api/acts/ad-b727-164-nlg-wheel-well-pressure-web/important-cases","documents":"/api/acts/ad-b727-164-nlg-wheel-well-pressure-web/documents"}}