{"id":"F2006B10451","name":"AD/HS 125/169 - Wheel Tie-Bolt Nuts","slug":"ad-hs-125-169-wheel-tie-bolt-nuts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116165,"registerId":"commonwealth-F2006B10451-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.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 CASR 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.001.png)  \n\nBritish Aerospace BAe 125 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/HS 125/169 Wheel Tie -Bolt Nuts 6/200","sectionType":"part","heading":"AD/HS 125/169 Wheel Tie -Bolt Nuts 6/2003 DM","content":"# AD/HS 125/169 Wheel Tie \\-Bolt Nuts 6/2003 DM\n\nApplicability: Models DH.125 Series, BH.125 Series, HS.125 Series, and BAe.125 Series aircraft, as listed in Raytheon Mandatory Service Bulletin (MSB) 32-3522, dated September 2002.\n\nModel Hawker 800XP aircraft, with serial numbers up to and including serial number 258581; equipped with Dunlop wheels part numbers AH51909, AH52075, AH52286, AH52206, AHA1287, AHA1606, or AHA1814.\n\nRequirement: Inspect the main landing gear wheels to determine the part numbers of the tie-bolt nuts, in accordance with Raytheon MSB 32-3522.\n\nIf any part number NAS1804 tie-bolt nut is found installed, before further flight, replace the nut with a new part number FN22A524 tie-bolt nut (or a new Dunlop tie- bolt nut part number H5227C-5CW, SN407C-054, or LH13318-5, which are authorised by Ra ytheon); in accordance with MSB 32-3522.\n\nNote: FAA AD 2003-07-07 refers\n\nCompliance: Within 10 landings or 12 days after 7 May 2003, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 7 May 2003.\n\nBackground: The FAA requires certain actions intended to prevent separation of a main landing gear wheel due to loose or missing tie-bolts or tie-bolt nuts, with consequent damage to aircraft structure or systems, decompression, loss of full braking ability, or injury to personnel on the ground.\n\n![](image.002.jpeg)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 1 May 2003\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"No indication in the AD that scope has been altered from its original intent. The directive applies only to the models and serial numbers referenced in Raytheon MSB 32-3522, requires inspection of tie-bolt nut part numbers and replacement of NAS1804 nuts with listed alternatives, and sets a 10-landing/12-day compliance window from 7 May 2003 (Applicability; Requirement; Compliance)."},"complexity_factors":["Targeted applicability: specific models and serial numbers listed in Raytheon MSB 32-3522 (Applicability) — narrows affected fleet but requires checking serial records.","Dependence on external instructions: compliance must follow Raytheon MSB 32-3522 (Requirement) and references FAA AD 2003-07-07 (Note/Background).","Part-number specificity: action triggered only if tie-bolt nut is NAS1804; replacements limited to FN22A524 or specified Dunlop part numbers (Requirement) — technical verification and parts sourcing required.","Short compliance window: must be done within 10 landings or 12 days after 7 May 2003 (Compliance) — creates scheduling pressure for operators.","Operational consequence: 'before further flight' replacement if NAS1804 found (Requirement) — immediate grounding risk and potential disruption.","Regulatory basis and discretion: issued under CASR 1998 subregulation 39.1(1) by CASA delegate (preamble/signature) — legally mandatory with delegate authority.","Multiple authorised replacements: Raytheon-authorised alternatives permitted (Requirement) — reduces single-supplier dependency but ties compliance to OEM authorisation."],"plain_english_summary":"This directive requires operators of specified BAe/Hawker 125-series aircraft to inspect main landing-gear wheels for the tie-bolt nut part number and, if NAS1804 nuts are fitted, replace them with approved FN22A524 or specified Dunlop nuts before further flight. It applies to the models and serials listed in Raytheon MSB 32-3522 (including Hawker 800XP up to SN 258581) and must be completed within 10 landings or 12 days after 7 May 2003. Operators bear inspection and replacement costs and any resulting downtime."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope — addressing a specific unsafe condition with specific wheel nuts on specific aircraft models. There is no evidence of scope creep; it remains a targeted safety intervention for a defined mechanical defect."},"complexity_factors":["Single, specific mechanical issue (wheel nut replacement)","Clear applicability section limiting affected aircraft to specific models and serial numbers","Straightforward requirement: inspect, and if condition X found, replace with part Y","Simple compliance deadline (10 landings OR 12 days)","Only 4 defined part numbers in the requirement section","No nested exceptions or conditional logic beyond the basic 'if found, then replace' structure","Single cross-reference to FAA AD and Raytheon service bulletin for technical details"],"plain_english_summary":"This CASA safety order requires owners/operators of specified BAe 125/HS.125 and Hawker 800XP jets (with certain Dunlop wheel part numbers per the Raytheon service bulletin) to inspect main landing gear wheels to see whether NAS1804 nuts are fitted—and, if found, replace them with the approved alternative before flight.  \n\nThe FAA found NAS1804 nuts can loosen or fall off, risking wheel separation with possible structural damage, decompression, brake failure or ground injury. Actions were due within 10 landings or 12 days after 7 May 2003."},"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-hs-125-169-wheel-tie-bolt-nuts","history":"/api/acts/ad-hs-125-169-wheel-tie-bolt-nuts/history","analysis":"/api/acts/ad-hs-125-169-wheel-tie-bolt-nuts/analysis","conflicts":"/api/acts/ad-hs-125-169-wheel-tie-bolt-nuts/conflicts","importantCases":"/api/acts/ad-hs-125-169-wheel-tie-bolt-nuts/important-cases","documents":"/api/acts/ad-hs-125-169-wheel-tie-bolt-nuts/documents"}}