{"id":"F2006B10085","name":"AD/G159/41 - Engine Mount - Inspection and Retirement","slug":"ad-g159-41-engine-mount-inspection-and-retirement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55550,"registerId":"commonwealth-F2006B10085-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"COMMONWEALTH OF AUSTRALIA CIVIL AVIATION","sectionType":"part","heading":"COMMONWEALTH OF AUSTRALIA CIVIL AVIATION ORDERS CIVIL AVIATION SAFETY AUTHORITY PART 105 SCHEDULE OF AIRWORTHINESS DIRECTIVES","content":"# COMMONWEALTH OF AUSTRALIA CIVIL AVIATION ORDERS CIVIL AVIATION SAFETY AUTHORITY PART 105 SCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nGULFSTREAM (GRUMMAN) G.159 SERIES AEROPLANES\n\nAD/G159/41 Engine Mount \\- Inspection and Retirement 2/85\n\nApplicability: All models. Requirement: Inspection:\n\n    Radiographically inspect the forward and aft engine mount tubes, LH and RH, over their entire lengths. The X-Ray beam may be oriented in any structurally convenient direction except that, in the case of the bottom horizontal tubes of the forward mount, it must be oriented vertically, in order to satisfactorily inspect the lower surface of the tubes.\n\n    2. Localised corrosion of the pitting variety is acceptable if the material lost is not more than the equivalent of a 1/4\" dia. hole through one tube wall and it is at least one tube diameter away from another corrosion pit. The detection of any pitting corrosion will need to be recorded for life limitation purposes. Compliance paras. 2 and 3 refer.\n\n    3. All radiographs which indicate the presence of corrosion which is not clearly less than the limitation of Para. 2 above shall be submitted to the Secretary for assessment.\n\nRetirement:\n\n    4. Retire from service the Grumman mount assemblies listed in Addendum 6 to Gulfstream I Customer Bulletin No. 241C.\n\nCompliance: 1. Unless already accomplshed, inspect before 3600 hours or six years component time in service, whichever is sooner, and thereafter at intervals not exceeding 12 months.\n\nNote: Previous inspections in accordance with AD/G159/24B may be considered as having met the inspection requirements of this AD.\n\n    2. Retire Grumman mount assemblies in which any corrosion has been detected (even though it may have been subsequently repaired)in accordance with the following:\n\n    For Grumman mount assemblies with more than 7 500 landings \\- Within 25 landings after the corrosion is detected, but not later than 30 days, or\n\n    b. For Grumman mount assemblies with less than 7 500 landings \\- Before exceeding 7 500 landings.\n\n    3. Retire Grumman mount assemblies in which corrosion has not been detected \\- Before exceeding 20 000 landings.","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":5,"scope_assessment":{"changed":true,"description":"This directive supersedes and combines AD/G159/24B and AD/G159/29 and alters scope by substituting radiographic inspection for ultrasonic methods and allowing a conditional life extension to 20,000 landings for Grumman mount assemblies with no corrosion history. It therefore broadens allowable service life in some cases while adding specific inspection, recording and submission obligations (Background; Requirement paras; Compliance paras)."},"complexity_factors":["Technical inspection prescription: specifies radiographic inspection of forward and aft mount tubes and orientation constraint for bottom forward tubes (Requirement para. 1).","Quantitative corrosion tolerance: defines acceptable pitting as no more than material loss equivalent to a 1/4\" diameter hole and minimum spacing one tube diameter (Para. 2).","Mandatory records and escalation: requires recording any detected pitting for life‑limitation purposes and submission of radiographs showing corrosion not clearly within limits to the Secretary (Para. 2–3).","Retirement rules tied to landing counts and inspection history: different mandatory retirement timings depending on whether corrosion is detected and whether mount has more or less than 7,500 landings, and a 20,000‑landing limit for non‑corroded mounts (Compliance paras. 2–3; Retirement para. 4).","Compliance timing complexity: initial inspection due before 3,600 hours or six years, whichever sooner, then at intervals not exceeding 12 months (Compliance para. 1).","Cross-references to external documents: retirement applies to assemblies listed in Addendum 6 to Gulfstream I Customer Bulletin No. 241C, and the AD supersedes earlier ADs (Retirement para. 4; Background).","Change of inspection modality and evidentiary standard: radiography is mandated because local experience judged it more reliable than ultrasonic methods, altering inspection practice and equipment needs (Background).","Conditional life-extension: the 20,000‑landing life extension applies only where there is no history of corrosion and is supported by manufacturer fatigue tests (Background)."],"plain_english_summary":"This airworthiness directive requires radiographic inspection of the forward and aft engine-mount tubes on all *Gulfstream G.159* aeroplanes, sets a measurable limit for acceptable pitting, requires recording and submission of suspect radiographs to the Secretary, and mandates retirement of listed Grumman mount assemblies. Inspections are due within 3,600 hours or six years and yearly thereafter; mounts with corrosion must be retired by specified landing-count thresholds, while non‑corroded mounts are limited to 20,000 landings; radiography replaces ultrasonics and manufacturer fatigue tests underpin the life extension."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original scope of ensuring engine mount integrity for Gulfstream G.159 aircraft. While it consolidates previous directives (AD/G159/24B and AD/G159/29) and extends service life based on new fatigue test data, it remains focused on its core purpose of inspection and retirement requirements for engine mounts. The life extension to 20,000 landings for corrosion-free mounts represents an evolution based on improved data rather than scope creep."},"complexity_factors":["Multiple compliance pathways based on landing counts (7,500 vs 20,000 landings)","Conditional retirement deadlines (25 landings OR 30 days)","Cross-reference to external documents (Gulfstream I Customer Bulletin No. 241C, Addendum 6, and FAA AD 84-20-08)","Technical measurement standards (1/4 inch diameter hole equivalent, one tube diameter spacing)","Specific radiographic orientation requirements for certain tubes","Grandfathering clause for previous inspections under AD/G159/24B","Dual time-based triggers (flight hours vs calendar time for initial inspection)"],"plain_english_summary":"This rule requires radiographic (X‑ray) inspections of the forward and aft engine‑mount tubes on Gulfstream G.159 aeroplanes to detect corrosion and metal fatigue; pitting must be recorded and suspect X‑rays sent to the CASA Secretary. Certain Grumman mount assemblies listed by the manufacturer must be retired immediately.\n\nFirst inspection is before 3,600 flight hours or 6 years, then annually. Mounts with prior corrosion face accelerated retirement (25 landings/30 days if over 7,500 landings or before 7,500 otherwise); clean mounts may remain to 20,000 landings."}},"importantCases":[],"_links":{"self":"/api/acts/ad-g159-41-engine-mount-inspection-and-retirement","history":"/api/acts/ad-g159-41-engine-mount-inspection-and-retirement/history","analysis":"/api/acts/ad-g159-41-engine-mount-inspection-and-retirement/analysis","conflicts":"/api/acts/ad-g159-41-engine-mount-inspection-and-retirement/conflicts","importantCases":"/api/acts/ad-g159-41-engine-mount-inspection-and-retirement/important-cases","documents":"/api/acts/ad-g159-41-engine-mount-inspection-and-retirement/documents"}}