{"id":"F2006B04620","name":"AD/BELL 222/5 - Ng Operating Speed Restrictions","slug":"ad-bell-222-5-ng-operating-speed-restrictions","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44372,"registerId":"commonwealth-F2006B04620-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 222/5 - Ng Operating Speed Restrictions","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)  \nBell Helicopter Textron Canada (BHTC) 222 Series Helicopters\n\nAD/BELL 222/5 Ng Operating Speed Restrictions 11/85\n\nApplicability: Bell 222U helicopters with Lycoming LTS101-750C-1 engines installed which have not been modified in accordance with LYC SB 101C-72-00-0079.\n\nRequirement: Install engine operating speed restriction placard/ decal P/N 222-075-221-101 or similar, which reads:\n\nAVOID CONT OPS 86% to 90% Ng\n\nbeneath gas producer speed indicators in accordance with Bell Helicopter Textron Alert Service Bulletin No. 222U-85-6.\n\nNote: Temporary Revision No. 85-1 to Model 222U Flight Manual BHT-222U-FM-1 is required whilst this restriction is effective.\n\nEffective: Forthwith.\n\nBackground: A number of contained turbine blade failures have occurred due to fatigue caused by vibration stresses when engines are operated in the 86% to 90% speed range. This Directive is issued restricting operation in this range until gas producer turbine wheels are modified in accordance with LYC SB 101C-72-00-0079.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1412},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This directive maintains its original narrow scope, targeting only Bell 222U helicopters with specific unmodified Lycoming engines to address a defined vibration-related safety risk. No expansion beyond the original technical safety purpose is evident."},"complexity_factors":["Technical aviation terminology requiring specialized knowledge (Ng, gas producer speed, contained turbine blade failures)","Precise conditional applicability based on specific engine model and modification status","References to external technical documents and part numbers (e.g., LYC SB 101C-72-00-0079, P/N 222-075-221-101)"],"plain_english_summary":"This mandatory safety rule orders operators of Bell 222U helicopters with Lycoming LTS101-750C-1 engines (not modified per LYC SB 101C-72-00-0079) to avoid operating engines between 86% and 90% Ng and to install a placard beneath the gas producer speed gauge reading: \"AVOID CONT OPS 86% to 90% Ng.\" It’s effective immediately because vibrations in that range have caused turbine blade fatigue and contained failures, creating an imminent safety risk."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-222-5-ng-operating-speed-restrictions","history":"/api/acts/ad-bell-222-5-ng-operating-speed-restrictions/history","analysis":"/api/acts/ad-bell-222-5-ng-operating-speed-restrictions/analysis","conflicts":"/api/acts/ad-bell-222-5-ng-operating-speed-restrictions/conflicts","importantCases":"/api/acts/ad-bell-222-5-ng-operating-speed-restrictions/important-cases","documents":"/api/acts/ad-bell-222-5-ng-operating-speed-restrictions/documents"}}