{"id":"F2006B04642","name":"AD/BELL 407/7 - Tail Rotor Hanger Bearing Support Inspection","slug":"ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44394,"registerId":"commonwealth-F2006B04642-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 407/7 - Tail Rotor Hanger Bearing Support Inspection","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) 407 Series Helicopters\n\nAD/BELL 407/7 Tail Rotor Hanger Bearing Support Inspection 5/99\n\nApplicability: Bell (BHTC) Model 407 helicopters serial numbers 53000, 53002 through 53065,\n\n53067 and 53069 through 53075.\n\nRequirement: Perform a shimming procedure on the tail rotor hanger bearing support and the bearing hanger on the tail boom in accordance with the procedures specified in BHTC Alert Service Bulletin (ASB) no. 407-97-7 dated 27 February 1997.\n\nNote: Transport Canada Airworthiness Directive CF-97-08, dated 08 July 1997 refers.\n\nCompliance: At the next scheduled inspection but no later than 01 August 1999\\. This Airworthiness Directive becomes effective on 20 May 1999.\n\nBackground: In service reports have shown that some aircraft have developed a gap between the tail rotor hanger bearing support and the bearing hanger on the tail boom. This situation, if not corrected could lead to serious vibration of the tail rotor drive shaft and, eventually, to total disintegration of the shaft. This Directive introduces a shimming procedure to eliminate the gap and the possibility of damaging vibration of the tail rotor drive shaft.","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 mechanical defect in a specific aircraft model. It has not expanded beyond its original safety purpose."},"complexity_factors":["Single, specific mechanical procedure with clear reference to manufacturer bulletin","Limited applicability to 66 specific helicopter serial numbers","Straightforward compliance deadline with single condition (next inspection OR fixed date)","No defined terms section, no cross-references to other legislation beyond a single note about Canadian equivalent","Simple cause-and-effect background explanation","Total length: approximately 200 words"],"plain_english_summary":"This safety order mandates owners/operators of Bell 407 helicopters with serials 53000, 53002–53065, 53067, and 53069–53075 to inspect and correct a gap in the tail rotor hanger bearing support by shimming per Bell Alert Service Bulletin 407-97-7. The gap can cause severe tail-rotor-drive vibration and possible catastrophic breakup. Compliance is required by the next scheduled maintenance, but no later than 1 August 1999; the order is effective 20 May 1999."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The Directive implements the manufacturer’s shimming procedure for a defined set of helicopters to eliminate a gap that causes vibration, matching the stated intent in the Background and Requirement. There is no indication in the text that the AD broadens or narrows scope beyond that original safety fix."},"complexity_factors":["Narrow applicability: specific Bell 407 serial numbers are listed (Applicability).","Single clear technical remedy: a shimming procedure prescribed by the manufacturer’s Alert Service Bulletin (Requirement).","Fixed compliance deadline tied to scheduled inspections and an absolute date (Compliance).","Dependence on technical maintenance work and access to manufacturer procedure — requires qualified personnel and parts but no new regulatory approvals (Requirement).","Regulatory enforcement by CASA and safety rationale supplied by service history reporting (Background)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of specified Bell 407 helicopters to perform a shimming procedure on the tail-rotor hanger bearing support and the bearing hanger on the tail boom, following BHTC Alert Service Bulletin 407-97-7, at the next scheduled inspection and no later than 1 August 1999. It obliges aircraft owners/operators to fund and arrange the work; the Civil Aviation Safety Authority enforces the directive because gaps can cause severe vibration and possible tail-rotor drive-shaft failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection","history":"/api/acts/ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection/history","analysis":"/api/acts/ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection/analysis","conflicts":"/api/acts/ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection/conflicts","importantCases":"/api/acts/ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection/important-cases","documents":"/api/acts/ad-bell-407-7-tail-rotor-hanger-bearing-support-inspection/documents"}}