AD/AS 355/9 - Main Gear Box Bevel Reduction Gear Module - Inspection of Bevel Ring Gear/Vertical Shaft Attachment Bolts

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 105, addresses the maintenance and safety standards for civil aviation operations within Australia, with a particular focus on the Eurocopter AS 355 (Twin Ecureuil) Series Helicopters. This legislation was enacted by the Australian Government to ensure the safety and airworthiness of aircraft, specifically targeting the identified problem of loose or sheared bolts in the main gearbox bevel reduction gear assembly of the AS 355 helicopters. The policy objective is to mitigate the risk of in-flight failures by mandating regular inspections and maintenance checks. This legislative instrument serves to enhance safety protocols and reduce the likelihood of mechanical failures that could compromise the integrity of the aircraft during operation. The enforcement of these regulations is overseen by the Civil Aviation Safety Authority (CASA) to ensure compliance with the specified inspection intervals and maintenance procedures. By adhering to these regulations, operators of AS 355 helicopters are required to perform visual and screw tightening checks at specified intervals to ensure the bolts securing the bevel ring gear to the vertical shaft remain intact, thus maintaining the operational safety of the aircraft.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105 concerning the Civil Aviation Safety Authority Schedule of Airworthiness Directives, applies to all Eurocopter AS 355 (Twin Ecureuil) series helicopters equipped with a particular main gearbox containing a bevel reduction gear assembly. The directive is explicitly targeted at those helicopters that have not undergone modifications as specified under A.M.S.07.7082 or A.M.S. 07.7083. This legislation is applicable within the Commonwealth of Australia, governed by the Civil Aviation Safety Authority (CASA), thus encompassing all states and territories under its jurisdiction. The regulation does not extend to helicopters that have been modified under the specified service bulletins. Additionally, the directive includes specific inspection requirements and compliance timelines to ensure the safety and airworthiness of the helicopters, detailing when inspections and checks must be conducted in relation to the hours of service. The directive mandates a series of inspections for the bevel ring gear/vertical shaft attachment bolts to prevent shearing and loosening, which have been identified as potential safety hazards. Compliance involves a visual check within 10 hours of service after 31st March 1983, followed by a visual check every 50 hours thereafter. A screw tightening check is required as a one-time inspection within 300 hours of service after 31st March 1983, and subsequent visual checks must be carried out every 300 hours of service post this one-time inspection. This directive ensures that the maintenance and safety standards are consistently adhered to by relevant operators and maintenance personnel.

Key Provisions

The Civil Aviation Regulations 1998, specifically PART 39 - 105, includes detailed directives regarding the airworthiness of various aircraft, including the Eurocopter AS 355 (Twin Ecureuil) series helicopters. In this context, AD/AS 355/9 pertains to the inspection of the bevel ring gear/vertical shaft attachment bolts in the main gearbox of these helicopters (section 1). This directive applies to all AS 355 helicopters equipped with a main gearbox containing a bevel reduction gear assembly, part numbers 355A.32.0600.00 and 01, that have not been modified under A.M.S.07.7082 or A.M.S 07.7083 (section 2). Operators and maintenance providers must adhere to several inspection requirements to ensure compliance with the regulations. Initially, within 10 hours of time in service after 31st March 1983, a visual check of the bevel ring gear/vertical shaft attachment bolts must be performed (section 3). Following this initial check, a screw tightening check is mandated within 300 hours of time in service after the same date, and this is a one-time only inspection (section 4). After the screw tightening check, a visual inspection must be conducted every 300 hours of time in service (section 5). These inspections are critical to identify any issues such as sheared or loose bolts, which could compromise the integrity and safety of the helicopter's operation. Failure to comply with these directives may result in serious safety hazards, potentially leading to severe operational disruptions or accidents. The regulations do not explicitly state civil or criminal penalties for non-compliance in the provided text, but non-compliance can result in the grounding of the aircraft until the issues are rectified. Operators and maintenance providers must ensure strict adherence to these inspection requirements to maintain the airworthiness of the AS 355 helicopters and to prevent any potential safety risks.