AD/BELL 412/31 - Fin to Tail Boom Junction

Overview

The Civil Aviation Regulations 1998, specifically Part 39, were enacted to establish and maintain a comprehensive regulatory framework for civil aviation in Australia, ensuring safety, efficiency and environmental protection in air navigation. One of the key components of this legislative instrument is the schedule of Airworthiness Directives, which includes AD/BELL 412/31 concerning the inspection of the fin to tail boom junction on Bell Helicopter Textron 412 series helicopters. This directive was introduced to address a specific safety concern identified in Bell 212 helicopters, where cracks were found in the tail boom area. The objective is to mandate a close visual inspection of the internal tail boom to fin junction area, particularly focusing on specific parts of the skin and flanges of the upper boom longerons, to prevent similar incidents in other aircraft of the same model. The directive requires compliance at the earliest opportunity, but no later than before further flight after 25 May 1992, highlighting the urgency and importance of addressing this safety issue promptly.

Scope and Application

The Civil Aviation Regulations 1998, specifically PART 39 - 105, applies to all Bell Helicopter Textron 412 Series Helicopters, mandating a critical inspection procedure to be performed on the fin to tail boom junction area. This requirement is applicable to all models of the mentioned helicopter series, underscoring the necessity for a thorough visual inspection to identify any structural integrity issues, such as cracks, in the specified areas. The regulation necessitates the removal of the tail boom lower elliptical inspection panel and directs attention to specific parts including Skin Part number 212-030-099-087 or -131, and the flanges of the left and right hand upper boom longerons. The inspection must be conducted at the earliest opportunity, but before further flight following 25 May 1992, to prevent potential safety hazards arising from undetected structural flaws. This directive is a response to a reported incident involving a Bell 212 model and extends to the Bell 412 models due to their structural similarity.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, mandates an airworthiness directive (AD) for Bell Helicopter Textron 412 Series helicopters, identified as AD/BELL 412/31. This directive, effective 25 May 1992, requires operators to remove the tail boom lower elliptical inspection panel (Part number 205-030-814-019) and conduct a thorough visual inspection of the internal tail boom to fin junction area. The inspection should focus on the skin part numbers 212-030-099-087 or -131 in the internal radius adjacent to, and immediately forward of, angle Stiffener Part number 205-030-801-007, as well as the flanges of the left and right hand upper boom longerons in the area adjacent to the same angle stiffener. This inspection is crucial to identify any potential cracks or structural issues that could compromise the safety of the aircraft. Operators of Bell Helicopter Textron 412 Series helicopters must comply with this directive by performing the inspection at the earliest opportunity, but no later than the specified date of 25 May 1992, before any further flight. This requirement stems from an incident involving a Bell 212 where a 250 mm crack was detected in the specified skin area, accompanied by adjacent cracks in the upper left hand longeron. These cracks were located in line with the forward edge of the gearbox support mount and progressed under the skin doubler, making external detection challenging. The directive applies not only to the Bell 212 but also to the Bell 412 due to the identical design of their tail booms. Failure to comply with the AD/BELL 412/31 could lead to significant consequences. Civil Aviation Regulations stipulate that non-compliance with airworthiness directives is an offence. Those found in breach may face penalties, including fines and potential criminal charges. The specific penalties are determined by the severity of the breach and the potential risk to aviation safety posed by the non-compliance. Ensuring adherence to this directive is critical for maintaining the safety standards required by the Civil Aviation Safety Authority. The directive aims to prevent similar incidents by requiring a detailed inspection of a specific area prone to structural failure. By mandating this inspection, the Civil Aviation Safety Authority seeks to ensure that all Bell Helicopter Textron 412 Series helicopters remain airworthy and safe for operation. This proactive approach underscores the importance of regular and thorough inspections in maintaining the integrity of aircraft and protecting the lives of those on board.