AD/HU 369/78 - Four Bladed Tail Rotor Hubs

Overview

The Civil Aviation Regulations 1998, as amended by F2006B10742, were enacted to ensure the safety and integrity of civil aviation within Australia. This legislative instrument specifically targets safety concerns related to the McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters, addressing an identified problem of fatigue cracks in four-bladed tail rotor hubs. The Civil Aviation Safety Authority (CASA) issued Airworthiness Directive AD/HU 369/78 to mandate inspections of these tail rotor hubs, aiming to mitigate risks associated with electrical arcing due to poor anode contact during the manufacturing process. The policy objective behind this directive is to enhance aviation safety by ensuring that affected helicopters are inspected and necessary repairs are carried out promptly. CASA urges maintenance organisations to inspect their spares inventory and take advantage of McDonnell Douglas Helicopter Company’s offer to replace unserviceable items free of charge.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105 concerning Airworthiness Directives, applies to all MDHC 369D and 369E series helicopters that are equipped with a four-bladed tail rotor hub bearing the part number 369D21700-3. This regulation is applicable unless the currently fitted hub has already been inspected in line with the requirement document. The legislation pertains to a Commonwealth-wide scope, overseen by the Civil Aviation Safety Authority. It mandates that the tail rotor hub of these helicopters be inspected in accordance with either MDHC S.I.N. DN-160 or EN-50, depending on the specific circumstances. The requirement is set to ensure safety and compliance with airworthiness standards, with particular attention to the issue of fatigue cracks that have been identified in one hub as a result of electrical arcing due to poor anode contact during the Tiodize coating process in manufacturing. The inspection must be carried out before the helicopter accumulates a certain amount of component time in service post 11 September 1989, with specific timelines depending on the serial number range of the hub in question.

Key Provisions

The Civil Aviation Regulations 1998, Part 39, specifically Section 105, outlines the Airworthiness Directives (ADs) that must be followed for maintaining the airworthiness of certain aircraft, such as the McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters. This particular directive, AD/HU 369/78, pertains to the four-bladed tail rotor hubs on these helicopters (Section 11/89). The directive applies to all MDHC 369D and 369E series helicopters that are equipped with a four-bladed tail rotor hub part number 369D21700-3, unless the currently installed hub has already been inspected according to the specified requirements. These helicopters must undergo an inspection of the tail rotor hub as per the Maintenance Document Specifications (S.I.N. DN-160 or EN-50) as applicable. The directive also notes that McDonnell Douglas Helicopters (MDHC) offers to replace any unserviceable items free of charge and encourages maintenance organisations to inspect their spares inventory to ensure compliance. For compliance, helicopters with hub serial numbers between 196 and 251 must be inspected before accumulating 10 hours of component time in service after 11 September 1989. For all other affected helicopters, the inspection must occur before accumulating 100 hours of component time in service after the same date. This directive was issued due to the discovery of fatigue cracks in one hub, which MDHC attributed to electrical arcing caused by poor anode contact during the Tiodize coating process during manufacture. The obligations imposed by this directive are clear and must be adhered to by all relevant parties. Maintenance organisations are required to inspect the specified helicopter tail rotor hubs in accordance with the designated maintenance specifications. Additionally, MDHC is obligated to offer free replacement of any unserviceable items found during inspection. The directive also mandates that inspections be conducted based on specific component time thresholds after the issuance date of the directive. Failure to comply with the requirements of this directive can lead to serious consequences. Although the regulations do not explicitly state penalties for non-compliance, the overarching principle is that non-compliance can result in the grounding of affected helicopters, which can have significant operational and financial repercussions for operators. Furthermore, the Civil Aviation Safety Authority (CASA) has the authority to take enforcement action against non-compliant operators, which could include fines, sanctions, or other regulatory measures. The severity of these consequences underscores the importance of adhering to the directive to ensure the continued airworthiness of the affected helicopters.