AD/DHC-1/14 - Flap Hinge Arms - Inspection and Modification

Overview

The Civil Aviation Regulations 1998, as amended through the legislative instrument F2006B08998, introduced specific airworthiness directives for the De Havilland DHC-1 (Chipmunk) Series Aeroplanes to address safety concerns regarding the flap hinge arms. Enacted by the Australian Government, these regulations aim to ensure the structural integrity and safe operation of the aircraft by mandating regular inspection and modification of the flap hinge arms. This legislative measure was introduced to mitigate the risk of corrosion, which could compromise the functionality of the flap hinge arms and, consequently, the overall airworthiness of the aircraft. The policy objective underpinning this directive is to maintain the highest standards of safety in civil aviation by addressing specific vulnerabilities identified in the design and operation of the Chipmunk Series Aeroplanes.

Scope and Application

The Civil Aviation Regulations 1998, specifically under Part 39 - 105 and the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, mandate stringent safety measures for De Havilland DHC-1 (Chipmunk) Series Aeroplanes. This legislative instrument applies to all models of the DHC-1 series, ensuring that operators and owners must adhere to precise inspection and, where necessary, modification protocols to maintain airworthiness. The regulations require operators to inspect the flap centre hinge arms for signs of corrosion, with particular attention to the internal surfaces. Should any corrosion be found, it must be addressed by either cleaning and protective coating if it is within permissible limits, or by replacing the hinge arms if the corrosion exceeds these limits. Additionally, a modification is mandated, requiring the drilling of a drain hole in the lower surface of the hinge arm to prevent future corrosion. These safety measures are crucial to the ongoing airworthiness of the aircraft and must be strictly observed, with inspections occurring at intervals not exceeding 12 months and modifications being performed forthwith upon identification of necessary conditions.

Key Provisions

The Civil Aviation Regulations 1998, under Part 39 - 105, contain specific airworthiness directives pertinent to the maintenance and safety of De Havilland DHC-1 (Chipmunk) series aeroplanes. One such directive is AD/DHC-1/14, which addresses the inspection and modification of flap hinge arms. This directive applies to all models of the DHC-1 series (Section 8/62). The primary requirement is that the flap centre hinge arms (P/N C1.W.353 and C1.W.354) must be inspected internally for corrosion. If small areas of shallow surface corrosion are detected, the hinge arms must be cleaned internally using sand blasting or another effective method and then coated with a suitable protective medium before further flight (Section 1(a) and 1(b)). If the corrosion exceeds specified limits, the hinge arms must be replaced with serviceable items (Section 1(c)). The internal inspection can be facilitated by using an intrascope or similar optical aid inserted through one of the 3/8 inch diameter holes in the base plate of the hinge arm. Additionally, a 1/8 inch diameter drain hole must be drilled in the lower surface of the hinge arm, at a distance of 0.75 inch from the ball race centreline (Section 2). Compliance with AD/DHC-1/14 necessitates regular inspections and modifications as stipulated. The internal inspection must occur at intervals not exceeding 12 months, ensuring that any signs of corrosion are identified and addressed promptly (Section Compliance - Inspection). The modification, which involves drilling the specified drain hole, must be carried out forthwith to maintain the integrity of the flap hinge arms (Section Compliance - Modification). These requirements are essential to prevent the structural weakness or failure of the hinge arms, which could compromise the safety of the aircraft. Failure to comply with the provisions outlined in AD/DHC-1/14 can lead to serious safety concerns. The Civil Aviation Regulations 1998 do not explicitly state the penalties for non-compliance in this context, but violations of airworthiness directives typically result in significant civil and potentially criminal consequences. Civil penalties may include fines and the grounding of the aircraft until the required inspections and modifications are completed. Criminal penalties might apply in cases where non-compliance leads to accidents or endangers flight safety, potentially resulting in imprisonment or heavy fines. The exact penalties would be determined by the Civil Aviation Safety Authority and could vary based on the severity and circumstances of the breach.