AD/DHC-6/71 - Fuselage Station FS 239 Frame

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 105, address the safety of DHC-6 (Twin Otter) Series Aeroplanes through Airworthiness Directives. Enacted by the Australian Parliament, this legislation aims to ensure that civil aircraft meet safety standards to protect passengers and crew. The policy objective is to mitigate risks by mandating inspections and repairs to prevent structural failures in aircraft. One such directive, AD/DHC-6/71, focuses on the fuselage frames of DHC-6 aircraft, requiring visual inspections for cracks at specific fuselage stations. The directive responds to documented incidents of cracking at fuselage station FS 239, aiming to ensure the airworthiness of these aircraft by setting clear compliance timelines and procedures for inspection, repair, and replacement as necessary. The Civil Aviation Regulations 1998 mandate that all DHC-6 aircraft must undergo inspections of the fuselage frames for cracks, with specific guidelines provided in de Havilland Service Bulletin 6/521. This directive applies universally to all DHC-6 aircraft and necessitates compliance within 1200 hours of time in service after 12 October 1995 or before 12 October 1996, whichever comes first. The regulation further stipulates that if any cracks are found within specified tolerances, repetitive inspections must be performed, while any cracks exceeding these tolerances must be repaired or the affected part replaced before further flight. This directive underscores the commitment to aviation safety by addressing known structural issues to prevent potential hazards.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, applies to all DHC-6 aircraft within the Commonwealth of Australia, focusing on ensuring the airworthiness of these aeroplanes. This regulation mandates that inspections must be conducted on the fuselage frames for any signs of cracks using visual methods as described in the Accomplishment Instructions of de Havilland Service Bulletin 6/521. This inspection requirement is crucial as it responds to previous reported instances of cracking on the skin flange of the machined fuselage frame at fuselage station FS 239. The directive necessitates compliance within 1200 hours of time in service after 12 October 1995 or before 12 October 1996, whichever comes first, with further actions depending on whether the detected cracks are within specified tolerances or exceed them. If cracks within tolerances are found, repetitive inspections must be performed according to the de Havilland Inspection Requirement Manual or specified revisions, while cracks exceeding the tolerances must be repaired or the affected part replaced before further flight. This regulation underscores the importance of stringent safety measures in civil aviation to prevent potential hazards.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, mandates the inspection of the fuselage frames of DHC-6 (Twin Otter) series aeroplanes for any cracks (AD/DHC-6/71). This inspection requirement applies universally to all DHC-6 aircraft. The inspection must be conducted visually, following the Accomplishment Instructions outlined in de Havilland Service Bulletin 6/521. Compliance with this directive is required either within 1200 hours of time in service after 12 October 1995 or before 12 October 1996, whichever comes first. If cracks are detected within the specified tolerances, further inspections must be carried out according to the de Havilland Inspection Requirement Manual, PSM 1-6-7 Temporary Revision 77, or as detailed in PSM 1-6-7 normal revision No. 8, when it is issued. Should any cracks exceed the specified tolerances, the affected area must be repaired or replaced before the aircraft is flown again. Under this regulation, the primary obligation imposed on the operators and owners of DHC-6 aircraft is to conduct a thorough visual inspection of the fuselage frames at the designated station (FS 239) for any signs of cracks. This must be done in accordance with the instructions provided in de Havilland Service Bulletin 6/521. The operators must ensure that the inspections are completed within the stipulated timeframe, which is either 1200 hours after 12 October 1995 or before 12 October 1996. If any cracks are found, appropriate actions must be taken as per the detailed instructions in the referenced service bulletins and manuals, which may include further inspections or necessary repairs or replacements. The Civil Aviation Regulations 1998 establish specific consequences for non-compliance with these airworthiness directives. Operators and owners of DHC-6 aircraft who fail to adhere to the inspection and repair requirements outlined in the legislation may face regulatory enforcement actions. The penalties for non-compliance can include fines and other legal repercussions, as stipulated by the Civil Aviation Act 1988 and other relevant regulations. The exact penalties can vary based on the severity and frequency of the non-compliance, but they are designed to ensure that all DHC-6 aircraft maintain their airworthiness and safety standards.