AD/BEECH 99/4 - Vertical Stabiliser Main Spar

Overview

The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority (CASA), was enacted to ensure the safety of civil aviation within Australia. Part 39 - 105 of these regulations addresses Airworthiness Directives, which are legally enforceable safety rules issued by CASA to correct an unsafe condition on an aircraft. The specific directive AD/BEECH 99/4 pertains to Beechcraft 99 Series Aeroplanes and focuses on the vertical stabiliser main spar, responding to the problem of cracking in this component identified in the fleet. The directive mandates a visual inspection of both flanges of the vertical stabiliser main spar and angle doubler, with specific compliance timelines and re-inspection intervals, aiming to maintain the airworthiness and safety of the aircraft. The policy objective of these regulations is to ensure that all civil aircraft operate under a stringent safety regime, thereby protecting passengers and crew from potential hazards. The authority to enact these regulations is derived from the legislative power of the Commonwealth of Australia, specifically under the authority of the Civil Aviation Act 1988, which empowers CASA to issue and enforce Airworthiness Directives to address identified safety issues. The directive is designed to mitigate the risk associated with the identified structural issue, ensuring that aircraft continue to meet safety standards throughout their operational life.

Scope and Application

The Civil Aviation Regulations 1998, under Part 39 - 105, mandate specific airworthiness directives for particular aircraft models, including the Beechcraft 99 series aeroplanes, which applies to aircraft with serial numbers U-1 to U-151. This legislation is enforced by the Civil Aviation Safety Authority and is applicable to the owners or operators of the specified Beechcraft 99, 99A, A99A, and B99 models. The directive requires a thorough visual inspection of the vertical stabiliser main spar and angle doubler using a borescope, as outlined in Beech Service Instruction 0530-134, to ensure the aircraft's safety. Compliance with this directive necessitates an initial inspection before the aircraft reaches 2000 hours of time in service or before 50 hours of time in service following 25 May 1995, whichever is later, and subsequent inspections must be conducted at intervals not exceeding 500 hours of time in service. Installation of a specified doubler over uncracked structure, or replacement of the stabiliser with certain part numbers, may exempt the aircraft from this directive. This regulation does not extend to other aircraft models or types not specified in the directive.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105 concerning the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, includes a directive for the Beechcraft 99 Series aeroplanes, designated AD/BEECH 99/4. This directive applies to Beech 99, 99A, A99A, and B99 aircraft with serial numbers U-1 to U-151. The primary requirement outlined in this directive is a visual inspection of both flanges of the vertical stabiliser main spar and angle doubler, using a borescope as detailed in Beech Service Instruction (SI) 0530-134. This inspection is mandated to identify any potential cracking in the vertical stabiliser main spar, a known issue documented in FAA AD 90-15-18. Compliance with AD/BEECH 99/4 involves conducting an initial inspection before the aircraft reaches 2000 hours of time in service or before 50 hours of time in service after 25 May 1995, whichever comes later. Thereafter, re-inspections are required at intervals not exceeding 500 hours of time in service. Installation of a doubler over an uncracked structure, as specified in Beech SI 0530-134, Figure 3, or replacement of the stabiliser with a part number 115-640000-605, -607, or -651, effectively nullifies the requirement for this inspection. These provisions aim to ensure the structural integrity of the vertical stabiliser main spar, which is critical for the safe operation of the aircraft. Failure to comply with the requirements set forth in AD/BEECH 99/4 could result in serious consequences. The Civil Aviation Regulations 1998 impose obligations on operators and maintenance personnel to adhere to the Airworthiness Directives. Non-compliance could lead to the aircraft being deemed unairworthy, thereby affecting its airworthiness certificate and potentially leading to enforcement actions. In cases where the non-compliance is found to have contributed to an accident or incident, it could also result in criminal charges against the responsible parties. The penalties for such offences can be severe, including fines and imprisonment, reflecting the gravity of the potential safety risks involved.