COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Piper PA-23 (Apache and Aztec) Series Aeroplanes
AD/PA-23/66
Amdt 2
Wing Structural Fatigue Limitation 12/89
Applicability: All models certificated at a MTOW of 4800 lb or greater. Requirement: Retire the main spar lower cap assembly from service.
Compliance: 1. For aircraft certificated at a MTOW of 5200 lbs, prior to exceeding 13000 hours component time in service.
2. For aircraft certificated at a MTOW of 4940 lbs, prior to exceeding 20700 hours component time in service.
3. For aircraft certificated at a MTOW of 4800 lbs, prior to exceeding 27300 hours component time in service.
4. For aircraft certificated at a MTOW of 5200 lbs and fitted with Met-Co-Aire wing tip fuel tanks, prior to exceeding N hours component time in service where N is given by the expression:
N = 13000 + (13000 - T) x 0.593 hours,
where T = lower main spar cap time in service at which tip tanks were fitted.
Note: The available fatigue data covers wing main spars only. The durability of other parts of the airframe has not been evaluated, and is therefore unknown.
Based on experience, the Authority is prepared to credit unevaluated structure with a retirement life equal to double the life for the lower main spar cap.
An extension may be available, but any application must be supported by a fatigue substantiation covering all the remaining primary structure. This should include empennage, wing centre section, wing rear spar, control surfaces, fuselages, etc.
The substantiation may take the form of a safe life assessment, or a sufficiently rigorous revised inspection schedule to ensure that any fatigue cracking which could occur in service will be detected before the aircraft is endangered.
Background: The retirement lives promulgated by this Directive have been determined on the basis of information provided by the manufacturer. Operation beyond the promulgated lives carries an unacceptable risk of the spar cap developing fatigue cracks.
This Amendment introduces retirement lives for 4800 and 4940 lb MTOW aircraft, as well as aircraft fitted with Met-Co-Aire wing tip fuel tanks.
Overview
The Civil Aviation Regulations 1998, specifically within Part 39, includes a legislative instrument (F2006B05493) that was enacted to address safety concerns in Piper PA-23 (Apache and Aztec) Series Aeroplanes. This amendment was introduced by the Civil Aviation Safety Authority (CASA) to manage the risk of fatigue cracks developing in the wing structural components, particularly the main spar lower cap assembly. The objective of this directive is to ensure that these aircraft do not exceed certain operational limits to maintain airworthiness and safety. The directive applies to all Piper PA-23 models certificated at a maximum take-off weight (MTOW) of 4800 lb or greater and mandates the retirement of the main spar lower cap assembly based on the component time in service, with specific timelines provided depending on the MTOW of the aircraft and additional conditions if wing tip fuel tanks are fitted. The directive emphasises the importance of adhering to these timelines to mitigate the risk of fatigue-related structural failure.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 105, pertains to the Civil Aviation Safety Authority’s Schedule of Airworthiness Directives, focusing on Piper PA-23 (Apache and Aztec) Series Aeroplanes. This legislation applies to all models of these aircraft certificated at a maximum takeoff weight (MTOW) of 4800 pounds or greater. The primary requirement outlined in this directive mandates the retirement of the main spar lower cap assembly from service, with specific timelines based on the aircraft’s MTOW and its component time in service. For instance, aircraft certificated at a MTOW of 5200 lbs must retire the main spar lower cap assembly before exceeding 13,000 hours of component time in service, while those certificated at a MTOW of 4800 lbs must do so before reaching 27,300 hours. Additionally, the directive provides a formula for calculating the retirement life for aircraft equipped with Met-Co-Aire wing tip fuel tanks, adjusting the hours based on the service time of the lower main spar cap at which the tip tanks were fitted. The directive also allows for extensions, subject to the submission of a fatigue substantiation that covers all remaining primary structure of the aircraft. The scope of the directive is limited to the main spar lower cap assembly, as other parts of the airframe's durability have not been evaluated, although an extension may be granted if supported by sufficient substantiation.
Key Provisions
The main operative sections of the Civil Aviation Regulations 1998, specifically in Part 39 - 105 concerning the Piper PA-23 (Apache and Aztec) Series Aeroplanes, are found in AD/PA-23/66 Amendment 2, which pertains to wing structural fatigue limitation. The requirement of this section is the retirement of the main spar lower cap assembly from service for specific models of the Piper PA-23 series. The applicability of this directive extends to all models certificated at a Maximum Takeoff Weight (MTOW) of 4800 lbs or greater (section 1). The compliance details are divided into different categories based on the MTOW of the aircraft. For example, for aircraft certificated at a MTOW of 5200 lbs, the main spar lower cap assembly must be retired prior to exceeding 13,000 hours of component time in service (section 1(1)). The specific hours of component time in service before which the main spar lower cap assembly must be retired vary depending on the MTOW of the aircraft and whether the aircraft is fitted with Met-Co-Aire wing tip fuel tanks (sections 1(2)-(4)).
The obligations and requirements imposed by this Act on the parties or entities it governs primarily revolve around ensuring the safety of the aircraft by adhering to the stipulated retirement schedules for the main spar lower cap assembly. Operators of Piper PA-23 series aircraft must closely monitor the component time in service of the main spar lower cap assembly and ensure that it is retired in accordance with the prescribed timelines. This is crucial to prevent the development of fatigue cracks, which could compromise the structural integrity of the wing and, consequently, the safety of the aircraft. Additionally, for aircraft fitted with Met-Co-Aire wing tip fuel tanks, operators must apply a specific formula to determine the precise retirement time based on the lower main spar cap time in service at which the tip tanks were fitted (section 1(4)). This directive underscores the importance of precise record-keeping and adherence to the specified timelines to maintain airworthiness.
In terms of consequences for non-compliance, the Civil Aviation Regulations 1998 do not explicitly outline specific offences, penalties, or civil/criminal consequences within the text of the legislation provided. However, non-compliance with airworthiness directives issued by the Civil Aviation Safety Authority (CASA) can lead to significant repercussions. Operating an aircraft beyond the stipulated retirement limits carries a high risk of structural failure due to fatigue cracks, which could result in catastrophic in-flight incidents. CASA has the authority to enforce compliance through various means, including grounding non-compliant aircraft, imposing fines, or taking legal action against operators who fail to adhere to airworthiness directives. The precise penalties and consequences would be determined based on the specific circumstances of non-compliance and the severity of the breach. The overarching goal of these regulations is to ensure the highest standards of safety in civil aviation, and adherence to them is mandatory to avoid severe legal and safety repercussions.