COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes
AD/AC/42
Amdt 7
Wing Main Spar Lower Cap W.S. 24 8/93
Applicability: Models 500, 500A, 500B, 500S, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680F(P), 680FL, 680FL(P), 680T, 680V, 680W, 681, and 720.
Requirement: 1. Serial numbers 1 to 1730 only
These aircraft were not fitted with a spar reinforcement when they left the factory. Unless already accomplished install a wing front spar external reinforcement kit in accordance with Aero Commander Service Change 81A or 81B.
2. All serial numbers
As required for the particular model and serial number, in accordance with Twin Commander SB 90C:
- modify the aircraft to improve access to W.S. 24;
b. modify the spar radius to improve its fatigue quality;
c. modify adjacent structure to eliminate interference; and
d. inspect for cracks and corrosion in the spar cap.
As noted in Twin Commander SB 90C, aircraft that have complied with earlier revisions of SB 90 may require additional work.
Compliance: 1. Install the reinforcement kit before the issue of an Australian Certificate of Airworthiness.
2. If at 22 July 1993 the aircraft has not already been modified and inspected at
W.S. 24, do so within 500 hours after 22 July 1993.
If at 22 July 1993 the aircraft has already been modified and inspected at W.S. 24, do the next inspection within 500 hours of the last one. In both cases re-inspect no less frequently than every:
- 500 hours for normal usage; or
- 200 hours for survey usage; or
- 100 hours for low level (less than 1000 feet AGL) survey usage.
Background: Wing station 24 has had a long history of fatigue cracking, including several fatal wing separations. Some form of spar reinforcement is necessary to lower stresses, to slow crack growth, to allow a practical inspection interval.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
This latest amendment introduces Revision C to Service Bulletin 90. Revision C adds some additional models to the inspection program, and reduces the inspection interval for survey aircraft based on recent - including Australian - experience which indicates rapid crack growth under the severe flight loads experienced during such operations.
Another change is the elimination of the threshold for modification and inspection. Cracks have been found that probably started earlier. All aircraft must now be inspected regardless of hours flown.
Overview
The Civil Aviation Regulations 1998, amended through the legislative instrument F2006B02101, introduced a series of airworthiness directives to address critical safety concerns, particularly fatigue cracking at Wing Station 24 of Twin Commander (Gulfstream/Rockwell/Aerocommander 500, 600 and 700) series aeroplanes. This amendment was enacted by the Australian Government to ensure the safety and airworthiness of these aircraft models. The problem addressed by this directive was the long-standing issue of fatigue cracking at Wing Station 24, which had led to several fatal wing separations. The objective was to mandate specific modifications and inspections to lower stress, slow crack growth, and establish practical inspection intervals to prevent such incidents. The amendment applies to a range of Twin Commander models, with specific requirements depending on their serial numbers. The compliance terms include mandatory installation of reinforcement kits and periodic inspections, reflecting the urgency and seriousness of the safety concerns identified.
Scope and Application
The Civil Aviation Safety Authority (CASA) has issued specific Airworthiness Directives (AD) under the Civil Aviation Regulations 1998 to ensure the safety of Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) series aeroplanes, particularly focusing on the wing main spar lower cap at wing station 24. These directives apply to specific models and serial numbers within the Twin Commander series, necessitating modifications and regular inspections to prevent fatigue cracking, which has been a recurring issue leading to fatal accidents. Compliance with these ADs is mandatory for aircraft to maintain their Australian Certificate of Airworthiness, with specific timelines and inspection intervals based on the aircraft's usage type. This legislative instrument extends its application nationally, ensuring all operators within Australia adhere to these safety standards. The regulations do not currently specify exclusions or exemptions, making it imperative for all relevant aircraft to comply with the outlined requirements. Subordinate instruments may further detail implementation and enforcement of these ADs.
Key Provisions
The Civil Aviation Regulations 1998, as amended, include specific Airworthiness Directives that govern the maintenance and safety of certain aircraft models. In particular, the regulation at PART 39 - 105 requires compliance with AD/AC/42 Amendment 7 for Twin Commander series aeroplanes, which includes models 500, 500A, 500B, 500S, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680F(P), 680FL, 680FL(P), 680T, 680V, 680W, 680L, 681, and 720. The directive outlines specific requirements for the installation of a wing front spar external reinforcement kit for certain serial numbers and mandates modifications to improve access to Wing Station 24, modify the spar radius, eliminate interference with adjacent structure, and inspect for cracks and corrosion. Compliance with these directives is mandatory before the issue of an Australian Certificate of Airworthiness.
For serial numbers 1 to 1730, the requirement is to install a wing front spar external reinforcement kit in accordance with Aero Commander Service Change 81A or 81B. This must be done before the issue of an Australian Certificate of Airworthiness. For all serial numbers, the aircraft must be modified to improve access to Wing Station 24, modify the spar radius, eliminate interference with adjacent structure, and inspect for cracks and corrosion in the spar cap. If the aircraft had already been modified and inspected at Wing Station 24 by 22 July 1993, the next inspection must be within 500 hours of the last one. In both cases, re-inspection must occur no less frequently than every 500 hours for normal usage, 200 hours for survey usage, or 100 hours for low-level survey usage.
The obligations imposed by this regulation include ensuring that all Twin Commander series aeroplanes meet the specified modifications and inspection requirements. Operators must install the required wing front spar external reinforcement kit and ensure that the aircraft is modified and inspected in accordance with the directive. Failure to comply with these obligations can result in the aircraft being deemed unairworthy, which can lead to grounding and potential enforcement actions by the Civil Aviation Safety Authority. The safety and airworthiness of the aircraft are paramount, and non-compliance can result in significant penalties.
The consequences for non-compliance with the Airworthiness Directives outlined in the Civil Aviation Regulations 1998 can be severe. The Civil Aviation Safety Authority has the authority to take enforcement actions against operators who fail to comply with the mandated modifications and inspection requirements. These actions can include fines, the suspension or revocation of an aircraft’s Certificate of Airworthiness, and other regulatory penalties. In cases of serious non-compliance that result in accidents or incidents, criminal charges may also be pursued, leading to potential imprisonment for individuals responsible for the oversight of the aircraft. The strict enforcement of these regulations is essential to maintaining the safety and airworthiness of the Twin Commander series aeroplanes.