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/92 Wing Skin Near Main Landing Gear 6/95
Applicability: All models except 690C and all 695 series. Requirement: 1. Location:
With your head up inside the wheel well you will see the heavy forgings which contain the bushings for the main landing gear trunnion. Note that each forging has two fingers which poke up through cutouts in the lower surface of the wing. It is the forward cutouts which are to be inspected for cracks.
2. Inspection from Underneath:
Clean the external skin around each forward cutout. With a mirror and a strong light, look for cracks in the external skin near the forward and aft radii of each forward cutout. (The aft radius may be hard to see.)
3. Inspection from the Top:
Remove the access panel in the top of the nacelle, then the underlying access panel in the top of the wing, to view the forward cutouts from inside the wing. With a mirror and a strong light, look for cracks in the internal doubler near the forward and aft radii of each forward cutout.
Compliance: Inspect at the next periodic inspection after 25 May 1995.
If not cracked, repeat the inspection every 1000 or fewer hours, or every 500 or fewer hours while the aircraft is flying low level surveys.
If only the skin is cracked, or if the crack in the doubler can be smoothly dressed out and dye checked without removing more than 6 mm from the edge, and if the skin crack has not grown past the nearest rivet, the aircraft may remain in service for up to 500 hours if the crack is re-inspected every 250 or fewer hours, or every 125 or fewer hours while the aircraft is flying low level surveys. The area must be repaired before further flight if the skin crack has grown beyond the nearest rivet, or a doubler crack cannot be dressed out as just described.
Background: Two aeroplanes have been found with cracks at cutouts in the lower surface of the wing. Both aeroplanes were 500S models, and both were flying low level surveys, however there is no reason to believe that other Aero Commanders with a similar wing won’t suffer the same problem. The cracks might be missed during routine maintenance, so special inspections have been specified to prevent major cracking and loss of wing strength.
Overview
The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority, were enacted to ensure the safety of civil aviation in Australia. This legislation includes detailed safety directives and operational requirements for aircraft, among which is the Airworthiness Directive AD/AC/92 concerning the inspection of wing skin near the main landing gear of Twin Commander (Gulfstream/Rockwell/Aerocommander 500, 600 and 700) series aeroplanes. This directive was introduced to address the identified problem of cracks in the wing skin near the forward cutouts of the lower surface, which was discovered in two aeroplanes during low-level surveys. The policy objective behind this directive is to prevent the occurrence of major cracks that could compromise the structural integrity of the wing, thereby enhancing aviation safety. The directive mandates specific inspection protocols to be conducted during periodic inspections and sets forth compliance timelines and conditions for continued service if minor cracks are detected.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 105, governs the airworthiness directives for the Twin Commander (Gulfstream/Rockwell/Aerocommander 500, 600 and 700) series aeroplanes, excluding the 690C and all 695 series models. This legislation applies to aircraft operators and maintenance personnel who must ensure that the specified inspections are performed on the wing skin near the main landing gear trunnion. The geographic scope of these regulations is national, applying across the Commonwealth of Australia, and they are enforced by the Civil Aviation Safety Authority (CASA). The regulations provide detailed instructions for the inspection of the forward cutouts in the lower surface of the wing, requiring both external and internal inspections for cracks, with specific intervals for these inspections based on flight hours and conditions. If cracks are detected, the regulations outline conditions under which the aircraft may remain in service temporarily and specify the repair requirements before further flight. These provisions are intended to prevent major structural issues and ensure the continued airworthiness of the specified aircraft models.
Key Provisions
The Civil Aviation Regulations 1998, specifically Part 39 - 105, mandate that certain models of Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes undergo regular inspections to ensure the integrity of the wing skin near the main landing gear trunnions. According to AD/AC/92, all models except the 690C and all 695 series are subject to these requirements (Section 1). The primary inspection target is the forward cutouts in the lower surface of the wing, which should be checked for cracks both from underneath and from the top of the nacelle (Section 2).
Compliance with these directives necessitates a thorough inspection process. Firstly, the external skin around each forward cutout must be cleaned, and any visible cracks must be identified. Secondly, an inspection from the top involves removing access panels to view the internal doubler near the forward and aft radii of each forward cutout, again looking for cracks (Section 3). The inspection must occur at the next periodic inspection following 25 May 1995. If no cracks are found, subsequent inspections should be conducted every 1000 or fewer hours, or every 500 or fewer hours if the aircraft is flying low-level surveys. If minor cracks are detected, the aircraft can continue to operate under certain conditions, provided the cracks are re-inspected every 250 or fewer hours, or every 125 or fewer hours if the aircraft is flying low-level surveys. However, if the cracks have grown or cannot be adequately dressed out, repairs must be made before further flight.
Failure to comply with these directives may result in severe consequences. The regulations impose obligations on operators and maintenance personnel to ensure that these inspections are carried out diligently and that any identified issues are addressed promptly. Non-compliance could lead to significant penalties, including fines and potential grounding of the aircraft. The exact penalties are not specified in the provided text, but under Australian civil aviation law, such breaches can lead to substantial financial penalties and legal action against the operators or responsible parties. Additionally, any failure to adhere to these safety directives could result in the revocation of the aircraft's airworthiness certificate, severely impacting its operational status and the safety of its passengers and crew.