AD/AT/23 Amdt 1 - Aft Fuselage Structure Upper Longeron and Upper Diagonal Tube

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AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AT/23 and issues the following AD under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

 

Airtractor AT-300, 400 and 500 Series Aeroplanes

 

AD/AT/23

Amdt 1


Aft Fuselage Structure Upper Longeron and Upper Diagonal Tube


10/2004

 

Applicability: Model AT-401, AT-401B, AT-402, AT-402A, and AT-402B aircraft, serial numbers 0716 through 1144.

 

Model AT-501, AT-502, AT-502A, AT-502B, and AT-503A aircraft, serial numbers 0037 through 0658.

 

Requirement: 1. For Models AT-401 and AT-401B aircraft, serial numbers 0716 through 1144:

 

Inspect the upper longeron and upper diagonal tube on the left hand side of the fuselage frame, just forward of the vertical fin front spar attachment, for cracks in accordance with Snow Engineering Co. Service Letter (SL) No. 218A, dated 10 November 2003, as specified in SL No. 195, re-issued 10 November 2003.

 

2.         For Models AT-402, AT-402A, and AT-402B aircraft, serial numbers 0716 through 1144:

 

Inspect the upper longeron and upper diagonal tube on the left hand side of the fuselage frame, just forward of the vertical fin front spar attachment, for cracks in accordance with SL No. 218A, dated 10 November 2003, as specified in SL No. 195, re-issued 10 November 2003.

 

3.         For Models AT-501, AT-502, AT-502B, and AT-503A aircraft, serial numbers 0037 through 0658:

 

Inspect the upper longeron on the left hand side of the fuselage frame, just forward of the vertical fin front spar attachment, for cracks in accordance with SL No. 195B, dated 10 November 2003, as specified in SL No. 195, re-issued 10 November 2003.

 

4.         For Models AT-502A aircraft, serial numbers 0037 through 0658.

 

Inspect the upper longeron on the left hand side of the fuselage frame, just forward of the vertical fin front spar attachment, for cracks in accordance with SL No. 195B, dated 10 November 2003, as specified in SL No. 195, re-issued 10 November 2003.

 

Note: FAA AD 2004-15-15 Amdt 39-13749 refers.

Airtractor AT-300, 400 and 500 Series Aeroplanes

 

AD/AT/23 Amdt 1 (continued)

 

Compliance: 1. Initially inspect upon the accumulation of 1,250 total hours time in service or within the next 100 hours time in service after 30 September 2004, whichever occurs later. Inspect thereafter at intervals not to exceed 100 hours time in service, until the upper and diagonal longerons are replaced and modified in accordance with SL No. 218B, dated 10 November 2003.

 

2.         Initially inspect upon the accumulation of 1,250 total hours time in service or within the next 100 hours time in service after the last inspection required by the original issue of this Directive, whichever occurs later. Inspect thereafter at intervals not to exceed 100 hours time in service, until the upper and diagonal longerons are replaced and modified in accordance with SL No. 218B, dated 10 November 2003.

 

3.         Initially inspect upon the accumulation of 4,800 total hours time in service or within the next 100 hours time in service after 30 September 2004, whichever occurs later. Inspect thereafter at intervals not to exceed 100 hours time in service, until the upper longeron is replaced and modified in accordance with SL No. 195A, revised 10 November 2003.

 

4.         Initially inspect upon the accumulation of 2,800 total hours time in service or within the next 100 hours time in service after 30 September 2004, whichever occurs later. Inspect thereafter at intervals not to exceed 100 hours time in service, until the upper longeron is replaced and modified in accordance with SL No. 195A, revised 10 November 2003.

 

This Amendment becomes effective on 30 September 2004.

 

Background: The FAA received reports of three occurrences of cracks found on the left hand upper longeron and upper diagonal support tubes where they intersect on the left side of the fuselage frame just forward of the vertical fin front spar attachment point, on Model AT-602 aircraft. The cracks were found by the pilot and/or ground crew when they noticed excessive movement of the empennage due to the loss of torsional rigidity.

 

Amendment 1 is issued in response to a new FAA AD, which adds certain AT-500 series aircraft to applicability, changes the compliance times, and incorporates new and revised manufacturer service information that contains a terminating action for the repetitive inspection requirement.


David Villiers

Delegate of the Civil Aviation Safety Authority 20 August 2004


The above AD is notified in the Commonwealth of Australia Gazette on 8 September 2004.

Overview

The Civil Aviation Safety Authority (CASA) enacted the Airworthiness Directive (AD) AD/AT/23 Amendment 1 on 30 September 2004. This AD specifically addresses safety concerns related to the upper longerons and diagonal tubes of certain Airtractor AT-300, 400, and 500 Series Aeroplanes. It was introduced in response to reports of cracks in the left-hand upper longeron and upper diagonal support tubes on Model AT-602 aircraft, which were identified by pilots and ground crews due to excessive movement of the empennage, leading to a loss of torsional rigidity. The directive aims to ensure the continued airworthiness of the affected aircraft by mandating specific inspection intervals and corrective actions as outlined by the relevant Snow Engineering Co. Service Letters. This amendment incorporates new information from the Federal Aviation Administration (FAA) and modifies the applicability and compliance requirements to enhance safety standards for these aircraft models.

Scope and Application

This Airworthiness Directive (AD) issued under the Civil Aviation Safety Regulations 1998 (CASR) applies specifically to Airtractor AT-300, 400, and 500 series aeroplanes, including models AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, and AT-503A within certain serial number ranges. The directive mandates inspections for specific structural components to ensure airworthiness. The geographic reach of this AD is national, applicable across Australia, as it is issued under Commonwealth legislation. There are no stated exclusions or exemptions in this AD, and compliance is mandatory for the specified aircraft. The AD can be extended or modified through subordinate instruments, but as it stands, it requires inspections at particular intervals based on accumulated flight hours, with detailed instructions provided for the inspection process to be followed. This AD became effective on 30 September 2004.

Key Provisions

This Airworthiness Directive (AD) pertains to the Airtractor AT-300, 400, and 500 series aeroplanes, specifically affecting certain models and serial numbers. It mandates inspections of the upper longeron and upper diagonal tube on the left side of the fuselage frame, just forward of the vertical fin front spar attachment, to check for cracks in accordance with specified service letters (section 2). Compliance with this AD is required for specific models and serial numbers, with the inspection schedule varying depending on the model and the time in service of the aeroplane (section 3). The AD imposes obligations on the parties involved, including the requirement to conduct inspections in accordance with the provided service letters and to adhere to the specified intervals until the longerons are replaced or modified. Operators and owners of the affected aircraft must ensure that these inspections are carried out by qualified personnel, and that any identified issues are addressed in line with the AD's requirements. Failure to comply with the AD could result in the aircraft being deemed unairworthy, potentially leading to grounding and other regulatory actions. The AD does not explicitly state any specific offences, penalties, or consequences for non-compliance. However, non-compliance with an AD can result in enforcement actions by the Civil Aviation Safety Authority (CASA), including fines, legal proceedings, or other regulatory sanctions. The severity of these consequences can depend on the nature and extent of the non-compliance, and CASA has the authority to enforce compliance through its regulatory powers under the Civil Aviation Act 1988 and other relevant legislation.

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Sourced from the Federal Register of Legislation at 26 August 2026. For the latest information on Australian Government law please go to https://www.legislation.gov.au.