AD/AC/93 Amdt 2 - Wing to Fuselage Attachment

Airworthiness directive (AD): A legally enforceable notice issued by CASA under the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988. Compliance is mandatory. Failure to comply renders the aircraft unairworthy and exposes the operator to enforcement action.

Service bulletin (SB) 223: The technical standard that details the inspection procedures. The directive incorporates SB 223 by reference, including its three revisions (original October 1996, Revision Notice 1 May 1997, Revision Notice 2 August 1997). The directive does not reproduce the full text of SB 223; operators must obtain it from the manufacturer or from CASA.

Crack detection: The central safety concern is that undetected cracks in the wing forward attachment brackets, straps, fuselage frame, and surrounding structure can lead to catastrophic structural failure of the wing-to-fuselage attachment. The directive treats crack presence as a critical condition: any cracked part must be replaced or repaired using an approved scheme before further flight.

Approved scheme: For repairs and alternative access provisions, the directive requires use of a scheme approved under the Civil Aviation Regulations (CAR 35 or equivalent). This means a design approval from CASA or an authorised person (e.g., an STC holder). Operators cannot simply choose any repair method; it must have regulatory approval.

Total time in service (TIS): The metric for compliance triggers is flight hours accumulated on the airframe since new. Note that the directive uses calendar dates and TIS thresholds, not calendar time. This means an aircraft with low utilisation may take many years to reach the TIS threshold, but once it does, the inspection must be done. The initial compliance date is tied to the effective date of the original directive (16 July 1998 for most models), with a 100-hour grace period.

Model applicability: The directive applies to all Twin Commander series models (500, 600, 700) and all serial numbers. However, specific requirements carve out certain models: models 520 and 560 are treated differently for Requirement 1 (they are excluded from Part I of SB 223, but are included in Requirement 2 separately), and models 690C and 695 are excluded from Requirement 3 entirely (covered by a separate AD). Pressurisation status matters only for Requirement 3 initial threshold (12,000 hours TIS for non-pressurised; 6000 hours TIS for pressurised). No distinction is made for pressurised vs non-pressurised in Requirements 1 and 2.

Alternative access holes: The directive explicitly states that the access holes specified in SB 223 are not mandatory. Operators may use alternative access provisions installed under a CAR 35 approved scheme, provided sufficient access is available. This is a significant flexibility element, reducing the cost and complexity of compliance for some aircraft, particularly those with STC modifications (e.g., titanium leading edge).

Cross-reference to FAA AD 98-08-19: Note 3 points to the corresponding FAA airworthiness directive. This is relevant because many Twin Commander aircraft are U.S.-registered or have U.S. maintenance histories. The directive ensures that Australian operators meet an equivalent level of safety, and the corrected reference eliminates confusion.

The directive directly impacts all owners and operators of Twin Commander (Gulfstream/Rockwell/Aero Commander 500, 600 and 700) series aeroplanes registered in Australia or operated under Australian airworthiness requirements. This includes private owners, charter operators, flying schools, corporate flight departments, and any entity that maintains or operates these aircraft. The directive is not limited by serial number, so every aircraft of these types in the Australian fleet is affected.

Maintenance organisations that hold CASA approvals for these aircraft types also bear the compliance burden. They must be familiar with the inspection procedures in SB 223 and the revision notices, ensure that maintenance personnel are trained, and manage the record-keeping for repetitive inspections. The directive does not specify who may perform the inspection, but under the Civil Aviation Regulations, only appropriately authorised maintenance personnel (e.g., LAME with type rating) are permitted to certify the work.

Parts suppliers and STC holders may also be affected indirectly. The directive requires repairs and replacements to use an approved scheme. This creates demand for SB 223-compliant parts and for approved repair designs. STC holders who have modified aircraft with titanium leading edges are particularly relevant because the directive addresses their access situation explicitly.

Regulatory bodies: CASA (and its delegates) are responsible for enforcing compliance. The directive also references FAA AD 98-08-19, so there is a cross-border interaction. Operators of dual-registered aircraft or those with a mixed maintenance history need to ensure that compliance with one AD does not inadvertently create a gap with the other.

The directive does not create any new penalties or rights for third parties (such as passengers or insurers). It is a standard type certificate holder and operator obligation. However, insurers may require evidence of AD compliance as a condition of coverage, so non-compliance can affect insurance premiums or claims.

The compliance cost falls entirely on the aircraft operator. For a typical fleet, the inspections require significant labour hours, special tooling (borescopes or other access tools), and potential downtime for repairs. The repetitive nature means the cost is ongoing. For aircraft with titanium leading edge STCs, the additional labour of removing and replacing the wing root fairing adds further expense. The directive's allowance of alternative access provisions may reduce costs for some operators, but only if they have already installed a CAR 35 approved alternative or are willing to obtain one.

Duty to inspect: The primary duty is to perform the three inspection tasks on the stated schedule. For Requirement 1, all aircraft except 520 and 560 must have the wing forward attachment brackets and straps inspected before 6000 hours TIS or 100 hours TIS after 16 July 1998 (whichever is later). Thereafter, re-inspection must occur at intervals not exceeding 1000 hours TIS. Compliance with the original issue of the directive (the 1995 version) is considered prior accomplishment. For models 520 and 560, Requirement 1 does not apply, but they must comply with Requirement 2 instead.

For Requirement 2, the inspection of brackets and straps in accordance with Part II of SB 223 has a more complex schedule. If cracks were found after 15 July 1998 when complying with Requirement 1, the aircraft must be inspected before further flight. Aircraft inspected before 16 July 1998 and found to have cracks must be inspected before 100 hours TIS after 16 July 1998 unless Part II was already done. If no cracks are found, repeat inspections at intervals not exceeding 1000 hours TIS. If cracks are found, the cracked part must be replaced or repaired before further flight, and then re-inspections continue at intervals not exceeding 6000 hours TIS. For models 520 and 560, the initial inspection is before 6000 hours TIS or 100 hours TIS after 16 July 1998, whichever is later; repeat intervals are the same: 1000 hours TIS if no cracks, 6000 hours TIS if cracks found and repaired.

For Requirement 3 (fuselage frame and leading edge attachment structure), non-pressurised models must be inspected before 12,000 hours TIS or 100 hours TIS after 16 July 1998; pressurised models before 6000 hours TIS or 100 hours TIS after 16 July 1998. Thereafter, repeat at intervals not exceeding 1000 hours TIS, regardless of crack findings. If cracks are found, repair or replace before further flight and continue at 1000-hour intervals.

Duty to repair or replace: If any crack is found during any inspection, the cracked part must be replaced or repaired using an approved scheme before further flight. The directive does not specify a grace period for the repair; the aircraft cannot be flown until the crack is addressed. This imposes a strict grounding condition.

Right to use alternative access: The directive explicitly states that the access holes specified in SB 223 are not mandatory. Operators may use alternative access provisions installed under a CAR 35 approved scheme, provided sufficient access is available. For aircraft with a titanium leading edge (via STC), where access holes in the leading edge are impossible, the inspection must be accomplished by removing the wing root fairing. This gives operators the flexibility to avoid drilling new holes in structures where that is impractical, but the alternative must be approved.

Right to rely on prior compliance: The directive states that compliance with the initial issue of the directive is considered prior accomplishment of Requirement 1. This means that operators who complied with the 1995 version do not need to repeat that specific inspection unless a later revision requires it. However, Requirement 2 and 3 have their own compliance times that may not be satisfied by prior work.

No duty to third parties: This directive does not create any private right of action. It is a regulatory instrument that imposes duties on operators and maintainers toward CASA. A passenger or other party cannot directly enforce the directive, though non-compliance could be evidence of negligence in a tort claim.

The directive is issued under the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988 (CAR). Non-compliance is a breach of those regulations, carrying potential penalties that include civil penalty orders and criminal prosecution. The specific penalty provisions are not restated in the directive itself, but under the Act, operating an aircraft that does not comply with an applicable AD is an offence. The maximum penalty for an individual can include fines and imprisonment; for a body corporate, substantially higher fines apply (as updated from time to time).

Enforcement is the responsibility of CASA. CASA may also issue a direction grounding the aircraft, suspend or cancel an Air Operator’s Certificate, or impose conditions on operations. The directive itself does not specify suspension or revocation, but standard CASA practice is to treat non-compliance with an AD as a serious safety matter.

The compliance date for Amdt 2 is 8 May 2008. For the underlying requirements (Requirements 1-3), the original compliance dates date back to 1998. Therefore, any aircraft that has not been inspected per the schedule in the 1998 version of the directive (or Amdt 1) is already in default, regardless of the typographical correction. The amendment does not restart the compliance clock.

Practical enforcement consequences include: the aircraft’s Certificate of Airworthiness may be suspended if a CASA inspector finds non-compliance during a ramp check or maintenance review. Insurance policies typically require compliance with all applicable ADs; non-compliance may void coverage or give the insurer grounds to deny a claim. In the event of an accident, non-compliance with a known AD could be cited as a cause, leading to greater liability exposure.

The directive does not specify enforcement actions for specific failures to meet the 100-hour grace period or the repeat intervals, but the standard approach is that any operation after the due date without the inspection having been completed is a breach. Operators should note that compliance times are measured in hours TIS, not calendar time, so an aircraft that reaches the threshold during a flight must have the inspection done before the next flight if that flight would exceed the threshold.

Civil Aviation Act 1988 and Civil Aviation Regulations 1988 (CAR): This directive is a legislative instrument issued under the Act. It imposes mandatory conditions on the type certificate and on the operation of these aircraft. It does not repeal or amend any other regulation, but it supplements the general airworthiness obligations. For example, CAR 41 (Airworthiness) requires that an aircraft must be maintained in an airworthy condition; compliance with this AD is part of meeting that requirement.

FAA AD 98-08-19: Note 3 corrects the reference to the FAA AD. The directive acknowledges that there is a corresponding U.S. airworthiness directive. For an aircraft that is registered in Australia but may have previously been maintained under FAA oversight, operators must ensure that compliance with this CASA AD does not conflict with the FAA AD. In most cases the requirements are equivalent, but differences in compliance times or approved repair schemes could arise. The directive does not say which prevails; logically, the aircraft must comply with the requirements of the state of registry. For Australian-registered aircraft, the CASA AD is the governing requirement.

Service Bulletin 213: Note 2 states that SB 213, mandated by a separate FAA AD, specifies inspections equivalent to Requirement 3 for models 690C and 695. This means those models are exempt from Requirement 3 of this AD, but they must comply with the separate AD (presumably also adopted by CASA or accepted via bilateral agreement). Operators of those models must locate and comply with that other AD.

CAR 35 approved schemes: The directive allows alternative access provisions that are installed in accordance with a CAR 35 approved scheme. CAR 35 deals with design standards and approvals for modifications and repairs. This means that any alternative access method must have been approved by CASA (or an authorised person) before it can be used as a substitute for the SB 223 access holes. Operators who wish to avoid drilling new access holes must either find an existing approved STC or obtain a new approval.

Other ADs: The directive makes no claim to consolidate all ADs on these aircraft. There may be other ADs covering other systems (e.g., engine mounts, flight controls, corrosion). Compliance with this AD does not relieve the operator of responsibility for other ADs.

Air Navigation Act 1920 (possibly): Not mentioned, but aircraft operations must comply with all applicable laws, including those concerning noise and emissions. This AD does not interact with those.

No pre-emption of contract or private agreements: The directive does not modify any contractual obligations between operators and lessors, lessees, or insurers. However, a failure to comply may constitute a breach of a maintenance contract or insurance policy condition.

The original issue of AD/AC/93 became effective on 9 November 1995. It mandated inspections addressing wing attachment cracks, likely with a version of the same SB 223 requirements. The source text does not detail the original content, but it states that compliance with the initial issue is considered prior accomplishment of Requirement 1. This implies the original AD covered at least the bracket/strap inspection.

Amendment 1 became effective on 9 November 2005. The source does not describe what changed, but the background of Amdt 2 refers to a previous amendment (Amdt 1) that is otherwise uncharacterised. Amdt 1 may have revised the compliance schedule or added Requirement 3, but the text does not say. The only certainty is that Amdt 1 did not correct the FAA AD reference error, which remained until Amdt 2.

Amendment 2 (this instrument) became effective on 8 May 2008. Its sole substantive change is stated: "This amendment is issued to correct a typographical error to the FAA AD reference in Note 3." There is no change to the requirement or compliance section. The error likely involved a wrong number or format for the FAA AD. The corrected reference is FAA AD 98-08-19.

All amendments are cumulative. Operators must comply with the requirements as they exist at the effective date of the latest amendment. Because Amdt 2 only changes Note 3, the compliance obligations from Amdt 1 (and any earlier amendment) remain in full force. Operators must have incorporated the corrected Note 3 for record-keeping and cross-referencing purposes.

The directive does not provide any transition period or grace for the typo correction, presumably because the correction does not impose new work. The effective date of 8 May 2008 simply means that from that date, the corrected reference applies.

No further amendments are mentioned in the source. It is possible that later amendments exist (post-2008) but they are not part of this instrument.

The source text contains no mention of any litigation, court cases, or tribunal decisions related to this AD or its predecessor amendments. This is typical for routine airworthiness directives; they are rarely litigated unless challenged on procedural grounds or enforcement action leads to a hearing.

It is possible that there have been cases in the Administrative Appeals Tribunal (AAT) or Federal Court concerning CASA decisions related to this AD (e.g., a refusal to grant an alternative means of compliance or a dispute over repair approvals), but no such cases are referenced in the instrument. A deeper search outside the source would be needed to confirm, but the instruction limits us to the source.

Given the directive’s long history (original 1995, amendment 2005, further amendment 2008), and the high value of Twin Commander aircraft, it is plausible that some enforcement actions have been taken. However, without citation, we cannot assert any. The prudent statement is that no litigation is noted in the instrument, and it appears to have been implemented without judicial challenge.

For practical purposes, operators should assume that non-compliance could lead to CASA enforcement proceedings, which could result in a civil penalty matter in a court. Defences might include that the AD was not properly served or that the operator took all reasonable steps to comply. But the directive itself does not create a defence of ignorance.

The typo correction is the main change, but the compliance dates are unchanged. An operator who relied on an erroneous FAA AD reference before May 2008 might have been confused about which FAA AD to follow. The correction eliminates that confusion, but it does not extend any compliance deadlines. Any missed inspection due to that confusion is still a breach.

The 100-hour initial grace period for many requirements is tied to “after 16 July 1998”. For an aircraft that has more than 100 hours TIS after that date, the inspection must be done before exceeding 100 hours TIS from that date, not from the effective date of Amdt 2. Operators who believed the clock restarted with Amdt 2 are mistaken.

Models 690C and 695 are not exempt from the entire AD. Note 2 says they are equivalent to Requirement 3 via SB 213, but they still must comply with Requirements 1 and 2 unless otherwise excluded. The AD does not explicitly exempt them from Requirements 1 and 2, so they are covered.

Alternative access provisions must be CAR 35 approved. An operator cannot simply decide to use a different access method without prior CASA approval. If the aircraft has a titanium leading edge STC that does not include an approved alternative access scheme, the operator must either remove the wing root fairing (which is allowed) or obtain a separate approval. The directive does not create a blanket right to deviate from the SB without approval.

The phrase “approved scheme” for repair or replacement. The directive says to “repair the aircraft using an approved scheme” and “replace any cracked part”. The replacement part may be a standard part from the manufacturer, but any repair must be approved. Even a simple weld repair would need CASA approval. Operators should not attempt field repairs without engineering approval.

Repeat intervals for Requirement 3 after a repair remain at 1000 hours TIS. This differs from Requirement 2, where after a repair the interval extends to 6000 hours TIS. Operators must track these separately. A crack in the fuselage frame does not earn the longer interval; it remains at 1000 hours.

The compliance tables reference “all affected non-pressurised models” and “all affected pressurised models” without defining which models are pressurised and which are not. The directive does not list the pressurisation status of each model. Operators must determine if their specific model is pressurised based on the type certificate data sheet. Getting this wrong could lead to an incorrect initial threshold.

Record-keeping. The directive does not explicitly state that records must be kept, but under CAR Part 4, maintenance records must include evidence of AD compliance. The absence of a paper trail will be treated as non-compliance.

Interaction with overseas maintenance. If an aircraft is maintained under an FAA repair station’s documentation, the operator must ensure that the FAA AD 98-08-19 and any subsequent revisions are complied with, and that the Australian AD is also noted. Dual compliance may impose additional administrative burden.

Compliance requires a systematic approach encompassing documentation, physical inspection, corrective action, and ongoing monitoring.

Step 1: Obtain the correct documents. Acquire Twin Commander Service Bulletin SB 223, dated October 24, 1996, including Revision Notice No. 1 (May 8, 1997) and Revision Notice No. 2 (August 18, 1997). Also obtain the CASA AD/AC/93 Amdt 2 as issued on 27 March 2008 (effective 8 May 2008). Note the correction to the FAA AD reference in Note 3: FAA AD 98-08-19. If you operate models 690C or 695, locate the separate AD that mandates SB 213 for equivalent inspections.

Step 2: Determine aircraft configuration. Identify the model, serial number, and pressurisation status. Check if any STCs (e.g., titanium leading edge) have been installed that affect access. Determine if alternative access provisions already exist under a CAR 35 approved scheme.

Step 3: Establish compliance schedule. Using the tables in the directive, calculate the initial inspection thresholds for each requirement:

• Requirement 1 (bracket/strap inspection): applicable to all except 520 and 560. Initial before 6000 hours TIS or 100 hours TIS after 16 July 1998, whichever later. Repeat every 1000 hours TIS.
• Requirement 2 (bracket/strap detailed inspection after crack): see complex schedule. For models 520 and 560: initial before 6000 hours TIS or 100 hours TIS after 16 July 1998. Repeat: if no cracks - 1000 hours; if cracks found and repaired - 6000 hours.
• Requirement 3 (fuselage frame/leading edge attachment): non-pressurised models initial before 12,000 hours TIS or 100 hours TIS after 16 July 1998; pressurised models initial before 6000 hours TIS or 100 hours TIS after 16 July 1998. Repeat every 1000 hours TIS regardless of findings.

If the aircraft has already been inspected before the threshold, document the time and findings. The directive states that compliance with the original issue satisfies Requirement 1 initial.

Step 4: Perform the inspection. Access the wing-forward attachment area. Use the access holes in SB 223 unless a CAR 35 approved alternative is used. For titanium leading edge, remove wing root fairing. Follow the inspection procedures in Parts I, II, and III of SB 223 as applicable. Record all findings, including crack location and size if any.

Step 5: Take corrective action if cracks are found. Replace cracked parts with new serviceable parts or repair using an approved scheme. No flight is permitted until the crack is addressed. The approved scheme must be a CASA-approved design (e.g., STC, repair design approval). Document the repair or replacement.

Step 6: Set up repeat intervals. After initial compliance, log the hour meter reading. Create a tracking system to alert when the next 1000-hour (or 6000-hour for Requirement 2 after repair) interval approaches. Use either a maintenance tracking software or a manual log.

Step 7: Record compliance in the aircraft maintenance records. Include the AD number (AD/AC/93 Amdt 2), date of inspection, hours TIS, findings, and any repairs. Reference the SB 223 revision used. This is essential for proving compliance to CASA and insurers.

Step 8: Monitor for future amendments. CASA may issue further amendments to this AD. Subscribe to CASA’s airworthiness bulletin service. Ensure that any future changes are incorporated into the compliance schedule.

Step 9: Coordinate with approved maintenance organisations. If the aircraft is maintained by a third party, provide them with a copy of the AD and the SB. Ensure that the maintenance release certifies compliance with this AD.

Step 10: Verify dual compliance if applicable. If the aircraft is also subject to FAA AD 98-08-19, confirm that the tasks are equivalent or that both are accomplished. Keep separate records if needed.