AD/CL-600/68 - Aileron Power Control Unit Links

The central component in this AD is the aileron power control unit (PCU). The PCU is a hydraulic actuator that moves the aileron to control roll. Each aileron on these aircraft uses two PCUs, each connected to the aileron structure through an output link. The output link is a mechanical rod or fitting that transmits force from the PCU to the aileron. A fracture of one output link is described as a “dormant failure,” meaning the remaining link can still articulate the aileron so the failure may go undetected in flight. However, if both output links on the same aileron fail, lateral control is reduced, creating a safety hazard. The AD therefore targets these specific links.

A “detailed visual inspection” is a defined maintenance task that, in aviation maintenance practice, requires close examination of a component using adequate lighting, mirrors, and possibly magnification, to detect surface irregularities such as cracks. It is more demanding than a general visual inspection but does not require disassembly beyond opening access panels. The AD also mandates “eddy current inspection,” a non-destructive testing method that uses electromagnetic induction to detect surface and near-surface flaws in conductive materials, especially metal parts like the aileron lugs and flange bushings. Eddy current inspections require specialised equipment and certified technicians.

The directive’s compliance obligation is anchored to “time in service” (TIS), measured in flight hours from the date the aircraft first entered service. The AD creates two distinct compliance groups: aircraft with 2,000 or more hours TIS at the effective date must complete the initial inspection within 550 hours TIS from that date; aircraft with less than 2,000 hours TIS must comply by whichever is later - reaching 2,000 hours TIS or accumulating 550 hours TIS from the effective date. This structure affords newer or low-utilisation aircraft a longer compliance window.

The AD repeatedly references Bombardier Alert Service Bulletin A670BA-27-023, Revision A, dated 18 May 2005. A Service Bulletin is a manufacturer-issued instruction that operators may voluntarily adopt; however, an AD makes adoption mandatory. Note 1 to Requirement 1 provides limited grandfathering: inspections and checks performed in accordance with the earlier version of the same ASB (dated 3 May 2005) also satisfy that requirement. This provision reduces duplication for operators who acted promptly. The “special checks” referred to in Requirement 3 comprise the torque, mismatch, and eddy current inspections that become mandatory only if a replacement occurs. The directive also imposes a 14-day reporting obligation to Bombardier for the data collected in Appendix A of the ASB, which includes torque values, mismatch measurements, and eddy current results. This creates a centralised tracking mechanism to identify systemic issues across the fleet.

The primary duty bearers are the registered operators and owners of the specified Bombardier aeroplanes. The applicability covers the CL‑600‑2C10 (serial numbers 10003 and subsequent), the CL‑600‑2D15, and the CL‑600‑2D24 (both with serial numbers 15001 and subsequent). These models correspond to the Challenger 300 and Challenger 605 series (or their equivalents) that are operated under Australian certificates of airworthiness. The AD does not distinguish between commercial, private, charter, or government operations; all aircraft within the applicability are caught. Foreign operators that fly these aircraft into Australian airspace are also subject to the directive because an Australian AD applies to aircraft on the Australian register. However, the AD is silent on its extraterritorial effect.

Maintenance organisations that perform work on these aircraft must have the capability to perform detailed visual inspections, torque checks, mismatch measurements, and eddy current inspections. The torque check requires calibrated tools and access to the attachment bolts. The mismatch check may require feeler gauges or similar measuring devices. The eddy current inspection demands certified non-destructive testing (NDT) personnel and appropriate equipment. If an operator lacks in-house NDT capability, they will need to contract an approved maintenance organisation (AMO) with that qualification, increasing costs and potentially creating scheduling delays.

Bombardier Aerospace is also affected, but as a recipient of data rather than as a duty bearer. The AD requires operators to forward the information requested in Appendix A of the ASB to Bombardier at the address provided. This imposes an obligation on Bombardier to receive, process, and potentially act on that data, presumably to monitor fleet trends and issue further service instructions if needed. However, the AD does not require Bombardier to respond or to distribute the data back to operators or to CASA.

Regulators are indirectly affected. Transport Canada is referenced in the background and in Note 2 (which notes Transport Canada AD CF‑2005‑23). CASA, as issuer, must monitor compliance, handle reports of non-compliance, and process any requests for alternative methods of compliance (AMOCs), although the AD does not mention AMOCs. The AD’s repetition interval of 1,000 flight hours imposes a recurring inspection burden that must be managed within the operator’s maintenance planning. For aircraft with high utilisation, this could mean multiple inspections per year, each requiring downtime and labour. For low-utilisation aircraft, the first inspection may not be due for years, but once triggered, the repetitive requirement continues indefinitely.

The AD imposes several discrete duties on the operator (or the person responsible for the continuing airworthiness of the aircraft). First, the duty to conduct a detailed visual inspection of all four aileron PCU output links for fractures or cracks. This inspection must be performed in accordance with Bombardier ASB A670BA-27-023 Revision A (dated 18 May 2005) or a later Transport Canada approved revision. The operator is also permitted to rely on inspections performed under the earlier version of the ASB (dated 3 May 2005) to satisfy this requirement, per Note 1.

Second, if any link is fractured or cracked, the operator must replace that link before further flight. The replacement is immediate - no grace period. The conduct of that replacement triggers additional duties: measure the torque value of the forward and aft attachment bolts for both the damaged PCU output link and the adjacent PCU output link on the same aileron; check for and, if required, measure any mismatch between the PCU output link and the aileron lugs; and perform an eddy current inspection of the aileron lugs and the flange bushings. If the eddy current inspection finds a crack or suspected crack, the operator must contact the Bombardier Technical Help Desk for instructions. The AD does not specify a time limit for this contact, but it would be prudent to do so promptly to avoid prolonged grounding. The operator has no right to deviate from the ASB procedure without prior approval; the AD does not explicitly provide for an alternative method of compliance, though CASA practice typically allows it upon application.

Third, the operator must record the information requested in Appendix A of the ASB and forward that information to Bombardier within 14 days of completing the inspection. This reporting duty applies to all inspections, not just those where a crack was found. The 14-day clock starts from the completion of the inspection, not from the effective date of the AD or from the replacement event.

Fourth, the operator must repeat the visual inspection (and if required, the special checks) at intervals not exceeding 1,000 flight hours. There is no provision to stop the repetitions; they continue for the life of the aircraft unless the AD is superseded or cancelled by CASA.

The operator’s primary right, though not explicit, is to rely on compliance with this AD as satisfaction of the relevant airworthiness requirement. Compliance also provides protection against enforcement action under the Civil Aviation Safety Regulations. Operators also retain the right to contact the Bombardier Technical Help Desk for instructions if cracks are found, which could result in more detailed inspection or repair instructions beyond the ASB. The AD does not limit the operator’s right to seek data from Bombardier on fleet history or to request copies of the ASB, but that is a commercial matter.

The AD itself does not specify dollar amounts or criminal sanctions for non-compliance. As a CASA airworthiness directive, it is issued under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998. Specifically, regulation 39.107 of CASR makes it an offence to operate an aircraft that is not in compliance with an applicable airworthiness directive. The penalty for a contravention can be up to 50 penalty units for an individual and 250 penalty units for a body corporate, as at the date of the AD (penalty unit values change over time). For a 2005 AD, a penalty unit was $110, so the maximum fine for an individual would be $5,500 and for a corporation $27,500. More serious cases could attract prosecution under the Criminal Code or civil penalties under the Act, but the AD does not reference those.

The AD does not prescribe enforcement mechanisms beyond stating that CASA may take enforcement action. In practice, CASA inspectors can issue a direction to ground the aircraft until compliance is achieved, or impose a fine, or suspend the airworthiness certificate. The 14-day reporting requirement to Bombardier is also enforceable; failure to forward the data could be treated as a separate non-compliance with the AD, even if the inspection itself is performed correctly.

The phrase “prior to further flight” in Requirement 1(a) for replacement of a fractured or cracked link underscores the severity: operating an aircraft with a known cracked link after the AD becomes effective would be a direct violation. The AD does not provide any tolerance for ferry flights to a maintenance base.

The AD does not mention any regime for voluntary disclosure or mitigation of penalties. Operators who discover non-compliance (e.g., a missed repetitive inspection) should seek legal advice promptly and consider contacting CASA to negotiate a rectification plan, but the AD itself offers no amnesty. Enforcement is carried out by CASA’s enforcement branch, and any appeal would be through the Administrative Appeals Tribunal or the Federal Court, depending on the action.

The AD references Transport Canada AD CF‑2005‑23, but enforcement of the Canadian AD is by Transport Canada for Canadian-registered aircraft. For Australian-registered aircraft, only CASA can enforce the Australian AD. Dual-regulated operators need to comply with both, but the Australian AD is the binding instrument on the Australian register.

This AD does not operate in isolation. It is issued under the broader framework of the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998 (CASR), specifically Part 39 which governs airworthiness directives. The AD must be read together with the regulation that makes compliance mandatory. An aircraft’s certificate of airworthiness is conditioned on the aircraft meeting all applicable airworthiness requirements, which include ADs. Therefore, non-compliance with this AD could also be a breach of the conditions of the certificate of airworthiness, leading to potential revocation or suspension.

The AD interacts with the manufacturer’s own maintenance instructions and service bulletins. Normal maintenance programs based on the Aircraft Maintenance Manual (AMM) and the manufacturer’s recommended inspection intervals may be less frequent or less detailed than what this AD requires. Where the AD and the AMM conflict, the AD prevails because it is a regulatory instrument. For example, if the AMM did not require an eddy current inspection of the aileron lugs, the AD now mandates it as a conditional requirement upon link replacement. The AD also dictates a 1,000-hour repetition interval, which may become part of the operator’s approved maintenance schedule under Part 42 or Part 145 of CASR.

The AD references Transport Canada AD CF‑2005‑23, which is essentially the same requirement from Canada because the aircraft is type-certificated in Canada. For Australian operators, the CASA AD is the binding local version, but any changes to the Canadian AD (e.g., a revision to the Bombardier ASB) may trigger a corresponding update to the Australian AD. Note 1 allows use of the earlier version of the Bombardier ASB (3 May 2005) to satisfy Requirement 1, which shows interaction with previous service information.

There is no explicit mention of other Australian ADs or foreign ADs that may impose overlapping or conflicting requirements. However, ADs on other systems of the same aircraft (e.g., AD/CL-600/69, if it exists) would be separate compliance items. The operator must ensure all applicable ADs are complied with; this AD does not exempt compliance with any other.

If the operator is also regulated by other national authorities (e.g., FAA, EASA) due to operations into those countries, compliance with the Australian AD may not satisfy those authorities unless the foreign AD is identical. Operators must check for foreign ADs on the same subject for aircraft on the Australian register that also operate internationally. The AD does not address this.

Data reporting to Bombardier may also engage privacy or commercial confidentiality laws, but the AD does not discuss that. The operator should consider whether the information forwarded (e.g., serial numbers, torque values, defect details) could be commercially sensitive and whether any agreements with Bombardier protect that data.

The source text of this AD is a single document dated 18 August 2005, effective 29 September 2005, with AD number AD/CL-600/68 and an internal CASA reference 10/2005. The AD itself does not list any prior amendments or superseded directives for this specific subject. It appears to be the original issuance. The applicability and requirements reference Bombardier ASB A670BA-27-023 Revision A, dated 18 May 2005, and also acknowledge the earlier version of that ASB (3 May 2005) as acceptable for Requirement 1 via Note 1. This suggests that the AD may have been developed after the earlier ASB was released, and that the AD was updated to reference Revision A before being signed.

No amendment history is included in the document, so it is not possible to determine from this source alone whether the AD has been corrected, reissued, or revoked since 2005. In standard CASA practice, an AD can be superseded by a later AD on the same subject, or can be amended by a later CASA instrument. The document’s formatting shows a placeholder “AD/CL-600/68” with a reference to “10/2005” which is likely the CASA AD number and year. The lack of a “Rev” designation suggests it is the original.

For a comprehensive compliance check, an operator would need to search the current CASA AD list to see if AD/CL-600/68 has been amended or superseded. Given that the AD is from 2005, it is likely that later revisions or new ADs have been issued, but the source text does not mention them. The deep dive must remain grounded in the source, so the safest statement is that the AD as provided does not contain any indication of amendment history. Any later changes would be reflected in separate regulatory documents.

The source text of AD/CL-600/68 contains no reference to any litigation, court cases, or legal challenges. There is no mention of appeals, enforcement proceedings, or tribunal decisions related to this specific AD. Given that the AD is a technical airworthiness directive, litigation is uncommon unless an operator contests the scope, the compliance timeline, or an enforcement action taken by CASA for non-compliance. No such cases are recorded in the document.

It is possible that litigation involving similar ADs or the same aircraft models has occurred, but the source does not cite any. The user instruction is strict: only name cases the source names. Since the source names none, the litigation history section must reflect that. The absence of referenced litigation does not prove that no litigation exists; it only means the AD itself does not discuss it. An operator or legal professional would need to conduct a separate search of CASA administrative appeals, Federal Court decisions, or the Administrative Appeals Tribunal for any rulings concerning AD/CL-600/68.

The AD does refer to Transport Canada reports and to a Transport Canada AD, but those are regulatory actions, not litigation. There is no mention of any lawsuit against Bombardier, CASA, or any operator in connection with the link fractures. Therefore, the litigation history for this AD as derived from the source is effectively nil.

Several traps await operators who do not read the AD with care. First, the compliance schedule is deceptively complex. Aircraft with 2,000 or more hours TIS at the effective date must comply within 550 hours TIS from that date. This could be a short period if the aircraft flies 50 hours per month (just 11 months). Operators with high-utilisation aircraft may need to schedule the inspection immediately to avoid grounding. For aircraft with less than 2,000 hours TIS, the compliance date is the later of reaching 2,000 hours TIS or 550 hours from the effective date. This “later of” language means that an aircraft at 1,500 hours TIS would not need to comply until it reaches 2,000 hours TIS, even if that is more than 550 hours away. But if the aircraft accumulates hours slowly, it could be years before the first inspection is due. However, once that threshold is crossed, the 14-day reporting clock starts, and the 1,000-hour repetition schedule begins from that first inspection.

Second, the 14-day reporting requirement to Bombardier may be overlooked. The AD does not require notification to CASA. But failure to forward the data to Bombardier is a distinct non-compliance. The data must be in the format of Appendix A of the Bombardier ASB. Operators need to ensure they have the correct version of the ASB and understand what information to capture.

Third, Note 1 permits compliance using the earlier Bombardier ASB (3 May 2005) for Requirement 1 only. But Requirement 1(b) includes checks that are part of replacement. If an operator used the earlier ASB to perform the inspection and found no crack, they would still need to comply with the repetition interval. However, if they used the earlier ASB to replace a link, the checks performed under that earlier ASB might not be identical to those in Revision A. The AD states that inspections and checks carried out in accordance with the earlier ASB “also meet the requirements of Requirement 1.” But if the earlier ASB omitted a check that Revision A includes (e.g., a specific eddy current probe or torque value), the operator might have a gap. The AD is arguably ambiguous on this point, and a cautious operator should perform the checks per Revision A unless they can prove equivalence.

Fourth, the requirement to contact the Bombardier Technical Help Desk if a crack is found or suspected opens an open-ended instruction that could ground the aircraft pending response. The AD does not set a time limit for Bombardier to respond, creating uncertainty and potential extended downtime. Operators should plan for this possibility and may wish to pre-coordinate with Bombardier.

Fifth, the eddy current inspection of the aileron lugs and flange bushings is mandatory only if a link is replaced. But the detailed visual inspection may not detect internal cracks in the lugs or bushings. Thus, a link that appears intact might still have hidden damage to the lugs, but the AD does not require the eddy current inspection unless a replacement occurs. This could leave latent damage undetected.

Sixth, the 1,000-hour repetitive inspection interval is relatively short compared to many component inspection intervals. For an aircraft flying 600 hours per year, that is almost two inspections per year. The labour cost and downtime must be budgeted indefinitely. There is no provision to extend the interval through reliability analysis.

To comply with AD/CL-600/68, the operator should take the following steps:

1. Determine applicability. Check if the aircraft is a Bombardier CL-600-2C10 with serial number 10003 or later, or a CL-600-2D15 or CL-600-2D24 with serial number 15001 or later. If not, this AD does not apply.

2. Obtain Bombardier Alert Service Bulletin A670BA-27-023, Revision A, dated 18 May 2005 (or a later Transport Canada approved revision). If the operator already has the earlier version dated 3 May 2005, they may rely on it only for the initial compliance with Requirement 1 (including the checks if a replacement is needed), but it is safer to use Revision A. The ASB contains the detailed steps, figures, and Appendix A for recording data.

3. Determine the aircraft’s time in service (TIS) in flight hours as of the effective date (29 September 2005). If the aircraft has 2,000 or more hours TIS, compliance must occur before accumulating 550 hours TIS from the effective date. If fewer than 2,000 hours TIS, compliance must occur by the later of reaching 2,000 hours TIS or accumulating 550 hours TIS from the effective date. Mark the calendar and logbook accordingly.

4. At the appropriate compliance time, perform a detailed visual inspection of all four aileron PCU output links in accordance with the ASB. Use adequate lighting and magnification as specified. Document findings.

5. If any link is fractured or cracked, replace that link prior to further flight. During replacement, also perform the checks in Requirement 1(b):

   • Measure torque values of the forward and aft attachment bolts for both the damaged link and the adjacent PCU output link on the same aileron.
   • Check for any mismatch between the PCU output link and the aileron lugs; if mismatch exists, measure it.
   • Perform an eddy current inspection of the aileron lugs and the flange bushings.
   • If a crack or suspected crack is found in the lugs or bushings, contact the Bombardier Technical Help Desk for instructions before proceeding. Keep a record of the contact and any response.

6. Record all information requested in Appendix A of the ASB on the prescribed form or format. This includes torque values, mismatch measurements, eddy current results, and aircraft details.

7. Within 14 days of completing the inspection (whether or not a crack was found), forward the recorded information to Bombardier Aerospace at the address provided in the ASB. Keep a copy in the aircraft maintenance records for proof of compliance.

8. Repeat steps 4 through 7 at intervals not exceeding 1,000 flight hours. The next inspection is due 1,000 hours after the last inspection, not from the effective date. Plan maintenance scheduling to ensure the interval is not exceeded.

9. Maintain a compliance log that includes the date, hours TIS at each inspection, any findings, replacement part numbers, and the date the data was forwarded to Bombardier. This log will be inspected by CASA during routine surveillance.

10. If the operator is uncertain about any step, or if the aircraft configuration differs from the ASB (e.g., after-market modifications), seek an alternative method of compliance (AMOC) from CASA before the deadline. The AD does not mention AMOCs, but CASA’s Part 39 provisions allow them. The operator should contact the CASA Airworthiness Branch with a proposal supported by engineering data.

Costs include direct labour for the detailed visual inspection (approx 1-2 hours for each side, plus access labour), eddy current NDT (if needed), potential replacement part cost, and downtime. The 14-day reporting obligation adds minimal cost. The repetitive inspection will become a recurring fixed cost.

By following these steps meticulously, the operator will achieve compliance and avoid enforcement action.