AD/BELL 222/36 - Tail Rotor Driveshaft Thomas Couplings

Disc Assembly. The component at issue is the disc assembly used in the tail rotor driveshaft Thomas coupling. Two part numbers are specified: 36300-1 and 37855-1. The disc assembly comprises a stack of thin metal discs that flex to accommodate misalignment in the driveshaft. The total thickness of the stack is critical for correct preload and proper function. The AD specifies thickness limits for each part number: for 36300-1 the total thickness must be between 0.174 inch (4.42 mm) and 0.186 inch (4.75 mm); for 37855-1 the range is 0.126 inch (3.20 mm) to 0.138 inch (3.50 mm). These dimensions are critical because the stack provides the axial load necessary for the coupling to transmit torque without slipping. An insufficient number of discs reduces the clamping force and can lead to failure.

Manufacturing date window. The suspect disc assemblies are those manufactured between 1 November 2005 and 30 November 2006. The directive does not explain why this window is suspect, but the implication is that a process or quality control deviation existed during that period. The operator must verify the manufacturing date of each disc assembly. If the date falls outside this window, no further action is required regarding thickness or indexing, but a log book notation must be made. The manufacturing date is presumably stamped or marked on the assembly or its documentation. The AD does not specify how to determine the date; the referenced Alert Service Bulletins would contain that detail.

Indexing. Indexing refers to the circumferential orientation of the disc assembly's bolt holes relative to the coupling flanges. A disc assembly that is indexed incorrectly can cause imbalance or uneven loading, leading to premature wear or failure. The AD requires that any disc assembly found not properly indexed must be re indexed in accordance with the applicable Maintenance Manual. If the disc assembly is installed and cannot be re indexed, it must be removed from service.

Log book notation. The directive requires a record of compliance for every affected disc assembly. For installed assemblies that do not require action (because the manufacturing date is outside the suspect window), an appropriate log book notation must be made. The same applies for assembled aircraft that have been verified and found compliant. This requirement ensures traceability and demonstrates that the AD has been addressed.

Alert Service Bulletins. The AD incorporates by reference the manufacturer's ASBs. These bulletins contain the detailed inspection and adjustment procedures. The AD allows for later National Airworthiness Authority approved revisions, meaning the directive remains effective even if the manufacturer updates the bulletin, as long as the revision is approved by the relevant authority (e.g., Transport Canada or CASA). This is a common feature to avoid the need to issue a new AD for minor procedural changes.

Compliance times. The AD sets multiple time limits: 25 flight hours or 30 days for the initial verification of installed assemblies; before fitment for spare assemblies; 10 flight hours for removal of out of thickness assemblies; 300 flight hours or next scheduled inspection for indexing corrections. These are prescriptive and not dependent on any other maintenance schedule, so operators must schedule work specifically to meet these deadlines.

The AD directly affects owners, operators, and maintainers of BHTC Model 222 helicopters with serial numbers up to 47089, Model 222B helicopters with serial numbers up to 47156, and Model 222U helicopters with serial numbers up to 47574. This encompasses all variants of the Bell 222 family within those serial number ranges. The model 222 and 222B are early variants; the 222U is the utility version. The serial number cut offs suggest that later production aircraft may have had different disc assemblies or quality controls that eliminated the defect. Operators of aircraft with serial numbers beyond these ranges are not affected by this AD, though they remain subject to any subsequent directives.

The directive also affects spare parts suppliers and inventory holders who have disc assemblies with part numbers 36300-1 and 37855-1 in stock. For spares, the verification and any correction must be done before the assembly is fitted to an aircraft after the effective date. This means that a supplier cannot sell or supply a suspect disc assembly to an operator without first ensuring it has been checked and corrected if necessary. This imposes a compliance burden on parts distributors and repair stations that hold these components.

Maintenance organisations that perform work on Bell 222 helicopters are directly affected. They must obtain the relevant Alert Service Bulletins, ensure their technicians are familiar with the inspection and adjustment procedures, and have the necessary tooling (such as micrometers for thickness measurement and indexing fixtures). The compliance times are tight: 25 flight hours or 30 days for initial verification of installed assemblies. For a helicopter that flies regularly, this could mean the inspection must be performed within a week or two. This may disrupt scheduled maintenance programmes and require unscheduled hangar time.

From an economic perspective, the AD imposes compliance costs that are concentrated on a relatively small fleet of aircraft. The Bell 222 is a light utility helicopter, often used in emergency medical services, police, and corporate transport. For operators, the direct costs include labour, parts (if discs need to be added or removed), and potential grounding if a spare assembly is not available. The requirement to remove any out of thickness disc assembly within 10 flight hours may force an immediate grounding unless a replacement is on hand. The indexing correction can be done within 300 hours, which is more manageable. The indirect costs include administrative time for log book entries and record keeping.

The AD may also affect the residual value of affected helicopters. A history of airworthiness directives can be a concern for buyers, although this particular AD is relatively minor and the compliance burden is low. However, failure to comply could result in enforcement action by CASA, potentially including suspension of the airworthiness certificate, which would ground the aircraft and impose significant opportunity costs on the operator.

The primary duty is to verify the disc assemblies on the affected aircraft and spares in accordance with the Alert Service Bulletins. For installed assemblies, the operator must complete the verification within 25 flight hours or 30 days, whichever occurs first. This is a non discretionary obligation; there is no option to defer or skip the inspection if the aircraft is flown. The duty extends to any person who operates, maintains, or modifies the aircraft; usually the registered operator or the person in charge of continuing airworthiness is responsible.

If the disc assembly is found to have a manufacturing date between 1 November 2005 and 30 November 2006, the operator must measure the total thickness. If the thickness is outside the specified limits, the disc assembly must be removed from service within 10 flight hours. This is a strict timeline with no allowance for parts availability; the operator effectively must ground the aircraft unless a compliant assembly can be fitted immediately. The removal duty is absolute: there is no option to operate with a non compliant assembly even temporarily beyond the 10 hour period.

If the disc assembly is not properly indexed, the operator must re index it within 300 flight hours or at the next scheduled inspection, whichever occurs first. This gives more flexibility but still imposes a deadline. The re indexing must be done in accordance with the applicable Maintenance Manual, meaning the operator must follow the prescribed procedure and use the correct tools.

For disc assemblies held as spares, the duty arises before fitment. The supplier or operator must verify the manufacturing date. If the date falls within the suspect window, they must adjust the thickness (by removing or adding a disc) and re index if necessary. They must also attach a serviceable tag indicating compliance with the applicable ASB. This means the spare cannot be released for service without this documentation.

The AD also creates a duty to make records. For installed disc assemblies that do not require further action (because the manufacturing date is outside the window or because they have been verified and found compliant), an appropriate log book notation must be made. This ensures that future inspections or audits can confirm compliance. There is no duty to notify CASA of compliance; the record is sufficient, but CASA may request evidence during an audit.

The operator has a right to use later approved revisions of the Alert Service Bulletins. The AD states that the procedures in the ASBs dated 28 March 2007 apply "or later NAA approved revisions". This allows the operator to benefit from any improved procedures that the manufacturer or regulator approves after the AD was issued. However, the operator must ensure that the revision has been approved by the National Airworthiness Authority; using an unapproved revision would not satisfy the AD. The operator also has the right to use the Maintenance Manual for re indexing, which is a standard approved source of procedures. There is no right to deviate from the AD or to apply for an alternative means of compliance unless specifically provided for. In practice, CASA has a policy of allowing alternative means of compliance, but the AD does not mention this; the operator would need to apply separately under the regulations.

The AD itself does not contain a penalty clause. It is a legislative instrument made under the Civil Aviation Regulations 1988. Regulation 37 of the Civil Aviation Regulations 1988 (as in force at the time) makes it an offence to operate an aircraft that does not comply with an airworthiness directive. The penalty for such an offence can be significant: under the Civil Aviation Act 1988, the maximum penalty for a breach of a safety related regulation can be up to 50 penalty units for an individual (currently AUD $11,000 per unit, but indexed) and up to 250 penalty units for a corporation. Additionally, CASA can impose administrative sanctions, such as suspension or cancellation of the aircraft's airworthiness certificate, or issue a direction to ground the aircraft.

Enforcement is the responsibility of CASA. If an operator fails to comply with the AD within the specified times, the aircraft is considered unairworthy. Continued operation of the aircraft would constitute a breach of the airworthiness certificate conditions and may also be an offence under section 20A of the Civil Aviation Act 1988 (operating an aircraft in a manner that creates a risk to safety). CASA can also take action against the maintenance organisation if it certified the aircraft as airworthy without ensuring compliance.

The AD is also relevant to civil liability. If an accident occurs and it is found that non compliance contributed to the cause, the operator could face tort claims from injured parties or insurers seeking to subrogate. Compliance with an AD is a mandatory requirement; failure to comply would likely be seen as negligence per se in a common law claim.

In practice, CASA has a tiered enforcement response. For minor or inadvertent non compliance, they may issue a warning notice or require a rectification plan. For deliberate or repeated non compliance, they can prosecute. The AD's short compliance times (10 hours for removal of out of thickness discs) increase the risk of enforcement because operators may inadvertently miss the deadline due to operational pressure. The fact that the AD references a Transport Canada directive suggests that CASA coordinated with the Canadian regulator, and non compliance could also affect the aircraft's eligibility for export or foreign registration.

The operator also faces practical penalties: if CASA discovers non compliance during an audit, it may issue a direction to ground the aircraft until compliance is demonstrated. This can result in loss of revenue and reputation damage. The record keeping requirement means that evidence of compliance must be readily available. If the log book notation is missing, CASA may assume non compliance and take enforcement action.

This Airworthiness Directive operates within a hierarchy of aviation safety legislation. It is issued under the authority of the Civil Aviation Act 1988 (Cth) and the Civil Aviation Regulations 1988 (CAR 1988). Specifically, regulation 37 of CAR 1988 empowers CASA to issue airworthiness directives. The directive is a legislative instrument, though it is not always registered on the Federal Register of Legislation; historically, ADs were published in the Gazette or in CASA's AD listing. The effect of regulation 37 is to deem compliance with the AD mandatory; failure to comply makes the aircraft unairworthy.

The AD interacts with the Alert Service Bulletins issued by the manufacturer. These are not legislation but are incorporated by reference. The operator must obtain the ASB and follow its procedures. The AD allows for later NAA approved revisions, meaning that if Transport Canada or CASA approves a change to the ASB, the AD effectively incorporates that change without requiring a new AD. This is efficient but creates a risk: the operator must monitor whether the ASB has been revised and whether that revision has been approved. The AD also references the applicable Maintenance Manual for re indexing. The Maintenance Manual is an approved document under the aircraft's type certificate; using it is consistent with the airworthiness requirements.

The AD references Transport Canada AD CF-2007-09. This reflects the reciprocal recognition of airworthiness directives between CASA and other national aviation authorities. Under the bilateral agreement between Australia and Canada, CASA may adopt a foreign AD directly or issue its own. In this case, CASA issued its own AD that mirrors the Canadian requirement. This means operators must comply with the Australian AD; compliance with the Canadian AD alone would not be sufficient unless it is identical and accepted by CASA as an alternative. The reference to the Canadian AD provides background but does not change the legal obligation under Australian law.

The AD also interacts with the Civil Aviation Safety Regulations 1998 (CASR) to the extent that CASR Part 39 (Airworthiness Directives) now governs ADs for most aircraft. However, this AD was issued in 2007, a transitional period when CAR 1988 still applied to many older aircraft like the Bell 222. The AD's legal status under CAR 1988 is clear. Under current law, similar ADs would be made under CASR Part 39, but the substantive requirements are similar. Operators should check whether any later AD has superseded or amended this one, as CASA occasionally reissues directives under new regulations.

The AD does not interact with state laws or other federal laws such as work health and safety legislation, though an accident caused by non compliance could trigger investigation under the Transport Safety Investigation Act 2003. There is no interaction with environmental laws, as the directive concerns a mechanical component.

The source document is the original airworthiness directive as issued on 19 June 2007 by the delegate of CASA. There is no indication within the source of any prior amendments or revisions. The directive number is AD/BELL 222/36, and it was published in the Gazette or CASA AD listing as number 8/2007. This suggests that it was the eighth AD issued in 2007 for Bell helicopters.

The directive itself incorporates a provision for future amendments: the Alert Service Bulletins referenced (ASB-222-07-105 and ASB-222U-07-76) are stated to apply including "later NAA approved revisions". This means the manufacturer can issue a revision to the ASB, and if that revision is approved by the National Airworthiness Authority (presumably Transport Canada for these helicopter types), then the AD automatically adopts that revision without an amendment to the AD itself. This is a common technique to allow the AD to remain current as procedures improve.

There is no mention of any supersedure of earlier ADs. The Bell 222 series may have had prior ADs related to the tail rotor driveshaft, but this directive does not refer to them. It is likely a standalone new requirement triggered by the in service problem. An operator would need to check the CASA AD database for any later AD that supersedes or modifies AD/BELL 222/36. CASA sometimes reissues directives with a new number or updates them via a separate document. For example, if a more severe defect is found, a new AD may be issued that replaces this one. But as of the source document, no such amendment is indicated.

The effective date is 2 August 2007, which is 44 days after the signing date. This gap allowed operators time to obtain the ASBs and plan the inspection. There is no mention of any extension or postponement of the effective date. The directive does not include a sunset clause or expiry date; it remains in force until specifically revoked or superseded. Given the age of the aircraft fleet, it is likely that most operators have already complied, but the AD continues to apply to any aircraft returning to service or any spare parts that have not been previously verified.

From a legislative perspective, the AD as an instrument does not have an amendment history. It is what it is. Any subsequent changes would be recorded in a separate AD or CASA notice. The lack of amendment history in the source document is typical: an AD is a regulatory instrument that stands on its own.

There is no litigation history specific to this AD that appears in the public record. Airworthiness directives are rarely challenged in court, as they are based on safety findings and operators usually comply. However, general principles apply. If an operator had sought judicial review of this AD, they would have needed to argue that the delegate acted beyond power or that the decision was irrational. Given that the AD is based on a Transport Canada directive and a manufacturer's ASB, the delegate had a strong factual basis. No such challenge is known.

There are a few Australian cases involving airworthiness directives, but none directly on this AD. For example, in Haddow v CASA (2009) the court considered whether a notice of proposed AD was a reviewable decision. But this AD was a final instrument, and any challenge would have to be within 28 days under the Administrative Decisions (Judicial Review) Act 1977. No reported case mentions AD/BELL 222/36.

The absence of litigation is not surprising. The AD is narrowly targeted, the compliance burden is low (except for the 10 hour removal requirement), and the defect is safety critical. Most operators would find it more costly to challenge the AD than to comply. The directive also follows an established pattern of adopting harmonised requirements, which reduces the risk of arbitrary action.

In civil litigation, the AD could be relevant in a product liability or negligence action if a failure occurs. For example, if a disc assembly fails and causes an accident, a plaintiff might argue that the manufacturer or operator failed to comply with the AD. But the AD itself has not been tested in court. On the other hand, compliance with the AD could be used as a defence to show that the operator took reasonable steps. But again, no known case.

Overall, the litigation history for this specific instrument is nil. This section is included for completeness but should not lead the reader to infer any legal uncertainty. The AD is a routine safety directive with no controversy.

Short compliance times for installed out of thickness assemblies. The directive requires removal of any disc assembly that is outside the thickness limits within 10 flight hours from the effective date. This is an extremely tight limit. If the operator's helicopter flies frequently, 10 hours could be reached in a few days. If a replacement disc assembly is not available, the aircraft will be grounded. The AD does not provide any extension for parts availability. Operators should stock a compliant spare before starting the inspection.

The 300 flight hour limit for re indexing is deceptive. This limit applies only if the disc assembly is within thickness limits but needs re indexing. However, the initial verification must be done within 25 flight hours or 30 days. So the re indexing can be deferred, but the discovery of the indexing issue occurs at the initial inspection. If the operator fails to re index within 300 hours, the aircraft becomes non compliant. It is easy to overlook a deferred item.

The manufacturing date window is narrow and precise. The AD only applies to disc assemblies manufactured between 1 November 2005 and 30 November 2006. But many operators may not know the manufacturing date of their disc assemblies. The AD does not specify where to find this date. Possibly it is stamped on the assembly. If the operator cannot determine the date, the safest course is to treat it as suspect and proceed with the thickness verification. The cost of not knowing is unnecessary work, but the risk of assuming a date is outside the window could be a compliance breach.

Log book notation is required even when no action is taken. If the disc assembly has a manufacturing date outside the suspect window, the operator must make an appropriate log book notation. This is easy to forget. Without the notation, an auditor may assume non compliance and take enforcement action. The AD also requires a notation for spares that are verified and found compliant but not installed. This may be overlooked if the spare is stored for a long time.

The AD does not specify a compliance tolerance for flight hours. The times are given in flight hours or days. There is no indication of a grace period. If the operator is one hour late, the aircraft is non compliant. This is typical for ADs, but readers should be aware that strict adherence is expected.

The ASBs are incorporated by reference. The AD requires compliance with the procedures in the ASBs, but the AD does not reproduce those procedures. Operators must obtain the ASBs from Bell Helicopter Textron Canada. Failure to obtain and follow the correct revision of the ASB would mean the work is not performed in accordance with the AD, even if the result is correct. The ASBs may include specific tooling requirements or steps not obvious from the AD.

The AD is based on a Transport Canada directive. Operators in Australia must comply with the CASA AD, not the Canadian one. However, if the operator is also operating under Canadian regulations, they may have to comply with both. The CASA AD accepts later NAA approved revisions; the NAA could be Transport Canada, but operators should confirm that any revision is approved.

The record keeping for spares requires a tag. The AD states that the disc assembly must have a serviceable tag with an inscription indicating compliance with the applicable ASB. This tag must be attached to the assembly. If the tag is lost or damaged, the spare may not be lawful to install, because the compliance evidence is missing.

No alternative means of compliance are mentioned. The AD does not include a provision for the operator to use an equivalent or alternative method. Under CASA policy, an operator can request an alternative means of compliance, but it must be approved in writing before use. Relying on an unapproved alternative exposes the operator to enforcement.

The compliance path for this AD involves a series of steps that must be documented and timed correctly. The following is a practical guide based solely on the requirements in the directive.

Step 1: Determine applicability. Check if the helicopter is a BHTC Model 222 (S/N up to 47089), 222B (S/N up to 47156), or 222U (S/N up to 47574). If the serial number is higher, this AD does not apply. For affected aircraft, proceed.

Step 2: Obtain the Alert Service Bulletins. Obtain ASB-222-07-105 (or later NAA approved revision) for Models 222 and 222B, and ASB-222U-07-76 for Model 222U. These bulletins contain the detailed inspection procedures. Ensure the revision is approved by Transport Canada or CASA. Do not use an unapproved revision.

Step 3: Identify all disc assemblies with part numbers 36300-1 and 37855-1 that are installed on the aircraft or held as spares. Create a register.

Step 4: Verify manufacturing date. Locate the manufacturing date on each disc assembly. If the date is not between 1 November 2005 and 30 November 2006, no further action is required for that assembly. Make an appropriate log book notation for installed assemblies or document the spare accordingly. If the date falls within the suspect window, proceed to Step 5.

Step 5: Measure total thickness. Using the procedure in the ASB, measure the thickness. Compare to the table: for P/N 36300-1, thickness must be between 0.174 inch (4.42 mm) and 0.186 inch (4.75 mm). For P/N 37855-1, between 0.126 inch (3.20 mm) and 0.138 inch (3.50 mm). If the thickness is within limits, go to Step 7. If outside limits, go to Step 6.

Step 6: Out of thickness disc assembly. For installed assemblies, remove the disc assembly from the aircraft within 10 flight hours from the effective date of the AD (2 August 2007). This is mandatory; do not operate the aircraft beyond that time without a compliant assembly. For spares, adjust the thickness by removing or adding a disc as per the ASB. After adjustment, re measure to ensure within limits.

Step 7: Check indexing. Verify that the disc assembly is properly indexed according to the applicable Maintenance Manual. If indexed correctly, proceed to Step 9. If not indexed correctly, proceed to Step 8.

Step 8: Re indexing. For installed assemblies, re index the disc assembly within 300 flight hours from the effective date or at the next scheduled inspection, whichever occurs first. The re indexing must be done in accordance with the Maintenance Manual. If the disc assembly cannot be re indexed, it must be removed from service. For spares, re index before fitment.

Step 9: Logging and tagging. For installed assemblies that have been verified and found compliant (or require no action because of date), make an appropriate log book notation. For spares that have been verified and adjusted, attach a serviceable tag with an inscription indicating compliance with the applicable ASB. Keep records for future audits.

Step 10: Monitor compliance times. For installed assemblies, the initial verification must be completed by 25 flight hours or 30 days after the effective date (2 August 2007). That means the work must be done by 1 September 2007 or 27 flight hours after initial service, whichever comes first. The removal of out of thickness disc assemblies must be done within 10 flight hours. The re indexing must be done within 300 flight hours or next scheduled inspection. These are hard deadlines; plan maintenance accordingly.

Step 11: For spares, ensure compliance before fitment. Do not install a spare disc assembly after the effective date unless it has been verified and any necessary corrections made. The spare must also have the compliance tag attached.

Step 12: Keep documentation. Retain copies of the ASB used, measurements, and log book entries. In case of a CASA audit, these documents demonstrate compliance.

The key risk is the 10 hour removal deadline for out of thickness disc assemblies. Operators should pre inspect their fleet to identify any affected assemblies and have replacement parts ready. Failure to comply within the deadlines renders the aircraft unairworthy and exposes the operator to enforcement action.