AD/B737/306 - Horizontal Stabilizer Trim Capability

The AD rests on a small set of interlocking technical and regulatory concepts drawn from the AD text and the Boeing service bulletin it mandates.

Applicability by part-number and weight: The AD is not universally applicable to all 737s. It applies only to 737-100 and -200 series aeroplanes certificated at takeoff weights in excess of 97,800 pounds and carrying specific actuator part numbers, namely P/N 10-61326-4 or P/N 10-61326-5. The AD’s Applicability field is explicit on this point. The AD also acknowledges manufacturing differences by line number: airplanes from line number 482 onwards were delivered with P/N 10-61326-6, which is the part that the AD treats as the terminating replacement. The AD text contains a conditional sentence that affects line 482 and onwards that operators need to parse practically.

Two alternative compliance tracks: The AD provides operators with two mutually exclusive mechanical paths. Option A is an inspection-and-test regime for actuators P/N 10-61326-4 and -5. It sets a numeric pass/fail criterion, 350 inch-pounds of stall torque, and requires removal and replacement for actuators below that threshold. Option A also mandates ongoing, repetitive torque testing thereafter for actuators that retain P/N 10-61326-4 and -5 status, with interval limits set by a chart (Figure 2) contained in the Boeing service bulletin. Option B is a conversion/remedial track: replace P/N 10-61326-4 or -5 with P/N 10-61326-6 using the service bulletin, and the replacement is the terminating action for the AD.

Reference to external technical document and regulatory approval: The AD does not itself specify the detailed test procedure or the chart values; it incorporates by reference Boeing Service Bulletin No. 737-27-1101 dated 1 February 1980 or any later revision that has been approved by the national aviation authority (NAA). The AD therefore creates a regulatory dependence on a manufacturer document and the NAA’s approval of revisions. That places procedural discretion (which revision may be used) with the NAA.

Numeric performance benchmark: The AD sets a concrete torque threshold, 350 inch-pounds, below which actuators must be replaced. It also requires that future testing intervals for P/N 10-61326-4 and -5 not exceed the maxima shown in Figure 2 of the service bulletin. The AD thereby translates a performance concern (assured horizontal stabilizer trim capability) into a mechanical measurable requirement and a maintenance cycle.

Terminating action: Replacing P/N 10-61326-4 or -5 with P/N 10-61326-6 is explicitly a "terminating requirement for this AD." That means operators who undertake the replacement remove the need to perform the repetitive testing required under Option A. The AD thus creates a trade-off between repeated testing costs and a one-off replacement cost and downtime.

Cross-reference to FAA AD: The AD contains a Note stating "FAA AD 80-09-05 Amdt 39-3760 dated 6 May 1980 refers." This places the CASA AD in a broader regulatory context and indicates that the FAA issued a related directive in 1980.

Textual inconsistencies and implementation dependencies in the AD: The AD text includes several places where part-number formatting and line-number phrasing could produce ambiguity in implementation and record interpretation. The AD refers consistently to P/N 10-61326-4 and -5 as subject parts, and to P/N 10-61326-6 as the replacement and terminating part. One instance in the Requirement B line transposes digits (P/N 10-63126-6) which is inconsistent with the remainder of the text. The AD also contains a conditional sentence that appears to create an odd scope for line numbers 482 and on; operators must interpret that language against maintenance records and physical inspection.

In short, the AD uses part-numbered applicability, a numeric torque threshold, NAA-approved service bulletin integration, a choice between ongoing testing and part replacement, and a terminating replacement option to achieve the stated aim of assuring horizontal stabilizer trim capability. The AD delegates test-interval and procedural specifics to the Boeing service bulletin and the NAA’s approval process.

Directly affected parties: The AD explicitly applies to "All Boeing 737-100 and -200 series aeroplanes certificated at takeoff weights in excess of 97,800 pounds and containing the horizontal stabilizer trim actuator P/N10-61326-4 or P/N 10-61326-5." That identifies aircraft operators and aircraft owners of those specific configurations as the parties with mandatory obligations under the AD. Maintenance organisations performing work on those aeroplanes will carry out the required tests or replacements.

Maintenance and parts suppliers: Where replacement is required, the AD references specific part numbers, meaning that operators will interact with suppliers or stock holdings of actuators P/N 10-61326-4, -5 and -6. The AD’s allowance to replace failed actuators with a "serviceable actuator P/N 10-61326-4, -5, or -6" affects spare-parts inventory policy for operators and suppliers.

Regulatory authorities and approvers: The AD ties compliance to Boeing Service Bulletin No. 737-27-1101 "dated 1 February 1980 or later NAA approved revision." That means the national aviation authority (NAA) is the authority that approves later revisions of the Boeing service bulletin for compliance purposes. The AD therefore affects regulatory staff and auditors who must accept or enforce the use of a particular service bulletin revision.

Pilots and flight operations: While the AD imposes no direct operational limitation in-flight, it addresses a component that affects stabilizer trim capability. Indirectly, flight crews may be affected by any scheduling or dispatch impacts resulting from maintenance downtime, replacement, or repetitive testing that requires the aircraft to be out of service.

Who pays: The AD places the compliance cost on the operators/owners of the applicable aeroplanes. All testing, replacement parts, labour costs, and aircraft downtime necessary to meet either Option A or Option B fall to the operator. The AD supplies no funding mechanism or compensation. The cost is therefore concentrated on owners/operators of the particular 737-100/200 models at the specified weight and with the specified part numbers.

Who decides: The AD prescribes that either testing or replacement must be carried out. The operator chooses which compliance path to follow, but operational choice is constrained by the AD’s technical requirements. Additionally, the NAA decides which later revisions of the Boeing service bulletin are "NAA approved," and that approval affects permitted procedures.

Timing and schedule impacts: The AD imposes a compliance deadline, "within the next six months after the effective date of this AD, unless already accomplished," with the effective date set at 30 August 2007. That fixes a finite window in which operators must carry out the required testing or replacement, and therefore creates scheduling pressure on maintenance facilities, spare parts supply, and aircraft utilisation.

Scope of effect due to production differences: The AD distinguishes aircraft by line number, noting "737 aeroplanes from line number 482 and on were delivered with horizontal stabilizer trim actuator P/N 10-61326-6." That means many later-build aeroplanes in the 737-100 and -200 series may not be affected at all because they already have the terminating part P/N 10-61326-6. However, the AD adds a conditional phrase that may make those later-production aeroplanes affected if earlier part numbers had been exchanged for P/N 10-61326-6; the net practical effect is that operators must check actual installed parts rather than rely solely on production line records.

In sum, the parties who pay and act are the aircraft owners/operators and their maintenance organisations, while the NAA retains the approval role over service bulletin revisions. The financial burden, logistical work, and any aircraft downtime are concentrated on those operators whose aircraft meet the AD’s part-number and weight criteria.

The AD sets out specific duties for operators of affected aircraft and allocates a narrow set of decision rights. The duties are mandatory; the AD prescribes actions rather than recommending them. The AD text frames obligations in a two-option format, with clear mechanics.

Primary duties:

• Identification. Operators must determine whether their aeroplane is subject to the AD by checking certificate takeoff weight and the installed horizontal stabilizer trim actuator part number. The Applicability field requires that only aeroplanes certificated at takeoff weights in excess of 97,800 pounds and containing actuator P/N 10-61326-4 or -5 are subject. This creates a duty to inspect maintenance records and installed parts.
• Within six months of the effective date (30 August 2007), operators must accomplish either Option A or Option B. The AD states "Accomplish either A or B below" and gives the work scope for each.
• Option A duties: For actuators P/N 10-61326-4 or -5, operators must "test the actuator stall torque in accordance with Boeing Service Bulletin No. 737-27-1101, dated 1 February 1980 or later NAA approved revision." Where an actuator is found to have less than 350 inch-pounds of torque, it "must be replaced with a serviceable actuator P/N 10-61326-4, -5, or -6." Thereafter, for P/N 10-61326-4 and -5 actuators, "conduct repetitive torque test per the 'Actual Stall Torque/Maximum Test Interval' chart, Figure 2, of that service bulletin at intervals not to exceed the maximum test intervals (hours) indicated by the curve on the chart." The AD thus imposes both an initial testing duty and a continuing testing duty with intervals determined by the service bulletin figure.
• Option B duties: Replace the horizontal stabilizer trim actuator P/N 10-61326-4 or -5 with stabilizer trim actuator P/N 10-61326-6 "in accordance with Boeing Service Bulletin No. 737-27-1101, dated February 1, 1980." The AD states that "Replacing ... with Boeing P/N10-61326-6 is the terminating requirement for this AD." If implemented, this acts as a one-off duty that removes the continuing testing duty.

Delegated and approval rights:

• NAA approval right. The AD permits the use of the Boeing service bulletin "dated 1 February 1980 or later NAA approved revision." That provision gives the national aviation authority a decisive approval role over later-revision conformity. The authority decides which later revisions qualify for compliance.
• Operator choice in compliance path. The AD gives operators an explicit right to choose between testing/repeat-testing (Option A) and replacement to terminate the requirement (Option B). This is not a discretionary waiver; operators must select and accomplish one option within the compliance window.

Specification of acceptable replacement parts:

• The AD specifies acceptable replacement part numbers. For actuators failing the 350 inch-pounds test in Option A, replacement may be with "serviceable actuator P/N 10-61326-4, -5, or -6." In Option B, the AD commands replacement with P/N 10-61326-6. The AD therefore defines which spare parts are acceptable for compliance.

Numeric performance metric:

• The AD gives a clear numeric pass/fail metric: 350 inch-pounds of stall torque. This sets a precise duty for maintenance staff to follow, with replacement required below that metric.

Recordkeeping and proof:

• The AD text as provided does not set out specific recordkeeping or certification language beyond the work descriptions and the effective date/compliance window. It does not specify what evidence will be accepted to demonstrate compliance for audit or continued airworthiness purposes. The duty to accomplish the AD therefore exists, but the AD does not itself detail documentation procedures within the supplied text.

Rights under the AD:

• The AD provides a right to terminate the ongoing testing obligation by carrying out the specified replacement to P/N 10-61326-6.
• Operators retain the right to choose which compliance route to follow, subject to the technical requirements and NAA approval of service bulletin revisions.

Constraints and interactions:

• The AD constrains operator choice by tying procedures to Boeing Service Bulletin No. 737-27-1101 and to "NAA approved" later revisions. Operators cannot unilaterally adopt alternative test methods or interval schedules beyond what is permitted by the service bulletin and the NAA’s approvals.

In short, the AD imposes mandatory duties to inspect, test, replace failing parts, and in some cases to adopt a program of repetitive testing. It grants operators a clear choice between a recurring testing obligation and a one-off replacement that terminates the AD’s continuing obligations. The NAA retains an approval role over acceptable service bulletin revisions, which affects permissible procedures.

The AD text supplied does not contain explicit penalty clauses, monetary fines, or administrative sanction schedules. The AD sets mandatory maintenance and replacement obligations, but it does not itself specify enforcement mechanisms or penalties in the text made available here.

What the AD does specify that is relevant to enforcement:

• Mandatory compliance requirement. The AD requires completion of either Option A or Option B within six months of the effective date unless already accomplished. Setting a clear compliance deadline is a standard regulatory enforcement mechanism because non-compliance is, in practice, a breach of airworthiness obligations.
• Effective date and authority. The AD is issued by the Civil Aviation Safety Authority, signed by a delegate. The AD becomes effective on 30 August 2007. The presence of an effective date and an issuing authority is a precondition for any enforcement action by the regulator, because the AD is a formal regulatory instrument.

What is not specified in the AD text:

• The AD does not state the legal consequences, criminal or civil, of failing to comply, nor does it specify a graduated enforcement regime. The AD also does not outline suspension, revocation, penalty, or administrative fine provisions in the text supplied.
• The AD does not detail verification, audit, or reporting procedures for evidence of compliance, nor does it specify whether specific forms, maintenance release entries, or certificates are required to be lodged with the regulator.

Implications for enforcement practice:

• Although the AD lacks explicit penalty language in the supplied text, the regulator’s issuance of an AD creates a mandatory standard. Enforcement would typically follow the regulator’s general enforcement and surveillance frameworks rather than the AD itself. The AD’s practical enforceability rests on the regulator’s power to require compliance with airworthiness directives and to take enforcement action under applicable aviation regulatory statutes or rules. However, those broader enforcement mechanisms are not set out in the AD text provided here.

Interaction with NAA approvals and service bulletin conformity:

• Because the AD requires adherence to Boeing Service Bulletin No. 737-27-1101 "dated 1 February 1980 or later NAA approved revision," enforcement will likely require proof that the procedures used were consistent with the service bulletin revision approved for compliance. The AD delegates procedural detail to the service bulletin and to the NAA’s approval competence, which means that enforcement actions would need to consider whether the test or replacement followed the approved procedures.

Reference to FAA AD:

• The AD contains a Note referencing "FAA AD 80-09-05 Amdt 39-3760 dated 6 May 1980." That cross-reference may be relevant in enforcement contexts where other jurisdictions have taken analogous actions or where records of prior compliance under the FAA AD exist, but the supplied AD text does not tie enforcement mechanics to the FAA AD.

In summary, the AD prescribes mandatory maintenance actions and a compliance timetable, but the supplied text does not articulate penalty provisions. Enforcement therefore sits with the issuing authority’s broader regulatory powers and procedures, not within the AD’s express language as provided.

Within the text available, the AD interacts with other regulatory instruments and technical documents by reference rather than by listing other domestic statutes or regulations. The AD’s operational and legal interfaces are specified through cross-reference to the manufacturer’s service bulletin and to a related FAA AD.

Incorporation by reference to a manufacturer document:

• The AD requires compliance "in accordance with Boeing Service Bulletin No. 737-27-1101, dated 1 February 1980 or later NAA approved revision." That effectively binds a CASA AD to a Boeing technical document and to whatever procedural and interval content that bulletin contains. The AD therefore operates as a regulatory overlay that makes mandatory specific actions contained in a manufacturer’s service bulletin, subject to any NAA approvals of later revisions.

Role of the National Aviation Authority (NAA):

• The AD’s permissive language for later revisions (i.e. "or later NAA approved revision") places the NAA in the role of gatekeeper. Any later service-bulletin revision becomes effective for AD compliance only if the NAA approves it. This creates an interaction between the AD and the NAA’s administrative approval process for service bulletin revisions.

Cross-jurisdictional reference:

• Note 2 of the AD states "FAA AD 80-09-05 Amdt 39-3760 dated 6 May 1980 refers." That explicitly anchors this CASA AD to a FAA AD issued in 1980. While the AD does not spell out the legal effect of that FAA AD domestically, the reference indicates a parallel or related regulatory action in another jurisdiction. Operators with records demonstrating compliance with the FAA AD may consider that history relevant, although the AD itself does not automatically accept FAA compliance in place of CASA-compliant actions; the AD’s compliance requirement is framed in domestic terms with Boeing service bulletin conformity.

Interaction with airworthiness certification:

• The AD applies to aeroplanes "certificated at takeoff weights in excess of 97,800 pounds," which intersects with the aircraft’s type certificate and its operational certification data. The AD thus interfaces with the aircraft’s certified weight category and the aircraft’s logbooks that record installed parts and modifications.

Parts approval and maintenance standards:

• The AD specifies parts by part number and describes replacement with "serviceable actuator P/N 10-61326-4, -5, or -6." Determinations about whether a part is "serviceable" generally rest with maintenance organisations and the NAA’s parts and components standards. The AD does not define "serviceable," so operators must consult maintenance regulations and the service bulletin procedures, and possibly the NAA’s guidance, to determine which parts qualify.

No explicit interaction with specific domestic legislative provisions:

• The supplied AD text does not cite the domestic aviation legislation or subordinate regulations that give CASA the power to issue ADs. It likewise does not refer to civil penalty regimes, enforcement statutes, or administrative procedures. Consequently, any interaction with broader domestic law (for example, civil aviation safety acts or regulations) is implicit rather than explicit in the AD text provided.

Practical implication of the AD’s references:

• Because the AD relies on an external Boeing service bulletin and on NAA-approved revisions, operators and maintenance organisations must manage compliance through the service bulletin regime and any approvals by the NAA. Documentation and audit trail for compliance will therefore likely need to show adherence to a particular service bulletin revision that has been accepted by the NAA.

To summarise, the AD interacts primarily by reference to Boeing’s service bulletin and to prior FAA action. It delegates procedural specificity to that service bulletin and institutional authority over later revisions to the NAA. The AD does not, within the supplied text, explicitly connect to particular domestic enforcement statutes, but it operates within the background framework of domestic aviation regulatory authority.

The AD text supplied contains a minimal amendment history. It does not record later CASA amendments or variations following the original issuance.

What the AD states about related historical actions:

• The AD includes a Note referencing an FAA document: "FAA AD 80-09-05 Amdt 39-3760 dated 6 May 1980 refers." That indicates that in 1980, the Federal Aviation Administration issued an AD on the same topic, and that the CASA AD identifies that FAA AD as relevant background or cross-reference. The presence of that 1980 FAA AD suggests that this CASA AD B737/306 aligns with an earlier foreign regulator action, but the supplied text does not provide a legislative timeline connecting the two beyond the reference.

Issuance and effective dates:

• The AD is signed by David Punshon, Delegate of the Civil Aviation Safety Authority, and dated 20 July 2007 in the document. The AD states "This Airworthiness Directive becomes effective on 30 August 2007." The compliance window is defined as "Within the next six months after the effective date of this AD, unless already accomplished." Consequently, the specified period for compliance would expire approximately on 28 February 2008 for actions not already completed.

Service bulletin revision allowance:

• The AD allows compliance in accordance with Boeing Service Bulletin No. 737-27-1101 "dated 1 February 1980 or later NAA approved revision." That provision is the only explicit mechanism the AD contains for subsequent technical amendment , namely, later revisions of the Boeing service bulletin become acceptable only if the NAA approves them. This is procedural flexibility rather than an amendment of the AD itself.

No recorded domestic amendments in supplied text:

• The AD as provided does not show any domestic amendments, re-issues, supersessions, or revocations by CASA itself. There is no list of corrigenda, no list of later ADs that modify this AD, and no text indicating that the AD has been rescinded or extended. The absence of such text in the supplied document means that, from this source alone, no amendment history beyond the initial issuance and the FAA cross-reference is recorded.

Textual inconsistencies that bear on amendment or interpretation:

• The AD text includes a minor inconsistency in part-number formatting, specifically the transposition in Requirement B where "Boeing P/N 10-63126-6" appears once while the rest of the document uses P/N 10-61326-6. Such inconsistencies can generate questions about whether a typographical error should be remedied by an amendment or interpreted in context by regulatory staff. The AD itself does not include an erratum or amendment to resolve that inconsistency within the supplied text.

In short, the supplied AD contains a single issuance event in 2007, allows for later NAA-approved service bulletin revisions, and cross-references an FAA AD from 1980. The document does not list subsequent amendments, corrections, or revocations within its own text.

The AD as supplied does not include any litigation history. There are no references in the AD text to judicial review, court challenges, enforcement litigation, or decisions about the AD that would be relevant to legal precedent. The document contains a cross-reference to FAA AD 80-09-05 and instructs compliance with Boeing Service Bulletin No. 737-27-1101, but it does not report any disputes or contested interpretations.

Practical consequences of the absence of litigation history in the text:

• Because the AD contains no litigation history or references to court rulings, all inferences about how courts have treated similar directives would require external sources not present in this document. The AD itself supplies no judicial interpretations to inform ambiguity in part numbers, line-number applicability, or the extent of the NAA’s approval authority for service bulletin revisions.

Administrative review and remedies:

• The AD does not set out remedies, appeal mechanisms, or administrative review processes in its text as supplied. If an operator wished to challenge the AD’s requirements or seek an alternative method of compliance, the AD does not itself specify the route or form of application for an alternative method. That process, if it exists, would be part of the broader regulatory scheme or CASA administrative procedures, none of which are included in the AD text provided.

Record and evidentiary role of the service bulletin:

• Litigation arising from compliance disputes would likely turn on the service bulletin’s procedures, NAA approvals, or maintenance records. The AD’s reliance on Boeing Service Bulletin No. 737-27-1101 means that procedural clarity would come from the service bulletin. However, the AD text supplied contains no litigation outcomes applying that bulletin.

In summary, the AD provides no litigation history or reported legal challenges within the supplied document. Any litigation or judicial interpretation must be sought outside the body of the AD as provided.

The AD text contains several practical pitfalls, ambiguities and operational points that a compliance-minded practitioner should flag. The AD is short, but it delegates technical detail to an external service bulletin. The consequences for operators depend on careful reading and records checks.

1. Part-number inconsistencies:

• The AD repeatedly identifies the relevant actuators as P/N 10-61326-4 and P/N 10-61326-5, and identifies the terminating replacement as P/N 10-61326-6. However, Requirement B includes an apparent transposition: "Replace the horizontal stabilizer trim actuator, Boeing P/N 10-61326-4 or -5 with stabilizer trim actuator, Boeing P/N 10-63126-6..." The sequence "10-63126-6" appears to transpose digits and is inconsistent with the rest of the AD. This discrepancy creates a concrete implementation risk because maintenance records, procurement systems, and parts catalogues operate by exact P/N matches. Operators need to verify the intended replacing part with Boeing documentation and the NAA before ordering or fitting parts.

2. Ambiguous line-number wording:

• The Applicability note states that 737 aeroplanes from line number 482 and on were delivered with P/N 10-61326-6, and then adds: "This AD will apply to those 737 aeroplanes line number 482 and on if P/N 10-61326-4 or -5 have been exchanged for P/N 10-61326-6." The conditional is awkward because it suggests that aircraft that were delivered with P/N 10-61326-6 might only be captured if a prior exchange occurred. Practically, the controlling question for applicability should be the current installed part number and the certificated takeoff weight, not the original delivery part, but the AD’s phrasing is potentially confusing. Operators should rely on current installed part numbers and consult CASA or the NAA for clarification where necessary.

3. Reliance on external Figure 2 for intervals:

• The AD requires that after initial testing, "for the actuators P/N 10-61326-4 and -5, conduct repetitive torque test per the 'Actual Stall Torque/Maximum Test Interval' chart, Figure 2, of that service bulletin at intervals not to exceed the maximum test intervals (hours) indicated by the curve on the chart." Figure 2 and the chart values are not included in the AD text. Operators must obtain and rely on Boeing Service Bulletin No. 737-27-1101 to determine the actual maximum interval values. Failure to use the correct Figure 2 could lead to non-compliance.

4. Definition of "serviceable":

• The AD allows replacement with a "serviceable actuator P/N 10-61326-4, -5, or -6." The AD does not define "serviceable" within its text. Maintenance standards and parts acceptance criteria will determine serviceability. Operators should ensure that any used or overhauled part meets the manufacturer's and NAA’s standards for serviceability; otherwise, fitting a part marked by the correct P/N may not satisfy the AD’s intent.

5. NAA approval for later revisions:

• The AD permits an operation "in accordance with Boeing Service Bulletin No. 737-27-1101, dated 1 February 1980 or later NAA approved revision." Operators may be tempted to use later Boeing revisions available from the manufacturer. However, the AD requires that later revisions be NAA approved. Using a later revision without NAA approval could create non-compliance risk.

6. No specified recordkeeping language:

• The AD does not set out documentation or proof-of-compliance requirements in the text supplied. Operators should not assume what documentation the regulator will accept. Maintenance records and logs should be prepared to demonstrate the work done, but the AD itself does not prescribe particular forms or certification entries.

7. Narrow weight applicability:

• The AD applies only to aircraft "certificated at takeoff weights in excess of 97,800 pounds." Operators must check their certificated takeoff weight and not assume applicability from model number alone. This is a discrete eligibility condition that could exclude certain 737-100 and -200 models, or include only a subset.

8. Timing pressure:

• The AD requires compliance within six months of the effective date (30 August 2007). Operators with multiple affected aircraft will need to schedule work to avoid conflicts with operational requirements. The AD does not phase compliance or stagger deadlines.

9. Cross-reference to FAA AD:

• The AD refers to FAA AD80-09-05. Operators who have previously complied with the FAA AD may assume they are already compliant, but the CASA AD sets its own standards through reference to the Boeing service bulletin and the NAA’s approval. Operators need to verify whether prior FAA-compliance actions meet the CASA AD's specific requirements.

10. No express remedy for technical ambiguity:

• If an operator’s maintenance records or part-tagging create ambiguity about which part is installed, the AD supplies no procedure for resolution. Operators should be prepared to physically inspect installations and consult parts tags and maintenance records. If ambiguity remains, operators should seek CASA or NAA guidance.

These "gotchas" create practical implementation risks that require operators to check parts lists, confirm service bulletin figures and revisions, resolve typographical inconsistencies, and maintain clear maintenance documentation. The AD’s short text increases reliance on the service bulletin and on NAA clarifications for safe, compliant implementation.

The AD provides two clear compliance pathways and a narrow timeframe. A compliance checklist, founded on the AD text and the referenced Boeing service bulletin, should be followed. Below is a stepwise compliance roadmap that follows the AD’s mandatory wording.

1. Determine applicability:

• Check the aircraft’s type and certificated takeoff weight. The AD applies to Boeing 737-100 and -200 series aeroplanes certificated at takeoff weights in excess of 97,800 pounds.
• Inspect maintenance records and the physical actuator to confirm the installed horizontal stabilizer trim actuator part number. The AD applies only to aeroplanes containing actuator P/N 10-61326-4 or P/N 10-61326-5, as stated in the Applicability field.
• If the aircraft is from line number 482 or later, confirm the actual installed part number because the AD notes those aeroplanes were delivered with P/N 10-61326-6. The AD’s wording on line-number applicability is conditional and requires identification of the current installed part.

2. Obtain Boeing Service Bulletin No. 737-27-1101:

• The AD requires performing actions "in accordance with Boeing Service Bulletin No. 737-27-1101, dated 1 February 1980 or later NAA approved revision." Obtain the Boeing service bulletin and confirm whether a later revision exists and whether it has NAA approval. Do not rely on an unapproved later revision.

3. Choose a compliance path (A or B) and schedule work within the compliance window:

• Compliance is required "within the next six months after the effective date of this AD" (effective date 30 August 2007). Schedule the chosen action within that six-month window unless the action has already been completed.

4. If choosing Option A (test and recurring testing):

• Follow the service bulletin’s prescribed stall torque test procedure for actuators P/N 10-61326-4 and -5.
• Apply the numeric criterion in the AD: replace any actuator found to have less than 350 inch-pounds of stall torque.
• Replace failing actuators with a "serviceable actuator P/N 10-61326-4, -5, or -6" per the AD. Ensure the replacement part meets serviceability criteria under applicable maintenance standards and any NAA guidance.
• For any actuator retained as P/N 10-61326-4 or -5, set up a recurring test schedule according to the "Actual Stall Torque/Maximum Test Interval" chart, Figure 2, in the service bulletin. Ensure that the actual test intervals do not exceed the chart’s maximum test intervals as indicated by the curve for the measured stall torque.
• Document each test and any replacements in the aircraft maintenance log and in the operator’s maintenance tracking system.

5. If choosing Option B (replacement as terminating action):

• Replace the horizontal stabilizer trim actuator P/N 10-61326-4 or -5 with P/N 10-61326-6 "in accordance with Boeing Service Bulletin No. 737-27-1101, dated February 1, 1980" as the AD prescribes.
• Confirm the part-number accuracy before fitment in view of the AD’s typographical inconsistency (the AD once lists P/N 10-63126-6). Cross-check the intended replacement P/N with the service bulletin and the manufacturer or parts catalogue to ensure the correct P/N 10-61326-6 is procured and installed.
• After replacement with P/N 10-61326-6, the AD states this is the "terminating requirement." Ensure the maintenance record explicitly notes this as compliance with AD/B737/306 and retains documentation of the replacement.

6. Documentation and evidence:

• Although the AD text does not specify recordkeeping format, maintain contemporaneous maintenance records that detail the action performed, the service bulletin revision used, serial numbers and part numbers of removed and installed actuators, torque test results (if Option A), and signatures of authorised maintenance personnel.
• If a later revision of the service bulletin is used, retain NAA approval documentation for that revision as evidence of compliance with the AD’s allowance for later NAA-approved revisions.

7. Resolve ambiguities with the NAA or CASA:

• Where the AD text contains inconsistencies or ambiguous applicability language, seek clarification from CASA or the NAA. In particular, confirm the correct replacement part number and the interpretation of the line-number conditional clause to avoid inadvertent non-compliance.

8. Logistics and procurement:

• Plan spare-part procurement for P/N 10-61326-4, -5 or -6 as needed. Where Option B is selected, secure supply of P/N 10-61326-6 parts in sufficient quantity to meet the replacement schedule. Consider lead times and availability constraints.

9. Maintenance organisation competence:

• Ensure the personnel performing the stall torque tests and replacements are certificated or authorised under applicable maintenance regulations. Use tooling and test equipment consistent with the service bulletin and record calibration and test equipment status.

10. Monitoring and ongoing compliance:

• If Option A is used, implement a programme to track torque test results and schedule the repetitive tests per Figure 2. Ensure that test intervals do not exceed the chart’s maxima and that any failing actuator is immediately replaced with a serviceable P/N 10-61326-4, -5, or -6.

11. Cross-jurisdictional records:

• If the operator previously complied with FAA AD 80-09-05, maintain records that link earlier FAA compliance to the CASA AD for inspection purposes, but do not assume prior FAA compliance automatically satisfies the CASA AD without confirming procedural equivalence and service bulletin revisions used.

In short, compliance requires confirming applicability, obtaining the specified Boeing service bulletin and any NAA approvals, choosing and executing Option A or B within six months of 30 August 2007, documenting the work, and resolving any textual or procedural ambiguities with the regulator. The AD does not provide forms or explicit record templates; operators must therefore rely on established maintenance recordkeeping practices and retain all materials that demonstrate compliance with the AD and the service bulletin used.