AD/B737/110 Amdt 2 - Rudder Yaw Damper Valve Replacement

The AD is built around a small and specific set of technical and procedural concepts.

• Engage solenoid valve of the yaw damper: The object of the AD is the engage solenoid valve used in the yaw damper subsystem of the Boeing 737 rudder/yaw system. The Directive requires an inspection to determine the valve’s part number (Requirement).

• Part number mapping and vendor identification: The AD lists vendor part numbers (Parker and Sterer) and the corresponding Boeing part numbers. Three Parker vendor part numbers are identified as unacceptable and require replacement: Parker P/N 59600‑5011 (Boeing P/N 10‑60811‑9), Parker P/N 59600‑5007 (Boeing P/N 10‑60811‑3), and Parker P/N 59600‑5003 (Boeing P/N 10‑60811‑1) (Requirement). Acceptable replacement parts are explicitly listed: Parker P/N 881600‑1001 (Boeing P/N 1060811‑13), Sterer P/N 45080‑1 (Boeing P/N 10‑60811‑8), and Sterer P/N 45080 (Boeing P/N 10‑60811‑3) (Requirement).

• Ambiguity and vendor ascertainment: The AD highlights a specific identification problem: two different vendor part numbers (Parker and Sterer) share the same Boeing part number 10‑60811‑3. The AD instructs operators that if Boeing P/N 10‑60811‑3 is found installed they must ascertain the vendor part number to determine whether replacement is required , because Parker P/N 59600‑5007 mapped to Boeing P/N 10‑60811‑3 is not acceptable, while Sterer P/N 45080 (also mapped to Boeing P/N 10‑60811‑3) is acceptable (Note 3). The AD further notes that some valves may be labelled only with “Bertea” rather than Parker or Parker‑Bertea, which can complicate identification (Note 3).

• Maintenance procedure reference points: The AD does not provide step‑by‑step installation tasks within the instrument itself; it directs operators to Boeing Maintenance Manual procedures in specific chapters (Chapter 22‑11‑61 or 22‑12‑21 for -100/-200; Chapter 22‑12‑21 for -300/-400/-500) for the procedural details (Requirement).

• Relationship to subsequent FAA AD: The AD records that incorporation of the new rudder control system mandated by FAA AD 2002‑20‑07 (AD/B737/201) is a terminating action for the requirements of this Directive (Requirement; Background). The AD states Amendment 2 was issued in response to that FAA AD (Background).

• Safety rationale: The Background gives the safety mechanism: investigations revealed anomalies in the Boeing 737 flight control system that could lead to reduced controllability or uncommanded control input, and the AD was issued to remove a potential source of failure within the yaw system (Background). That safety claim is the stated motivation for the required inspection and replacement.

These concepts explain how the instrument changes operator obligations: by creating a mandatory identification exercise (inspect part number), requiring replacement when certain vendor part numbers are present, and by specifying the approved replacement part numbers and procedural references.

The Directive directly affects operators and maintainers of Boeing 737-100, -200, -300, -400 and -500 series aeroplanes (Applicability). That includes:

• Operators/airlines that have these airframes on their certificates of registry. The Directive’s inspection and replacement requirements are obligations for the operator unless already accomplished (Requirement).

• Maintenance organisations and personnel who are responsible for conducting inspections and performing valve replacements. The AD directs the use of specific Boeing Maintenance Manual chapters for procedures, so maintenance staff must consult and follow those chapters (Requirement). Shops responsible for PCU removal and reinstallation are implicated because the AD ties inspection timing to the next PCU removal for maintenance as an allowable compliance milestone (Compliance).

• Parts and component managers in operator and MRO (maintenance, repair and overhaul) supply chains. The AD requires identification of vendor part numbers and prohibits continued use of certain Parker parts. Inventory checks, procurement of acceptable replacement valves, and documentation of part provenance (vendor P/N versus only Boeing P/N labelling) fall to parts personnel (Requirement; Note 3).

• The manufacturer and authorised vendors: Boeing and the listed valve vendors appear in the mapping of part numbers and in the maintenance‑procedure references. The AD effectively requires operators to use parts that correspond to specific vendor P/Ns and Boeing P/Ns; suppliers who provide valves will therefore be called on to supply the acceptable vendor parts listed in the Directive.

• Regulators and certifying authorities: The AD is issued by the Civil Aviation Safety Authority (CASA) (delegate signature given), but it cross-references FAA ADs and Boeing in‑service reports. The Directive’s status as an AD makes it part of the continuing airworthiness regulatory framework for affected aircraft within CASA’s jurisdiction (Background; Requirement).

Who pays: The source text does not allocate explicit cost recovery or funding. Practically, operators incur the direct costs of inspections and of replacement parts and labour, and maintenance organisations will perform work at operator cost. Parts suppliers may gain replacement contracts. The AD does not specify compensation, penalty charging, or cost subsidies; those matters are not addressed in the text.

Duties

• One‑time inspection: Operators must "perform a one time inspection of the engage solenoid valve of the yaw damper to determine the Part Number (P/N) of the valve" unless the action has already been accomplished (Requirement). This inspection is the precondition to any replacement obligation.

• Replacement obligation: If the inspected valve is one of the listed Parker vendor part numbers , Parker P/N 59600‑5011 (Boeing P/N 10‑60811‑9), Parker P/N 59600‑5007 (Boeing P/N 10‑60811‑3), or Parker P/N 59600‑5003 (Boeing P/N 10‑60811‑1) , the operator must replace it with one of the specified acceptable valves: Parker P/N 881600‑1001 (Boeing P/N 1060811‑13), or Sterer P/N 45080‑1 (Boeing P/N 10‑60811‑8), or Sterer P/N 45080 (Boeing P/N 10‑60811‑3) (Requirement).

• Procedural conformity: The inspection and replacement must be carried out "in accordance with procedures specified in Chapter 22‑11‑61 or Chapter 22‑12‑21 (for 737‑100 and ‑200 series aircraft) of the Boeing Maintenance Manual as applicable; or Chapter 22‑12‑21 (for 737‑300, ‑400, and ‑500 series aircraft) of the Boeing Maintenance Manual" (Requirement). This means the AD delegates the detailed method to Boeing's prescribed maintenance procedures rather than specifying step-by-step tasks in the Directive.

• Compliance timing: The inspection must be completed within five years or 15,000 flights after 25 February 1999, or at the next time the PCU is removed for maintenance, whichever is earlier (Compliance). Replacement requirements are coupled with a "Before further flight" timing requirement (Compliance). The AD also records that "The compliance times remain unchanged by this issue" (Compliance).

• Termination: If an operator complies with AD/B737/201 (FAA AD 2002‑20‑07), that accomplishment constitutes terminating action for the requirements of this Directive (Requirement). In practice, this creates an alternative path to ending the obligation under this AD, by incorporating the supplanting modification required by the other AD.

Rights and operational flexibilities apparent from the text

• The Directive recognises prior compliance: The opening clause in the Requirement states "Unless already accomplished", which acknowledges that operators who have already performed the inspection/replacement need not perform duplicate work (Requirement).

• Timing flexibility tied to PCU removal: The AD allows a longer horizon for the one‑time inspection by permitting it to be deferred until the next time the PCU is removed for maintenance, provided that occurs before the five‑year or 15,000 flight deadline (Compliance). This gives operators a scheduling option for inspections that can consolidate maintenance tasks.

• Option to terminate via incorporation of FAA AD action: Operators who have or will incorporate the modification mandated by FAA AD 2002‑20‑07 have a recognised terminating action for the obligations in this Directive (Requirement).

What the Directive does not state

• The AD does not set out record‑keeping formats, documentary proof, or a process for CASA acceptance of compliance within the text. It also does not specify enforcement mechanisms, fines, or penalties (the text contains no enforcement or penalty clauses). The instrument likewise does not provide a warranty or procurement mechanism for replacement parts.

All duties are explicitly expressed in the "Requirement" and "Compliance" blocks of the AD.

The AD text supplied does not set out specific enforcement measures, civil penalties, or criminal sanctions. The AD prescribes mandatory maintenance actions and compliance times (Requirement; Compliance), and it identifies the technical risk motivating the Directive , system anomalies that could lead to reduced controllability or uncommanded control input (Background). However, within the four corners of the Directive as provided, there is no operative text describing penalties for non‑compliance, administrative enforcement steps, or escalation procedures.

The instrument’s enforcement implications are therefore limited to what the AD explicitly prescribes: operators are required to carry out the inspection and replacement actions within the stated time frames and according to Boeing maintenance procedures. The Directive also includes a "Before further flight" requirement for the replacement obligation (Compliance), which operationally implies that affected aeroplanes must not continue in service with an unacceptable valve installed beyond that point, but the AD itself does not state the consequences of failing to comply.

Because the AD cross‑references FAA ADs and Boeing documents (Requirement; Background), it is possible that enforcement or evidentiary interaction with other regulatory or oversight processes will occur in practice, but such arrangements are not described in this text. Similarly, the AD does not describe how operators should submit evidence of compliance to the regulator, or whether CASA will audit or certify compliance; these implementation and enforcement mechanisms are outside the AD text provided.

Readers should therefore note that while the Directive is prescriptive about the safety actions required and the timing, the AD as provided does not record penalty provisions, reporting protocols, or an administrative enforcement ladder. Those matters may be covered in broader regulatory instruments, guidance material, or in CASA’s compliance procedures, but they are not part of the source text supplied.

The AD expressly cross‑references and interacts with other aviation airworthiness instruments and manufacturer documents.

• FAA Airworthiness Directives: The AD states that "Accomplishment of the requirements of AD/B737/201 (FAA AD 2002‑20‑07) constitutes terminating action for the requirements of this Directive" (Requirement). Amendment 2 to this AD was issued in response to FAA AD 2002‑20‑07 (Background). The Directive also refers to a prior FAA AD: "Note 1. FAA AD 97‑09‑15 R1 Amdt 39‑10912 refers." These references mean the AD acknowledges and defers in part to earlier and contemporaneous FAA directives; in particular, incorporation of the FAA‑mandated modification (AD/B737/201) will relieve an operator from the obligations of this AD.

• Manufacturer documentation: The AD directs operators to the Boeing Maintenance Manual procedures in specified chapters (Chapter 22‑11‑61 or 22‑12‑21 for -100 and -200 series; Chapter 22‑12‑21 for -300, -400 and -500 series) for the procedures to accomplish the inspection and replacement works (Requirement). The AD also references Boeing In‑Service Activities Reports (95‑03‑2725‑10 and 95‑04‑2725‑10) as sources of additional information concerning interchangeability of solenoid valve part numbers (Note 2). By doing so, the Directive embeds the manufacturer’s maintenance standards and interchangeability guidance into the required method of compliance.

• Part numbering and vendor identity: The AD deals with the mapping of Boeing part numbers to vendor part numbers and instructs operators to ascertain vendor part numbers where Boeing part number alone is ambiguous (Note 3). This creates a procedural interaction between an operator’s parts management practices and the maintenance obligations under the AD.

• Termination via modification: The AD makes compliance with another AD (FAA AD 2002‑20‑07) a terminating action for this Directive. This creates an inter‑AD relationship in which the later or broader FAA requirement, once complied with, supersedes the more limited obligations here (Requirement; Background).

The AD does not explicitly refer to civil aviation legislation, administrative law processes, or to CASA’s enforcement powers. Nor does it incorporate or amend statutory provisions. Its interactions are predominantly with other ADs and with manufacturer maintenance manuals and in‑service documents. The Directive therefore operates as a technical, airworthiness maintenance mandate that is linked to manufacturer and foreign regulator documents rather than as an instrument that amends primary legislation within the text provided.

The AD text contains a concise amendment history embedded in its Background and header material.

• Original issue: The original issue of this Airworthiness Directive became effective on 17 July 1997 (Background). The header shows the AD designation AD/B737/110 and indicates Amendment 2 as the present instrument number (AD/B737/110 Amdt 2).

• Amendment 1: The Background states that Amendment 1 "clarified component identification and reflected the requirements of the Country of Origin Aviation Authority." The AD does not provide the date or the detailed text of Amendment 1 in the supplied extract, but it records the subject matter adjustment as identification clarification and alignment with the originating authority’s requirements (Background).

• Amendment 2: The AD being examined is Amendment 2, which the Background says "is issued in response to FAA AD 2002‑20‑07, which requires incorporation of a new rudder control system; which when incorporated, supersedes the requirements of AD 97‑09‑15 R1, the Requirement document of this Directive." The AD records that Amendment 2 becomes effective on 29 September 2005 (Compliance). The instrument bears the signature line "David Punshon, Delegate of the Civil Aviation Safety Authority" dated 19 August 2005.

• Notices and cross references: The AD contains embedded notes that relate to earlier FAA ADs and to Boeing in‑service activity reports: Note 1 references FAA AD 97‑09‑15 R1 Amdt 39‑10912; Note 2 references Boeing In‑Service Activities Report 95‑03‑2725‑10 (for 737‑100 and ‑200 series) and 95‑04‑2725‑10 (for 737‑300, ‑400 and ‑500 series) for additional information about interchangeability of solenoid valve part numbers (Requirement; Note 2).

• Header labelling: The AD header repeats the AD designation and amendment number several times and includes the title "Rudder Yaw Damper Valve Replacement" and the date code "10/2005" (header). These repetition lines indicate the administrative identification and the date of the amendment.

The supplied text therefore documents the Directive’s lineage from the original 1997 issuance, through an intermediate Amendment 1 that clarified component identification, to the present Amendment 2 in 2005 which responded to FAA AD 2002‑20‑07 and acknowledged that compliance with that FAA AD constitutes terminating action for the requirements of this AD (Background; Requirement; Compliance). The AD does not include, within the supplied text, the full wording or dates of Amendment 1 or the prior AD texts, beyond the summary statements recorded in Background and Notes.

The AD as supplied contains no references to litigation, court decisions, or administrative appeals relating to the Directive or its implementation. The text does not report any court challenges, determinations, or statutory litigation linked to the AD. It lists related FAA ADs and Boeing in‑service reports but does not mention any disputes or adjudicated matters.

Given the absence of litigation material in the document, no conclusions about legal challenges, precedents, or judicial interpretation can be drawn from the source text. Practitioners seeking litigation history or case law relevant to enforcement, interpretation, or the technical mapping of part numbers would need to consult separate judicial and administrative records outside this AD, as the supplied instrument includes only the prescriptive and background material for the airworthiness requirement.

The AD contains several concrete operational and identification pitfalls that can create compliance risk if not addressed carefully.

• Shared Boeing part numbers masking vendor difference: Note 3 warns that two different vendor part numbers (a Parker and a Sterer P/N) share the same Boeing P/N 10‑60811‑3. If an operator inspects only the Boeing part number and finds 10‑60811‑3, that alone does not identify whether the installed valve is the Parker P/N 59600‑5007 (which must be replaced) or the Sterer P/N 45080 (which is acceptable) (Note 3). The AD therefore requires ascertainment of the vendor P/N where Boeing P/N 10‑60811‑3 is found. Failure to identify the vendor part number could lead to unnecessary replacement or, conversely, continued operation with an unacceptable valve.

• Incomplete labelling: The AD notes that some engage solenoid valves may be labelled only "Bertea" rather than "Parker" or "Parker‑Bertea" (Note 3). This incomplete labelling can complicate vendor P/N identification and requires additional steps (for example, tracing procurement records or physical inspection) to determine whether the part is an unacceptable Parker part.

• Timing interplay with PCU removal: The AD permits the inspection to be deferred until the next PCU removal if that occurs before the deadline (Compliance). Operators relying on this scheduling flexibility must track PCU removal dates accurately. If an operator miscalculates the five‑year or 15,000‑flight deadline or does not have procedures to flag the PCU removal event as a compliance milestone, they risk missing the deadline.

• Mixed part number lists and cross references: The Requirement and its accompanying Notes reference multiple cross‑mappings of vendor P/Ns to Boeing P/Ns. Operators must ensure that their inventory and procurement systems can handle both vendor and Boeing part numbers, and that the maintenance team uses the vendor P/N to determine compliance obligations.

• Procedural chapter selection by model: The AD points to different Boeing Maintenance Manual chapters depending on series: Chapter 22‑11‑61 or 22‑12‑21 for 737‑100 and ‑200, and Chapter 22‑12‑21 for 737‑300, ‑400 and ‑500 (Requirement). Using the wrong chapter or following the wrong series procedure could lead to improper installation or documentation.

• Termination via other ADs: Compliance with AD/B737/201 (FAA AD 2002‑20‑07) constitutes terminating action for this Directive (Requirement). Operators may assume that meeting FAA AD requirements automatically absolves them under CASA’s AD, but the AD requires actual accomplishment of the FAA AD’s requirements to be accepted as terminating action. Operators need to maintain documentary proof that the FAA AD action has been completed if they rely on that terminating action.

• Ambiguity in "Before further flight": The Compliance block includes a "Before further flight" requirement without specifying which exact circumstance invokes it in the same sentence. The most directly supported reading from the text is that replacement, when required because an unacceptable valve is present, must be effected before further flight. Nevertheless, operators should treat any finding of an unacceptable valve as requiring immediate remedial action consistent with "Before further flight" to avoid unintended continued operation.

• Reliance on Boeing in‑service reports for interchangeability: Note 2 points to Boeing In‑Service Activities Reports for additional interchangeability information. Operators who do not consult these referenced reports risk missing subtleties about which vendor parts are interchangeable. The AD makes those reports part of the informational framework for correct part identification.

Each of these gotchas arises directly from the AD text (Requirement; Note 2; Note 3; Compliance). Addressing them requires attention to vendor‑level part identification, inventory labelling, maintenance scheduling, and documentary proof of terminating modifications.

The AD sets out a precise but narrow compliance pathway. Below are the concrete steps and considerations, grounded in the Directive text.

1. Confirm applicability

   • Determine whether each aeroplane is a Boeing 737-100, -200, -300, -400 or -500 series aircraft (Applicability). If not, the Directive does not apply.

2. Determine whether the work has already been accomplished

   • The Requirement begins "Unless already accomplished". If the one‑time inspection and any necessary replacement have already been performed in accordance with equivalent standards, document the prior work and retain evidence (Requirement).

3. Schedule the inspection

   • The one‑time inspection of the engage solenoid valve must be completed within five years or 15,000 flights after 25 February 1999, or at the next time the PCU is removed for maintenance, whichever is earlier (Compliance). Operators should check flight records, maintenance logs and PCU removal schedules to determine the applicable deadline for each aeroplane.

4. Perform the one‑time inspection

   • Inspect the engage solenoid valve of the yaw damper to determine the vendor part number (Requirement). The AD makes clear the inspection’s purpose is to ascertain the vendor P/N, not merely the Boeing P/N.

5. Ascertain vendor part numbers where Boeing P/N is ambiguous

   • If Boeing P/N 10‑60811‑3 is present, the operator must ascertain the vendor part number because two different vendor P/Ns map to that Boeing P/N and they have different acceptability under the AD (Note 3). If a valve is labelled only "Bertea," additional steps may be needed to trace vendor provenance (Note 3).

6. Replace unacceptable valves

   • If the inspected valve is one of the following Parker vendor part numbers:
     • Parker P/N 59600‑5011 (Boeing P/N 10‑60811‑9);
     • Parker P/N 59600‑5007 (Boeing P/N 10‑60811‑3);
     • Parker P/N 59600‑5003 (Boeing P/N 10‑60811‑1); then replace it with one of the approved valves:
     • Parker P/N 881600‑1001 (Boeing P/N 1060811‑13),
     • Sterer P/N 45080‑1 (Boeing P/N 10‑60811‑8),
     • Sterer P/N 45080 (Boeing P/N 10‑60811‑3). Replacement must be accomplished "in accordance with procedures specified in Chapter 22‑11‑61 or Chapter 22‑12‑21 (for 737‑100 and ‑200 series aircraft) of the Boeing Maintenance Manual as applicable; or Chapter 22‑12‑21 (for 737‑300, ‑400, and ‑500 series aircraft) of the Boeing Maintenance Manual" (Requirement).

7. Observe the "Before further flight" requirement

   • The compliance block states "2. Before further flight." The Directive requires replacement where indicated prior to further flight (Compliance). Treat any discovery of an unacceptable valve as requiring removal and replacement to prevent operation with the non‑compliant part.

8. Use Boeing maintenance procedures

   • Do not improvise installation or inspection procedures. Follow the Boeing Maintenance Manual chapters specified for the relevant series to perform the inspection and replacement tasks (Requirement). Those chapters contain the procedural steps and torque/installation data not reproduced in the AD.

9. Consult Boeing In‑Service Activities Reports for interchangeability guidance

   • Note 2 directs operators to Boeing In‑Service Activities Report 95‑03‑2725‑10 (737‑100/-200) and 95‑04‑2725‑10 (737‑300/-400/-500) for additional information about interchangeability of solenoid valve part numbers. Use those reports to inform whether a given vendor P/N is interchangeable or acceptable.

10. Document and retain evidence of compliance

    • While the AD text does not prescribe specific record formats, operators should document inspection findings (vendor and Boeing P/Ns), replacement work orders, parts serial numbers and procurement traceability, and the maintenance manual procedures followed. If relying on compliance with AD/B737/201 (FAA AD 2002‑20‑07) as terminating action, retain the corresponding modification records to show accomplishment (Requirement).

11. Procurement and parts management steps

    • Ensure procurement systems can order the listed acceptable vendor parts by vendor P/N, and that stores personnel can distinguish vendor P/Ns from Boeing P/Ns. Avoid relying on Boeing P/N alone where Note 3 warns of potential ambiguity. Check incoming parts labels for vendor identifiers or supplier certificates that state the vendor P/N.

12. Consider scheduling synergies

    • Where possible, schedule the inspection to occur at the next PCU removal to take advantage of the AD’s allowance to perform the inspection at that maintenance event, provided it occurs within the five‑year/15,000‑flight window (Compliance). Coordinate with MROs to integrate the inspection/replacement with other maintenance tasks to reduce aircraft downtime.

13. Verify termination options

    • If an operator intends to comply with FAA AD 2002‑20‑07 (AD/B737/201), understand that performance of that AD’s requirements will be treated as terminating action for this Directive, but the operator must actually accomplish the FAA AD’s required modification and retain evidence (Requirement; Background).

By following these steps, an operator can implement the AD’s technical requirements: inspect the engage solenoid valve to determine vendor P/N, replace any disallowed Parker valves with one of the listed acceptable valves, perform work to Boeing maintenance procedures, and meet the specified timing rules (Requirement; Compliance; Note 2; Note 3). The AD’s effective amendment date for the present Amendment 2 is 29 September 2005 and the original issue date is 17 July 1997, which may assist in tracing prior compliance records (Compliance; Background).