James D. Seipel Acting Manager , Design , Manufacturing , & Airworthiness Division Aircraft Certification Service Advisory U.S. Department of Transportation Circular Federal Aviation Administration Subject: Service Bulletins Related to Date: 06/16/2014 AC No: 20-176A Airworthiness Directives and Indicating FAA Initiated by: AIR-140 Approval on Service Documents This advisory circular (AC) presents best practices for drafting service bulletins (SB) related to an airworthiness directive (AD). This AC also provides information and guidance on ex parté communication and alternative methods of compliance (AMOC), as well as means for avoiding overlapping and conflicting actions in SBs and maintaining airworthiness of AD-mandated design changes. This revision, AC 20-176A, includes guidance for indicating FAA approval on a service document.
If you have any suggestions for improvements or changes, you may use the template provided at the end of this AC.
Table of Contents
Chapter 1. General Information1
1-1. Purpose1
1-2. Applicability1
1-3. Cancellation1
1-4. Explanation of Changes2
1-5. Background2
1-6. Scope3
1-7. Definitions3
1-8. Discussion4
Chapter 2. User-Friendly Service Bulletins5
2-1. General5
2-2. SB Improvements5
2-3. Standardized Format and Content5
2-4. Safety Intent and Configuration Description7
2-5. Ambiguous Language8
2-6. Notes9
2-7. Figures, Illustrations, and Drawings10
2-8. Logic-based Diagrams10
2-9. Mandatory versus Flexible Language10
2-10. Critical Task Differentiation12
2-11. Streamlining Development and Revision of SBs16
2-12. Ex Parté17
Chapter 3. Avoiding Overlapping and Conflicting Actions in SBs18
3-1. General18
3-2. Tracking and Management Process18
Chapter 4. AMOCs19
4-1. General19
4-2. Sharing AMOCs with DAHs19
4-3. DAH Determination for Global AMOCs19
4-4. Posting Global AMOCs on Website20
4-5. Minimizing AMOC Requests for Part Changes20
4-6. 24/7 AMOC Support20
Chapter 5. Maintaining Airworthiness of AD-Mandated Design Changes22
5-1. General22
5-2. Maintenance of an AD-Mandated Design Change22
5-3. Availability of Maintenance Procedures or ICA22
5-4. Allowing Flexibility23
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Table of Contents (Continued)
5-5. Flagging Procedures23
5-6. SB-to-AD Cross Referencing23
Chapter 6. FAA Approval of Service Documents24
6-1. General24
6-2. FAA-Approval of a Service Document24
6-4. Indicating FAA-Approval24
6-5. Revisions to Service Documents25
Appendix A. Examples of Notes in SBs (1 page)A-1
Appendix B. Examples of Notes that Provide Flexibility in SBs (2 pages)B-1
Appendix C. Examples of Concepts to Clarify Illustrations (4 pages)C-1
Appendix D. Example of Logic-Based Diagrams (1 page)D-1
Appendix E. Related FAA Publications (1 page)E-1
Appendix F. Acronyms (1 page)F-1
Appendix G. Advisory Circular Feedback Information (1 page)G-1
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Chapter 1. General Information
1-1. Purpose.
a. This advisory circular (AC) provides:
(1) Best practices and recommendations for design approval holder (DAH) for developing service bulletin (SB) descriptive data to resolve an unsafe condition, including guidance for:
(a) Avoiding overlapping and conflicting information in SBs, and
(b) Maintaining compliance with an airworthiness directive (AD)-mandated design change.
(2) Guidance for owners and operators to share alternative methods of compliance (AMOC) with DAHs, as well as recommendations for DAHs to:
(a) Review Federal Aviation Administration (FAA)-approved AMOCs to determine whether they are candidates for global AMOCs;
(b) Consider a process for posting global AMOCs on the DAH website;
(c) Help minimize the number of AMOC requests to an AD requiring part changes; and
(d) Develop a process for 24/7 AMOC support.
(3) References for industry-wide guidance on ex parté communication in AD activities.
(4) An acceptable means, but not the only means, for indicating FAA approval of engineering data in a service document.
b. The guidance in Chapters 2 through 5 is derived from FAA and industry experience on SBs related to ADs and AMOCs. While it is not mandatory, implementation of any, or all, aspects of this AC will enhance the AD process, facilitate continued compliance with an AD, minimize the need for AMOCs, and reduce the potential for fleet-wide AD compliance issues that could disrupt air transportation. This AC describes an acceptable means, but not the only means, for drafting SBs related to ADs.
1-2. Applicability. This AC is for manufacturers who draft service documents, including DAHs of aircraft, aircraft engines, propellers, and appliances who draft SBs that are, or will be, associated with an AD. The AC is also for owners and operators who must comply with an AD, or request approval of an AMOC.
1-3. Cancellation. This AC cancels:
a. AC 20-176, Design Approval Holder Best Practices for Service Bulletins Related to Airworthiness Directives, dated December 19, 2011.
b. AC 20-114, Manufacturers’ Service Documents, dated October 22, 1981.
1-4. Explanation of Changes. This revision includes the following changes:
a. Provides a definition for FAA designee and service documents as used in this document (see paragraphs 1-8c and 6-2a).
b. Clarifies guidance for referring to other documents in an SB (see paragraphs 2-3b(2) and 2-3c).
c. Clarifies when to use the required for compliance (RC) label (see paragraph 2-10e(3)).
d. Adds new guidance related to revising or changing an SB with the RC label (see paragraph 2-10f).
e. Clarifies ex parté guidance (see paragraphs 2-12a and 2-12b).
f. Revises guidance for later-approved parts to align with FAA Order 8110.117, Service Bulletins Related to Airworthiness Directives (see paragraphs 4-5c, 4-5d, and 4-5e).
g. Adds guidance regarding the information a DAH must submit to the FAA or organization designation authorization (ODA) to use later-approved parts without an AMOC (see paragraph 4-5d).
h. Adds a new chapter 6 to include guidance previously addressed in AC 20-114 for approval of service documents.
1-5. Background.
a. In early March and April 2008, events of suspected noncompliance with ADs prompted the FAA to establish an AD Compliance Review Team (AD CRT) consisting of FAA and industry subject matter experts. The team reviewed compliance issues related to AD 2006-15 15, McDonnell Douglas Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC 9-87 (MD-87), and MD-88 Airplanes (Task 1), and the general process for developing and implementing ADs for commercial airplanes (Task 2).
b. The AD CRT documented its findings and recommendations from the Task 2 review in a report1 that focused on the process of developing and implementing ADs, as well as ensuring compliance by owners and operators. The recommendations do not fundamentally change the AD process, but provide suggested enhancements and improvements. The response to some of those recommendations is addressed in this AC (i.e., Recommendation Nos. 1 and 9, and parts of Recommendation Nos. 3 and 4).
1 Process Review Technical Report – A review of the Title 14, Code of Federal Regulations, part 39 airworthiness directives process for commercial airplanes, dated July 8, 2009.
c. The AD CRT’s report acknowledged that the AD-friendly SB initiative,2 developed in 2001 between the FAA and a commercial transport airplane DAH, has improved the format and quality of SBs specified in ADs as the appropriate source of compliance information. By applying agreed-upon principles for writing SBs (e.g., standardized format/location of information, use of acceptable terminology, etc.), SBs can be referenced as the primary source of information for product applicability, compliance times, and key actions in an AD in lieu of rewriting the SB information in the AD itself.
1-6. Scope. This AC, except Chapter 6, addresses only SBs that are, or will be, referenced in an AD as an additional source of information about the unsafe condition, or as a document that will be incorporated by reference (IBR’d) in an AD. Development of SBs for other purposes is outside the scope of this AC. Chapter 6 applies to all service documents, including those not related to an AD.
1-7. Definitions. For the purposes of this AC, the following definitions are used:
a. AD Action. One of the following types of rulemaking documents issued under Title 14 of the Code of Federal Regulations (14 CFR) part 39 by the FAA, including supersedures, revisions, and corrections to those documents:
(1) Notice of Proposed Rulemaking (NPRM), including a supplemental NPRM (SNPRM);
(2) Final rule after NPRM or SNPRM;
(3) Final rule, request for comments (i.e., Immediately Adopted Rule (IAR), No-Notice Final Rule (NFR), or Federal Register Version of an Emergency AD (FRV)); or
(4) Emergency AD.
b. Drawing. A document created to define a configuration. Drawings may include other engineering information such as specifications, dimensions, materials, and processes.
c. FAA Designee. A designated engineering representative (DER) or a unit member (UM) for an ODA holder who has been delegated authority to approve or recommend approval of engineering technical data on behalf of the FAA.
d. Figure. An illustration, photograph, chart, graph, table, form, note, symbol, callout, text, or dimension (or any combination thereof) that supports or clarifies the written instructions.
e. Global AMOC. An AMOC of general applicability that applies to two or more owners or operators.
2 “Agreed Principles and Practices on AD Friendly Service Bulletins Between the Seattle Aircraft Certification Office (SACO), Los Angeles Aircraft Certification Office (LAACO) and Boeing Commercial Airplanes,” dated March 31, 2006.
f. Illustration. A pictorial graphic.
g. IBR. A method of referring to material already published elsewhere instead of publishing it directly into an AD. Documents IBR’d in an AD become part of the AD. The FAA must obtain approval from the Office of the Federal Register (OFR) to IBR material, including an SB or portion of an SB, in an AD.
h. Product. An aircraft, aircraft engine, propeller, and appliance.
i. RC. A method of notating which steps in an SB must be completed for compliance with an AD. Steps with the RC notation have a direct effect on detecting, preventing, resolving, or eliminating the unsafe condition identified in an AD.
j. SB. Document used to convey service information to owners and operators of products
(e.g., modifications, inspections, etc.).
1-8. Discussion.
a. The FAA issues an AD when an unsafe condition is found to exist in a product and the condition is likely to exist or develop in other products of the same type design.
(1) The action(s) specified in an AD are intended to detect, prevent, resolve, or eliminate the unsafe condition. Those actions can either be written directly into the regulatory portion (“body”) of the AD, or another document such as an SB can be IBR’d. Compliance with an SB, or a portion of an SB, that is IBR’d in an AD is mandatory.
(2) An AD might also refer to an SB as an additional source of information about the subject of the AD. These SBs are not submitted for IBR approval; therefore, reference to these SBs does not constitute a regulatory requirement and accomplishing the action(s) in the SB is not required for compliance with the AD.
b. It is the owners/operator’s ultimate responsibility to ensure that FAA approval was obtained if FAA approval is required before using the advice, recommendations, alterations, repairs, etc., prescribed in service documents. For this reason, it is desirable for the DAH to assist the owner and operator by indicating in the body of service documents specifically what information was approved by the FAA or its designees.
Chapter 2. User-Friendly Service Bulletins
2-1. General. This chapter provides best practices and recommendations on how DAHs can improve the quality and usability of SBs associated with an AD action. It also provides guidance for streamlining the SB development and revision processes for such SBs, and provides references for where to find information on ex parté communication.
2-2. SB Improvements.
a. An SB that may be referenced in an AD as an additional source of information about the unsafe condition or IBR’d in an AD, should be written so owners and operators can understand and follow the accomplishment instructions. The following SB improvements will be discussed further in this chapter:
(1) Providing a standardized format and structure so the reader can easily locate important information on effectivity, compliance times, and accomplishment instructions (see paragraph 2-3).
(2) Including a clear and concise description of the safety intent of the SB as well as a precise description of the new configuration that removes the unsafe condition (see paragraph 2-4).
(3) Writing clear, concise, and unambiguous technical instructions that minimize the possibility of omission, error, or extensive judgment (see paragraphs 2-5 and 2-6).
(4) Giving clear, detailed illustrations appropriate to the task, and that help the user understand how to sequence and accomplish the tasks and/or steps (see paragraphs 2-7 and 2-8).
(5) Allowing use of industry standards or practices acceptable to the FAA (see paragraph 2-9).
(6) Differentiating critical tasks and task sequences requiring exact conformance from tasks that can be flexible, advisory, or common acceptable procedures (see paragraph 2-10).
(7) Streamlining the SB development and revision processes (see paragraph 2-11).
b. The concepts presented in this AC apply to development of new or revised SBs and are not intended to be applied retroactively, except when deemed necessary by the DAH and FAA (see paragraph 2-4b).
2-3. Standardized Format and Content.
a. The format and content of an SB should follow industry specifications for technical documents. Refer to the following documents:
(1) Air Transportation Association (ATA) Spec 2200, Information Standards for Aviation Maintenance.
(2) S1000D, International Specification for Technical Publications.
b. The accomplishment instructions in an SB should address resolving the unsafe condition identified in the AD. S ometimes, however, procedures are already published in other DAH documents which accomplish this goal. As such, the following guidelines are provided to help determine what procedures should, or should not, be included in an SB:
(1) When appropriate, include the following types of procedures in the SB:
(a) Inspection or test procedures that do not exist in a published DAH document available to other parties.
(b) Critical requirements in procedures that exist in manuals that are not FAA- approved (e.g., torque values, gap measurements, electrical bonding, etc.). List in the SB the critical requirements that must be met to comply with a planned AD and refer to the procedure in the manual that is not FAA-approved as an accepted procedure to achieve those requirements (see paragraph 2-9).
(c) Revised procedures when the original procedure(s) are in error.
(2) Do not duplicate (e.g., copy) the following types of procedures in an SB if affected owners and operators have the procedures in other documents (see paragraph 2-3c below). Instead of repeating the procedure, refer to the other document(s) for that task. F or example:
(a) Procedures that exist in other documents accessible by other parties (e.g., DAH SBs/manuals, component SBs, and supplier SBs).
(b) Common industry practices, including, but not limited to, the Standard Overhaul Practices Manual (SOPM) and Standard Wiring Practices Manual (SWPM).
(c) Tests for all components or systems that may be disturbed during incorporation of an SB. An SB should specify only the testing necessary to ensure the new or modified system operates as intended after the modification is complete (i.e., unsafe condition is resolved). Any additional functional tests that may be necessary due to an interruption to other airplane systems can be addressed in a note in the SB (see appendix A, paragraph 5).
c. For a requirement to use other documents to be enforceable, the affected operators must have actual notice of them. As such, before relying on references to other documents in SBs that will be IBR’d, confirm that affected operators actually have the referenced document.
d. If an SB uses mandatory language (e.g., “use,” “in accordance with”) to reference another document for completing a task required for compliance with an AD (reference paragraphs 2-9 and 2-10), include the revision level and date of the other document(s) within the SB. To prevent the need for an AMOC approval each time the revision level changes in the document referenced in the SB, the phrase "or later approved revision" may be added when specifying the revision level.
e. Use the following guidelines to refer to other document(s) in an SB:
(1) Specify the specific section(s) of the document that are applicable. Do not provide a blanket reference to the other document if only portions of the other document are applicable.
(2) Do not refer to documents that simply refer to other documents. Instead refer to the end document that provides the actual instruction.
(3) Do not refer to documents that do not provide sufficient information to perform the task (e.g., “Cad plate per SOPM AA-XX-YY” if document SOPM AA-XX-YY does not specify the type of cad plating for the specific part).
2-4. Safety Intent and Configuration Description.
a. When drafting an SB that might be IBR’d in an AD, the SB should contain a paragraph entitled “Safety Intent.” For ADs that will change the configuration of a part (e.g., a design change), a “Configuration Description” paragraph is also required. Place the paragraphs next to one another upfront in the SB (e.g., after the “Reason” paragraph). These paragraphs are intended to enhance and focus awareness of the safety issue during the development and approval of the SB as well as during implementation and subsequent maintenance.
(1) The “Safety Intent” paragraph should explain what accomplishment of the SB is intended to do (i.e., prevent, resolve, or otherwise remove the unsafe condition). T he description should be a succinct and clear statement of the specific technical objective of the instructions. For example, “The safety intent of this SB is to prevent electrical arcing between a wire bundle and control cables in the main wheel well, which, if not corrected, could cause a hydraulic or electrical fire.” The goal is to explain in technical terms what the affected part and failure mode or malfunction is, and how it will be prevented, resolved, or otherwise removed by accomplishing the SB. This differs from the “Reason” paragraph in most SBs, which typically provide the history and reason for taking the SB action.
(2) If accomplishing the SB will change configuration, a “Configuration Description” paragraph should be included that provides a succinct, high-level description of the design change that will result from accomplishing the instructions. For example, “Incorporating this SB results in installing a new wire bundle (P/N 123456) between the J135 and J234 connectors, and installing several standoffs of increased length to hold the wire bundle clear of contact.”
The “Configuration Description” should:
(a) Be limited to the features that will prevent development or recurrence of the unsafe condition, once the configuration has been implemented. The paragraph can provide the greatest value in SBs that specify ‘high risk’ modifications (e.g., instructions that are complex, workmanship intensive, or susceptible to reversal in operations).
(b) Assist in understanding the post-installation mandated configuration. The “Configuration Description” may guide, but cannot be used as the final determinant of compliance with an AD.
(c) For an AD that will require installation of a different part, the part number of the new part should differ from that of the original. If changing the part number (i.e., “rolling” the part number) is impractical, identify the “modification level” of the part. The configuration description for this case should control the part by the “modification level” in addition to the part number identification.
(d) Identify a specific part, sub-assembly, or assembly of a component affected by the safety intent. An affected component “part number” may contain both “good” and “bad” parts, sub-assemblies, or assemblies. But because the part number of the component might not have been changed or “rolled” to differentiate the configurations, identification using the component part number alone is inadequate. Therefore, the configuration description for such a case should control the specific parts, sub-assemblies, or assemblies in addition to the part number identification of the affected component.
b. For SBs originally written for reliability or economic enhancements that subsequently are found to provide correction of a safety issue, those SB should be revised to include the “Safety Intent” and “Configuration Description” paragraphs per the guidance in this AC.
2-5. Ambiguous Language.
a. Avoid unclear and confusing terms when writing an SB. See table 1 below for examples of ambiguous language used in SBs and how to rewrite them for clarity.
Table 1. Examples of Ambiguous and Unambiguous Language Instead of … Use … The sensor may not operate properly in cold temperatures The sensor may not operate properly in cold temperatures below 32 degrees Fahrenheit (0 degrees Celsius) Apply sealant as necessary Apply firewall sealant in gaps, holes, or voids in the nacelle strut door assemblies of the engines Make sure there is adequate clearance Inspect for minimum one inch clearance between wires Look for unsatisfactory elongation of holes Inspect bolt holes in the horizontal stabilizer for elongation.
See Table 1 for acceptable limits for bolt holes.
When in the area, inspect for … Inspect the right main landing gear wheel well for arcing damage Inspect for discrepancies Inspect for frayed wires, incorrect clearance or evidence of chafing
b. To prevent the use of ambiguous language in SBs, each DAH should develop guidance for using unambiguous language and consider implementing one or more of the following items:
(1) Training. Provide training to authors of SBs to stress the adverse impact of using ambiguous terms and the importance of providing clarity and accuracy.
(2) Tools. Use computing tools or checklists to prevent, or search for and eliminate ambiguous terms.
(3) Processes. Implement processes during the authoring, review, validation, and 8
DAH internal approval of SBs that will prevent the use of ambiguous terms.
(4) Draft Review. For SBs related to transport airplanes or engines installed thereon, implement a process during validation to allow the draft SB to be reviewed by the lead airline (see paragraph 2-11c(8)) so that ambiguous terms can be eliminated prior to issuance of the SB.
2-6. Notes.
a. Notes in SBs generally provide information related to the accomplishment of instruction steps. However, notes are informational only, and since they are generally unenforceable, they should not contain any requirements. Authors, therefore, are strongly encouraged to review notes to ensure they do not contain any critical step(s) for accomplishing the corrective action(s).
b. Unless specified otherwise, notes apply to figures, illustrations, and drawings within the SB. Refer to appendix A for examples of notes that can be used in SBs.
c. When possible, write notes such that the SB user has an acceptable level of flexibility to accomplish the tasks (e.g., specify alternative materials; allow acceptance to use other approved methods, techniques and practices, etc.). Refer to appendix B for examples.
d. If referring to other documents within an SB, ensure that the notes specified in the referenced document do not conflict with notes in the SB. If there is a conflict, add a note in the SB to specify which note takes precedence.
e. For SBs related to transport airplanes or engines installed thereon, seek lead airline review of the notes (reference paragraph 2-11c(8)) so that those who will be implementing the SB have an opportunity to make suggestions as necessary.
f. Notes should be placed at the beginning of the accomplishment instructions or adjacent to the relevant information (e.g., figure, illustration, etc.), as appropriate, and may include items such as:
(1) Referring to a list or document of acceptable alternative parts, materials, and processes;
(2) Specifying or referring to other documents for standard tolerances and dimensions;
(3) Providing warnings and cautions that apply to the entire set of accomplishment instructions;
(4) Specifying standard practices that apply to the entire set of accomplishment instructions;
(5) Providing definitions for inspections specified in the service information; and
(6) Referring to DAH maintenance documentation.