Are Service Bulletins Mandatory? Manufacturer Data, ADs and the A&P Oral

October 27, 2026 · Primary sources checked October 27, 2026

Service bulletins are not automatically mandatory merely because a manufacturer labels them that way. The applicable airworthiness directive, operating rule, or authorized inspection-program requirement determines the obligation. When answering “are service bulletins mandatory?” for the Airframe and Powerplant (A&P) oral and practical (O&P) test, identify that authority before giving a yes-or-no answer.

FAA, Service Bulletins and the Aircraft Owner, AFS-850 20-04, PDF 1 (no printed page number), If Service Bulletins are not Mandatory, Can I Ignore Them? · FAA-H-8083-30B, Aviation Maintenance Technician Handbook–General (2023), printed 2-33, PDF 82, Service Bulletins (SB) · 14 CFR §39.27 · 14 CFR §91.403(c)

Who issued the document, and what does it do?

Aircraft manufacturers issue service bulletins (SBs); the Federal Aviation Administration (FAA) issues airworthiness directives (ADs). The FAA safety fact sheet Service Bulletins and the Aircraft Owner describes SBs as information about safety, maintenance, and product improvement. The same sheet calls ADs legally enforceable regulations under 14 CFR part 39.

FAA, Service Bulletins and the Aircraft Owner, AFS-850 20-04, PDF 1 (no printed page number), Are Service Bulletins the Same as Airworthiness Directives? · 14 CFR §39.3

The Aviation Maintenance Technician Handbook–General says SBs are good information that an owner should strongly consider implementing. The handbook says SBs are not required unless they are referred to in an AD note or compliance is required as part of the authorized inspection program. Keep “should strongly consider” distinct from a requirement to comply.

FAA-H-8083-30B, Aviation Maintenance Technician Handbook–General (2023), printed 2-33, PDF 82, Service Bulletins (SB)

Follow the AD when service instructions are incorporated

Section 39.27 explains that when an AD incorporates a manufacturer’s service document by reference, that document becomes part of the AD. The AD may modify the document’s directions. If the two conflict, you must follow the AD requirements.

14 CFR §39.27

Our study advice: when a directive names a bulletin, read exactly what the directive requires, including the identified revision and any exceptions. Do not assume the bulletin’s newest edition or every recommendation in its pages has automatically become the AD requirement. The governing language is in the applicable directive.

Part 91 includes other controlling requirements

Section 91.403(a) places primary airworthiness responsibility, including Part 39 compliance, on the owner or operator. Section 91.403(c) also addresses aircraft whose manufacturer’s maintenance manual or instructions for continued airworthiness (ICA) contains an Airworthiness Limitations section. No person may operate such an aircraft unless the mandatory replacement times, inspection intervals, and related procedures in that section, or the alternatives the paragraph specifies, have been complied with.

14 CFR §91.403(a) · 14 CFR §91.403(c)

The alternatives in §91.403(c) are those set forth in an Administrator-approved operations specification under Part 121 or 135, or in accordance with an inspection program approved under §91.409(e). The paragraph covers the Airworthiness Limitations section of a manufacturer’s maintenance manual or ICA and does not mention service bulletins. A general statement that “Part 91 makes everything optional unless there is an AD” leaves out that rule.

14 CFR §91.403(c)

Section 43.13(a) separately requires a maintenance performer to use the methods, techniques, and practices in the current manufacturer’s maintenance manual or ICA, or other methods, techniques, and practices acceptable to the Administrator, except as §43.16 provides. The rule also requires the tools, equipment, and test apparatus needed to complete the work under accepted industry practices. The FAA’s Siilats letter reads the “acceptable to the Administrator” option to mean a maintenance provider is not bound to follow only the manufacturer’s maintenance information, so long as what is used is acceptable to the FAA.

14 CFR §43.13(a) · FAA Siilats legal interpretation, December 3, 2015, printed 3, PDF 3, Section 43.13 discussion

An operator’s inspection program needs a specific answer

The FAA’s December 3, 2015 Siilats interpretation addresses a manufacturer-recommended inspection program selected under §91.409(f)(3). The letter’s answer is that maintenance service bulletins incorporated in that program are not mandatory, except for the parts, if any, that contain inspection requirements and were included in the program when the owner or operator adopted it. If the FAA has mandated a bulletin by rule, such as an AD, compliance would also be mandatory. Once selected, that program remains the one the owner or operator must follow, regardless of any later manufacturer revision, unless the revision is mandated by an FAA-issued AD or other FAA rule. Other maintenance practices in the program, such as how to repair or replace items, including references to service bulletins, are not considered mandatory by the FAA unless an AD or other FAA rule requires them.

FAA Siilats legal interpretation, December 3, 2015, PDF 1 (no printed page number), Opening answer on §91.409(f)(3) · FAA Siilats legal interpretation, December 3, 2015, printed 2, PDF 2, Selected program and later revisions · FAA Siilats legal interpretation, December 3, 2015, printed 3, PDF 3, Other maintenance practices

The letter’s footnote 1 says its reasoning, that manufacturer maintenance service bulletins are not part of the inspection program, also applies to aircraft inspected under §91.409(a) and (b), the annual and 100-hour inspections. The footnote also warns that the reasoning may not apply to §91.409(f)(1) or (2) programs used by Part 121 or 135 operators, because those programs may require the operator to follow and comply with later-issued revisions and, sometimes, manufacturer-issued service bulletins. The FAA says “may”; a blanket statement that every SB is mandatory for all Part 121 or 135 aircraft would go beyond that source.

FAA Siilats legal interpretation, December 3, 2015, PDF 1 (no printed page number), Footnote 1

A one-sentence O&P rehearsal answer

The Airman Certification Standards (ACS) list manufacturer publications, including service bulletins, in AM.I.I.K11, and include compliance requirements for manufacturer-specified methods, techniques, and practices in AM.I.I.K13, and manufacturer-specified maintenance and inspection intervals in AM.I.I.K14. A useful rehearsal distinguishes the kind of requirement before explaining its source.

FAA-S-ACS-1, Aviation Mechanic General, Airframe, and Powerplant Airman Certification Standards, printed 14, PDF 19, AM.I.I.K11 · FAA-S-ACS-1, Aviation Mechanic General, Airframe, and Powerplant Airman Certification Standards, printed 14, PDF 19, AM.I.I.K13 · FAA-S-ACS-1, Aviation Mechanic General, Airframe, and Powerplant Airman Certification Standards, printed 14, PDF 19, AM.I.I.K14

Our sample answer: “A service bulletin is mandatory for this aircraft only to the extent an applicable AD, operating requirement, or its authorized inspection program requires compliance, so I would identify that authority and the required action.” Follow with the actual directive, limitation, or program provision when the scenario supplies one.

A manufacturer’s “Mandatory,” “Alert,” or “Emergency” heading emphasizes a significant safety concern. The FAA safety sheet says never to ignore service bulletins when safety is involved and specifically says not to ignore recommended or optional SBs. Evaluate the safety information even when the regulatory answer does not require that bulletin’s implementation.

FAA, Service Bulletins and the Aircraft Owner, AFS-850 20-04, PDF 1 (no printed page number), If Service Bulletins are not Mandatory, Can I Ignore Them? · FAA, Service Bulletins and the Aircraft Owner, AFS-850 20-04, PDF 1 (no printed page number), Opening paragraph · FAA, Service Bulletins and the Aircraft Owner, AFS-850 20-04, PDF 2 (no printed page number), If Service Bulletins are not Mandatory, Can I Ignore Them?

The Siilats letter says that if inspection of an item addressed by a service bulletin shows the item is not airworthy, corrective action must be taken to remedy the discrepant condition before the aircraft may be approved for return to service and operated. In many cases, following the manufacturer’s maintenance manual, including an applicable service bulletin, may be the most expedient resolution, but the letter says the maintenance provider may use other methods, techniques, and practices acceptable to the FAA, so long as the resulting product is at least equal to its original or properly altered condition. A bulletin’s advisory status does not authorize operating with the unairworthy condition.

FAA Siilats legal interpretation, December 3, 2015, printed 4, PDF 4, Correcting an unairworthy condition

Related guides

• AD applicability and compliance records
• Reading the type-certification reference
• Regulatory requirements for maintenance
• Matching a question to its source

Primary sources

• FAA, Service Bulletins and the Aircraft Owner, AFS-850 20-04
• FAA-H-8083-30B, Aviation Maintenance Technician Handbook–General (2023)
• 14 CFR §39.27
• 14 CFR §91.403(c)
• 14 CFR §39.3
• 14 CFR §43.13(a)
• FAA Siilats legal interpretation, December 3, 2015
• FAA-S-ACS-1, Aviation Mechanic General, Airframe, and Powerplant Airman Certification Standards
• FAA Mechanic Test Generator FAQs, updated May 22, 2023

Before the oral

Rehearse without references: the FAA Mechanic Test Generator (MTG) FAQs say the applicant is not allowed to use reference material during the oral. Explain why a requirement applies, not just whether a bulletin has bold lettering. The FAQs say each oral test adds one question for every ACS code missed on the knowledge test and has a minimum of four randomly generated questions in each section: General, Airframe, and Powerplant. Our advice: start with the ACS codes on your Airman Knowledge Test Report (AKTR), then add questions that test the boundaries of your answer.

FAA Mechanic Test Generator FAQs, updated May 22, 2023, PDF 3 (no printed page number), Oral-related Questions / How is the oral portion of the test changing? · FAA Mechanic Test Generator FAQs, updated May 22, 2023, PDF 4 (no printed page number), Oral-related Questions

Practice the mandatory-or-advisory explanation.

About this guide: drafted with AI from the FAA sources listed on this page and checked claim by claim against them. Not reviewed by an A&P mechanic or DME. How we make our guides