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Service Bulletins and the Aircraft Owner

#FlySafe GA Safety Enhancement Topic

FAA Safety Briefing
Cleared for Takeoff
5 min readSep 13, 2021

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Manufacturers issue aircraft Service Bulletins to inform owners and operators about critical and useful information on aircraft safety, maintenance, or product improvement. Compliance with Service Bulletins may or may not be mandatory, but you should never ignore them when it comes to safety.

Service Bulletin ad.

Are Service Bulletins Mandatory?

The short answer is — it depends. If you are operating your aircraft under 14 CFR part 91, a service bulletin is advisory, and compliance is not mandatory unless it is included in an Airworthiness Directive. Keep in mind that even when a service bulletin is not mandatory, you should always pay attention to it as a means to ensure your safety. Let’s unpack this further.

Are Service Bulletins the Same as Airworthiness Directives?

No. The FAA issues Airworthiness Directives (AD) and aircraft manufacturers issue Service Bulletins (SB). ADs are legally enforceable regulations, in accordance with 14 CFR part 39, to correct an unsafe condition that exists in a product. Compliance with an AD is mandatory for continued airworthiness.

Manufacturers issue aircraft Service Bulletins in response to identified maintenance and manufacturing defect issues to give owners and operators critical and useful information about aircraft safety, maintenance, or product improvement. Compliance may or may not be required depending on the type of operation and whether or not it is included in an AD.

If Service Bulletins Are Not Mandatory, Can I Ignore Them?

No. Manufacturers issue SBs to call attention to improvements you should make to enhance your safety. It is also just good sense to heed the advice of the aircraft manufacturer who is providing important information about your aircraft.

Service Bulletins may contain instructions on cylinder torque specs. These photos show the result of a fatigue failure of the №2 cylinder studs and through bolts and the fracture of the crankcase that led to the loss of engine power, which could have been prevented by following the instructions from the manufacturer.
Service Bulletins:1) Inform you about the manufacturer’s recommended inspection and maintenance items for your aircraft.2) Help you detect trends and spot weaknesses.3) Advise you about items that may be wearing faster than anticipated or items that you or your mechanic might overlook.

When a SB displays the words “Mandatory,” “Alert,” or “Emergency” in big red letters, it is emphasizing a significant safety concern, and manufacturers may ask the FAA to issue a specific AD to address the unsafe condition. These mandatory SBs can also get included in an AD as an additional source of information about the unsafe condition. If a SB is included in an AD, then compliance with that SB is mandatory for continued airworthiness.

Examples of different types of Manufacturer Service Bulletins.
Examples of different types of manufacturer Service Bulletins.

However, do not ignore “recommended” or “optional” SBs. Take note and ask your mechanic to check these items during inspection.

Service Bulletins call attention to improvements you should make to enhance your safety. Do not ignore them.

Make it a best practice to read, or ask your mechanic to review, any SB that the manufacturer issues for your aircraft. If cost is a concern, discuss this with your mechanic to determine the best course of action. The SB may only be reporting a product improvement that does not affect airworthiness or your safety.

Here’s What Can Happen If You Ignore a Service Bulletin

Photos of the Cessna T337 crash.

On July 7, 2017, a Cessna T337 with faulty fuel gauges crashed in a wooded area after running out of fuel. Textron Aviation published a mandatory SB that required inspection of the fuel quantity indicating system to verify that each fuel gauge showed the precise fuel amount. It also required an initial inspection within 100 hours of operation and subsequent recurring inspections every 12 months. Examination of the airplane’s maintenance logbooks revealed no evidence of compliance with the mandatory SB. The aircraft was a total loss. Fortunately, the pilot and passenger survived with minor injuries, but it could have been much worse. They learned an expensive lesson about the importance of SBs.

Where Can I Find Service Bulletins For My Aircraft?

Image of Continental Aerospace Tehnology’s Service Bulletin website.
Screenshot of a manufacture’s Service Bulletin database.

SBs are available online, and they are free. Take a look at any engine or airframe manufacturer’s website and you’ll find up to date information on the safety issues identified from accident reports, service difficulty reports, and any other data used for safety analysis and product improvement.

You can also find information, guidance, recommendations, and airworthiness concerns for your aircraft free of charge in the FAA’s Special Airworthiness Information Bulletin (SAIB) database. It is searchable by SAIB number or by aircraft make and model. Subscribe and get the latest ADs and SAIBs delivered straight to your inbox.

Service Bulletins are a great way to stay informed about product improvements and safety issues that affect your aircraft. Take an active role in maintenance by reviewing inspection results and discussing ADs and SBs with your mechanic.

Watch Service Bulletins in 57 Seconds

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FAA Safety Briefing
Cleared for Takeoff

Official FAA safety policy voice for general aviation. The magazine is part of the national FAA Safety Team (FAASTeam).