Aircraft manufacturers issue 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 should never be ignored, the FAA Safety Team (www.FAASafety.gov) advises in this recent guidance.

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 (AD). 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.

Are service bulletins the same as airworthiness directives?
No. The FAA issues ADs and aircraft manufacturers issue service bulletins. 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 service bulletins 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:

• Inform you about the manufacturer’s recommended inspection and maintenance items for your aircraft.
• Help you detect trends and spot weaknesses.
• Advise you about items that may be wearing faster than anticipated or items that you or your mechanic might overlook.

When a service bulletin 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 service bulletins can also get included in an AD as an additional source of information about the unsafe condition. If a service bulletin is included in an AD, then compliance with that service bulletin is mandatory for continued airworthiness.

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

Make it a best practice to read, or ask your mechanic to review, any service bulletin 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 service bulletin 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 
On July 7, 2017, a Cessna T337 Skymaster with faulty fuel gauges made a forced landing in a wooded area near Greenwood County Airport (GRD) in Greenwood, South Carolina, after running out of fuel. Textron Aviation published a mandatory service bulletin 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 hrs. of operation and subsequent recurring inspections every 12 months. 

Examination of the airplane’s maintenance logbooks revealed no evidence of compliance with the mandatory service bulletin. The aircraft was a total loss. Fortunately, the pilot and passenger survived with minor injuries, but it could have been much worse.

Where can I find service bulletins for my aircraft?

Service bulletins are available for free online. Take a look at any engine or airframe manufacturer’s website and you will 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 at https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/MainFram…. 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 service bulletins with your mechanic.