Mandatory Service Bulletins: Are they really mandatory?

Mandatory Service Bulletins

Are they really mandatory?

By Joe Escobar

Is a manufacturer's mandatory service bulletin mandatory or not? This topic pops up in hangars regularly and tends to polarize A&P's and IA's alike. They either feel strongly that they are or they are not (with the majority believing they are not). There does not seem to be a middle ground.

Looking to the past
Perhaps the best way to start out this discussion is get a perspective of past regulations and conformance practices. A Charles Taylor recipient from my area shared the following with me about his experiences as an A&E mechanic:

What checklist to use?


According to 14 CFR Part 43, a mechanic or IA needs to use a checklist when performing an annual or 100-hour inspection. If the aircraft manufacturer has a checklist available, must it be used or can a checklist based on Appendix D of part 43 be used? Technically, according to the regulation either one can be used. But consider this: A Baron had a gear up landing. The investigation revealed a failed gearbox. The maintenance records indicated that a checklist based on Appendix D of Part 43 was used to perform recent annuals. The manufacturer's checklist shows the mechanic how to inspect and service the gearbox, while Appendix D of Part 43 does not. The gearbox had more than 3,200 hours without any documented servicing. TBO on the gearbox is 2,000 hours.

"I would go to work about two hours before everyone else, so I stopped by the post office and picked up the mail. The CAA sent out an AD note to registered owners of the same type airplane whenever any serious defect was discovered. The school I worked at had a subscription to the current aircraft specifications from the CAA, and service information from each of the airplane manufacturers, so we could keep our airplanes current. I would sort it all out and read everything with my morning coffee. By the time I was ready for my second cup of coffee, the boys had the airplanes out on the line and I would go out and check each and every one of them before they were flown every day.

I would immediately take care of any write-up a pilot made, and every 25 hours of flight time I would inspect the engine, clean and gap the spark plugs, change the oil and clean the screen, check the tires for wear and proper pressure, and check and lubricate the flight controls. If we received an AD in the mail, I would immediately do whatever the AD said.

Once every 12 months I would bring each airplane into the hangar for a periodic inspection, a very detailed inspection and specification update. I thoroughly cleaned the airplane inside and out, complied with all the current service bulletins and verified that the airplane conformed to its current aircraft specifications. When I was done, I would prepare a periodic inspection report for the CAA safety inspector and he would come out and issue the airplane a new airworthiness certificate."

That Charles Taylor recipient was the source of all knowledge at the small airport where he worked. Everyone looked up to him and respected his judgment, especially the pilots. Only he could say when an airplane was ready to fly. He always says, "Base your decisions on regulations, not on someone else's opinion."

Influences on perception
It is well known that our environment influences our perception. What we are is based on where we were when we started learning. If you take a look around your local FSDO, you may notice that many FAA inspectors have military backgrounds. The military and major airlines are organizations. An organizational background produces organizational thinking and since the organization owns the aircraft, the ownership responsibilities become functional responsibilities within the organization rather than the responsibility of one individual.

Within the military, organizational thinking becomes authoritative thinking. There's a chain of command, and if you're not in the chain of command, you have no authority. Any question becomes a matter of who has the authority.

Within major airlines there are groups such as; operations, maintenance, dispatch, engineering, etc., with each group performing a specific function. Any question becomes a matter of who performs that function. Organizational thinking works great within organizations. It's only when organizational thinking is applied to individuals who are not part of an organization that problems arise. For a person with an organizational background, trying to think outside the organization is like trying to drive on the left side of the road.

Another interpretation-influencing factor is that military aircraft don't have airworthiness certificates. Annually conforming an aircraft to current aircraft specifications is a bizarre concept to a person with a military background. And within the military, manufacturer's representatives are simply advisors. A recent FAA Order said manufacturer's service instructions are advice. Advice is optional and anything that's both costly and optional is frequently not done, especially in today's environment.

The Federal Aviation Regulations are comprehensive, intentionally worded in debatable language, and subject to interpretation. In recent interpretations we see organizational thinking influences such as who has authority and who performs that function.

Authoritative thinking vs. best maintenance practices
Authoritative thinking statement - "Manufacturer's mandatory service bulletins are not mandatory unless they're referred to in an AD."

Years ago, the FAA's position on this subject was on a case-by-case basis. Recently the FAA has recognized a need for standardization and invented Instructions for continued airworthiness. When a manufacturer finds a problem with its product through service experience, it places a service bulletin in the instructions for continued airworthiness, which makes the service bulletin mandatory.

Lets read some regulations that may apply to manufacturers' mandatory service bulletins. The Federal Aviation Act of 58, The Standard Airworthiness Certificate, and Part 21 say standard airworthiness is conformity to the type design and condition for safe operation (Ref. 21.183). But type design is subject to change. Certification basis is grandfathered. Lets look at the regulation for type design changes.

§21.99 Required design changes (b) In a case where there are no current unsafe conditions, but the Administrator or the holder of the type certificate finds through service experience that changes in type design will contribute to the safety of the product, the holder of the type certificate may submit appropriate design changes for approval. Upon approval of the changes, the manufacturer shall make information on the design changes available to all operators of the same type of product.

The manufacturer shall make information on the design changes available to all operators of the same type of product. The manufacturer does so with a mandatory service bulletin.

§43.11 Content, form, and disposition of records for inspections . . .
(b) Listing of discrepancies and placards. If the person performing any inspection required by Part 91 or 125 or §135.411(a)(1) of this chapter finds that the aircraft is unairworthy or does not meet the applicable type certificate data, airworthiness directives, or other approved data upon which its airworthiness depends, that person must give the owner or lessee a signed and dated list of those discrepancies
.

If a mechanic inspects an aircraft, and at the time of that inspection, discovers that the aircraft does not conform to the type design, or other approved data upon which its airworthiness depends, he or she must list it as a discrepancy. Within the military, aircraft inspections are condition inspections, and conformity to the type design is nonexistent. Within major airlines, their fleet management programs often make the manufacturer's mandatory service bulletins look like yesterday's news, and are given to engineering for evaluation. But within general aviation maintenance, the manufacturer is the only source available for authoritative maintenance data, which must be understood (Ref. 65.81) and must be followed (Ref. 43.13).

Best maintenance practices statement - Complying with mandatory service bulletins is common sense. Most mandatory service bulletins become AD notes in due time.

Organizational thinking vs. best maintenance practices
An organizational thinking statement - "AD compliance is a maintenance function." From within an organization, AD compliance is a maintenance function. Without an organization, AD compliance is an owner or operator responsibility. Lets look at the regulations.

§39.3 General. No person may operate a product to which an airworthiness directive applies except in accordance with the requirements of that airworthiness directive.

§91.403 General. (a) The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with Part 39 of this chapter.

§43.11 Content, form, and disposition of records for inspections . . .
(b) Listing of discrepancies and placards. If the person performing any inspection required by Part 91 or 125 or §135.411(a)(1) of this chapter finds that the aircraft is unairworthy or does not meet the applicable type certificate data, airworthiness directives, or other approved data upon which its airworthiness depends, that person must give the owner or lessee a signed and dated list of those discrepancies.

If a mechanic inspects an aircraft, and discovers that an applicable AD has not been complied with, he must list it as a discrepancy. And unless the AD indicates compliance during that inspection, the owner or operator may have already violated Part 39.

A best maintenance practices statement - "The owner or operator is responsible for (Ref. 91.403) and tracks the current status of (Ref. 91.417) AD compliance." However, AD compliance is a safety concern and safety is everybody's business. AD notes are freely available on the Internet and should be read by everyone active in aviation.

In the end, the question of mandatory service bulletins depends on your perspective. Even if authoritative or organizational thinking influences your approach, best maintenance practices should be considered when performing any inspection. After all, it just makes common sense.

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