Part 43: Our Rule: Written by mechanics for mechanics

July 1, 2004
Of the 199 Parts and a zillion words that make up FAA regulations in Chapter 1 of Title 14, Aeronautics and Space in the Code of Federal Regulations, only one Part speaks solely to us

Of the 199 Parts and a zillion words that make up FAA regulations in Chapter 1 of Title 14, Aeronautics and Space in the Code of Federal Regulations, only one Part speaks solely to us, mechanics. Part 43 is that rule. It sets the requirements for what kinds of U.S. registered aircraft we can work on, who can work on the aircraft, who can sign off the aircraft’s logbook; it defines our performance rules and record keeping.

If you permit me to wax metaphorically, Part 43, Maintenance, Preventive Maintenance, Rebuilding and Alteration, is one of the three core regulations or foundation stones that set the standards for our aviation industry. The other two are Part 21, Certification Procedures for Products and Parts, and Part 91 General Operating and Flight Rules. These three rules achieved "star status" because they are the only regulations identified on the FAA Form 8100-2 Standard Airworthiness Certificate. But star status aside, what is even more amazing is the fact that Part 43 contains only 13 rules and six appendixes. That is all the regulation it takes to set the airworthiness maintenance requirements for performing work on 185,000 U.S.-registered aircraft.

43.13: Performance Rule

For the next three minutes of your time, I would like to cover just one rule in Part 43. It’s section 43.13, Performance Rule. I picked this rule because it uses only three paragraphs to set the standards for the work we perform. It is also the one rule that is quoted 95 percent of the time in the Letter of Investigation sent by the FSDO to some hapless mechanic who is accused of noncompliance of the regulations.

The rule, section 43.13 Performance rules (general), is an old rule going back almost 60 years. It even predates the FAA and the Federal Aviation Regulations (FAR). How can I tell? Easy, the rule number 43.13 has an odd number suffix. When the FAA took over from the Civil Aeronautics Administration on April 1, 1958, the FAA immediately began to re-codify the old Civil Aviation Regulations into the new FAR format. Even back in the good old days, any new rulemaking had a lot of legal hoops to jump through. So it is not surprising that it took eight years until all the rules were changed over. So in August of 1966 all of the re-codified FAR Parts were identified with odd numbers and each individual rule or section had an odd number suffix. So tomorrow, as you thumb through the FARs in quest of a loophole and you find an even number part, like Part 36 or an odd part with a even number suffix rule like, 43.2, now you know it means these parts and rules were added to the FAR sometime after August of 1966.

You ’shall’ use current data and adequate tools

Now to the rule! FAR 43.13 contains three paragraphs. Paragraph (a) contains two requirements. The first requirement for a person performing maintenance on an aircraft or appliance is that they "shall" use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance manual or Instructions for Continued Airworthiness prepared by the manufacturer, or other methods, techniques, and practices acceptable to the Administrator, except as noted in section 43.16. Note that the first paragraph sets the tone for the rule. It uses the word "shall." This is a word with hair on its chest because "shall" is used as an imperative and not in the permissive sense as in words like "should" or "may." So the rule requires the mechanic to have current data from the manufacturer or other data acceptable to the Administrator. This reference to other acceptable data allows the mechanic to use data similar to FAA AC 43.13-1B and 2A to work on older aircraft like J3-cubs, and 7 AC Aeroncas that never had a manufacturer’s maintenance manual. The rule’s one exception speaks to section 43.16 Airworthiness Limitations. This rule allows a mechanic to perform maintenance that is called out in an air carrier’s FAA approved operations limitations or an inspection program approved under section 91.409(e). Note that an old rule (43.13) references a new rule (43.16), so 43.13 was revised at the same time 43.16 became effective.

Necessary tools, equipment

The second requirement of this paragraph requires the mechanic to have the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices. If any special equipment or test apparatus is recommended by the manufacturer, the mechanic must use that equipment or apparatus or its equivalent acceptable to the Administrator.

OK, this paragraph says a mechanic has to have the right tools or test equipment to do the work. Now back when I had calluses on my hands and I could part my hair, my lower toolbox drawer had all kinds of "special tools." Over 99 percent of them were box or open end wrenches that were modified by hammer, torch, and bench vice to extreme angles that allowed me to get a bite on that elusive nut or fitting buried behind an unmovable object in an inaccessible location.

However, the rule is not speaking to those kinds of mechanic modified tools. What the rule is talking about when it uses the word "equivalent" is the other 1 percent of the tools each of us has stashed in our toolboxes or tool rooms. You know the one; it’s the wind-driven counter-clockwise safety wire twister that you made for $99.95 that is the "equivalent" of the $1,499 nuclear powered counter-clockwise safety wire twister that is called out in page 187 of the manufacturer’s maintenance manual as the tool to be used to safety wire the frazzlebath valve on the main auxiliary biofeed transfer pump.

Since it is the mechanic or certificated organization who determines if the "home designed special tool" is equivalent to the manufacturer’s "special tool," it is in your own best interest to have something down in writing on how that determination of special tool equivalency was determined, when it was determined, and who determined it. Also, if the "equivalent" special tool requires some sort of calibration, the calibration times and standard to be used should also be noted in the mechanic’s documentation or company’s manual. I am offering you this advice so you can have a better answer than I had when I had to answer those embarrassing questions from an FAA inspector who just happened to notice one of my special tools peeking out of the lower drawer of my toolbox.

Equal to the original, not better than

Paragraph (b) of the rule is where an often repeated maintenance myth began. The paragraph starts off by saying that each person maintaining or altering or performing preventive maintenance shall do that work in such a manner and use materials of such a quality that the condition of the aircraft will be at least equal to its original or properly altered condition. When I went to A&P school, the instructors always told us that if you do the work at least equal to or better than, the original, then the FAA can’t write you up. But the rule does not say "better than." Besides, if you repair a part by making it better than the original, you have in fact altered it. So stick with "equal to" and send "better than" to your memory’s recycle bin. The paragraph also uses the words "properly altered condition." This is speaking to the three ways you can alter a Type Designed product. They are Supplemental Type Certificate (STC), Airworthiness Directive (AD), or FAA Field Approval. So if you have to do a repair on a PMA part that is part of an STC you have to get the data from the STC holder or other approved source.

Follow the manual

Paragraph (c) allows Part 121, 129, and 135 operators respite from paragraphs (a) and (b) of the rule and instead requires them to meet the performance requirements spelled out in their operating limitations and manual. Not fair, you say! We give the big boys relief from meeting manufacturer’s manuals and Instructions for Continued Airworthiness requirements and the work does not have to be "equal to" the original or properly altered condition. Not so! In reality, air carriers are held to a much higher standard of performance than Part 91 operators because they have to meet the requirements in their continuous airworthiness maintenance manuals and other special requirements found in their operating limitations. To ensure that the big boys do not take a sabbatical from complying with the regulations, the FAA headquarters has ensured that each FAA certificating managing office (CMO) and the air carrier are joined at the hip just to prevent that from happening.

In closing, all you have to remember to stay out of trouble 95 percent of the time when working on aircraft are the performance rules in section 43.13. They are:

  1. Have available and use the manufacturer’s current data and any special tool or its equivalent.
  2. Do the work at least equal to the original or properly altered condition.
  3. Airline mechanics, follow your company’s manual.

As it turned out Part 43’s 12 other rules are not hard to understand either. This is because Part 43 was written by mechanics for mechanics and is designed to be light on the number of words and heavy with substance. But then again, what did you expect, after all, Part 43 is our rule.

About the Author

Bill O'Brien