EAA Sport Aviation

maintenance
& restoration

one. Unless you are modifying or attaching something to a primary structure, you are not having an appreciable effect on the structural strength of the aircraft.

There are similar definitions in 8110.46 for performance, powerplant operation, flight characteristics, or “other qualities affecting airworthiness.” Read these definitions carefully in your evaluation of whether an alteration is major or minor.

Part 43 Guidelines

Part 43 Appendix A of the FARs specifically defines major

alterations to airframes, powerplants, propeller, and appliances. These regulations also shed some light on how the FAA wants us to determine major versus minor alterations. Fortunately, both 8110.46 and Part 43 Appendix A continue the same theme; major alterations are changes to the foundations of the aircraft certification. If you are changing how a system works, the basic structural integrity, or the certified operational characteristics of the aircraft, you are making a major alteration.

For example, let’s consider an alteration to the aircraft’s electrical system. Is adding a new circuit to the existing power bus a major alteration? Not unless it exceeds the basic capacity of the system. It’s the system design that we’re concerned with. Adding a backup alternator or a new electrical bus are both examples of major alterations.

Part 43 Appendix A asks: “Does the proposed alteration change the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, deicing, or exhaust systems?” If it does, it’s a major alteration.

Continuing Controversy Because of this type of confusion, Aircraft Electronics Association has been working closely with the Small Airplane Directorate to better clarify the intent of the regulations concerning electrical system alterations. They have had numerous discussions with FAA leadership concerning what constitutes a major change to the electrical system of the aircraft. All parties agree that major changes are those that would affect the basic certification of the aircraft by the manufacturer. These include changes in power generation, distribution, and regulation. Expect to see new guidance materials from the FAA on this matter soon.

Jeff Simon is the president of Approach Aviation, a provider of educational products, tools, and supplies for aircraft owners. To learn more about aircraft ownership and maintenance, visit www. ApproachAviation.com or call 877- 564-4457.