Aircraft Maintenance: Managing configuration changes
Whether you are swapping out seats to make room for cargo, removing doors for photo shoots, or adding floats for the summer or skis for the winter, there’s a lot more involved than simply pulling out a seat and going flying.
The most popular general aviation aircraft are designed to accommodate a variety of missions. Reconfiguring aircraft seating for cargo or removing a door for a photo shoot can be a simple task physically. However, it can be easy to forget that aviation is highly regulated, and we need to abide by the rules in order to stay safe and legal.
Proper performance involves a careful and informed approach to a task that may seem trivial, but could have dire consequences if performed incorrectly. Take the example of removing or installing seats. Removing seats seems simple enough, but if you are removing the seats to carry cargo that means that you are responsible for properly securing the cargo. This could mean using built-in hard points and installing cargo nets. Installing seats is even more critical, as many accidents have been caused by improperly installed seats that were not properly secured to the seat tracks. If you are removing doors or windows, there may be other considerations regarding the safety and security of the occupants and any loose items on board.
Swapping out wheels for floats or skis is generally a much more involved task, but the same rules apply. Every step in the maintenance manual must be carefully followed to ensure that the aircraft is safe and airworthy following the modification.
Proper performance also means understanding and accounting for the weight and balance change to the empty weight of the aircraft. This leads us to proper documentation. Seats, doors, windows, floats, or skis are not the same as passengers and carry-on baggage and should not be accounted for in the same way. It is not legal, or appropriate, to simply pull out a couple of seats, run a typical preflight weight and balance calculation, and take off.
Changing the configuration of the aircraft is, in fact, a maintenance task that alters the aircraft (albeit one that is legal for the pilot to perform). Therefore, the modification must be documented, and the weight and balance form in the maintenance logs must account for the new configuration. This isn’t as onerous as it may seem, and it doesn’t need to clutter up your aircraft logbooks.
I recommend creating a single, comprehensive aircraft weight and balance document that includes several configurations for the aircraft. Each configuration includes an identifier such as “All seats installed,” “Front seats only,” or “Doors removed.” Within each configuration section, include a brief description of the configuration, as well as the resulting empty weight, moment, and useful load. The document can be several pages if required, and should conclude with the name, date, signature, and certificate type of the person who created it. Although it is legal for an aircraft owner or operator to create this weight and balance document in the maintenance logbook, you may want to enlist the help of your mechanic to make sure you do it properly. A copy of this aircraft weight and balance must be kept in the aircraft at all times.
Documenting the configuration changes can be done in a similarly expedient manner. Using a separate “configuration change” logbook, make an entry for every change in the same way you would for any maintenance task. This should include the date of the modification, the aircraft hours, a description of the work performed, reference to the weight and balance configuration now in effect, the name of the person performing the modification, and their certificate type and number.
For example:
12/2/2024, 1576.4 total time
Installed rear seats 3,4,5,6 in club seating configuration IAW aircraft POH and verified security of all seats and seat belts. Refer to W&B configuration “6-Seats, Club Seating” for all flight operations.
John Q. Pilot Cert. No. (signature)
It’s also critical to ensure that you are following the proper procedures for every change, and I recommend following the maintenance manual and having simple checklists to make sure that nothing gets missed. For example, many seat installations require that separate seat stops be installed to protect against sliding completely off the track. Having a checklist can make sure you don’t miss a critical step in the process.
It’s easy to think of aircraft configuration changes as simple enough to negate the need for proper performance and documentation. However, I would caution against this approach. According to FAR 91.7 (b), “The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight.” This means that the pilot is responsible for the current configuration of the aircraft, as well as for ensuring that any changes were properly performed, and that the work was documented including a current aircraft weight and balance. Should an incident occur, you can bet that investigators and attorneys will be looking for a paper trail. Following these simple guidelines will ensure that you remain both safe and legal. Until next time, I hope you and your families remain safe and healthy, and I wish you blue skies.
