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From the DAR Side

Gross weight — Can it be changed?

By Joe Norris, EAA Flight Training Manager & AB-DAR

February 2018 - Ever since the sport pilot/light-sport aircraft regulations were instituted a little more than a decade ago, many homebuilt aircraft builders have chosen to set 1,320 pounds as the maximum gross weight of their aircraft. Many of these aircraft have factory-recommended gross weights in excess of 1,320 pounds, but the builders chose to stick with the LSA limit so that their aircraft would be eligible for operation by sport pilots.

The advent of BasicMed has changed the game. Many pilots now have the opportunity to fly aircraft with gross weights in excess of the LSA limits without the requirement to hold an FAA-issued medical certificate. This has caused increased interest in raising the gross weight on these existing experimental aircraft. The two questions are can it be done and, if so, how? The answers are maybe and it depends.

The answer(s) will be found in the aircraft’s operating limitations. Remember that the operating limitations are issued to an experimental aircraft as a part of its airworthiness certificate. As such, the operating limitations must be carried in the aircraft at all times. So, make sure the operating limitations are in the aircraft! I always recommend to my applicants that they make a copy of the operating limitations to keep with the aircraft maintenance records so that the original document never has to leave the aircraft.

Once you find the document, look for a paragraph that mentions a “major change.” The paragraph may start out with something like, “After incorporating a major change,” or it may start out with, “A major change ….” Changing the maximum gross weight of an aircraft would definitely qualify as a major change, so the owner/operator of the aircraft would need to follow the guidance contained in that paragraph to approve the gross weight change.

The process for incorporating a major change has changed significantly over the years, so it’s important to check the operating limitations that were issued to a particular aircraft to make sure that the proper procedure is followed. For example, aircraft that were certificated many years ago may contain the following statement: “A major change invalidates this airworthiness certificate.” That’s pretty drastic but not insurmountable. If this is the case for your aircraft, the only option would be to apply for a recurrent certification and have a new airworthiness certificate and operating limitations issued to the aircraft that reflect the new gross weight.

Fortunately, over time the major change process has become less onerous. For a period of time, the guidance called for the owner/operator to notify the cognizant FAA flight standards district office and receive its response in writing before operating the aircraft after incorporating a major change. But since the late 20th century the process has been even easier.

Most operating limitations issued since 2000 only require that the owner/operator contact the FSDO to verify that the proposed flight test area is acceptable. The builder then makes an entry in the aircraft’s records describing the change and placing the aircraft back into Phase I, to flight-test the major change. This Phase I period must be at least five hours in duration, but can be longer if necessary. During this period, the builder would test the aircraft at the higher gross weight, carefully recording the performance parameters required, which typically include verifying VX and VY speeds, the stall speed in landing configuration, and the CG at which this data was recorded.

Once this data has been gathered and the five-hour flight test is completed, the owner/operator will make an entry in the aircraft records as called out in the operating limitations. You will note that the wording of this major change signoff is the same as the verbiage used to complete the initial Phase I flight testing of the aircraft. Once this testing has been completed and the data recorded in the aircraft records via the appropriate entries, the aircraft is then authorized to operate at the new gross weight during normal (Phase II) operations.

Note that, throughout this article I have used the term “owner/operator.” I did this to point out that a person does not have to be the builder of the aircraft to carry out a major change. There is no restriction on who does maintenance, repair, or modification to an amateur-built aircraft. As long as the guidance found in the operating limitations is followed, anyone can perform a major change.

Finally, here are couple of things to keep in mind. First, remember that once the aircraft has been operated at a maximum gross weight in excess of the LSA limit, it can never again be made eligible for operation by sport pilots. You can’t lower the gross weight and go back to sport pilot operations. Raising the gross weight is a one-way street with regard to sport pilot eligibility. Second, this process should only be carried out on designs that have been authorized at the higher gross weights by the designer or kit vendor. It would be unwise and unsafe to operate an aircraft at a gross weight that is greater than the designer specified. To do so would place the operator in uncharted waters with regard to safety margins and could possibly lead to structural failure. That could ruin your day!

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