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Operating Limitations – Major or Minor Change?
Continuing our discussion of experimental, amateur-built operating limitations, I want to talk about something that is a constant source of conversation and questions – the “major change.” One of the benefits of owning or operating an experimental aircraft is that you are free to, well, experiment! The aircraft isn’t tied to any sort of FAA type design or specification, so there are few restrictions on the changes a person might wish to make or who may make them. As with all things, however, one must make sure to check and see what the operating limitations allow and require. One thing you’ll find in all operating limitations will be requirements for incorporating a “major change.” What’s a major change, you ask? Well, that’s where the conversation and questions start.
Let’s begin with the requirements as they appear in the current version of amateur-built operating limitations. Amateur-built operating limitations issued under current FAA guidance will contain the following item:
After incorporating a major change as described in § 21.93, the aircraft owner is required to reestablish compliance with § 91.319(b) and notify the geographically responsible FSDO [Flight Standards District Office]
of the location of the proposed test area. The aircraft owner must obtain concurrence from the FSDO as to the suitability of the proposed test area. If the major change includes installing a different type of engine (reciprocating to turbine) or a change of a fixed-pitch from or to a controllable propeller, the aircraft owner must fill out a revised Form 8130-6 to update the aircraft’s file in the FAA Aircraft Registry. All operations must be conducted under day VFR conditions in a sparsely populated area. The aircraft must remain in flight test for a minimum of 5 hours. The FSDO may require additional time (more than 5 hours) depending on the extent of the modification. Persons nonessential to the flight must not be carried. The aircraft owner shall make a detailed logbook entry describing the change before the test flight. Following satisfactory completion of the required number of flight hours in the flight test area, the pilot must certify in the records that the aircraft has been shown to comply with § 91.319(b). Compliance with § 91.319(b) shall be recorded in the aircraft records with the following, or a similarly worded, statement: “I certify that the prescribed flight test hours have been completed and the aircraft is controllable throughout its normal range of speeds and throughout all maneuvers to be executed, has no hazardous operating characteristics or design features, and is safe for operation. The following aircraft operating data has been demonstrated during the flight testing: speeds Vso _______, Vx _______, and Vy _______, and the weight ______, and CG location _________ at which they were obtained.”
That’s a lot of words! Let’s break it down. The first sentence includes a key item regarding where to find the definition of a major change, guiding us to FAR 21.93. Here’s what it says (the pertinent part):
[C]hanges in type design are classified as minor and major. A “minor change” is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product. All other changes are “major changes.”
Note that the regulation actually calls out the definition of a “minor change” and goes on to state that anything not fitting that definition is a major change. Typical regulatory-speak! The real key here, though, is that it says a minor change will have “no appreciable effect” on the items called out. This is where the discussion
really gets interesting, because in order to make a determination of whether a change is major or minor, we need to know what’s considered an “appreciable” change. Look high and low, however, and you won’t find an official FAA definition of “appreciable.” You’re on your own. You will need to use your best judgment to determine whether or not the change you wish to make will have an “appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product.” (The “product” being your aircraft in this case.) There’s no one-size-fits-all answer to this question, so you really need to apply some logic and consideration and try to make a reasonable decision.
The way I answer the question when someone asks whether or not a particular change is major or minor is to apply two lines of thinking. First, if you really have to think hard and still can’t quite convince yourself that the change you’re making is a minor change, then it probably isn’t! In that case, just go ahead and follow the requirements for incorporating a major change as called out in your operating limitations. Second, if you think you’ve convinced yourself that the change you wish to make is indeed minor, think about what you’d say if you were called in front of an FAA Administrative Law Judge to explain your decision. If you feel you have a good, solid explanation that will convince the FAA judge that your change is indeed minor, then you’re in good shape. If not, consider it a major change and act accordingly. Of course, you can always call the local FAA FSDO and ask one of the airworthiness inspectors what they think, but they don’t have a definition of “appreciable” either and typically aren’t intimately familiar with experimental aircraft or operating limitations, so be prepared. Bottom line, use your best judgment and err on the conservative side.
Okay, so now you’ve decided that what you have is a major change. What do you need to do? The limitations say you’re supposed to contact the cognizant FSDO and get concurrence on the suitability of the proposed flight-test area. What you’re doing when incorporating a major change is putting the aircraft back into a Phase 1 flight-test situation to test the change, so you need to have an approved flight-test area. If the aircraft is still based at the same airport where the initial flight tests were conducted, you can simply request the same flight-test area and you’ll probably get it. Otherwise you can either suggest something to the FSDO inspector and see if they like it or ask them what they recommend. As with most dealings with the FAA, it’s better to be proactive and suggest something rather than sitting back and taking what they want to give you. Either way, make sure you get the approval for the flight-test area in writing so that you can have a record of what was agreed upon. Note also that if you’re changing from a piston to a turbine engine or from a fixed to a constant-speed propeller (or vice versa), you need to file a new application for an airworthiness certificate with the FAA.
While waiting to hear back from the FSDO on the flight-test area, you can make a detailed entry in the aircraft maintenance records describing the change. This is required before any flight testing actually occurs. Once you have concurrence for the flight-test area and you’ve made the entry in the aircraft records, you can actually fly the aircraft with the major change incorporated. This is a flight-testing program much the same as your initial fight tests, so the same parameters apply – no passengers, day VFR only, within the sparsely populated restricted area, etc. The test is required to be at least 5 hours, but for some changes the FSDO may require more than 5 hours. Typically the 5 hours will be sufficient.
The last thing you need to make sure to do is close out the flight-test period by making the appropriate entry in the aircraft records as called out in the operating limitations. You’ll notice this is the very same verbiage as used when you completed the original flight-test period. And just like the original period, the aircraft isn’t released from the flight-test restrictions until this entry is made in the aircraft’s records. This is a very important step that is sometimes missed. Remember, the job isn’t finished until the paperwork is done!
So that covers what’s required by the current version of amateur-built operating limitations. But what if your aircraft was certificated under an earlier version of FAA guidance? Let’s take a look at some of the earlier versions of major change requirements so we can see the differences.
If your aircraft was certificated from late 1999 to January of 2003, you’re in luck! You have the most liberal of all major change limitations. Your operating limitations will look like this:
After incorporating a major change as described in § 21.93, the aircraft owner is required to re-establish compliance with § 91.319(b). All operations will be conducted VFR, day only, in a sparsely populated area. The aircraft must remain in flight test for a minimum of 5 hours. Persons non-essential to the flight shall not be carried. The aircraft owner shall make a detailed logbook entry describing the change prior to the test flight. Following satisfactory completion of the required number of flight hours in the flight test area, the pilot shall certify in the records that the aircraft has been shown to comply with § 91.319(b). Compliance with § 91.319(b) shall be recorded in the aircraft records with the following or a similarly worded statement: “I certify that the prescribed flight test hours have been completed and the aircraft is controllable throughout its normal range of speeds and throughout all maneuvers to be executed, has no hazardous operating characteristics or design features, and is safe for operation. The following aircraft operating data has been demonstrated during the flight testing: speeds Vso ______, Vx ______, and Vy ______, and the weight ______, and CG location ______ at which they were obtained.”
This might almost look exactly like the limitation I previously quoted, but it’s a very important “almost.” The big difference is that there’s no requirement to gain concurrence from the FSDO for your flight-test area. Under this limitation there’s no requirement to contact the FAA
at all when incorporating a major change, regardless of what the change might be! You just simply make the entry describing the change in the aircraft records before flying the aircraft, then go test the change for a minimum of 5 hours. Once you’ve done so, you make the entry closing out the flight test and you’re good to go. That’s as simple as it gets!
For aircraft certificated earlier than late 1999 the differences are greater. For much of the ’80s and ’90s the major change provisions in the operating limitations stated that the owner/operator had to contact the FAA and receive a response in writing before flying the aircraft after incorporating a major change. This usually involved describing the change to the FAA FSDO inspector and negotiating the procedure for approval. There was no set standard in the FAA guidance, such as a minimum 5-hour flight test. The FAA dictated the requirements on a case-by-case basis.
Even more significantly, operating limitations issued up until the early ’80s simply stated that any major change invalidated the airworthiness certificate. It means that anytime a major change is incorporated into the aircraft the FAA will have to come and reinspect the entire aircraft for issuance of a new airworthiness certificate. There are many airplanes operating today that still hold these old operating limitations, so it’s wise to check and see what you have if you’re flying an older homebuilt.
Pilots of homebuilts still operating under these older versions of the limitations can apply to the FAA for an updated version. This is probably a good idea. Not only do you get the updated language for major changes, but you also get the most current language regarding flight over densely populated areas, pilot-in-command requirements, and night/IFR requirements as well. It pays to go through the process of updating your operating limitations. You’ll need to work with your local FSDO to update, but if the folks there don’t seem sure of what to do, you can contact me or any of the folks in the EAA Aviation Services department (
info@eaa.org) and we’ll set them straight!
We’ll continue our discussion of operating limitations in next month’s
Experimenter. Until then, make sure your operating limitations are onboard your homebuilt when you’re flying, and make sure you know what they allow and require!
) Apologies for the thread creep here. I had to Google GWRRA to get the translation. It brought back a funny occurrence. I've had Maine motorcycle license plate 9 since 1998; my father had it from 1954 until he died. One day I and the HOG got the red light in Brunswick, Maine. I was stopped beside a beautiful Gold Wing which I noticed had Maine plate 9A. So I said to the operator, "That's a low number." "" Yep; they don't come any lower that that one."" "I have one lower." ""Not possible; what is it?" "Number 9." ""No, you can't it doesn't exist. I asked for it but they told me there's no such number; the lowest you can get is 9A."" "Well, 9 is mine; it's been in the family since 1954."
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