It’s hard to believe that pilots who have spent thousands of hours building their own airplanes—reading instruction manuals, studying avionics wiring, and knowing the details of their powerplants—have very little knowledge of the very last part of the build: the paperwork pertaining to licensing and the airworthiness certificate. Experimental aircraft are issued “special” airworthiness certificates, and those come with specific operating limitations, typed on several sheets of paper, that are legally part of the certificate. It is illegal to operate a U.S. registered aircraft without the airworthiness certificate on board. And since the operating limitations are part of that certificate, it is against the rules to fly the aircraft without those ops lims in the machine.
Early operating limitations for N5827N, a homebuilt Stits Playboy that would later become known as the RV-1. Note that they are less than half a page.
Operating limitations are unique to a specific aircraft, and while they share much between them, you can’t assume that your ops lims are identical to your neighbor’s. The guidance used by FAA inspectors and DARs has been modified over time, and with those changes have come revisions to the generic, boilerplate ops lims. An extreme example is that many years ago, you needed a new airworthiness certificate every year (and the ops lims said so), while today they are good for the life of the aircraft. You need to know what is in your operating limitations to make sure you are in compliance with the rules—and for you to do that, you first need to have them available.
It is amazing to me how often I talk with pilots of experimental aircraft that have no idea what is in their operating limitations—or that they even exist. I have asked to see a machine’s ops lims when doing a pre-purchase inspection and received a blank stare from the owner. Sometimes, a light bulb goes on, and they show me their POH, thinking that the limitations I refer to are things like stall speed and VNE. Nope. Other times, I have described them and the same light bulb goes on. “Oh yeah, I think I remember getting those when I had my inspection. I have them in a file cabinet back home!” Wrong answer again. I hope you don’t get ramp checked because you don’t have a valid airworthiness certificate in the airplane (Remember “ARROW”? The “A” stands for airworthiness certificate).
Operating limitations contain all sorts of interesting things. For instance, they describe the exact wording of your sign-off from Phase 1, putting the airplane into Phase 2. Has that wording been put in the logbook as required? In order to make the entry, you need to know VS, VX, VY, and the CG and weight at which they were obtained. Some pilots have no idea what those numbers are, so how could they have complied with the ops lims?
Operating limitations for N5827N after it was purchased by Richard VanGrunsven, significantly modified, and renamed the RV-1.
Oh yeah—what about that annual sign-off that has to say, “This aircraft has been inspected on [this date] in accordance with the scope and detail of Appendix D of Part 43 and found to be in a condition for safe operation”? I have seen so many different write-ups (or lack thereof) saying that an airplane is airworthy, that it has had an annual inspection, etc., but none of these comply with the ops lims, which are supposed to be in the aircraft and therefore easy to consult. And, as a matter of fact, the last set of ops lims I looked at said that the wording had to be “similar to” the statement above—which actually seems to indicate that the FAA is slightly relaxing its iron hold on the specific wording. But each airplane’s operating limitations must be complied with for that airplane, so read yours.
(By the way, ignorance of operating limitations is not restricted to owners and builders. I have seen presentations by FAA inspectors who simply said the wrong thing, indicating ignorance of the very rules they are required to enforce. And the truth is, none of this is hard. It’s certainly not rocket science. It’s all in black and white, and very easy to read—you just have to take the time to do so.)
Why does any of this matter? Well, the FAA can be fairly picky about the rules, and there are, unfortunately, a number of FAA inspectors who are not particularly friendly toward experimental aircraft operators. That means they can be mighty picky if you get ramp checked or if you have an incident that calls for them to check your paperwork. People get busted for poor paperwork, no matter if it makes a real difference in safety or not—so it pays to know what good paperwork looks like and to have yours in order.
And lest my many FAA friends think I am picking on them, let me say that I have seen more misinformation spread by experienced experimental operators than by anyone else. I have seen mechanics, inspectors, and multi-time builders advise people incorrectly when it comes to operating limitations, so it is no mystery how bad ideas spread.
If you own an experimental aircraft, go find the ops lims (hopefully, they are in the aircraft) and give them a read. Make sure you know what is in them. Make sure your logbook entries comply with those limitations. And make sure you understand exactly what each line in those limitations means.
After all, it is important to know your limitations—and those of your aircraft.
Paul Dye, Kitplanes Editor in Chief, retired as a Lead Flight Director for NASA’s Human Space Flight program, with 40 years of aerospace experience on everything from Cubs to the space shuttle. An avid homebuilder, he began flying and working on airplanes as a teen, and has experience with a wide range of construction techniques and materials. He flies an RV-8 that he built, an RV-3 that he built with his pilot wife, as well as a Dream Tundra they completed. Currently, they are building a Xenos motorglider. A commercially licensed pilot, he has logged over 5000 hours in many different types of aircraft and is an A&P, EAA Tech Counselor, and Flight Advisor, as well as a member of the Homebuilder’s Council. He consults and collaborates in aerospace operations and flight-testing projects across the country.