A few decades ago, those who study aviation mishaps began to recognize that very few incidents were the result of a single, instantaneous event. Rather, most were caused by a chain of small errors, all of them building to an inevitable bad ending. Inevitable, that is, unless you simply broke the chain—stopping the eventual climax from occurring by catching the problem along the way.
A good example of this would be a pilot who is transitioning to a retractable-gear airplane that has an automatic gear extension system. While this sounds like a great idea for normal operations, it can be a real problem when learning an airplane’s slow-flight characteristics—alarms go off, the gear drops out—it is a poor learning environment. Many instructors teach the student how to override the system. But sometimes, the override is left in. They fly back to the airport, get distracted, and what do you know—a perfectly good automatic gear extension system is powerless to stop the gear-up landing. For this to occur, the pilots have to disable the system and forget to re-enable it and get distracted and ignore the warning horn. Take away any one of these and the flight ends with the wheels rolling on the pavement, rather than being tucked in the wells.
Some might even argue that the fault lies earlier on—with the idea of the gear extension system—or the idea of the override. That would make it a problem of design, or design philosophy. In the certified aircraft world, pilots and
operators start with the assumption that the design has been thought-out and the procedures in the checklists and manuals are adequate (if followed) to protect the pilot from mishaps. In any aircraft, pilots are still susceptible to becoming victims of maintenance issues—but they usually can be assured that the airplane was designed and assembled to a set of standards and has been inspected to meet its type certificate.
In the Experimental world, we need to start with a different assumption. We build (and sometimes design) these airplanes ourselves, sometimes in a vacuum, with little help or oversight. Sometimes we decide that we have a “better idea” than the original kit or plans designer. That’s OK—that’s what experimenting is all about. Unfortunately, sometimes, we are wrong. A modification that we thought was the cat’s meow turns out, instead, to be a mousetrap—just waiting to spring on us at the wrong moment. In other cases, we might be building per plans, but a distraction at just the wrong time in the shop—the cat tips over the bucket of Clecoes, toppling little roller bearings all over the floor and creating chaos in the build area—and we forget that we hadn’t fully tightened that B-nut on the fuel line. Or we left the fuel pump wire disconnected. Or forgot to tighten down an axle nut. Building errors do occur, and sometimes they simply aren’t caught, no matter how many qualified eyes and hands go over the aircraft. Design errors are the same. And this is unique to our little corner of general aviation. While the statistics show that the greatest danger to GA pilots continues to be GA pilots, a significant number of Experimental aircraft accidents still come back to design and construction. For this reason, we’re starting a new feature that we hope to run every month, highlighting the kinds of mistakes that are unique to those of us flying aircraft that we built. If you want to learn how scared you can get by running into bad weather or running out of fuel, there are other magazines that cover those stories well.
But if you have a story that puts you in the category of “being in the air, wishing you were on the ground,” and it is attributable to a design or build error, we’d like you to share it in “Error Chain.” Confession isn’t just good for the soul—it can save lives and airplanes by alerting others to things that get Experimenters in trouble. In our debut article, learn about a remarkable off-airport landing in an RV-10 that suffered an engine failure due to a loose oil line. The lessons that Jeremiah Jackson learned are shared (by him) for the good of everyone who leaves the safety of the earth’s surface in an Experimental airplane.
As much as we wish that no one ever has these kind of mishaps, we know there are many stories to share. We look forward to seeing your own stories in future issues. Let’s break the chain of errors and keep our fellow fliers safe to fly another day.
Paul Dye 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 currently flies an RV-8 that he built in 2005 and an RV-3 that he recently completed with his pilot wife. A commercially licensed pilot, he has logged over 4500 hours in many different types of aircraft. When not writing on aviation topics, he consults and collaborates in aerospace operations and flight testing projects.