Free Flight

Learning complex systems means knowing how they work.

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Give a man a fish, and he eats for a day. Teach a man to fish, and hell never go hungry. (Plus, hell borrow your boat, motor and nets, and never bring them back…)

This saying can be applied to teaching and learning complex avionics systems such as EFISes and autopilots. There’s a saying in aerospace that, boiled down, indicates that there is a difference between knowing how to work something and knowing how it works. You can know how to work a system by following a set of written instructions or procedures. This is great as long as everything performs as you and the designer expect it to, you operate it only under the exact conditions for which the procedure was designed and there are no malfunctions. If any of these conditions are not met, then the trained or written procedure might not be applicable. If you don’t have an alternative procedure for the exact alternative conditions and you don’t know how to adjust for this, then you can really be lost-literally as well as figuratively!

Knowing how something works, on the other hand, is to understand it at a level that allows you to write your own procedures for whatever conditions might exist. Understanding systems in detail-knowing what external conditions are required for them to operate, how they are connected internally and externally, and what they can be expected to do-gives you the ability to adapt to changing conditions, and this is what can make you and your aircraft exceptional performers. Just as in the natural world, where the ability to adapt gives certain animals an edge over those that cannot, being able to alter your techniques and procedures to changing conditions will allow you to use the systems to maximum advantage and increase your margin of safety (and success) when conditions are less than ideal.

How do your various boxes communicate with each other? A thorough understanding of electronic connections and data lines will help you troubleshoot on the fly, and prevent minor technical glitches from becoming a threat to safety.

Book Learning

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Because I believe in this philosophy, it makes me a little nervous when someone asks for the exact operating procedures for a complex system, or they try to learn it from a step-by-step manual approach. I am always worried that if they encounter a situation that isn’t covered by the book during, say, an instrument approach, things could turn ugly. Yes, Standard Operating Procedures are our friend, when the systems are fully known, and there is a lot of collective experience in their operations. Just ask any military or airline pilot. The process there is to operate it (the aircraft, the system…) by the book, and you cant get in trouble. But this is the sticking point for us in Experimental aviation. Many of our systems have only recently been designed, and many builders combine equipment in new and unique ways.

It is hard to find two homebuilts wired or set up the exact same way. That is, in fact, what draws many of us to these machines, the idea that we can build exactly what we want. But it makes it difficult to share operating procedures with one another. I can stand and talk with a group of pilots that all have the same EFIS but slightly different autopilots, and we can easily get confused about how to fly an approach. Nobody is wrong-we all just have different systems. I have read a lot of discussions about how to fly coupled approaches with a particular EFIS, a GPS and an autopilot, and I come away with a headache because it can be hard or impossible to follow the narrative if I don’t have the same setup.

Uncommon Knowledge

For this reason, I believe that it is really important to realize that it takes a tremendous understanding of how your airplane is wired, and how it is set up. You have to know how boxes talk to each other-RS-232? ARINC? Analog lines?-and what kind of sentences they trade. Are they one-way links, or do they have a dialogue? In the case of communication failures between boxes, what do they do? If you cant answer these questions, or don’t understand them, then you might want to do some more studying before trusting your life to the suite you have installed in your airplane. If these were factory airplanes with long test programs and certified manuals, it would be less important-youd just read the book and be ready to go. But the fact of the matter is that while we know very well how an RV airframe flies with a particular engine, when it comes to modern avionics, many of us really are test pilots. And a good test pilot is an engineer that has really, really studied how his systems work.

Why is this so important? It is no fun to come up on the outer marker in bad weather and discover that your complex system has decided to turn in a direction that you didn’t expect. You might be surprised that I spent a large portion of my Phase 1.5 doing approaches, tracking radials, inputting flight plans-all to see what the airplane would do. (Not familiar with the term Phase 1.5? Thats the period between flying off the legally required 40 hours and about the 100-hour point where I knew what the airplane really did.) I designed my avionics system and did all the wiring. But for those who have not put as much time into understanding how the system works, it is just as important to go out and try stuff, sit down and read the manuals, and just plain understand the system as an engineer-not just an operator. Sure, I have a personal bias here-I am an engineer. But I have seen enough pilots struggling with systems they don’t understand, and I have read enough accident reports of pilots who were overwhelmed by their systems in bad weather to hope that we all approach our complex aircraft with a healthy dose of respect…and curiosity!

Now exactly how does that flight plan get from the GPS to the EFIS again?


Paul Dye is an aeronautical engineer, commercial pilot and avid homebuilder with 30 years of leadership experience in aerospace operations and flight testing. He is also an EAA tech counselor and flight advisor who currently flies an RV-8, which he built, and is working on an RV-3.

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Paul Dye
Paul Dye, KITPLANES® Editor at Large, 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.

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