Build It Better: Show Me the Data!

Show Me the Data!



Powered, heavier-than-air aviation has been around now for a little more than a century, which still qualifies it as a fairly young human endeavor. Yet in those 100 years, quite a bit of information and data have been generated on how to build and operate flying machines. Much of this knowledge has been written down, and much more has been passed on orally from generation to generation—pilots telling pilots, mechanics telling mechanics and engineers telling anyone who would listen. Information that is passed on like this has a way of taking on a life of its own and often evolves as it goes, changing a little with each telling until occasionally it is unrecognizable from the original truth. Sometimes, this makes no difference—tall tales can be quite entertaining when the weather is low, and we sit around the lounge trying to best one another. But other times—those times when lives depend on the validity and veracity of the information—the truth and accuracy of what we pass on is vital. For those cases, I have a simple rule: Show me the data!

Whether we are building, maintaining or flying an airplane, we are bound to have questions and will need to find out how certain tasks are supposed to be done. Whenever I ask a question of someone or receive advice (solicited or otherwise), I have gotten into the habit of asking about the source of that data. I want to know if it is written down somewhere, or if the advice/answer giver is simply passing on what he was told by somebody else. It makes a difference, especially for technical issues and matters involving rules and regulations.

But in matters of safety, it is essential. And maybe nowhere in the aviation world is it more so than in the high-speed, high-energy world of human space travel. Things can go very wrong, very quickly when you are traveling at the speeds and with the explosive forces of spacecraft climbing into orbit. In the Mission Control Center in Houston, there is a room full of engineers who support the people running the missions. For many decades, engineers have walked into this room. Over the door hangs a simple sign—brief and to the point, just the way engineers like it. “In God we trust!” it reads. “All others must bring data!”

Assumptions have no place in aviation, whether you’re talking about the diminutive Belite or the mighty Boeing 747.

Speculation-Free Zone

There are no facts in mere speculation, and facts are what we want: Analysis, test results and good old physics govern everything. It’s rare that gut-level instinct is trusted without some sort of data to back it up. Everything must have a traceable source, even things that are known to be good practices—they are documented somewhere.

The Apollo 1 crew was lost because they were encapsulated in a pure oxygen environment at 16 pounds per square inch (a virtual bomb waiting for a spark), and testing had always been done that way. No one questioned why, or how dangerous it could be. In 1986, the Space Shuttle Challenger was lost because there was no documented lower temperature limit for the booster rockets, and management felt that it would be OK—but they had no test data to back up that claim. (In fact, there was some data that proved the opposite; it simply wasn’t documented well enough.) The space business is extremely unforgiving, as is the rest of aviation. Mistakes may lead to death whenever a human being is transported more than 10 feet above the ground, at more than running speed, and the system fails.

Down on Earth

Hearsay information exists in many different parts of the aviation world. Mechanics are constantly passing on tricks and tips they have been taught by other mechanics. Sometimes this information is correct, but many times it contradicts what is published in the bible of aviation maintenance, Advisory Circular 43.13 (Parts 1 & 2). When someone makes a recommendation but it sounds contrary to what I believe to be good practice, I ask the person to show me where it is written down. Is it really OK to substitute a pulled rivet for a solid rivet in a particular structural application? Well, you can look that up. Is it acceptable to inflate tires to the maximum pressure on the carcass for each and every airplane? Maybe you should check in the airplane-specific (and FAA-approved) maintenance or operation manuals. Do you really need to use AeroShell Grease 6 in your propeller hub? Why not consult what Hartzell has to say about this in its FAA-approved maintenance manual?

This same caution applies in the operations world. Can you really fly an ILS without a marker beacon receiver but with a handheld GPS to identify the final approach fix? Better look that one up before you commit to it. (To save you the trouble, I’ll give you the answer: You can’t.) How does that downwind turn thing work again? Do you slow down as you turn away from the wind, and therefore stall because you’re going slower? Dr. James H. Doolittle wrote his master’s thesis on that subject in the 1920s, and the answer is no. Is it OK to enter a right-hand pattern at a field where there is no traffic on the radio, even if the airport has a standard, left-hand pattern? No, it’s not, and you don’t have the right to break the rules just because you’re alone and it’s more convenient. Besides, that student in the J-3 Cub doesn’t have a radio, and you may have missed him turning left base because he was below you and painted green like the treetops.

Radio Daze

Let’s take a common operating technique that has been debunked numerous times yet still seems to hang on. “Any traffic in the area, please advise,” is heard many times on common traffic advisory frequencies every day, yet section 4-1-9(g) of the Aeronautical Information Manual clearly states that this phrase is not a recognized self-announce position or intention phrase and “should not be used under any condition.” That’s pretty straightforward, isn’t it? It’s about as stern as the government can get, and even though the AIM is said to be non-regulatory, failure to follow its recommendations can easily lead to a “careless and reckless” charge from the local flight standards district office.

Measure twice, cut once…but be sure the measurement you’re using is validated, current and appropriate.

This recommendation has been in the AIM for quite some time, yet some pilots persist in using the “Any traffic?” phrase. I began hearing it about 20 years ago, when commuter airliners started dropping into uncontrolled fields after being handed off from air-traffic control to the local frequency. They were on an approach and would be on top of the field almost immediately, and this was a fast way to “fish” for traffic because they hadn’t been listening from a long way out like most general aviation pilots do (or are supposed to do) as they approach the field. I can’t prove it, but I suspect this was either documented or taught by airline operating manuals at one time. Pilots in general aviation heard it and figured that’s what the big boys do, so they picked it up. Again, I suspect, but can’t prove, that this technique was promoted in some of the ab initio programs that produced certificated flight instructors headed for the regionals. They wanted to sound like pros, so they passed it on to their students.

There’s no reason to assume when sources of correct data are all around you. An engine data plate has a wealth of, well, data.

The problem, of course, is that the phrase is ludicrously arrogant and meaningless. If you listen to the traffic at an airport for 2 minutes and everyone is self-announcing as they should, then you’ll know where the traffic is. If you don’t listen and simply barge in expecting everyone to respond to your request, you are inconsiderate and unlikely to get a response. Now I don’t intend this to be a diatribe against the phrase, merely an example of the kind of thing that gets passed from pilot to pilot as the thing to do, but it is not documented or even recommended by any written procedure. It provides a perfect opportunity for a person to ask, “I had never heard of doing that before. Is the procedure written down somewhere?”

The same can be said when it comes to the “beach ball” frequency—123.45 MHz. Many pilots use it for air-to-air communications because they have heard pilots arrange to meet there. Ever looked it up? International Civil Aviation Organization Annex 10 says, “123.45 MHz shall be designated for use as an air-to-air communications channel to enable aircraft engaged in flights over remote and oceanic areas, out of range of VHF ground stations, to exchange necessary operational information and to facilitate the resolution of operational problems.” The continental U.S. is not considered out of range of VHF ground stations.

Nothing is as good as measuring for yourself, but be sure your tools are as accurate as your approach to the build.

“In God we trust. All others bring data” is a clarion call, a challenge to everyone in aviation to be the best, the sharpest and the smartest they can be. It is a summons to excellence, and to precision. Some things aren’t written down simply because they are still being discovered—after all, a century of flight is pretty short compared to the many centuries that humans have been building ships or constructing bridges (both of which can harm people if done improperly). The consequences of being wrong in aviation are sudden and often violent. We can’t afford to take someone else’s word for it. Whether you are building, flying, maintaining or simply talking in the lounge, know the source of information. Sometimes these sources are good enough, if the source is trusted and known to be thoughtful and knowledgeable. But accepting information that has simply been passed on without attribution is potentially dangerous. A good library is a great resource, as it offers the opportunity to verify what others say. Don’t trust your life to rumors and assumptions. Go look it up!

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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 and SubSonex jet that he built, an RV-3 that he built with his pilot wife, as well as a Dream Tundra and an electric Xenos motorglider they completed. Currently, they are building an F1 Rocket. A commercially licensed pilot, he has logged over 6000 hours in many different types of aircraft and is an A&P, FAA DAR, EAA Tech Counselor and Flight Advisor; he was formerly 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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