This piece originally ran in Lisa’s Airworthy column in the June 2023 issue of EAA Sport Aviation magazine.

 

Four years ago, I made a mission out of finding out what technical counselors, flight advisors, A&P mechanics, and designated airworthiness representatives thought were the top reasons for technical failures in the first 40 hours after a build. I also looked at the research by Ron Wanttaja, EAA 275698, on first-flight accident causes.

Recently, I checked back in with the experts to see how much progress we have made and to address lingering issues. It turns out we have made progress in reducing first-flight accidents and in reducing flight-ending technical problems, but this may be more because the aircraft kits have gotten better and less because flight testing techniques have improved.

We’re still seeing systems issues in the first 40 hours. Here’s an update on what they are, and how you can avoid them in your current and future builds. Keep in mind that these are anecdotal rather than from scientifically built surveys. The range of kit complexity and the completeness of instructions is enormous, making it tough to accumulate data. Assembling a quick-build kit will be different than building from a plan design.

In between the ends of the spectrum fall systems integrations such as the setup of fuel, electrical, avionics, hydraulic, and mechanical systems to get in the air. Even if the instructions are top-notch, there will be opportunity for error. Since most builds fall in between these two extremes, these tips should be useful.

An analysis of accident causes by Ron Wanttaja in 2018 revealed areas where errors were most common — systems installation and workmanship. Setup is not far behind these two large categories. Most of the errors I talk about fall into these three buckets.

Electrical Errors

I see problems in electrical systems most often when harnesses are not supplied with the kit and have to be made up by the builder. When I built my airplanes in the 1990s, it was typical to either make up the electrical system for the airplane or contract it out. Now, many kits have some or all of the harnesses ready to install. While this has cut back on the errors, I still see common problems.

Many errors involve electrical connections. Crimps are not done using a high-quality tool that applies pressure in the right places. Some builders who have worked on cars assume techniques are the same with their airplane. The difference will be the ability to coast to the side of the highway when a wire comes off. I also see many wires that are not bundled up and secured, and many that are impossible to troubleshoot because we don’t know where they go.

What to do

• Use the right tool and pull on the connection to make sure it’s tight. Make sure every crimp is effective and follow the instructions that the manufacturer gave you.
• Bus bars and connections. In automotive work, we may have used fork and spade terminals on bus bars and on connections. Since your airplane is subject to higher vibration loads, don’t use a fork terminal where a loosening screw can release it. Use a ring terminal. Yes, it’s more work to install. You may think quick-connect makes sense because they are easily removed, but that’s the problem; they are easily removed. Some circuits will use these connections, and you won’t be able to change them. In this case, check that they are tight on grip, and if necessary, use needle-nose pliers to apply pressure carefully to fork and spade unions, ensuring a good fit.
• Direct harness versus loop harness sections. The first time you have to pull your panel out and work on the wiring side of it, you will be glad you put in a loop. Pull the panel and place it up on the fuselage on a towel where you can see it instead of cursing when you realize all the wires are too short. How do you think I found that out?
• Don’t decide to practice soldering joints for the first time on the airplane wiring. Get training. Incorrectly done solder joints produce cracks and failures.
• Use standoffs or wraps where harnesses align with or cross metal components or tubing.
• If a problem crops up, it will be handy to know where the wire goes (what system). It takes more time, but just using some masking tape with circuit info until you can finish and properly label everything will be helpful.

Hardware Errors

Missing hardware, incorrect attachments, and missing safety wire are abundant on some projects. Nearly all these errors are not there on purpose, but because the builder did not get the skills training. One of my favorite sayings is, “We don’t know what we don’t know,” and this is why you should engage a technical counselor and others who may know more than you do about aircraft hardware.

Biggest offenders are missing rivets, nuts, and bolts (yes, missing), using the wrong material (grade) such as low-grade (no markings) bolts and nuts, and using the wrong fasteners for rotating parts.

What to do

• Before your project starts, do some soul searching and consider attending EAA workshops to get some hands-on training in the technology you are building.
• Use AC-43-13 as a reference as you are building, along with the kit documentation.
• Carefully follow hardware instructions from the manufacturer. If you’re assembling a kit from well-known manufacturers, nearly all the hardware will be supplied with detailed instructions. Although this is helpful, you should still have a working knowledge of why certain fasteners are used in specific places, especially if you are going to apply for the repairman certificate.

Engine Installation

Errors consist of clearance problems where components are chafing, not properly sealing items going through the firewall, and missing heat protection. It is the engine bay where everything else in the aircraft seems to have a terminus. At the same time you are figuring all of this out, you are eager to get taxiing and in the air. The collision of these two emotions can cause important items to get missed.

Control cable adjustments are often not fine-tuned or tightened prior to the first flight, causing cables to disconnect, which produces either a wide-open throttle or loss of power. And of course, anything else that falls off can create a small or catastrophic failure. I’ve also seen a lack of full travel on control grips and linkages that were not fully attached or safetied.

Fuel issues include using the wrong filter media, causing a clog as soon as takeoff power is applied, and a variety of fuel contamination issues.

What to do

• Follow directions to the letter; if there’s something that is confusing, get help.
• Have other knowledgeable experts review your work.
• Be patient and take time with the details.
• Use checklists and then double-check the checks.

Changes to the Kit

Because you are assembling an experimental amateur-built kit, you may believe the sky’s the limit on experimentation. I’ve seen engine changes, seat and bulkhead changes, and even wing, aileron, and rudder design changes. The errors arrive as handling problems, weight and balance problems, and system failures.

What to do

• Stick to the instructions for the kit you are building. You’ll have a safe and proven aircraft. If you want to make changes, contact the manufacturer. If it’s something the manufacturer thinks will work well, it is likely to give you the attention you need to make it happen. As a technical counselor I had one builder tell me, “Oh, no, I can’t ask the manufacturer, it will be shocked and say no.” This is inviting danger. I was able to talk him out of it, but it is happening.
• It’s fine to explore changes, but stick to the tried-and-true alternatives, and always get advice, even if you’re already a structural design engineer.
• When Ron Wanttaja, EAA 275698, looked at the accident statistics, he learned a lot about engine choices and the importance of sticking with the manufacturer-recommended engines.

Repair Projects and Restoration Project Errors

These are unintended errors from not going far enough in your teardown. These errors include not identifying structural damage underneath fabric or inside panels, and not checking related service bulletins or airworthiness directives for potential existing problems.

What to do

• When we are repairing an aircraft, it’s hard to determine how far to explore. For example, if we are fixated on re-covering an aircraft, we may not be thinking of corrosion or hidden broken ribs.
• If you are working on a certified aircraft, check manufacturer service letters, bulletins, and airworthiness directives.
• Assume the arrival of surprises when you make repairs or undertake a restoration. If you find things that worry you, like excessive corrosion, stop and do a detailed inspection, even if you have to do more teardown.
• Find experts and get advice. The more eyes on your project, the better the chance you will discover the problems before finishing and then saying, “Oops.”

Keys to Success

There are five keys to avoiding build errors that bite you in the first hours of operation after completing a homebuilt aircraft, a major repair, or restoration.

1. Do a self-assessment and get hands-on training if you need it. Think through the complexity of the project you’re choosing. A kit from a well-established manufacturer will minimize potential building errors, whereas a plansbuilt project will be more complex with more ways to leave the proven pathways.
2. Follow directions and get help and advice on anything that confuses you. Don’t make major changes to the airplane without checking with the manufacturer first.
3. Join the builder’s group and find out what issues or problems other builders encountered. Take advantage of any EAA chapters near you.
4. Assemble and use the best flight test plan you can. I recommend the EAA Flight Test Manual.
5. Engage the free services of a technical counselor and flight advisor.

To err is human. But to be human is to be smart, thoughtful, and able to anticipate potential problems and solve them before they bite.

Lisa Turner, EAA Lifetime 509911, is a manufacturing engineer, A&P mechanic, EAA technical counselor and flight advisor, and former designated airworthiness representative. She built and flew a Pulsar XP and Kolb Mark III and is researching her next homebuilt project. Lisa’s third book, Dream Take Flight, details her Pulsar flying adventures and life lessons. Write Lisa at Lisa@DreamTakeFlight.com and learn more at DreamTakeFlight.com.

Post Comments

comments