By Lisa Turner, EAA Lifetime 509911
This piece originally ran in Lisa’s Airworthy column in the August 2022 issue of EAA Sport Aviation magazine.
Ed rolled the hangar door open and felt the heat hit him as if he were walking into a blast furnace. Beads of sweat formed on his face as he walked over to the Beechcraft, flipping on the light switch on the way.
Let me get this airplane outside. Even in the sun, it will be cooler than in here, he thought.
Removing the chocks, he grabbed the tug handle and moved the airplane over the threshold and onto the apron.
His friend Keith came around the corner with several duffels.
“I hope you have air conditioning in your airplane,” he said. “I feel like we are getting baked today.”
“Ha! Sure. It’s called ‘air-venting,’” Ed said.
“Ready to go?”
“No, I need to finish the preflight. I got started last night but then had to go run some errands.”
“Okay, I’ll load up. I’m looking forward to going to the lake. It’s been a long week. Hopefully it’s a little cooler up there.”
Ed walked around the 1949 A35 and thought about how distinctive the V-tail was. Previous owners had done a good job keeping it in shape. He wanted to do the same, but it was a learning curve. He’d only acquired the airplane a week ago.
I need to get some kind of detailed checklist that shows me what to look for, he thought as he viewed the dog-eared page he had been given by the previous owner. “Check,” it says. For what?
The two men finished packing and got into the aircraft. There was little traffic at the small nontowered field, and they took off after a short run-up.
As they climbed, the air grew cooler through the vents. “That’s better,” Keith said, wiping his brow.
“I told you the aircraft had special air conditioning,” Ed said.
As they reduced power and settled in at cruise, there was a sharp bang and the left side engine cowling sprang up like a jack-in-the-box. Before either man could react, the cover ripped off its hinges and hit the windshield, cracking it and disappearing behind them.
The airplane entered a left-hand downward spiral as Ed, in shock, tried to bring the aircraft back under control. After one turn and losing 1,000 feet of altitude, he brought the Bonanza under control and reduced power.
“Wow! That happened fast,” Keith said. “Good job on the controls.”
“Yes, calamities are sudden. Look at the other side of the cowling. That looks like it’s going to come off, too. Let’s get back to the airport before we suffer any more damage. Obviously, I forgot to check something.”
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Keeping Things Attached
Flying and working on general aviation aircraft over the years turns up some dramatic stories. As you’re listening or reading, you hope for happy endings. While Ed and Keith’s story ended without a serious accident, it could have turned out differently. I’d rather the pilot lounge be a boring place than pilots beginning with, “Wait until you hear this.”
Our airplanes are a cornucopia of attachments. The section on hardware in FAA AC 43.13-1B, Acceptable Methods, Techniques, and Practices — Aircraft Inspection and Repair, is 74 pages long. That’s a lot of hardware. How do we keep everything attached? Here are the top five trouble areas.
Cowling and Body Panel Fasteners
Experimental amateur-built and certified aircraft cowlings and exterior panels are held together in many ways. The manufacturer tries to make the fittings easy to use for inspections but also durable enough to not open or cause the door or panel to depart the machine in flight.
In one instance, a pilot did not check all the compartments on his Stearman before performing aerobatics. The cockpit cover fell out of the baggage compartment when the airplane was inverted, and it wrapped around the tail surfaces. Remarkably, the pilot landed without incident but was quite embarrassed when he saw his friends laughing at the cover stuck to the airplane.
Turn-to-lock (“turnlock”) type fasteners are the most common in securing inspection plates, doors, and other panels on our airplanes. The clear advantage of these fasteners is that they allow easy removal for inspection and servicing.
Turnlock fasteners are manufactured and supplied by a number of manufacturers under various trade names. Some of the most common are Dzus, Camloc, and Airloc. Some aircraft simply use screws and nut plates. They are secure, and like the turnlocks, you can see if one is not in all the way. (If you’re looking.)
Whatever the attachment method is, make sure your periodic inspections include a check of the integrity of the mounts, plates, and other components, such as springs. These items are easily and routinely overlooked. Over time, wear and tear can create failure areas.
On your preflight, check that all panels are fully closed and locked or screwed in place. On your annual or condition inspection, check the condition of all fasteners and mounts.
A piece of hardware can be assembled correctly and safetied and still be a problem over time. An example is turnbuckles hidden deep in the fuselage. If we forget to check the integrity of the attachments on our condition or annual inspection, we can find a situation where attachments fail and we don’t know it.
What happens? There is a stainless-steel swaged cable end (specifically MS21260) that is threaded into the brass barrel of the turnbuckle. A corrosion fracture can occur under the safety wire wrap, and the swaged end separates at that point. The only thing saving the pilot from loss of control is the safety wire wrap. To prevent this from happening on condition inspections or annual, you should unwrap the safety wire from the fitting and inspect it with a magnifying glass for cracks and corrosion. It sounds like a lot of work, but wouldn’t you rather keep the redundancy of an intact fitting with safety wire?
Note: With the supply chain issues in recent years, some designated airworthiness representatives and A&P mechanics have found counterfeit AN hardware. This is an alarming turn. If you’re purchasing an aircraft, get a thorough prebuy from someone qualified who can identify quality issues.
Crimps, Connections, and Boots on Electrical Wiring
This is far more of a problem on homebuilts because of the variation in both building materials and building techniques. But it can also be a problem on older certified aircraft that have not been inspected rigorously, especially in corrosive environments.
On homebuilts, some builders don’t realize that using aircraft-grade wiring, terminals, and boots will yield secure and trouble-free service for years. Using automotive-grade materials may work at first, but they are subject to faster corrosion and don’t have the strength that aviation-grade hardware employs. Aviation-grade tools (such as the crimpers) also make a big difference in quality and longevity. Sure, it all costs more, but we’re not building and flying specifically to save money.
These troubles can be serious. Loss of panel function, loss of alternator charging, loss of lighting, and inability to start (or stop) the engine can all be due to wires falling off, intermittents, or shorts when bare wires are contacting other wires or the frame.
This happens to us all. Given the hundreds of connections and pieces of hardware on our aircraft, it’s normal and easy to not see something missing. But once we know that, and we know what we’re looking for, it becomes second nature to look for safeties. For those new to flying, this is a learning curve that gets better with experience. You might recall your first preflight that was not attended by your instructor. You did your best, but did you feel as if you didn’t know what you should be looking at? That’s normal.
Look for holes in bolt heads and tabs that are empty. If you’re a beginner at safety wiring, get your local technician to show you the right way. Again, I refer to AC 43-13. It has the best instructions for how to safety wire nearly anything. I remember the FAA A&P practical test I took long ago. One of the first things the examiner did was show me a large, elaborately safety-wired component as he snipped all the wires off in a flash and I looked at it in horror.
Note: Some folks think that the torque seal we place on hardware is there to stop the piece from backing out. It’s not a safety. It’s only there to help us with inspections, and it’s excellent for that purpose. But don’t use torque seal or thread locker to safety hardware unless the manufacturer calls for the thread locker specifically.
Using the Right Fastener in the Wrong Place or the Wrong Fastener in the Right Place
On certified aircraft, we replace hardware with exactly what came off (with new) in order to comply with the regulations. This is important because the specific nut, bolt, or screw was chosen for suitability and durability. This may not be so easy when we’re building our airplanes. The key is to make sure we’re using what the manufacturer specified and installing it according to the directions. Use both the directions that came with your kit if it’s a homebuilt and AC 43-13 to install and inspect hardware for both certified and homebuilt aircraft.
Examples of mistakes include using nylon locking nuts in the engine compartment, where high-temperature nuts should be used; using nylon locking nuts in a situation with rotating or tension loads that require a castle nut with pin; using a plain bolt where a drilled head bolt is required (to be safetied); and not using a check nut (“jam nut”) where called for to lock down an assembly.
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Two ends on a spectrum trip up many of us. The first is familiarity. We are so used to seeing something over and over again and are not looking for a change or a difference. This habit at the extreme causes us to actually not see anything different in the component we’re inspecting. Our brains see it as it is supposed to be.
The other end of the inspection spectrum is thinking we will see something wrong automatically and it will somehow jump out at us. Here, unfamiliarity replaces familiarity as the driver. Since we’re not sure what to look for, we don’t see it.
In both cases, the answer is awareness and training. First, become aware of your bias. Do some self-searching. Only you can answer these questions about yourself — and it’s private so your honesty will pay real safety dividends. Where are your weak areas? What additional reading can you do? What training can you attend?
In the case of familiarity, slowing down a little and using a checklist will help. Slowing the inspection gives the brain a second chance to recognize something that is not as it should be. Inspections should be as distraction free as you can make them and without attempts at multitasking. Pretty tough assignment for humans, but it will make you more effective.
In the case of unfamiliarity, the checklist augmented with periodic training or reading about the function of components will help you notice correct from incorrect. Ask a pro to take you through some inspections and watch carefully. You’ll see how they are really tuned in.
Safety is always higher when you have multiple layers of protection. Awareness, knowledge, and using complete and accurate lists go a long way in getting things attached and keeping them attached.
Lisa Turner, EAA Lifetime 509911, is a manufacturing engineer, A&P, EAA technical counselor and flight advisor, and former DAR. 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.