By Lisa Turner, EAA Lifetime 509911
This piece originally ran in Lisa’s Airworthy column in the December 2024 issue of EAA Sport Aviation magazine.
Technicians were deep into their chores and barely noticed Tim as he walked through the hangar to the back office. Walt, a designated mechanic examiner, looked up from his paperwork.
“You must be Tim,” he said. “Welcome. Congratulations on passing the written exams. We’ll start this morning with the practical, and do orals tomorrow.”
They shook hands and went out into the shop. Walt pointed out a Cessna 172 in the corner.
“Kate will pull the airplane out and do a warmup for you,” he said. “Change the oil and filter, gap and install the cleaned set of plugs, clean the gascolator, and make a list of any problems you see on this clipboard. I’m sure you’ll find this all super simple. I’ll be over to check on you. First, though, look at this safety wiring setup as I snip it all off. Then you can redo it.”
Tim looked at a metal casing on a stand with complex safety wire routings. He gasped as Walt began snipping it all off. He wished he’d snapped a picture with his phone, but it was too late.
“Have fun,” said Walt, returning to the office.
Thirty minutes later, Tim was still wrestling with the safety wiring when Kate came over.
“Your practice airplane is ready for service now,” she said, pointing to the 172. “I can see you’re enjoying the safety wiring. We all went through it. Dreadful.”
Tim abandoned the casing and went over to the Cessna. Walt looked out the office window and watched as Tim tentatively went about the tasks. Walt noticed Tim didn’t ask for a torque wrench before putting the spark plugs back in the engine and didn’t ask for the cutter to open the oil filter. He decided to go down and talk to him.
“Tim, I’m sorry, but this isn’t working out,” Walt said. “I’m noticing little things, like the filter inspection and torquing the plugs. I’m not seeing the important details.”
“Right, things aren’t going well,” Tim said. “I need to spend more time in training. I’m not ready.”
* * *
You don’t have to be an A&P mechanic to perform certain maintenance tasks on your airplane, but you do need to understand how to do it right. The FAA lists 31 tasks that, as an owner/operator, you can do on certified aircraft. If you have an experimental light-sport aircraft or experimental amateur-built aircraft, you can legally do any maintenance on it. If you have an S-LSA, what you can do is determined by the manufacturer and will be listed in the aircraft documentation.
Simple May Not Be Simple
Many of us have found ourselves in situations where we got in over our heads. The Dunning-Kruger effect says, in effect, we don’t know what we don’t know. Instead of stopping and backing up, we forge ahead and hope for the best. When this happens in a plumbing project, we can turn the water off and wait for the professional. Missing details in airplanes can cause far more serious consequences.
I’ll cover five common maintenance tasks on our airplanes, and add some advice on traps to avoid and best practices to incorporate. Because airplanes are so diverse, you may see something different from what I describe. Remember that the procedures and techniques contained in your maintenance manuals and your pilot’s operating handbook are the ones to follow.
If you have a homebuilt without these instructions and specifications, consult with the manufacturer (if you can) and with the owners/builders groups for information. Remember that the FAA’s AC 43.13-1B is an excellent resource to accompany the other information you have for the airplane. Find a link to this and other relevant resources at EAA.org/Extras.
If the manufacturer offers additional information, such as videos, they will be detailed and helpful if this is all new to you. Entire articles have been written just about oil filter inspections, for example. The EAA videos, articles, and workshops can round out your skills, as can working with your local EAA chapter to get hands-on practice.
What Can Go Wrong and How to Avoid
Fuel Filters/Gascolators/Sediment Bowls
Whether you’re working on your homebuilt or your certified aircraft, follow the advice the manufacturer gives you. While this is clear with certified airplanes, it may not be clear or it may be missing on the experimentals.
- Clogged fuel filter. Ron Wanttaja, EAA 275698, noted in a 2018 power-out accident analysis that fuel contamination and fuel design mistakes make up 20 percent of the power-loss cases in homebuilts. While design problems are not likely with certified production aircraft, production airplanes can suffer from fuel contamination. As a technical counselor, I see a hodgepodge of filters scattered throughout the fuel system on homebuilts, all points for clogging or forgetting.
- Not using the right type of filter. Make sure you’re using the right type with the right screen density. Construction debris is common in filters and gascolators in the first 50 hours of operation. Early maintenance and multiple inspections are critical.
- Forgetting to safety the gascolator/sediment bowl if you have one. It’s easy to overlook.
Installing Spark Plugs
Whether you clean the spark plugs or replace them will depend on what the manufacturer tells you to do, and depend on the type of engine you have installed in your airplane. Typically, the automotive-type plugs are inexpensive enough to replace. If you have an airplane with aircraft-type spark plugs, realize they are easily damaged when cleaning and handling. I recommend working with an A&P the first time you service them.
- Not checking and adjusting the gap using the right tools.
- Not using anti-seize compound. The next time you or your A&P removes the plugs, it may be more difficult without the thread lubrication. Anti-seize compound also helps distribute heat. Leave the last several threads clean so that the electrodes don’t get fouled.
- Not using a torque wrench, and overtightening the plugs.
Replacing Tires and/or Tubes
Replacing tires sounds like a straightforward job. It can be, but can also hold some traps for the unwary.
- Jacking up the airplane and not using a safety block. I hear, “It will just take a minute.” Jacks can fail in a day — or in a second.
- Not marking orientation for balanced reassembly of wheel halves before taking it apart. Oops. This should go on your checklist.
- Not using tire talc on the inside on reassembly. This acts as a lubricant and reduces the chance of accidentally folding or pinching the inner tube when you reassemble.
- Overinflating the tires. Some mechanics think this will help seat the tire. It’s not a good idea. If seating appears to be a problem, it’s possible you caught the inner tube between the halves. Deflate and check. Several cycles of deflation and inflation will give you the best result.
- Not knowing what the correct tire pressure is. No, it’s not the “max pressure” listed on the tire. This is a recipe for a blowout and injury. Look in the pilot’s operating handbook or the aircraft manual for this information and then transfer that number into your preflight list.
After my last article on tire care, several readers wrote to say they were using tire pressure monitor devices to check pressures on the preflight. The sensor is housed in the valve stem and communicates with a handheld unit that can be mounted wherever you choose. This is a great idea, especially when your tires are encased in wheelpants.
Systems are also available for certified aircraft, but they may be more expensive since they require FAA approval with an STC.
Changing the Oil and Filter
A critical contributor to the health of your engine is the oil and filter change. Here are a few things that can go wrong.
- Oil ends up everywhere. This happens when you grab the filter after loosening it, and it falls out of your hands. There’s nothing quite like engine oil getting on everything, including you. The great characteristics that make oil so slippery inside your engine make for a mess outside the engine. The solution is to expect the escape. Depending on the location, I use a plastic bread baggie around the filter base as I loosen, after placing several plastic grocery-type bags under that with some paper towels to catch the rest.
- Not inspecting the filter’s internal oil pleats for signs of trouble. You should do this at every oil change. If you begin to see shiny metal bits, it’s time for a professional to weigh in.
- Forgetting to re-safety. This is easy to forget. Double-check.
- Using a cheap, off-brand filter. Don’t. Use what the manufacturer recommends. Yes, there are important differences, including whether it contains a bypass spring or not.
- Overtightening the oil filter. Follow the manufacturer’s recommendations. This is usually around 15-17 foot-pounds of torque measured by how far you turn the canister, for example, three-quarters of a turn.
If you have a Rotax four-stroke engine, oil changes are wonderfully straightforward with a separate oil sump, filter, and magnetic plug to check. Use the maintenance manual for the steps.
Replacing Seat Belts
I know what you’re thinking. This has got to be the simplest maintenance task on the planet. It may be, but there are a few traps to know about.
- The biggest trap on certified aircraft is buying and installing automotive belts. Don’t forget that seat belts must be FAA-approved. You’ll see a tag on them with this information. Technical standard order approval indicates that a part has met the specific requirements laid out by the FAA, ensuring its suitability for installation in certified aircraft.
- In experimentals, owners may ignore manufacturer instructions and install belt anchors in the wrong place. Belts should be installed so that the occupant can’t slide out from under them, and anchor points must be reinforced so that the belts hold properly in a high-force crash.
General Advice on Best Practices
Don’t rush. Performing inspections and conducting maintenance is not the time to “try to fit it in.” I’m not saying there aren’t handy shortcuts, but you need to be thorough and thoughtful every time you are working on your airplane.
Take the time to assemble everything you will need beforehand, including your maintenance and repair manuals and handbooks. No matter how good you get at this, you’ll still forget a tool or part once in a while.
Conduct an inspection when you’re done with the work. Even better, get someone else to look at your work. You may not be comfortable having another qualified person inspecting what you’ve done, but push through this feeling. It will give you a higher level of safety and quality. Run the aircraft, and then check again. Finally, perform a short test flight to make sure everything is operating the way it should.
Use a calibrated torque wrench. Nearly everything on an aircraft is sensitive to how tight you make an assembly because the materials are lighter. “Just so” and “that’s about right” won’t cut it.
Safety wiring is another skill to master. Get some practice time with an A&P. If you’re unsure about the work you’re about to undertake, consider going to an aircraft repair and maintenance shop and watch how they do it.
Get and use the correct tools for the jobs you’re undertaking. If you’ve proven to be a reliable “borrower” (i.e., you return them promptly), you can probably get them from the local shop or your EAA chapter. Otherwise, get your own. No one said wrenching on your aircraft would be investment-free.
If you’re wrenching on your homebuilt, you have the authority to decide what parts to use. But if you are working on your Cessna 152, parts must be approved (FAA/PMA). These are parts that have received approval (PMA) from the FAA and can be sold as an alternative to the OEM part. You should use what the manufacturer recommends with any aircraft, experimental or not, because this builds in safety.
Don’t forget the logbook entry. Make your maintenance entries as detailed and legible as you can so you’ve got a record of information that can help you in the future with any troubleshooting, and for the benefit of future owners.
Finally, ask yourself if this maintenance is enjoyable and confidence-building. If it’s not, find a good mechanic.
The story I began with ended well. Tim spent another few months in training for his A&P mechanic practical tests, which he passed with confidence.
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 a Pulsar XP, a Kolb Mark III, and half of a RotorWay Exec helicopter. Her book, Dream Take Flight, details her Pulsar flying adventures. Lisa loves hearing from readers. Write her at Lisa@DreamTakeFlight.com.