Previously printed in November 2018 EAA Sport Aviation
By Lisa Turner, EAA 509911
“Let’s go flying,” Tom said.
“Great,” I replied.
The doors groaned on the rails as we opened the hangar. Cobwebs hung everywhere. There was a musty smell in the air. Sunlight cut a path across the littered concrete floor as a tiny mouse ran for cover. None of these things detracted from the excitement of seeing the yellow J-3 Cub in the center of the space surrounded by dusty boxes, a few chairs, and a tool cabinet.
“Here, help me move some of this stuff,” Tom said.
I slid several boxes out of the way and rolled the cabinet to the side, taking a good look at the Cub.
“Whoa. How long has it been since you’ve had the airplane out flying?” I asked.
“Uh, probably three months at least … well, maybe longer. You know what happens. You plan on flying and then something else comes up,” Tom said.
“Well, we’re not just going to hop in and fly right now, that’s for sure.” I looked at the layer of dust on the airplane and what looked like a flat tire. “You’ll need to do some investigative work and then an extra thorough preflight.”
Tom sighed. “You’re right. I guess we’re not going flying, at least not right now.”
“I’ll help,” I said.
I made a list of problems: flat tire, bird’s nest under the cowl, mud dauber trail in the pitot tube, mice evidence in the back seat, and a liberal coating of dirt everywhere. I made a note to remove the covers and check the rib lacing integrity since mice consider the cord wax a meal and the string as nesting material. A suction cup check on the fabric next to the ribs would tell the whole story.
“Are you sure you put this away in running condition?” I asked.
“It was fine,” Tom said.
“There’s one thing you can do in the future to prevent these surprises.”
“I can’t imagine what that would be.”
“Fly the plane!”
“Yeah, right. With my schedule? Good luck with that.”
We all wish we could fly as often as possible, but other responsibilities get in the way. When aviation is our recreation and not our work, we can find long stretches in between our flying fun. And then there is weather and climate thrown into the mix.
What happens to our airplane when we don’t fly regularly?
- Things get sticky. From oleo struts to door hinges to wheel bearings, lubricants become less flexible and dry out.
- Tires lose air and gain flat spots.
- Protective films become thinner on cylinder walls, cam lobes, and lifters.
- Rubber and plastic parts deteriorate.
- Contaminants and water collect in the fuel.
- If you’re running autogas with ethanol, serious and rapid degradation occurs.
- Birds, wasps, and mice discover a cozy new home.
And more. Strange things begin to happen with lots of time passing between flights. It’s almost eerie.
Here are some things you can do to prevent surprises, limit downtime, and make your airplane last longer.
Storage. Take stock of the environment your aircraft is in. In a perfect world with a topped-off bank account, my airplane would be next to my car in a large air-conditioned and heated garage, and I’d fly every single day. Since I don’t have any of that, I’ll settle for a heat and cold ravaged hangar. Anything you can do to protect your airplane from the elements will help preserve it.
- Plug or cover holes, such as static ports, pitot tubes, and fuel and air vents.
- Keep the aircraft clean.
- If your aircraft is all metal, consider applying a fluid-thin film coating (such as ACF-50 or CorrosionX) in aircraft cavities. It does a great job but can be a little messy.
- To help prevent tire flat spots in storage, move the aircraft slightly once a week or place it on jacks for longer term storage.
- If the aircraft is outside, try using a cover to prevent airborne contaminants from landing on the aircraft and to protect it against sun damage.
Fuel. Storing your airplane with full fuel tanks reduces the moisture that can condense in a partially filled tank. If your airplane has rubber fuel bladders, full tanks will minimize cracking over time. Don’t worry about the age of aviation fuel unless your airplane has sat for two years or more. Ben Visser, an aviation fuels and lubricants expert, lab checked numerous avgas samples after two years and found no degradation. If your airplane hasn’t run in two years, the gas will be the least of your worries.
Mogas vs. Avgas. While avgas will remain stable for years, mogas is a different story. If you are using a reliable source of ethanol-free mogas in your Rotax-powered or other autogas-approved engine installation, fresh fuel should be stable for up to six months. If you use mogas with ethanol, all bets are off. Even though Rotax says you can run up to 10 percent ethanol in your engine, my opinion is to try to avoid ethanol entirely.
I remember well one Rotax engine tech school session where the instructor showed the class what happens to different gasoline grades and types over time. A line of labeled glass beakers filled with fuel mixes sat on the desk. He pointed to a beaker with a mogas and ethanol mix marked at four weeks. At the bottom third of the glass was an ugly line of ethanol alcohol and water sludge.
Premium auto fuel without ethanol is actually becoming easier to find. Many experimentals have tanks with less than 20 gallons and burn less than 5 gph, making it less onerous to fill the tanks with several gas containers from the station. We love flying our homebuilts and will go to great lengths to supply quality fuel to them, but for larger homebuilts using mogas, it’s still difficult to find airports supplying it. An internet search can provide current maps of supplies, such as www.Pure-Gas.org.
Engines. The biggest downside for an engine sitting for months without use is corrosion damage. Over time the protective oil film on cylinder walls, cam lobes, and lifter faces thins to the point where rust (iron) begins to form. The result during the next engine start is a high degree of wear in the initial minutes, and then the iron disperses into the oil as a contaminant. There’s a direct correlation between the length of inactivity and the amount of iron you will see in your oil analysis.
Continental Motors service information letter, SIL99-1, Engine Preservation for Active and Stored Aircraft, outlines a very detailed procedure for what it considers short-term (up to 90 days) and long-term (longer than 90 days) storage. Similarly, Lycoming outlines the procedure for its engines in Service Letter No. 180 B, Engine Preservation for Active and Stored Aircraft. Rotax recommends a simple oil change and plugging procedure for storage if the engine will not be used for more than a year.
Given that the engine manufacturers would like you to fly every week, how do you handle those inevitable stretches when you can’t fly? Here are some tips.
- Keep your aircraft in a hangar if possible. This will reduce the moisture production that comes from the heating and cooling cycle outside.
- Add some climate moderation to your hangar. High humidity and drastic temperature changes wreak havoc on materials. If you can add a dehumidifier, it’s a good idea. Moisture is the enemy.
- If you keep your aircraft outside, use a cover that does not trap moisture (breathable but waterproof).
Oil additives. More controversy? Some aircraft owners swear by Marvel Mystery Oil, and others by Slick 50 or AvBlend. Mike Busch, EAA 87836, one of the most astute aviation engine experts out there, recommends ASL CamGuard. I agree with Mike that any extra protection you can use against engine corrosion is a good idea. The engine manufacturers would rather stay out of the discussion, not recommending any additives. Both ASL CamGuard and AvBlend are “accepted” (not “approved”) by the FAA, which only means that the FAA doesn’t think either of these products will damage your engine. It is highly unlikely that either of the two FAA-accepted additives would void an engine warranty, according to Mike. My advice is to do your own research and double-check with the engine manufacturer.
Rotax engines are a different animal when it comes to additives. The manufacturer states that all additives the engine needs are already in the recommended oil. Rotax engine oil also lubricates the gearbox, where additives could interfere with clutch friction. Once again, the recommendation is to check with the manufacturer of your specific engine.
Ground runs. Should you or shouldn’t you? Debate rages over engine ground runs versus flying the airplane long enough and at high enough temperatures to burn off moisture. My opinion is to avoid ground running your aircraft as a replacement for flying. While a ground run does get the oil circulating, it does little to burn off all of the acids and moisture in the system.
Battery. If your airplane sits for months at a time, consider buying a trickle charger for the battery.
Longevity: The Top Five
Here are the top five things you can do to prolong the life of your aircraft.
- Hangar your airplane. Any interior climate moderation you can do is a bonus.
- Fly the airplane as often as you can. If you know it will be sitting for more than a month, follow the engine manufacturer’s advice on storage procedures.
- Don’t pull the prop through by hand to lubricate the engine while the airplane is inactive. This will scrape oil off surfaces and accelerate, not delay, corrosion.
- Avoid ground runs without flying. If you go flying, make it an hour and make sure temperatures are at their recommended values.
- Visit the aircraft periodically to make sure something hasn’t happened to it while you’ve been away. Mice, wasps, and birds come to mind. Once these creatures settle in, it only gets worse with time.
Do you have an experimental aircraft? Follow these same tips, and find out what your specific engine manufacturer says about storage procedures.
Here’s one last thing. If it’s been a while since you’ve flown, especially if you’ve just restored your aircraft to flying from after a period of storage, a detailed preflight is critical. Remove covers as you would for a condition inspection or annual inspection, and trace through all of the systems for integrity. Check filters and drains. Make sure all of the tape and covers are off the vents. Use a flashlight to look inside every space you possibly can. Be as thorough as possible.
Now, let’s go flying!
Lisa Turner, EAA 509911, is a manufacturing engineer, A&P, technical counselor, flight advisor, and former designated airworthiness representative. She built and flew a Pulsar XP and Kolb Mark III, and is currently restoring a Waco UPF-7 with her husband. Lisa is a member of the EAA Homebuilt Aircraft Council and Women in Aviation International. For more from Lisa, read her monthly column in EAA Sport Aviation Magazine.