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Consequences of a plane not flying often?

Cardiff Kook

PATRON
Sisters, OR
I've been looking to purchase a plane.

I have noticed in reviewing the logs some planes for sale don't fly much.

When does this become a problem? Is under 5 hours a year for five years an issue?

Engine in question is an 0-200. All planes hangared.
 
Corrosion in the engine, airframe, electrical system . . . That said I’ve purchased multiple airplanes that sat for years. You just need to negotiate figuring what it will cost if everything goes bad!


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Hangared matters to a point, more controlled environment. Location in the US matters a fair amount more. Coastal areas worst. Humidity and salt air. Florida is called corrosion corner for good reason when it comes to airplanes.
Under 5 hours a year for 5 years matters a lot no matter what if thats all that happens between flights ie no storage efforts/rust preventative measures taken etc etc. What Denny said about Lycoming 100% spot on. Lycoming cams at the top of the engine. Continental engines just the opposite. There are other factors, cause and effect that play in here but the bottom line is there’s no such thing as regular use being bad for your aircraft and it’s engines longevity. I’d rather wear it out than rust it out.
 
I would factor that into my negotiation
I bought a Skyhawk with the H2AD emgine out of Denver that averaged .3 hours per year (taxied to shop and annualledfor 6 years. I put 1000 hours on it and it was still strong when i sold it
Another , a RV6 out of Amarillo was seldom flown and it spalled the cam in 100 hours
Ya never know


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The engine's obviously the important thing, but an infrequently used aircraft will likely see a longer period (i.e. at the start of the low hours each year) of hard landings and bounces than a more regularly used one.

…don't ask how I know.
 
I'd get the engine borescoped on something that flew < 5 hours per year for 5 years before I bought it. Borescope and maaaybe oil analysis might tell if there is a problem. Engine corrosion is the main concern. If you're in the high dessert of Arizona it might not be a problem at all. The engine might be junk if it was in Puerto Rico.

In this video, RAM recommends operating the engine 1 hour at "operating temperatures" per week. So ideally you want about 50 hours per year on the motor. Anything less than 25 hours per year (an hour every 2 weeks) and I'd be doing a borescope, compression, check, maybe an oil analysis before buying, or be negotiating the price of the airplane with a discount for an overhaul.

I take my airplane out of the hangar and fly it for an hour every 2 weeks in the winter if I can get a day good enough. It flies a lot more than that in the summer, luckily in winter the corrosion potential should be lower because the air is drier.

Additionally, the type of oil used can play a factor. Straight weight oils allegedly adhere residually to engine internals better during periods of disuse. For that reason, on my 182 that only flies about 100 hours per year and an hour every 10 days or so in winter, I run W100 plus in summer and W80 plus in winter. Multi weight oil is more likely to run off quicker during periods of disuses. Reference: https://www.avweb.com/ownership/which-oil-should-i-use/

Disclaimer: I'm not a mechanic or even a very good owner or pilot.
 
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A borescope + compression test + oil analysis is not very expensive, I'd never buy any airplane without that. Lately, I have decided I will pull a lifter as well.

John
 
By all means have a mechanic who knows what he's doing do a borescope inspection!! I didn't do that on our airplane, and now we're having to buy another engine.
 
I bought a 135 Lycoming 0290D2 from old Don Johnson in about 1995, it had been in his hanger since 1970! He had stored it 'upside down' on a tire, ( cam down) So when I pulled the clys off to check em out, upon inspection we observed the cam to be in perfect condition. All the 'sidewalk' lawyers
Had all said, engine will be junk! So 4 years later and about 400hrs later, on that old motor. I bolted 4 overhauled clyinders onto it. Cam was still fine. Go figure.
 
Some old timer AP/IA recently told me he had more issues with engine sitting out West vs East. Extreme Opposite from what I’d been taught. He said the extreme temperature swings out West made engine corrode more and the rubber/gaskets to rot out. Said the East states doesn’t have the daily temperature swings like the high desert. How true is this or is he full of it?
 
Some old timer AP/IA recently told me he had more issues with engine sitting out West vs East. Extreme Opposite from what I’d been taught. He said the extreme temperature swings out West made engine corrode more and the rubber/gaskets to rot out. Said the East states doesn’t have the daily temperature swings like the high desert. How true is this or is he full of it?

One data point for Arizona. The O-360-A4A on my PA-28 was overhauled back in 1988 and has run nearly 3,000 hours since then. When cylinder 3 was pulled at about 2,800 hours the exposed cams and followers were perfect. No other cylinders have been pulled. It has flown less than 400 hours in the last 10 years all on Aeroshell W100.

Not a lot of temptation to fly it now I have the FX-3. It needs a new home.
 
I will throw in my two cents, which is about what this is worth. But having watched this issue over the years I’ve come to the following conclusion. When an engine sits you get rust and corrosion on the inside. When that engine starts being used it’s like having rubbing compound or lapping compound run through the engine. I don’t know how many times I have seen people buy a low use engine, and after 25 or 50 hours they are saying “this is wonderful, I got lucky, the engine runs great doesn’t use oil, everything is wonderful”.
And then, after about 100 or 150 hours the engine turns into junk. Don’t let anybody tell you for one minute that a low time engine that has a long time since the overhaul is a good engine. You are rolling the dice with about a 95% chance that engine will never make TBO.
A 150 or 200 hour engine that has seen 15 years since the overhaul, will never make TBO. You’ll feel lucky 50 or 100 hours and then you’re gonna end up overhauling the engine. I have seen this over and over and over.

Bill
 
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Small Continentals sit idle for years better then Lycomings do. My Pa11 on floats sat on the bank of a river for 5 years after the owner died. Had under 400 hours on it. It was still running strong at 2200 hours when I wrecked it. Friend bought a Champ that sat for over 15 years and the little A65 still runs great.

Glenn
 
The 1949 O-235 in my PA16 had 2600 hrs on it when I took it apart in 1998. Everything looked great. Rings wore out. I have found 4 Lycomings in a little over a year making metal. Found the issues by cutting and inspecting the oil filter. One engine was 20 years old and had flown very little, two Carbon Cubs, one flew a lot but didn't get the oil hot enough, the other flew 30 minutes at a time, same thing. We were changing cylinders on my Dad's 320 and both of us looked the cam over twice, all good. 100 hours later the cam went. Waiting on cam and lifters from Lycoming on another one that hadn't flown much in recent years. It is a crap shoot, roll the dice or pull a cylinder and look.
 
My experience? 1200 hour 0-320, flown regularly, hangared, well maintained. Removed from a Cub for an 0-360 upgrade. Did a cold compression test off the airplane. 2 cylinders in the 60s. 1 in the 20s. 1 at zero. Figured I’d get the cylinders repaired so pulled them. The cam was junk. Like the surface of the moon. A guy can do everything right and the engine may still be a corroded mess. On the other hand I know lots of planes that get flown infrequently and accumulate very few hours, and have for years. They’re doing fine.

Yep, roll the dice and take your chances. The only constant is all engines wear out. The unpredictable part is when.

Edit- If you talk to old pilots they’ll tell you the rate of corrosion failures has increased dramatically in recent decades. Some blame fuel changes. Some blame steel changes. Some will say modern pilots don’t fly as much. I think we have better instruments and better maintenance than they used to use so we find things that used to go unnoticed. Maybe it’s a combination of lots of factors.
 
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Thanks for all the replies.

Would a borescope of engine see all this or is it no possible to really know? Oil analysis?

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You have to pull a jug to see this stuff. Just like Bill Rusk says, this was about 150 hrs (18 months) into regular use, 9 years and 750 hrs SMOH. With those numbers I didn't expect trouble. Half of the cam followers were bad, the other half looked good. Crank was pitted in the front main journal. This was in a coastal location for the first 6 years after OH. 20201007_092222.jpeg20201007_092336.jpeg

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You can not see the cam with a borescope. Oil analysis is great if it is trending and have caught them that way. Oil filter with some time on it is good or pulling cylinders and looking. One of the ones I found recently was on a low time, lot of calander time Carbon Cub. Had ferrous metal in the filter. Dumped the data off the engine monitor and saw short flights, low oil temps so used that data to deduce the lifters and cam were going. Split the case and lifters were bad, cam was not effected yet.
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I am looking at one now that had a new cam and lifters installed in 2016. They were the DLC lifters. It hasn't flown much since but am less concerned about it because there have not been any issues with the Diamond Like Coated lifters spalling like the old ones.
 

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Worse is the pilot that flys very little.

Had good luck with older Lycoming like pre 70's. Newer seem to have junk cams.
 
As bad as an engine sitting is, running it at low power settings seems to be just as bad. Lycomings like to be run hard. The one I had on my TriPacer ran a lot better after a couple hundred hours towing signs than when I first got it. Ended up selling it with almost 3000 hours on it and it was still running strong.


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