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Help with RV purchase...engine question

Flynfrfun

Active Member
Hi everyone. I'm new here, but have been lurking for quite a while. I've searched the archives and not really found the answer to my question.

I'm in the market to purchase an RV6 or 6A hopefully later this year. I've come across several planes that have sat for 1+yrs. The owners says that they started and warmed up the engine regularly and some said they even changed the oil occasionally. Should I shy away from this? I've heard that starting and warming up and engine w/out actually flying it is worse than just letting it sit. I believe the reason was that any time the engine is running it is creating water in the crankcase. If you don't fly it and get the oil up to temp for 30mins or so, the water doesn't have a chance to boil off. So starting regularly on the ground and warming it up just adds more water than letting it sit.

Thanks for any input and sorry if this has been discussed before.
Josh
 
Yes, you are correct. Some will debate whether it it better to let is sit unused for one year or do short runs every month. Obviously neither is good. I am in the camp of the former. Extended short runs can create a mixing of oil and water (you've probably seen the milky oil at some point. WHen this happens, the water is held in suspension in direct contact with steel parts, such as the crank journals and crates a different problem than increased humidity in contact with steel parts that have had their oil film removed via gravity.

In the cases your looking at, you have good information to know what has happened. However, most planes will be several years old and will have periods in there history where you have no meaningful information and will have no real idea if a plane sat for 6 or more months without being used. The fact that a 10 year old airplane has been used regularly in the last 2 years does nothing to limit the risk that it sat for a year at some time. This is not entirely true with cam wear, but a point to be considered.

A plane that sits for a year or is run for 10 minutes once a month is not a guarantee of problems. Further, flying the plane once a week is also not a guarantee of running to TBO, though it is more likely. I would be far more worried about planes with Cylinder that have ADs or known poor longevity than with a plane that sat for 1 year.

I am in the camp that you do the best you can in making an educated assessment of ALL factors and value it accordingly. MANY, if not most, planes sits idle for far longer than they should for minimizing corrosion. However, limiting your choices to only planes that have documented use every 15 days is going to severly limit your pool of choices.

If you have concerns over engine usage and risk, deduct $10K from the value to account for necessary engine repair. In the end, they are many ways to get burned. If I found a plane that was great in every other aspect, but it sat for 12 months I would devalue it some compared to others, but would still happily buy it if the price was right.

Some of this depends upon your skill. Letting an engine sit creates risk of corrosion. In this case, the typical failure is the cam. Other corrosion is typically not an issue to reduce TBO. Possibly a risk of cyl wear, but not likely to go beyond that fixable by a hone/ring job, if anything. If you are mechanically competent, you can tear down the engine and replace the cam. Re-hone, new rings and reassemble. Will cost about a grand and take a few weeks of your time.

I encourage you to make a balanced view of any plane and not eliminate specimens due to issues like this. Assess the risk and cost of repair and factor that into the determined value. Obviously don't pay more than the value that you determine for each aircraft.

Larry
 
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Hi everyone. I'm new here, but have been lurking for quite a while. I've searched the archives and not really found the answer to my question.

Josh, I don't think there is a single absolute answer to your question.

There are different oils and different additives, all with their own claims. There are real differences in materials, and further differences in surface treatments. Climactic differences count, as do local conditions, like airborne salt content. Crankcase water content is mostly a function of blowby, and even that varies a lot between engines.

Two weeks ago I borescoped a 1993 vintage 80 hp 912 with taxi time only, after which it sat in a hangar for many, many years. I couldn't find rust anywhere, including the crankcase and gearbox.

I've seen a three year old, 75 hour 0-200 with rust flowers everywhere.

Point is, the best bet is "assume nothing, inspect everything".
 
Any Lycoming with a hollow crankshaft should be inspected IAW Lycoming SB505B for corrosion pitting on the inside of the crank flange. I recently had an O-320 tear down performed due to a prop strike, and even though the crank flange was stamped PID per the SB, pitting was found and the crank scrapped. The possibility of this would be increased due to engine inactivity.
Jake
 
Good advice from Larry, Dan, and others.
Just one guys experience, I purchased an airplane that sat for a year in an unconditioned drafty hangar in Oregon. Logs where incomplete notes taken off of the hangar wall whereby after each flight he would write the date and time on the wall. Very, very, sketchy.
I paid the right price considering, and at that, it was still all I could afford in the day. I flew that airplane for ten years and 600 hours then sold it for twice what I paid for it. Stuck one valve through that time ($300 fix) and that was it.
So, for the right price, and a little luck, you can make out really well. You could also end up with a nightmare. As Dan mentions, inspect what you can to increase your chances, and as Larry said, pay accordingly just in case.
 
Thanks for the info guys. It's good to not be hearing "Run...don't walk away from these planes!". Sounds like it will be a bit of a jump of faith no matter what. I will approach it with the idea of doing the best I can, but have a fat bank account just in case;). I am planning on a pre-buy inspection from someone familiar with RVs for sure.

The one thing that jumped out at me was Larry's comment:
I would be far more worried about planes with Cylinder that have ADs or known poor longevity than with a plane that sat for 1 year.

I will be only considering 0320/0360 engines. Are there any variants of these engines with poor longevity? I hadn't heard of that before. I have heard of the 0320H2AD engine's issues.
Josh
 
As they said, get it inspected.

These pictures are for the Lycoming I had that was overhauled in 1959 and never run until I put it on my RV 2005. I pulled the jugs to inspect the inside and replace all the seals. As you can see, it was spotless.


(Click to enlarge)
 
Thanks for the info guys. It's good to not be hearing "Run...don't walk away from these planes!". Sounds like it will be a bit of a jump of faith no matter what. I will approach it with the idea of doing the best I can, but have a fat bank account just in case;). I am planning on a pre-buy inspection from someone familiar with RVs for sure.

The one thing that jumped out at me was Larry's comment:


I will be only considering 0320/0360 engines. Are there any variants of these engines with poor longevity? I hadn't heard of that before. I have heard of the 0320H2AD engine's issues.
Josh

It's more that some of the aftermarket cylinders installed have issues, such as the ECI variants within an AD requiring replacement and others, such as chrome, having issues with oil burning. It was not intended to raise that specific issue (hopefully your pre-buy will identify things like that). It was more about the fact that the universe of risk goes WAY beyond the one item you mentioned. You should not be scared from any of this. I would strongly suggest taking a full weekend to search and absorb the breadth of knowledge available on this site. That will leave you much better prepared to deal with some of the real world issues that can arise, how often they arise and what factors seem to cause them.

Best of luck.

Larry
 
As they said, get it inspected.

These pictures are for the Lycoming I had that was overhauled in 1959 and never run until I put it on my RV 2005. I pulled the jugs to inspect the inside and replace all the seals. As you can see, it was spotless.


(Click to enlarge)


On the flipside, I bought an engine whose bottom end was pulled from a plane and sat for 20 years. I don't know what they did or why it was pulled, but the oil was heavily water-entrained (milky color). This caused considerable corrosion of the steel parts (particularly nasty, as the oil encapsulation prevents evaporation, so water stays in direct contact for a long time) Fortunately the crank could be ground down, but had to go to .060" This is a unique case and doesn't necessarily apply to your situation. Just giving the breadth of the spectrum and causality of these issues.

Larry
 
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It's more that some of the aftermarket cylinders installed have issues, such as the ECI variants within an AD requiring replacement and others, such as chrome, having issues with oil burning. It was not intended to raise that specific issue (hopefully your pre-buy will identify things like that). It was more about the fact that the universe of risk goes WAY beyond the one item you mentioned. You should not be scared from any of this. I would strongly suggest taking a full weekend to search and absorb the breadth of knowledge available on this site. That will leave you much better prepared to deal with some of the real world issues that can arise, how often they arise and what factors seem to cause them.

Best of luck.

Larry
Larry, I'm not scared by any of this. But I AM scared of what my wife will do to me if I buy a plane and need an overhaul the following month:eek:
Josh
 
I don't know but if it were me, I wouldn't run from these aircraft. The engine situation can be assessed fairly easily. If the engines were ground run regularly and the oil was brought up to temperature i.e. above 160 degrees. I think the insides will be pretty good. If you are serious about and aircraft and worried about water and rust in the engine. Look and see. Borescope will reveal rust on the cylinder walls if they are nitride or steel. Remove the rockers and if there was water in the oil it will be present in the rocker boss area. Also the inside of the rocker covers will likely be very rusty. If you are still worried pull two cylinders off. Get the seller to pay or pay half. It is in his best interest to know what is in there for the next buyer if you decide you don't want it after the inspection or when he is negotiating the price with you. A good mechanic can have two cylinders on and off the aircraft in less that an 8 hour day. Not a big investment, If the aircraft is what you really want. If the internal inspection shows a problem then negotiate the price to have it fixed off the purchase price. If it shows all is well then put it back together and buy with confidence.
Ig the aircraft was stored in a controlled environment hanger or in a very dry part of the country. I wouldn't be concerned at all.
Anyway the engine could be a worry but it can also be assessed and get you an aircraft that you might otherwise have walked away from.
Good Luck,
Mahlon
 
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