AeroShell 15w-50, Lycoming O-540, 25 hours, Piper

[wings&wheels]

Here is an update on our bird. Haven't seen many other aircraft analyses here, so I'll keep folks entertained.

Engine is a 540 ci, horizontally opposed, air & oil cooled 6 cylinder, 235 hp w/ a constant speed propeller (controlled by engine oil presssure through a governor) and uses 100 octane leaded av fuel (100LL). The engine has approximately 300 hours left to overhaul.

Copper continues to be elevated for the last 3 samples, but the other metals look fine but generally increasing which we expect given the age of the mill. We were thinking that the elevated Cu was due to inactivity, however my mechanic now suspects a rocker bushing and we'll be looking into the top of the engine at the next annual inspection.

hf=hours flown

hf 25 17 24 23 20 28 19 Univ avg
Al 03 03 03 03 03 03 03 06
Cr 04 02 03 04 04 03 04 04
Fe 18 12 12 14 14 15 13 26
Cu 09 08 07 04 02 03 02 05
Pb 3239/2211/3027/2923/2085/2569/2145/3860
Ni 01 00 01 00 00 01 00 02
Sn 01 00 00 02 01 00 01 01
Si 04 04 05 05 05 04 05 06
Ca 01 02 01 01 00 01 01 05
Mg 06 04 04 06 06 08 05 03
Ph 1153/1076/1140/998/912/1103/1060
Zn 02 01 02 02 01 01 02 03

All others 0

Vis 91.3

Fuel, H2O & insolubles
Thoughts, comments? Rgds, w&w

 

[Last_Z]

Wow! This really is a 180* turn from what we are used to here. There are no conventional additives in this stuff except for the phosphorus. I know that lead has to be for antiwear...I don't see that coming from leaded gas.

Anyway, I am totally uneducated on this type of report, but it seems fine to me; although iron did spiked quite a bit.

 

[wings&wheels]

Piston engine aero oils have very low levels, if any, of additives that could leave ash or other deposits in the combustion chamber as the deposits could cause pre-ignition or detonation. The oils are classified as "ashless dispersant". Most recip aero engines consume a fair amount of oil, this engine burns about 1qt in 6-7 flight hours (approximately a little over 1,000 statute miles), so chamber deposits are an issue.

The lead is primarily from blow-by as the fuel even though it is called "low lead", has 3-4 times the level of lead additives that leaded auto gas had. The engines also have fairly loose tolerances leading to a fair amount of blow by.

 

[Last_Z]

Low lead my tail! I'd be scare to spill some of that gas on my hands!

 

[JohnBrowning]

It has been a long time since I looked at an UOA from a Lycoming 0-540. Now with that said I will say that it appears to rather mondane. Nothing is jumping out at me even the copper is not way out of line it could very well be from sitting. It is not hard to pop the valve cover off to check the rocker bushing. I am sure you have pulled them off before to check for valve deposits.

 

[MolaKule]

Are sure the hours flown is correct?

I would have used a progression of hours (from 17 to 28) to better see any trending. For example you have 17 hours next to 25 hours. I would go from 17 to 28 hours from left to right and leave the Universal Average off unless it is truly an industry database average.

I see nothing substantial if there was some inactivity. Some rusting and copper corrosion can occur with inactivity and may be wear. Is the rocker bushing soft steel or is it a bronze bushing?

 

[MolaKule]

The anti-wear agent in these oils is a phosphorous compound, usually a phosphate ester, and the dispersant is usually a non-metallic ester-based compound as well.

You won't see any metallic compounds for detergents as they contribute to ash and potential combustion chamber "hot-spots."

This sentence should have said, "I see nothing substantial if there was some inactivity. Some rusting and copper corrosion can occur with inactivity and may NOT be wear. Is the rocker bushing soft steel or is it a bronze bushing?"

 

[wings&wheels]

JohnBrowning..."mundane" is good in this situation..

The rockers are bronze bushings on a steel shaft. We are going to look in the rocker boxes at the next annual and if we don't see anything, we'll look at the propeller next. We had the prop overhauled three years ago, and the Cu started climbing two intervals later. While I can't see how the pitch change mechanism could cause the increased metal, it is coincidental.

For those not familiar with constant-speed props, there is a governor that feeds engine oil under pressure to a cylinder in the propeller hub to change blade angle.

 

[Geoff]

If the prop is held in place by engine bearings, then possibly the increased wear after the prop service is due to some out of balance component.