I am looking at an airplane that has an O-540 and was overhauled only a few hundred hours ago. It has chrome cylinders and has been making chrome and tin above normal levels. Tin was elevated and is now back to high normal. Some of the values have gone up and down a bit. If anyone is familiar with reading these I could use some advice. Happy to share the reports I have with someone if interested.
Oil Analysis on an airplane I am looking at
- Thread starter Skylark23
- Start date
Post the results for us to review.
There were a couple labs used as you can see with 2/28 results in duplicate. Engine is O-540 with 360 hours SMOH by an engine shop
| Date | Engine Hours | Iron | Copper | Nickel | Chromium | Aluminum | Silicon | Tin | Lead |
| 8/7/19 | 11 | 279 | 28 | 4 | 21 | 43 | 51 | 38 | 1597 |
| 3/17/20 | 35 | 207 | 25 | 5 | 31 | 27 | 16 | 15 | 2021 |
| 7/23/20 | 61 | 171 | 16 | 3 | 23 | 21 | 9 | 8 | 2439 |
| 8/2/21 | 104 | 85 | 8 | 2 | 22 | 16 | 7 | 4 | 1660 |
| 2/28/22 | 115 | 87 | 7 | 2 | 22 | 16 | 8 | 1 | 1918 |
| 2/28/22 | 115 | 62.6 | 6.8 | 1 | 17.5 | 12.7 | 4.9 | 0.3 | 1354 |
| 6/6/23 | 263 | 70 | 11 | 2 | 42 | 15 | 10 | 4 | 4541 |
| 8/21/23 | 310 | 37.6 | 6 | 0.8 | 23.3 | 9.1 | 4.9 | 2 | 3569 |
| 11/21/23 | 360 | 44.8 | 7.9 | 1.6 | 21.9 | 11.2 | 2.6 | 0.7 | 3077 |
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4RNB
What result do you get when you do an internet search for lead in oil analysis?
What does your mechanic say?
How long has the plane been on the market?
Any additives? What oil?
Gotta love a Blackstone report, averages, normal values, and commentary.
What does your mechanic say?
How long has the plane been on the market?
Any additives? What oil?
Gotta love a Blackstone report, averages, normal values, and commentary.
What are your specific concerns with the analysis? Those reports are not a diagnostic tool per se but used in conjunction with compression tests, borescope checks, etc. to monitor engine health. But for a quick glance I don't see any issues -- however, without knowing the sampling technique, results of the oil filter checks, operating environments, etc. can't offer more than a basic guess. Just as with any monitoring systems they all have their limitations without knowing the big picture.
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Domenick
First normalize your numbers to 50 hours for a more accurate orange to orange comparison. It's still not perfect.
Your numbers seem wonky. Are the data points at consecutive oil changes? If the data represents non-consecutive oil changes, it's much, much less valuable.
PPM*50/hours_since_oil_change = normalized PPM
For example:
03/17/2020 Cr 31*50/21 = 73.8
06/06/2023 Cr 42*50/148 = 14.2 (why 148 hours between oil changes?)
Your numbers seem wonky. Are the data points at consecutive oil changes? If the data represents non-consecutive oil changes, it's much, much less valuable.
PPM*50/hours_since_oil_change = normalized PPM
For example:
03/17/2020 Cr 31*50/21 = 73.8
06/06/2023 Cr 42*50/148 = 14.2 (why 148 hours between oil changes?)
They sent off samples to two different companies
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Domenick
And so we see why consistency matters. Switching analysis vendors, resets your trending to zero.
Analytical equipment and procedures factor into the results.
Some of the numbers are *close*, but the Pb numbers are interesting. That's a huge difference for an easy test. Kind of makes you wonder where the analytical work for the airport lead contamination studies was done.
chemgeek
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chemgeek
Oil analysis is like having an MRI done: you discover a lot of interesting things that are mostly inconsequential.
My main concern about the commercial outfits doing this is that they often do not include uncertainties (e.g. 95% confidence limits) or detection limits in their analyses, information that is critical in understanding the significance of the reported results. (This is a topic I drill into my analytical chemistry/instrumental analysis students.) "4172 ppm Pb" sounds very impressive and definitive, although it is extremely unlikely that this value is known to 4 significant figure precision. More likely, it is something like 4200 +/- 900 ppm at 95% confidence. In addition, sampling homogeneity, viscosity management, and the calibration/validation methodology have a large impact on the accuracy and precision of the results. If you make three systemically biased replicate measurements you can get a completely reproducible but incorrect measurement with a narrow confidence limit.
Oil analysis should be considered as a crude trend analysis tool that supplements, but does not supplant normal engine maintenance and inspection procedures. I would never make any decision about engine maintenance based on oil analysis alone. I've never done oil analysis on my aircraft except as a teaching exercise for my students. Getting accurate, precise, and validated results is much more challenging than one might expect, even if you have the most expensive and capable toys for doing it. No single method can quantify all relevant wear metals or elements well.
My main concern about the commercial outfits doing this is that they often do not include uncertainties (e.g. 95% confidence limits) or detection limits in their analyses, information that is critical in understanding the significance of the reported results. (This is a topic I drill into my analytical chemistry/instrumental analysis students.) "4172 ppm Pb" sounds very impressive and definitive, although it is extremely unlikely that this value is known to 4 significant figure precision. More likely, it is something like 4200 +/- 900 ppm at 95% confidence. In addition, sampling homogeneity, viscosity management, and the calibration/validation methodology have a large impact on the accuracy and precision of the results. If you make three systemically biased replicate measurements you can get a completely reproducible but incorrect measurement with a narrow confidence limit.
Oil analysis should be considered as a crude trend analysis tool that supplements, but does not supplant normal engine maintenance and inspection procedures. I would never make any decision about engine maintenance based on oil analysis alone. I've never done oil analysis on my aircraft except as a teaching exercise for my students. Getting accurate, precise, and validated results is much more challenging than one might expect, even if you have the most expensive and capable toys for doing it. No single method can quantify all relevant wear metals or elements well.
I don't see anything there to be very concerned about.
Universal averages don't matter if you're using chromed cyls, because the data they baseline from will be chrome and non-chromed cyls. If you tell Blackstone that you have chromed cyls, they will adjust the reporting to compensate for that.
It's a tool. You use it in combination with what you see on the filter pleats and any changes in oil consumptions or darkening rates. i.e., if you start seeing more flakes in the filter pleats, and you start seeing increases in metals that match the general characteristics of the flakes, you probably have some actionable information. We found it useful, when looking at overall trends, to decide we could safely push our last engine a couple hundred hours past TBO.
Universal averages don't matter if you're using chromed cyls, because the data they baseline from will be chrome and non-chromed cyls. If you tell Blackstone that you have chromed cyls, they will adjust the reporting to compensate for that.
It's a tool. You use it in combination with what you see on the filter pleats and any changes in oil consumptions or darkening rates. i.e., if you start seeing more flakes in the filter pleats, and you start seeing increases in metals that match the general characteristics of the flakes, you probably have some actionable information. We found it useful, when looking at overall trends, to decide we could safely push our last engine a couple hundred hours past TBO.