Oil condition monitoring? Just not needed by you?

[Geoff_H]

I am just wondering how many of us subscribe to NDT of our engines. After all the engine is rather critical to sustained flight. How many get their oil condition tested to see upcoming engine problems? How many know many different conditions, including piston wear can be determined well in advance of them happening by sending off a sample of oil to one of the many condition monitoring places?

[facthunter]

Just cut the filter open and run a magnet around the opened out filter element. That is a practice used throughout the aviation industry . Oil condition monitoring is more for truck fleets where you are trying to run the oil longer. It does do the other things but it's not cheap.. Nev

[onetrack]

Oil monitoring has been used by the earthmoving and mining industries for over 40 years, to prevent major losses caused by failures in very large and very expensive diesel engines.

 

It is effective, it is comprehensive - but it's dependent on two things. One is, a baseline must be established to determine "normal" levels of specific metals contamination (chrome, copper, lead, tin, aluminium, iron, etc).

 

Second, you need to know and understand the specific metals makeup of the particular engine you're examining - and where those metals are located in the engine.

 

Once you have someone with that specific experience, the oil monitoring process can be quite effective. But it is isn't cheap -and Facthunters recommendation is the primary method, and the cheapest solution.

[Downunder]

I probably see more value personally, in putting the money that would go into oil sampling, into extra oil changes....

[Yenn]

Oil testing is common in the USA. What it will do is provide a base to look for changes. That means that if you get an increase in some chemical in the oil, they can suggest what may be causing it. Say for example your Lycoming starts getting increased iron, it would make you suspect worn cam lobes, or increased tin could be bearing wear. It really needs to be used over as many oil changes as possible to spot trends. I don't know what the cost is, nor even if it is done in Australia or it has to be sent somewhere else.

[Geoff_H]

It can be done in Australia, just need mass spectrometer. But with an aviation specialist they will give heaps of additional information, they need to know what engine the oil is from. It is not that expensive when considering the cost of an outfield landing. Magnetic particles in oil tells you about a condition of the engine a long way into a failure.

O paid around $400 for around 10 samples, plus USA postage.

[Geoff_H]

I have used these people. Aircraft | Blackstone Laboratories

[old man emu]

Wouldn't the number of hours an engine runs be one of the factors in deciding if oil condition monitoring was needed? Big machinery, say in mines, works for about 3000 hours per month, so that's a lot of wear and tear. How many light aircraft would rack up even 50+ hours per month? I agree with Downunder - better to change the oil and filter regularly. The trends highlighted by conditioning monitoring take a lot of hours to show up.

[Geoff_H]

Blackstone would disagree, failure can be detected long before anything is obvious to the naked eye. The smallest of quantities show up with a mass spectrometer. They can even say if an engine is not wearing in properly. Many owners of top end GA aircraft do testing from engine new or overhaul. I find it interesting that it appears that LSA owners don't see the value in oil testing as a preventative measure.

[old man emu]

I find it interesting that it appears that LSA owners don't see the value in oil testing as a preventative measure.

 

There's no argument that oil testing has some sort of value in it. For LSA owners there can be many types of value from oil testing. Some are economic. Some are for assurance and protection against possible engine failure. One could add more to the list. It is, however, the result of a cost/benefit analysis.

 

Geoff H said it cost him $400 for ten samples going to the USA. There are labs here in Australia, but I haven't got pricing information. Take a Jabiru engine as an example. It takes 2.3 litres of oil. That's a tad under $30 per oil change. 400/30 = 13.3 oil changes. If you change the oil every 25 hours, $400 will buy you 13 x 25 = 325 hours. To establish a trend, you would have to send away a sample every 25 hours, and how many 25-hour tests would you decide upon to be the number to determine a trend?

 

And how many months would the averagely used LSA aircraft take to log 325 hours?

[FlyingVizsla]

Mr FV swears by oil sampling, but the way we do it is a waste of time. He was used to heavy machinery testing where the oil sample was analysed, compared with baselines, alerts were issued and advice on engine was routine. He didn't have to understand any of the chemical elements.

 

We buy oil sampling kits through Caltex - about $43.50 which includes a replay paid satchel - and have about 4 floating around unused. He has done tests through Komatsu and Caltex. They all give readings for particles etc, but none give him any analysis. They are littered with "Unknown" "Diagnosis Not Applicable" "Interpretation not available" "refer results to an aircraft engineer" "results may not .. be acceptable" with blank graphs. He works on "tell 'em nothing, take 'en nowhere" and as a consequence they can't tell him anything. He relies on someone ringing him to alert him to a problem (as they did with heavy plant) but they won't, so he assumes everything is OK.

 

Here's an example of an oil test. On the back are 6 blank graphs.

01081402.PDF

[Geoff_H]

I often flew in IFR in the dark, night VMC in the outback. Engine failure would probably meant my death. Maybe that is why I put so much emphasis on engine health. I don't think that there is any economic value, unless when buying an aircraft it could alert to an engine with issues.

[facthunter]

Perhaps you overcomplicate it.. Thinking people are not safety inclined if they don't do what you recommend is a bit hard on those who do it differently. It's NOT a matter of doing this test or you are negligent and your engine will fail. Do you cut open the filter each oil change? . A lot of the ways some operate are not stable enough to produce results that mean much with the type of use many of our planes get. If your engine vibrates or misses or seems down on power, get it checked straight away. Pull it through before use when it's sat for a while. Don't use stale fuel...These are practical checks that would mean more in direct safety relevance. Aero engines don't wear out like a lot of cars and motorcycles Trucks and tractors do. They are usually pulled out of service long before the engines are worn out. They sit unused too which is a safety issue.. Nev

[old man emu]

They sit unused too which is a safety issue.. Nev

 

It's probably the lack of use that is the main cause of wear in engines of small aircraft. Sounds back to front, but an engine sitting unused can't cough out the nasty combustion products, nor can it prevent corrosion caused by the engine 'breathing' with changes in air pressure as weather systems move by.

 

Perhaps instead of going through the process of getting oil condition tests, a wise owner might spend some time plugging the tail pipe and the air intake. Whip out a plug from each cylinder and squirt in some inhibiting oil and put the plugs back in.

[facthunter]

OME the water doesn't have to come from the atmosphere. Burning HYDROcarbons makes water. Make sure the motor is completely HOT when shut down. Plugging the exhaust does no harm. I squirt WD in the exhaust of mowers and pumps etc to stop the exhaust valve rusting in the guide about 5 minutes after shutting it down. It's too hot if you do it straight away. It also prolongs the life of expensive Japanese motorcycle mufflers.

[Geoff_H]

I had oil filters cut open and magnetic full as well. The major reason for oil testing was detecting engine problems from wear etc that has started but is not able to be detected by any other means. I flew the craft every week where possible. As a professional engineer I have always been a believer in preventative maintenance. Aircraft engines are the same as automobile engines. Automobile engines are used for far longer than aircraft engines and have no mandatory overhaul times. Most wear in my Mooney came from the engine idling waiting for the oil to get to temperature so that the constant speed propeller or the pistons getting hot before the bore and ceasing would not happen on take off.

Is appreciate that engine failure in visual conditions usually only means an outfield landing, with possible damage. Night flying is far more dangerous, I have not done it for years. now that I am older and suffering from the normal degredation of night vision.

[Bruce Tuncks]

Having read Mike Busch, I looked into oil testing for Jabiru engines, and found that there is no database of results to use for a baseline. So Nev's filter examination is as good as you can do, and it may be better than the analysis of unseen wear particles. Plus frequent oil changes and general careful maintenance. Lycomings do have a database so they are different.

I certainly don't fly at night and nearly all my flying is within glide range of a landable paddock , with the notable exception of when airspace restrictions force me to fly lower than safety demands .

[Bruce Tuncks]

Here's a question... imagine a 700 hour Jabiru engine which has good compressions, has never had a significant amount of metal in the filter, has 25 hour oil changes and uses super-magnets on the oil filter to remove and monitor ferrous wear particles. What advantage could I expect from spectroscopic oil analysis? What if this were to be instead of my next two planned jobs, which are (1) to buy and use a good reverse-viewing endoscope so that I can examine the valves and the inside of the combustion area and (2) try and buy into a syndicate for a dynamic vibration meter or design and install a vibration meter for the instrument panel.

[Geoff_H]

For vibration on fixed surfaces I use my phone. There are a number of fast Fourier transform analysis apps that will also give data as to what is exciting the vibration. I clamp my phone to the surface.

[Geoff_H]

I no longer need these oil testing kits. They are prepaid just posting cost to USA. Free to anyone that wants them. Useless to Jabiru engines and 2 stroke engines, any others wanting them please pm. My project uses 2 stroke engines so no further use to me. Used this brand when I had the Mooney

[Alan]

Out of curiosity and because I had access to the tools when I first got my Jabiru I did some oil analysis work. ( I agree it is of very little value in comparison with the filter cut). In addition to routine spectro oil analysis, I used Ferrography (extraction and classification of wear particles up to about 150µm) to look at the oil during running in [i can probably dig out the photographs of the wear particles from the lab archives if any body is interested]. By heat treating (330°C for 90 sec) the particles once deposited on the glass slides, it is possible to differentiate the high grade alloys from mild steel and cast iron. When looking at oil from a reciprocating engines either diesel or petrol it is suprising how little of the ferrous wear product comes from the cyclinder material.

 

We also collected vibration spectra from several Jab 230 3300s as one of them had an unusual vibration. Other than variations in frequency amplitudes they all had very similar spectra - surprise! The rouge vibration turned out to a be a front wheel spiining up during flight - a flap on the wheel spat fixed that.

 

Regards

 

Alan

[Geoff_H]

Vibration analysis is another very useful NDT tool. In industry the X, y and z axis vibration signature will be taking after commissioning. You were able to have other machines to compare with when something went wrong. I see all NDT as a health check, seeing possible problems long before they show up a problem. The best results for these tests is no result.

Vibration analysis is really terrific for gearboxes, Meshing frequency can show a tooth starting to have problems. Good thing is that you can check the vibration with a mobile phone. I was able to determine the natural frequency of my house by measuring its vibration when the metro tunnelling machine passed under next door's house. Useless information, could be useful to earthquake proof the house ?. Ok I just love engineering, from 14 years of age when I discovered what an engineer was until now at 72. Now I just design my project.

[facthunter]

The highest load areas are the cams and lobes and temperature issues with the exhaust valves and guides and the piston ring groves with carbon build up especially with the top one. A lot of what is taken for carbon is dust mixed with it. Oil darkening is usually a rich mixture. Cloudy oil is water in the oil. Nev

[M61A1]

Vibration analysis is another very useful NDT tool. In industry the X, y and z axis vibration signature will be taking after commissioning. You were able to have other machines to compare with when something went wrong. I see all NDT as a health check, seeing possible problems long before they show up a problem. The best results for these tests is no result.

Vibration analysis is really terrific for gearboxes, Meshing frequency can show a tooth starting to have problems. Good thing is that you can check the vibration with a mobile phone. I was able to determine the natural frequency of my house by measuring its vibration when the metro tunnelling machine passed under next door's house. Useless information, could be useful to earthquake proof the house ?. Ok I just love engineering, from 14 years of age when I discovered what an engineer was until now at 72. Now I just design my project.

As a maintainer I would love to learn more about vibration analysis, but I'm not sure my brain will handle it. I thinks it's almost full, as I'm having trouble making new stuff fit.

I find tracking and balancing helicopter rotor blades fascinating, but we are limited in our adjustments to what the program tells us to do. Different systems with different programs seem to get similar outcomes from different methods, but sometimes they seem to make no sense.

 

We use oil analysis all the time (every 50 hours) on gas turbines, sometimes we send particles away for analysis, but I'm not sure it would be cost effective for a cheap ultralight.

[Geoff_H]

M61A1 those gas turbines that you work on, are they Siemens gas turbines? Are they near Dalby?

Vibration analysis is simple. Get a set of vibration traces, use a program to convert the vibration to frequency and amplitude (fast Fourier transform maths) using an ap freely available. Then look for things that happen at the largest frequency, how fast the machine is going, meshing speed of gears (all in hz). Finding a match in frequency will usually lead you to the problem.