Rotax 912 making oil?

[planesmaker]

Interesting case recently of a 912 making oil, preflight revealed oil tank full almost to the top. Needless to say aircraft was not flown. It appears fuel has somehow got into the sump, first thought fuel pump (done only 70hrs) but surely that is what the drain on the pump is for. Carby floats was another thought however any fuel leaking past needle from flooded Carby bowl would have to flow up over an incline in the inlet manifold, it would rather flow out the back of Carby. After a search on internet someone who had seen this said it was diesel contamination in fuel. I would never had considered this possibility, searching further I found a person who actually experienced this very thing and could trace it back to diesel contamination. I will try to post a link. Just writing this to let others know and be careful about fuel supply.

 

 

[planesmaker]

Here is a copy of article.

 

Dear Forumites

 

Herewith an incident I had with diesel in petrol. I'm sharing this to create awareness, so here goes:

 

On Saturday I decided, on short notice, to fly to a meeting Outjo to Otjiwarongo (1/2hr), and from there to Tsumeb (2hrs). From the word go I was late for the meeting and had less than an hour to get my Hawk ready. I needed petrol and found my normal fuel container 3/4 full. Which was weird, because I always empty them (What doesn't fit in before a flight gets added after), but what was inside looked and smelled like unleaded, so I just added petrol at the pumps to fill them completely and off I went.

 

During warming up I noticed a little bit of blue smoke coming from the exhaust when looking at it against the sun. By the time I got the hangar doors closed I had already forgotten all about it. En route to Otjiwarongo I found that I burned 11.8l/h instead of the normal 11.0 @ 4,900rpm, but put it down to weird and ignored it further. The EGT's looked slightly lower than normal, but the weather was cooler so that explanation was tagged to the problem. In Otjiwarongo all was normal. I even took a friend for a short scenic flight before I departed to Tsumeb. During the pre-flight in Otjiwarongo I didn't check the oil level. How much oil can one lose in 40 minutes, right? En route I noticed that the 912 UL seemed to run slightly erratic, the revs dipped from 5,000 to 4,800 every now and then. When I applied full throttle the engine responded fast and willingly and settled back on 5,000 easily. This puzzled me, but it was turbulent and I was busy dodging rain showers, so I found another convenient explanation: Obviously the turbulence I ran into caused the motor to labour every now and then. Problem analysed and explained away.

 

On landing in Tsumeb I found my oil container brim-full and every drop of oil that couldn't fit into the tank (which was a lot) spread evenly over the tail feathers. After a whole day of trying to find an explanation (it isn't easy at all to explain 1.5l of oil gained during the flight) I latched onto a possible solution and traced the fuel supply. The "petrol" came from a diesel car that was wrongly filled with petrol at the pumps. The mixture was drained and stored for further use. I had actually witnessed the whole operation and was also concerned that "my aircraft fuel containers" were used for the job, but I'd mos know about it and not forget. Right.

 

The 912 is fine. Except for a red face, so is the pilot. The spark plugs were cleaner than I have ever seen them, it looked like a layer of coke had been loosened from the pistons. We drained and refilled both oil and fuel and changed all filters. The magnetic oil plug was clean except for a single sliver of metal. I'll have the oil analysed to check, but the Hawk behaved very well during the flight back to Outjo, which was conducted at ample altitude for a possible emergency landing.

 

I fly a low compression 4-stroke. With a higher compression engine like the 912 ULS the story may have ended differently, or finally. Thus to repeat my instructor's lessons:

 

• Don't be rushed when tending to your aircraft.

 

• Make sure about your fuel supply. Repeat, make *sure* about your fuel supply.

 

• Don't take deviances from normal lightly. My fuel consumption wasn't normal, neither were the lower EGT's and definitely not the fluctuating revs.

 

 

[kgwilson]

This happened to me when our company petrol tank was wrongly filled with diesel. I just filled up my tank as usual and away I went. About a week later I checked the oil level and found it half an inch higher than the full mark. All the companies cars that had been filled in that time were checked and there was a major maintenance issue for a while as they were all drained & cleaned etc. No harm done as it was detected quickly enough.

 

 

[Thruster88]

For me the most interesting aspect of the story is not the oil dilution but that humans can make almost unexplainable mistakes. I have some experience

 

 

[facthunter]

To err is human. To forgive divine. They say. Flying doesn't need much error. Diesel will end up in the sump but really lowers the octane figure. In a Turbo charged engine you would be lucky to survive the take off with even a few % in there. Nev

 

 

[Yenn]

Diesel has brought down Lycoming engine plane in very short time. Diesel is heavier than petrol so will be lower in the tank.

 

Refuel your Lycoming powered aircraft with diesel and you will run on petrol in the lines and carbie, then change over to diesel, just as you need full throttle and are close to the ground. the CHT will skyrocket and the only way to save the engine from detonation is to reduce power drastically. Not a good idea when on climb out and low.

 

 

[facthunter]

Even a hero tractor will dilute the oil if the heat exchanger isn't vapourising the fuel. Engines are supposed to run at the correct temperature. . Too cold and the oil goes milky due to water accumulating in it.. Diesel doesn't evaporate much unless it's exposed to very high temps. Diesel engines usually have more compression rings than a petrol engine.. Nev

 

 

[Thruster88]

Even a hero tractor will dilute the oil if the heat exchanger isn't vapourising the fuel. Engines are supposed to run at the correct temperature. . Too cold and the oil goes milky due to water accumulating in it.. Diesel doesn't evaporate much unless it's exposed to very high temps. Diesel engines usually have more compression rings than a petrol engine.. Nev

Oil dilution is a real problem in old tractors with crook injectors, unless it's also burning heaps of oil, then happy days:roflmao:

 

 

[onetrack]

Oil dilution is a problem with many modern diesel engines, let alone trying to burn it in a petrol engine. Regular oil testing will show up oil dilution in diesels, diesel in a petrol engine will go past the rings in sizeable quantities.

 

Fuel containers holding fuel must be under your tight control if you want to ensure fuel integrity. Letting others near your fuel containers, or letting them use your fuel containers, and you don't know what you'll end up with in them.

 

It's like cutting open drums. I caught an old mate cutting open a 200L oil drum with an oxy-acetylene torch a couple of years ago (because he was scrapping the drum and cutting it up).

 

I went ballistic, and said to him, "Joe, don't you know how many blokes have been killed cutting open drums with gas axes?"

 

He protested, and said, "It's O.K., I know its only ever had oil in it!".

 

And I said, "Yep, you think you know it's only ever had oil in it - but more than one bloke has been in your workshop, and who knows, someone could have tipped a litre of dirty petrol in there!"

 

"That's all it takes to kill you". He wouldn't believe me, he was older and knew better. Luckily, he was right that one time. He retired not long afterwards and closed his shop, so I was glad for that.

 

 

[facthunter]

Yes it often leaves the shape of your head in part of it when it explodes. Generally you are very dead. and the drum could have been empty for years. It's a pressure vessel. A thimble of volatile solvent is plenty to blow it skyhigh. An angle grinder may produce a similar result as an oxy torch . . IF you must cut it in halves and it's freshly emptied, fill it with water and roll it into a ditch or creek and cut it with a Hatchet and medium hammer Don't push your luck. Nev

 

 

[Yenn]

There is no time limit for fuel explodability. A tank in England blew up less than ten years ago. I was aware of it and knew that it hadn't held petrol for at least ten years in 1961.

 

More recently I looked into removing fuel tanks used during the war at Gladstone. Massive tanks 6m deep and 15 or more metres diameter. It became too expensive an operation even with the tops removed and steam cleaned the danger from lead trapped in the steel tank walls was too much.