Belly Oil

Hi Roger,

I think most pilots will know that oil will be ejected from the breather if engine/tank overfilled.

My question was about position of oil tank, therefore oil level, relative to engine.

My oil tank is positioned  at the high end of the Rotax installation recommended range - could this contribute to oil being ejected?

"Oil Eater" - doesn't seem to be readily available in Australia - I use isopropanol on the heavier deposits & then wash with automotive detergent. Works well.

Rather than have to do this on a regular basis I would rather drastically reduce or totally prevent, the oil being ejected/deposited in the first instance.

Recognising that there will always be an oil mist/vapour from the breather, I had hoped that someone had experince/knowledge of a catch suitable for Rotax 912 ULS.😈

Quote: "My oil tank is positioned  at the high end of the Rotax installation recommended range - could this contribute to oil being ejected?"

It shouldn't be a factor.

Thanks Roger,

Do you happen to know of a Rotax 9 compatible crankcase breather catch can?😈

Random thought;

If using a Rotax airbox or similar, could the oil breather discharge into a suitably modified air box?

This arrangement, crankcase breather into inlet manifold/air filter canister, is common in the automotive world.

The posative, no oil discharge onto aircraft belly/environment is obvious, what, if any, negative ramifications?😈

Someone must have thought venting the oil tank into the induction system was a "Very Bad Idea", since it's been specifically prohibited for TC'd aircraft in the US since at least 1945. The prohibition was retained in various iterations of US airworthiness standards (and later EASA equivalents) until they were changed from prescriptive to "performance-based" standards in 2017. Unfortunately I can't find any official records of why they thought it was a bad idea, which isn't helpful for assesing whether it's actually risky or not in an experimental aircraft.

I might be stating the obvious, but have you tried running a lower oil level? Until 2003 (refer to SB 912-040), the "max" level on the dipstick was 20 mm lower than the current "max" level. I've found that in my aircraft, running the oil level at about halfway between the "min" and "max" marks makes a noticeable difference. (That's still 5 mm above where the "max" level was when my aircraft came out of the factory)