Oil Breather Tube Orientation

You want anything that may get in the tube like possibly a little oil overflow from the tank being too full or any moisture  accumulation to drain out and not get stuck up in a bend that would block air flow. You want the tube to remain fully open and breathable at all times. You also don't want the tip out in the air stream.

Thanks Roger,

Sems to me that volatile fractions (water/fuel/tc) will be easily pass through & out the breather tube, no matter its initial orientation, after all these are in their gaseous state and the posative crankcase pressure will ensure speedy exit. 

Oil droplets are another matter - If the system is overfilled, an upward oriented pipe may restrict (slow not prevent) the expulsion of heavier fractions (oil droplets) but unless there is a physical blockage the oil would still exit.

Is it not possible that an initial upward orientation, encouraging heavier droplets to fall back into the tank, by so doing, reduce oil being ejected "overboard" onto the belly of the aircraft?

Could the non sealing tank cap, vent oil droplets ?

Has anyone actually tried this ? If so what if any negative/posative results ensued?😈

"Has anyone actually tried this ?"

Hi Sean,

if this was okay then people all over might be using it this way and Rotax would publish something about it in the Installation manual. I've never seen or heard of anyone doing this.

Roger Roger - conformity is the bain of invention. 

If your Wright brothers,  et al,  had the  "everyone would be doing it" approach, we may not be debating the ins/outs of an aircraft engine, on this Forum.

As for the Word According to Rotax - Christians eventually stopped burning heretics (those that questioned the Bible). The Irish being a possible exception.😁

In truth, this is  but a passing slight random thought. I doubt any benefit but you never know.

😈

Sean said ...

"Is it not possible that an initial upward orientation, encouraging heavier droplets to fall back into the tank, by so doing, reduce oil being ejected "overboard" onto the belly of the aircraft?

Could the non sealing tank cap, vent oil droplets ?

Has anyone actually tried this ? If so what if any negative/posative results ensued?"

Given that the top of an oil tank should have only atmospheric pressure at most it is possible that any oil drops may fall out rather than be taken away by the vent line.  The oil tank cap is a simple cam type with a rubber material and is not designed for working under positive pressure from the oil side.  We only see leakage at that cap when doing an oil purge using compressed air as in first oil fill on a new engine installation or change of oil hoses or oil cooler when we do a purge.  If the cap was to breath in any normal conditions of flight we would see oil staining on the oil tank to and indeed the oil tank area in general.  For the most part is is dry and no "oil droplets" are seen.  

In general the best practice is to run a vent line down (gravity wise) rather than up to allow built up residue easy access for venting.  Just my view.

Cheers