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Hi,

(Reference: Sonex Legacy(A)/Rotax 912 ULS)

One again I seek your collective council.

I am struggling with the unpleasant  idea of putting holes in my lower cowling, to accommodation the oil tank breather and the fuel pump drain. We have spent so much time  and effort on making a custom cowling, the last thing I want to do is put holes in it IF there is an alternative.

It seems to me that two translucent, in cowling, catch cans, - one for the oil tank breather and one for the fuel pump drain, is a more attractive possibility. 

Translucent so that the level of any "captured" fluids can be readily seen at pre flight inspection.

Further;

The fuel pump drain is only there for a failure of the fuel pump diaphragm - draining petrol overboard may not warn the pilot of the failure. A catch can would hopefully hold the fuel until inspection (no flying that day). If 5 year replacement up to date should rarely have anything in it.

The oil tank breather is likely to emit a nearly continues oily vapour/mist. Capturing the condensed vapour will - give a measure of oil blow by, over time ( I can keep a record) - reduce unsightly staining of the aircraft underbelly.

So;

What do you think of the concept? (pros/cons?)

If you have done this - where did you get your catch cans?

  • Re: Catch Cans

    by » 2 years ago


    The "oil tank breather" catch can would also have to be vented.

    Alan


  • Re: Catch Cans

    by » 2 years ago


    Your breather tubes are not supposed to be out in the air stream. So if your cowling is open at the bottom like most just keep these two tubes cut back inside the cowl edges an inch or two. The oil tank breather is always venting air from the tank because that's what returns the oil back to that tank from the bottom of the engine case.


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Catch Cans

    by » 2 years ago


    Alan Arnold wrote:

    The "oil tank breather" catch can would also have to be vented.

    Alan

    Absolutely!! In fact both must be vented however they can be vented within the engine compartment.

    My hope would be that the oil breather catch can would act like a "break tank", allowing the heavier fractions within the vapour to condense/settle out & remain in the can..


  • Re: Catch Cans

    by » 2 years ago


    Roger Lee wrote:

    Your breather tubes are not supposed to be out in the air stream. So if your cowling is open at the bottom like most just keep these two tubes cut back inside the cowl edges an inch or two. The oil tank breather is always venting air from the tank because that's what returns the oil back to that tank from the bottom of the engine case.

    Thanks Roger,

    There is a reason behind my mad suggestion.

    My engine cooling system is a little unusual - the coolant radiator is cooled (we hope) by the exit air from the cowling. There is no big hole at the bottom of the cowling. In practise the means that as far as is possible the cowling must be air tight. Yes I know the exhaust is going to be a problem - we have planned for flexible seals around its exit point. 

    Back to the topic at hand; does anyone have experience with catch cans (I believe they were originally invented for competition level aerobatic aircraft). Even if you dont have experience, what would you speculate the problems might be. 


  • Re: Catch Cans

    by » 2 years ago


    Does anyone have experience with catch cans?

    (I believe they were originally invented for competition level aerobatic aircraft).

    Even if you dont have experience, what would you speculate the problems might be? 


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