Back on topic: I think the Decathlon comes with the
expensive Frank Christen full inverted 801 oil system,
but the Citabria does not.
What a lot of RV homebuilders do is install a slobber
pot (oil/air separator) on the crankcase breather, to
try to capture some of the oil that might be vented
overboard during some inadvertent negative G.
I remember the Grob had this problem. It would
dump a quart of oil down the side of the airplane if
you made the tiniest error and went a little negative.
Really weird engineering for an aerobatic trainer but
hey it's German so it has to be better than anything
made in North America, like a Lycoming engine, a
Hartzell propeller, or a Zivko airframe.
[img width=500 height=333]
http://www.aeroresource.co.uk/wp-conten ... kc_002.jpg[/img]
Not sure about the paperwork status for a certified
aircraft, of an aftermarket slobber pot.
For experimental, check out the "half Raven"
http://www.vansairforce.com/community/s ... hp?t=51286