Opposed engines are simple and strong. Inverted engines are much
more complicated.

First: The cylinder extends into the crankcase so that oil thrown off
the bearings doesn't drain off the case walls and run into the
cylinders. Could cause hydraulic lock, certainly would use a lot more
oil.

Second: That oil can't be stored in the crankcase. There has to be a
separate oil tank, usually on the firewall.

Third: The oil has to be pumped out of the engine into the tank. My
Auster had a Gipsy Major inverted inline, and it had THREE oil pumps:
one to pump oil from the tank into the engine's workings for
lubrication, and two more to scavenge the case; one pumped oil out of
the front, the other out of the back. Because the engine gets tipped
up and down so much in an airplane, two outlets are necessary lest oil
pile up and start running into the jugs at the low end. One pump can't
do them both, or it would be happy to suck air from the high end
instead of pulling the oil out of the low end.

Fourth: The rockers and valve stems need either pressure lubrication
and ANOTHER scavenge pump, or, as with the Gipsy, the covers are taken
off occasionally and filled with oil. A pain, that is.

In spite of all that, I like the looks of the inverted
installation, confirming that, like so much of homebuilding and the
rest of general aviation, emotions usually trump common sense. (Just
look at the beautiful but huge, ridiculously expensive projects some
of us average-income guys start on, and are never able to finish.
Emotions over common sense.)


Dan