<< Yes but sustained inverted flight will cause severe oil foaming no

matter

 what you do. The proper cooling and oil circulation in the rotor
 depends on the gravity vector pointing straight down most of the

time.

 In a coordinated high G turn the vector is pointed in the right

direction. >>

The oil cooling and circulation *within* the rotor has little to do

with

the

direction of the gravity vector. The motion of the rotor imparts

radially

inward and outward accelerations to the oil depending on the postion

of

the

oil in the rotor and depending on the crank angle. At some point,
acceleration of the entire engine would dominate the acceleration

field

within the rotor, but I think that outside acceleration would have to

be

enormously high to be significant.

No argument that the direction of the gravity vector affects oil

drainback to

the sump, and for this reason I am skeptical of the plugs up

orientation

(perhaps not so much as Paul, however). If the oil doesn't effectively

drain

back to the sump, too much oil could potentially reside in the rotor,

and

that would have a deleterious effect on cooling.

Jon Lauter
Rotary Power Marine Corporation

All right, I 've stood by the side lines long enough.  What ever the
problems there may be with the Plugs Up orientation, oil drain back is not
one of them.  Consider it for a moment, if anything restricted the return
oil flow from the central housing to the pan,  to the point that it

"backed

up", then it would only be a matter of moments before the the building oil
pressure in the center housing would blow past the oil seals.

What pressure Ed? Nobody said anything about pressure.  It is only the oil
level in the rotor we are concerned with. And that, as Jon pointed out,
affects
the cooling of the rotor. Also the oil squirter itself could be affected.

Since it does
not, then there must be a sufficient path for oil return to the pan.

Either

there is an adequate path for oil return or there is not.  If not, then

the

oil will eventually fill the center housing and push past the seals.

I don't think so. I think the main concern with the drain back has always
been the level of the oil in the rotors. Nobody ever mentioned blowing
by the oil seals on here as I recall.

Indications would be copious amounts of smoke just as there is when the

oil

ring seals fail. I have run a Plugs Up installation for 160 hours and no
smoke, others have run them much longer and none have enougher any problem
with oil drain back.  Other problems perhaps, but not oil drain back.

There

is simple no emperical evidence/data to indicate a problem with oil drain
back.

 The biggest draw backs of a Plugs Up from my perspective (and I have a
Plugs Up installation) are:

1.   You have to fabricate a special oil pan and suck oil through a longer
pick up tube.

 2.   Another drawback, is that if you are considering a turbocharger

(and I

am), yes it hangs nicely on the bottom away from other things, BUT, you

will

have to have a scavenger pump to pump the turbo oil back to the oil pan.
Another possible point of failure

3.   An additional, draw back is Tracy Crook's PSRU won't fit (at least

not

without some modifications to the mounting plate).

With the engine in its normal orientation, you do not have to deal with

any

of the above, good enough reasons in them selves to question whether any
perceived advantage of plugs up is worth the effort.  Right Paul? {:>}

So I agree with Paul that there are drawbacks, but from my perspective,

the

only proven draw backs are  installation related.
The reason most of us rotated the engine in the first place was to:

1.  Gain better cowl clearance for some high profile items (such as the

old

distributor and water pump) Not necessary with crank angle sensor  of

today

and if you are willing to trim the water pump housing nozzel - depending

on

your particular airframe requirements.

2.  Place hot exhaust on bottom - ideal for exiting the cowling on an

RV(at

least)

3.  That is the way Lou Ross recommended (and where most of us early guys
got our PSRU) and at the time had no better source of information.

So bottom line, ask yourself whether you really need to go Plugs Up?

Best Regards

Ed Anderson

Ed, you forgot to mention that engine you cooked. I think your
subconscious is suppressing that memory :-) It was your experience
that really turned me off on plugs up.

Also I might add a tangential muffler replacing the exhaust manifold and a
side exit for the exhaust pipe is ideal for a rotary. Tracy flew for years
with a .035 (0-too thin :-)) stainless steel tangential muffler under the
cowl.
An .049 SS muffler would not be that much heavier and a side exhaust would
allow a
single rad under the engine. A side exhaust is ideal for a turbo needless
to say.

Paul Lamar

To all on the list, and especially Ed Anderson:
I am certainly of the belief that one good test is worth 1000 expert
opinions. Ed, you seem to have success with plugs up, and that is why my
skepticism is tempered. I don't know that plugs up will necessarily cause the
problems that I have raised. I firmly believe that at some installation angle
those problems will arise, but perhaps plugs up is just not far enough. My
main reason for the post was to indicate that the motion of the oil *within*
the rotor itself has little to do with gravity, accelerations, or engine
orientation. However, once the oil exits the rotor into the oil drains,
gravity, accelerations and engine orientation have everything to do with oil
scavenging. Your experience seems to indicate that plugs up is OK from this
point of view, but certainly you are closer to the "edge" running plugs up
than you would be in a conventional installation. We just don't know where
the "edge" really is....

Jon Lauter

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org