Pitts crankcase breather tube hole drilling

[digits]

Hi all,

I have pitts (owner maintenance woohoo!) without any breather/whistle holes in the crankcase breather tube. After some online and offline advice I should drill some holes in there. Even though I am quite sure in which hose to drill them, I thought I'd double check with the pitts experts here.

So I have a christen inverter oil system. 3 big rubber hoses come out of the oil separator. 2 of those hoses go back to the engine, one of them goes to the firewall. I was thinking of drilling 2 holes about 2 inches apart on the inside of a bent close to the separator in the hose that goes to the firewall. There is a longer hose attached inside the firewall that goes to the tail of the airplane.

2 questions:
1) would this be the best location
2) would you use a standard canadian tire hand drill to do this, or is there a specialized tool? What size of drillbit should I use?

My mechanic was supposed to come by to double check, but he cancelled and I really want to go flying this weekend :-)

Regards,
digits

[Colonel]

All you need is one decent-sized hole in the tube that
runs to the tail, just ahead of the firewall.  Drill it on
the top.  At least a quarter inch.  3/8ths is fine, too.

During the summer, use electrical tape to seal it off
tight - go around a few times.  When winter comes,
take a razor blade and slit the tape across the center
of the hole.  If there is excessive pressure because of
ice in the tail, it can blow out there.

When you start doing really aggressive acro, you will
encounter times that the slobber pot does not drain,
and you will start to vent oil out the tail tube.  When
that happens, you can get a little oil on the firewall with
this scheme.  Not as much as you might expect.

In normal flight, and old man acro, the slobber pot
will always drain, and the hole won't make any mess.

Only if you do a lot of negative G or lots and lots of
rolls, will you see a significant quantity of oil travel
out the tube to the tail, because the slobber pot is
not draining fast enough.

Lycoming says losing a quart per unlimited sequence
is to be expected.

PS  Take the slobber pot off every once in a while
and rinse it out with varsol.

[Colonel]

And of course, welcome to the club!!

[img]http://www.skipmodeldesigns.co.uk/wp-co ... l-logo.png[/img]

[David MacRay]

I don't understand jealousy but if I were to take up the sport digits would be a cause. Have fun post a picture. You can blotch out identifying features. I'm most interested in the panel actually.

[Colonel]

An actual Pitts panel:

[img][/img]

You can tell it was one of my students  ;D

[digits]

Thanks!!

Regarding the panel: a G meter with a stuck negative g limit needle. a compass that always turns north, rpm gauge, an ASI and altimeter. That's it ;-)

[Colonel]

G-meters seem quite fragile and terribly expensive:

[img width=500 height=465][/img]

[digits]

Quite weird. A 15 dollar computer chip can measure the same thing, probably even more accurately.

[cgzro]

My S-1T has the 'whistle slot' about 1.5" from the firewall fitting. So in the summer I slide the hose over the hole secure with the climb and in the winter I slide the hose forward exposing the hole (and secure with the hose clamp). Then in the winter I put a wrap of tape around with a cut in it as Andy suggests to minimize the oil mess on the fuse/firewall.


Have to say though I fly down to about -7C, perhaps 25-30 minute full throttle flights and I've never seen any ice on the breather at the tail. I did however insulate the tube from the firewall all the way to the tail and perhaps that helps. It may be more of an issue if you are doing a long cross country at a lower power setting and not blowing hot oil down the tube every few seconds ;) which is more typical of my winter flights ;)


Oh congrats on the purchase .. the Pitts is an addictive plane .. you can never outgrow it I don't think.

[Colonel]

I've seen ice building up inside the tube at the
tailwheel of a Pitts.

[img width=500 height=375][/img]

The colder it is, the more of a hazard this is,
which I guess makes sense.

One very cold February day (below -20C) the
oil breather of an R22 plugged completely at
the gas pumps.  I dug it out with a jackknife.
Disgusting brown emulsification (see above).
It had a couple of tiny holes, drilled up about
1.5 feet (?) from the end of the tube, which
saved the crank seal.

Same guy blew the crankcase seal at least
twice, on his R44.  Likely no vent holes drilled.