CO mystery - any ideas?

Bruce Cunningham wrote:

the cure is sometimes that in the rear
inspection covers on the sides of the tail in front of the stabilator,
they have a edge bent outward to scoop air into the tail and keep
exhaust out. These scoops or inspection plates have to be mounted with
the scoop facing forward so that they face the airstream. People have
installed the covers with the scoop facing down or backwards, usually
after an annual etc., and then they start getting CO in the cabin.

Are these the round inspection plates like those one finds all over the
airplane, or something different?

Is the "scoop" really noticable, or a slight bending?

- Andrew

Andrew Gideon wrote in message gonline.com...
Bruce Cunningham wrote:

the cure is sometimes that in the rear
inspection covers on the sides of the tail in front of the stabilator,
they have a edge bent outward to scoop air into the tail and keep
exhaust out. These scoops or inspection plates have to be mounted with
the scoop facing forward so that they face the airstream. People have
installed the covers with the scoop facing down or backwards, usually
after an annual etc., and then they start getting CO in the cabin.

Are these the round inspection plates like those one finds all over the
airplane, or something different?

Is the "scoop" really noticable, or a slight bending?

- Andrew

Yes they are. They are a combination scoop/inspection cover. The scoop
is about a 1/4 inch high outward joggle of the inspection plate just
in front of the stabilator. The open part must face the airstream,
that is, forward. There is one on each side. I don't know if 182s have
this. I think maybe some 210s do. If your plane is supposed to have
them and doesn't, in all likelyhood that is the problem. The scoop is
a Cessna part and can be ordered. It was the fix Cessna found when CO
was an issue on the Cardinal RG, maybe other models. My fixed gear
Cardinal does not have them. The exhaust, flow around the fuselage,
and openings are different so it doesn't need them. I sent you an
email with photos of a plane both with and without the scoops. Hope
that's you're problem. It will be easy to fix if it is. Guys have
spent months and thousands of dollars to find a leak when this was the
problem. In some instances, all it took was 5 minutes to turn the
scoops in the right direction, as they don't work if they're not, in
fact they sometimes make it worse.

Regards,
Bruce Cunningham
N30464

Andrew Gideon wrote in message gonline.com...
Our Cessna R182 is getting CO in the cockpit. We've now had three different
shops look at it multiple times, all to no (complete) effect. They've done
things like resealing the firewall, the gear-wells, the exhaust, and the
like. But still we get CO.

We've swapped CO detectors around between planes, so the detectors' results
are trusted.

One interesting oddity: turning cabin heat on does seem to get rid of the
CO.

We've noticed no difference made between type of flight. I personally have
had readings both while XC and while maneuvering (practicing commercial
maneuvers), and at various altitudes. Others have reported the same.

At this point, we're at something of a loss. The next thing we're trying is
to extend the exhaust pipe. The presumption is that this would get the CO
into the slipstream and away.

Extending the exhaust pipe is asking for trouble. There have been a
few exhaust systems failures, and at least one fatal crash, that have
been caused by extending the pipe. The added mass changes the
vibration characteristics of the system, with the extra weight causing
more flex in the pipes near the cylinders as the engine rocks, and
breakage can occur. A busted system inside the cowl is really bad.
Find the entry point. You might note lead stains around the
inside of the entry inside the fuselage. 100LL has lots of lead and
we've found entry points that way.

Dan

That's raises an interesting point. With 100 LL having so much lead, is
there also a problem of chronic lead poisoning over a long time from a small
amount of exhaust getting into the cabin? Obviously it's not an acute
problem, but what about over time?

--
Bob (Chief Pilot, White Knuckle Airways)

I don't have to like Bush and Cheney to love America

"Dan Thomas" wrote in message
om...

Find the entry point. You might note lead stains around the
inside of the entry inside the fuselage. 100LL has lots of lead and
we've found entry points that way.

Dan

Check for any cracks at the joint of the pipe and the flange that bolts
to the head. Also at the joint between the muffler and the riser if
you have one.


"Andrew Gideon" wrote in message
online.com...
Our Cessna R182 is getting CO in the cockpit. We've now had three
different
shops look at it multiple times, all to no (complete) effect. They've
done
things like resealing the firewall, the gear-wells, the exhaust, and the
like. But still we get CO.

We've swapped CO detectors around between planes, so the detectors'
results
are trusted.

One interesting oddity: turning cabin heat on does seem to get rid of the
CO.

We've noticed no difference made between type of flight. I personally
have
had readings both while XC and while maneuvering (practicing commercial
maneuvers), and at various altitudes. Others have reported the same.

At this point, we're at something of a loss. The next thing we're trying
is
to extend the exhaust pipe. The presumption is that this would get the CO
into the slipstream and away. But that "presumption" is really more of a
"guess" or even a "hope".

Anyone have any suggestions or ideas or experiences that might help us?

Thanks...

Andrew

OtisWinslow wrote:

Check for any cracks at the joint of the pipe and the flange that bolts
to the head. Also at the joint between the muffler and the riser if
you have one.

*Everything* forward of the firewall has been checked, and much of it
resealed, a couple of times. That's why I'm looking for something "else".

But thanks...

Andrew

P.S. Since we're on the subject, though: "the head" of what?

"Andrew Gideon" wrote in message
online.com...
OtisWinslow wrote:

Check for any cracks at the joint of the pipe and the flange that bolts
to the head. Also at the joint between the muffler and the riser if
you have one.

*Everything* forward of the firewall has been checked, and much of it
resealed, a couple of times. That's why I'm looking for something "else".

But thanks...

Andrew

P.S. Since we're on the subject, though: "the head" of what?


Cylinder head? doh!

allen

"Bob Chilcoat" wrote in message ...
That's raises an interesting point. With 100 LL having so much lead, is
there also a problem of chronic lead poisoning over a long time from a small
amount of exhaust getting into the cabin? Obviously it's not an acute
problem, but what about over time?


Probably some risk involved, but the monoxide is a much more
immediate risk so that long-term exposure to lead isn't an issue:
you'll die in a crash before the lead gets you. I suppose we'll see
leaded fuel disappear from aviation sooner or later anyway.

Dan


"Dan Thomas" wrote in message
om...

Find the entry point. You might note lead stains around the
inside of the entry inside the fuselage. 100LL has lots of lead and
we've found entry points that way.

Dan

Andrew Gideon wrote:
OtisWinslow wrote:


Check for any cracks at the joint of the pipe and the flange that bolts
to the head. Also at the joint between the muffler and the riser if
you have one.


*Everything* forward of the firewall has been checked, and much of it
resealed, a couple of times. That's why I'm looking for something "else".

The only time I get CO in the Navion cockpit is when sitting on the ground
with the canopy open pointed into the wind.

I thought I'd let you all know what's going on.

First, a mechanic with whom we checked claimed to be familiar with the
Cardinal's scoops, and said that the R182 had no such thing. Given that
the tail structure of the Cardinal is so different from other Cessnas,
apparently, this isn't too surprising. But I have to admin: I'm still not
completely certain.

However, we've had the extensions installed (although I've yet to see them;
the airplane pulled out as I arrived at the airport yesterday). The
airplane has flown 6.9 tachometer hours since then, and has been showing a
steady zero reading on the CO detector.

So...it looks good at the moment.

- Andrew