co during climb with cowl flaps open

[amekler]

can anyone tell me what is causing the CO to rapidly rise in my 2000 bravo during climb(cowl flaps opened) then go down in cruise?

Alan

see photo

[LANCECASPER]

Here are a few places to start:

Pressurize your exhaust system and check for leaks. Look on your belly pan to see if you are missing any camlocs. Check for a leaky front door seal.

[Hector]

Had a friend with same issue but in a piper. Turned out it was the door seals. During a climb (high AoA) the exhaust flows around the fuselage a bit different and was making its way inside the cabin through the door. Did not have any issues during cruise or descent. Have no idea if this applies to a Mooney but something to check if you run out of ideas.


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[amekler]

Thanks

will check

Air Vents were open

could this be the source?

[exM20K]

5 hours ago, amekler said:

Thanks

will check

Air Vents were open

could this be the source?

The overhead vents should help. Is this new behavior for your plane? It is typical of what I have experienced in the 231 and Acclaim, though your levels are higher than the 20-30 I routinely observe.  High AOA, full power, full rich operation is putting out a bunch of CO all directed at the bottom of the cabin, and the cabin is far from airtight.  As @LANCECASPERsuggests, check the front door seal. In climb or cruise, try placing a small piece of paper over the door edge in various places, especially the bottom rear corner. You may be surprised how much quieter it gets.  That Venturi is creating a negative pressure differential in the cabin, which helps the CO find its way in.

 

I believe this CO intrusion is why the factory air conditioning is not to be used in climb.

 -dan

[amekler]

dan,

 I'll check the door seal. The co is 2 or less on the ground and in cruise.

Alan

[Ragsf15e]

The door seal is the most obvious place, if that isn’t it, there are other leaky spots in the floor (esp near rudder pedals), gear wells, and even old (unsealed) holes in the firewall. 

[N201MKTurbo]

So, I don't think the door seal is the problem. Most of the door has negative pressure. If you have a leaky seal it sucks most places. The only place where there is positive pressure is the middle of the bottom edge. This is why it is hard to close a door when it is opened in flight.

The whole cabin has negative pressure compared to the outside. If it didn't the vents wouldn't blow much. I would look at CO coming through the belly. Lots of gaps and lap joints downstream of the exhaust. The most important thing is sealing up the gaps between the belly and the cabin. They are taped up from the factory, but the tape seems to dissipate over time. Mostly because of maintenance, new interiors, avionics installs etc.

[Fly Boomer]

On 6/15/2024 at 7:09 PM, amekler said:

can anyone tell me what is causing the CO to rapidly rise in my 2000 bravo during climb(cowl flaps opened) then go down in cruise?

Can't say I understand the timing, but some say the tail could be the source.

[Ragsf15e]

On 6/15/2024 at 5:09 PM, amekler said:

can anyone tell me what is causing the CO to rapidly rise in my 2000 bravo during climb(cowl flaps opened) then go down in cruise?

Alan

see photo

One other consideration… since it’s only in climb, it’s most likely exhaust going out the exhaust pipe that’s getting into the cabin through one of the ways discussed above.  If you were seeing it in cruise or on the ground, I’d be looking for an exhaust leak before it exits the engine compartment.  However, looking through the exhaust is a reasonable step.  It can be pressurized and soap bubbles if needed too.

[N201MKTurbo]

13 minutes ago, Ragsf15e said:

One other consideration… since it’s only in climb, it’s most likely exhaust going out the exhaust pipe that’s getting into the cabin through one of the ways discussed above.  If you were seeing it in cruise or on the ground, I’d be looking for an exhaust leak before it exits the engine compartment.  However, looking through the exhaust is a reasonable step.  It can be pressurized and soap bubbles if needed too.

If there is an exhaust leak into the cowl, it will get blown out the cowl flaps. The airflow through the cowl is substantial. That being said, you should inspect the integrity of the firewall at every annual. Any voids should be sealed for many reasons. Any CO coming out the cowl flaps, have the same issues as exhaust from the pipe, just at a slightly different place.

[Ragsf15e]

7 minutes ago, N201MKTurbo said:

If there is an exhaust leak into the cowl, it will get blown out the cowl flaps. The airflow through the cowl is substantial. That being said, you should inspect the integrity of the firewall at every annual. Any voids should be sealed for many reasons. Any CO coming out the cowl flaps, have the same issues as exhaust from the pipe, just at a slightly different place.

Yeah I agree with that in cruise.  I had a significant exhaust leak and it just barely raised my cruise CO.  It was very noticeable on climb and on the ground though.  I did have a few old “pass through” holes in the firewall that are now sealed.  It might have been the big dog of “leaks” too as an exhaust riser came completely disconnected from the cylinder…

[amekler]

I never see it on the ground even during a runup

Alan

[Ricky_231]

On 6/16/2024 at 12:09 AM, Hector said:

Had a friend with same issue but in a piper. Turned out it was the door seals. During a climb (high AoA) the exhaust flows around the fuselage a bit different and was making its way inside the cabin through the door. Did not have any issues during cruise or descent. Have no idea if this applies to a Mooney but something to check if you run out of ideas.


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I heard a similar story from my A&P but in a mooney. Apparently if there's a gap/opening between the baggage compartment and the tail cone, exhaust can make its way inside the cabin via the tail cone, through the gap. Unverified - just a story.

[exM20K]

1 hour ago, Ricky_231 said:

I heard a similar story from my A&P but in a mooney. Apparently if there's a gap/opening between the baggage compartment and the tail cone, exhaust can make its way inside the cabin via the tail cone, through the gap. Unverified - just a story.

With flaps full on the ground, look at the area above the lowered flaps: huge, open void.

-dan

[EricJ]

3 hours ago, Ricky_231 said:

I heard a similar story from my A&P but in a mooney. Apparently if there's a gap/opening between the baggage compartment and the tail cone, exhaust can make its way inside the cabin via the tail cone, through the gap. Unverified - just a story.

Generally there are gaps/holes/seams all over the bottom of the airplane, and the only thing separating you from that is a floor with a lot of gaps/holes/seams, and the space in between them is open to the tail, where there are also a lot of gaps/holes/seams.   That's all in addition to the firewall, doors, etc.

Usually there's not just one way that stuff is getting in, but there may be a "biggest contributor" that you can plug up to make a difference.

Helped a buddy try to seal up an IAR a couple years ago and it was basically the entire airplane was leaky.   We did a lot with a leaf blower and soapless bubbles.   I did similar on my airplane but it was a bit easier to get it down to reading small numbers on the CO detector.   I don't think it's worth trying to plug every hole.   If the CO reads small numbers most of the time and zero or close to it in cruise, that's good performance.

[Fly Boomer]

16 minutes ago, EricJ said:

soapless bubbles

What is this?

[EricJ]

10 minutes ago, Fly Boomer said:

What is this?

Aircraft spruce used to sell some pre-mixed, but I don't see it there any more.   Dang...that was a handy way to get it.

There's a recipe in the M20J SMM in section 28-13-00, specifically for finding leaks in fuel tanks.

It's just a way to use air to spot leaks easily without using soap (or anything alkaline) that could damage aluminum.