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Carbon Monoxide incident - Mooney No longer Stranded


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My airplane is stranded in San Luis Obispo (KSBP) with a CO leak from somewhere, so if anyone able to help locate a mechanic that can fix it there, or have options, would be hugely helpful. Here’s what happened.

I’ve always been a huge supporter of having an electronic CO monitoring device at all times and it was needed yesterday.

I was taking off from PRB to fly with friends and my portable CO experts monitor alarmed. Reading was 40 ppm which then went above and got a High display. Got to level flight, held the monitor through the side window. Did not come down. I then turned around and landed with side window open, cabin heat, cabin vents closed. I felt fine and let the device go down to 0 ppm on the ground. Luckily a mechanic was flying with us and we took off the cowlings and no leaks were noted on visual inspection, and another friend had a Sentry CO monitor which I took up in the pattern to see if it was a sensor issue problem and mine went off to high again, but the Sentry read normal. No notifications of any abnormal reading to ForeFlight from the Sentry unit and I tested it on the ground and it beeps and was connected and tested ok.  So thought was maybe the CO experts monitor may be off since the   Sentry read normal. To be sure I went to Lowes and bought 3 ( yes three) home CO monitors , Two had digital displays.

Went up again towards SBP, babying the engine, watching my monitors. Noted that fuel pressure was lower and oil temp was warmer on idle than it usually was which I attributed it to being a very hot day. So got up, flight following to SBP and all seemed normal, with 0 ppm reading from all monitors on the short flight to SBP. Got 2/3 the way there and all seemed good. So I called flight following to ask for a clearance to my home base LGB. About a minute after I received clearance, ALL 4 of my CO monitors went off, (The CO experts one and the 3 Home ones) with one reading shot up to 137ppm rising. I then changed destination back to SBP with approach, opened the window, I did start to feel a headache at that time. Since I could see the airport I landed. Felt a little funny for a few minutes but quickly resolved. 
 

Still looking for a mechanic who can get to KSBP who can fix this, so any help would be appreciated. Have a few calls in but so far no luck.

Im glad that I had my device as would have had no warning otherwise, and this may have had a different outcome if I didn’t have an electronic monitor and am HUGELY grateful to the Mooney and Bonanza pilots and friends who helped including Tim, Joker, Hoser, Susan, Buttercup, Steve, Chris and a whole lot more thanks! 
 

Once all this is done I’m going to insist on having TWO CO monitors with digital displays in operation all of the time. I have a panel installed guardian CO monitor that recently went inop as needs sending in as likely expired.

Still have no idea what’s causing this, but hoping to get a mechanic soon there to fix. Assistance would be welcomed 

John

4A16631D-DC5F-433B-A64F-67EE7A92C086.jpeg

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1 hour ago, JohnB said:

My airplane is stranded in San Luis Obispo (KSBP) with a CO leak from somewhere, so if anyone able to help locate a mechanic that can fix it there, or have options, would be hugely helpful. Here’s what happened.

I’ve always been a huge supporter of having an electronic CO monitoring device at all times and it was needed yesterday.

I was taking off from PRB to fly with friends and my portable CO experts monitor alarmed. Reading was 40 ppm which then went above and got a High display. Got to level flight, held the monitor through the side window. Did not come down. I then turned around and landed with side window open, cabin heat, cabin vents closed. I felt fine and let the device go down to 0 ppm on the ground. Luckily a mechanic was flying with us and we took off the cowlings and no leaks were noted on visual inspection, and another friend had a Sentry CO monitor which I took up in the pattern to see if it was a sensor issue problem and mine went off to high again, but the Sentry read normal. No notifications of any abnormal reading to ForeFlight from the Sentry unit and I tested it on the ground and it beeps and was connected and tested ok.  So thought was maybe the CO experts monitor may be off since the   Sentry read normal. To be sure I went to Lowes and bought 3 ( yes three) home CO monitors , Two had digital displays.

Went up again towards SBP, babying the engine, watching my monitors. Noted that fuel pressure was lower and oil temp was warmer on idle than it usually was which I attributed it to being a very hot day. So got up, flight following to SBP and all seemed normal, with 0 ppm reading from all monitors on the short flight to SBP. Got 2/3 the way there and all seemed good. So I called flight following to ask for a clearance to my home base LGB. About a minute after I received clearance, ALL 4 of my CO monitors went off, (The CO experts one and the 3 Home ones) with one reading shot up to 137ppm rising. I then changed destination back to SBP with approach, opened the window, I did start to feel a headache at that time. Since I could see the airport I landed. Felt a little funny for a few minutes but quickly resolved. 
 

Still looking for a mechanic who can get to KSBP who can fix this, so any help would be appreciated. Have a few calls in but so far no luck.

Im glad that I had my device as would have had no warning otherwise, and this may have had a different outcome if I didn’t have an electronic monitor and am HUGELY grateful to the Mooney and Bonanza pilots and friends who helped including Tim, Joker, Hoser, Susan, Buttercup, Steve, Chris and a whole lot more thanks! 
 

Once all this is done I’m going to insist on having TWO CO monitors with digital displays in operation all of the time. I have a panel installed guardian CO monitor that recently went inop as needs sending in as likely expired.

Still have no idea what’s causing this, but hoping to get a mechanic soon there to fix. Assistance would be welcomed 

John

4A16631D-DC5F-433B-A64F-67EE7A92C086.jpeg

John, check in the pax foot well using the CO monitor, it should help you find the leaks. That was where the Bravo I had triggered the Sensorcon I have and I was able to plug up the ultra small opening I found. Good call on not getting CO poisoning

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Great outcome! 

Question: I recall reading that one shouldn't open the windows because that creates low pressure in the cabin, which forces more CO into the cabin.

What is the best strategy - open, or close?

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Hi John,

I know @ilovecornfields is based there and has a mechanic there, he'll be able to recommend someone.

If there is an exhaust leak somewhere, which sounds likely, at least part of your exhaust will need to come off and be sent to an aircraft welder for repair. The only good thing about exhaust leaks is that they are usually pretty obvious and easy to find.   

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1 hour ago, hais said:

What is the best strategy - open, or close?

Problem is, you don't know where it's coming from.  With the window open or closed may not play as big a role and minimizing the potential CO source.

My personal guess just from a logical standpoint in the K would be to open all the ceiling and the two side air vents all the way.  Then CLOSE the center console heat and vent as the CO is likely coming in through that vent which is connected to the heater and travels through the engine compartment.  It will be a cold descent from altitude even in the summer.

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53 minutes ago, PeteMc said:

Problem is, you don't know where it's coming from.  With the window open or closed may not play as big a role and minimizing the potential CO source.

My personal guess just from a logical standpoint in the K would be to open all the ceiling and the two side air vents all the way.  Then CLOSE the center console heat and vent as the CO is likely coming in through that vent which is connected to the heater and travels through the engine compartment.  It will be a cold descent from altitude even in the summer.

Great question @hais, I agree with @PeteMc and did that, overhead vents wide open, side floor vents were already open, and anything that comes from the engine (cabin heat, center console cabin vent) completely closed. Opening the side window has helped me in the past when I get CO from surrounding jet traffic, once I'm completely clear of them. I did think about slowing and opening the left side window and using right rudder to slip, so that if it were coming from the engine out of the cowling, a slip away might stream those fumes to the right side of the airplane preferentially and leave the left side more able to receive fresh outside air. I didn't try that as was not in any textbook that I'm aware of but just a thought I had to try something to reduce exposure.  

2 hours ago, kortopates said:

Hi John,

I know @ilovecornfields is based there and has a mechanic there, he'll be able to recommend someone.

If there is an exhaust leak somewhere, which sounds likely, at least part of your exhaust will need to come off and be sent to an aircraft welder for repair. The only good thing about exhaust leaks is that they are usually pretty obvious and easy to find.   

Paul, that's great to know both! The SLO mechanics seem pretty busy!

4 hours ago, bluehighwayflyer said:

Right on!  Excellent ADM. Thanks for sharing and looking forward to learning the cause.  Makes me wonder if I should start carrying around two or three of these things instead of my current one.  :)

Thanks! Will definitely post the cause once it's figured out. 2 is now the new minimum for me.

3 hours ago, Sue Bon said:

I just ordered two to replace my zero :o

I'm so glad that you had yours and that everything worked out!!!

Yes Sue, Blue, Good call on getting more than one device I think. The logic behind me wanting TWO digital electronic readout devices now after yesterday's event is that these units require recalibration every 2-5 years and it's easy to forget and if you do forget, might not be accurate or in my case finding a mechanic who can swap out the panel mounted one.

Also if I know an actual accurate CO PPM number, I can make better decisions about it. In thinking about this scenario if it happens again, I would use the ppm numbers to guide my decisions, for example if I see 10 ppm or so, I'm probably not going to interrupt my trip if not too far and then have my mechanic look at it when I get back to home base. If 40+ PPM I would do what I did in this case land at an airport with services, if 400+ PPM I'm probably going to look for the nearest flat surface to land on or glide to (i.e. if I am at 16k feet and have good places to glide to and get a 400+ number, I might shut engine off and glide rather than risking that time of exposure)  None of this is written in stone, but that's what I might do if this happens again (which I of course hope it won't!) 

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Also at San Luis Obispo area… @MooneyMitch….

Good catch on the CO…

Inviting @DanM20C our CO measuring guru… Dan has done a great job bringing this topic to the mainstream…

First line of defense for the Bravo with a  CO issue… check those pesky V-band clamps connecting exhaust tubes near the turbo charger…. They are expensive, have a specific torque, and reuse limitations…

Best regards,

-a-

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1 hour ago, carusoam said:

Also at San Luis Obispo area… @MooneyMitch….

Good catch on the CO…

Inviting @DanM20C our CO measuring guru… Dan has done a great job bringing this topic to the mainstream…

First line of defense for the Bravo with a  CO issue… check those pesky V-band clamps connecting exhaust tubes near the turbo charger…. They are expensive, have a specific torque, and single use limitation…

Best regards,

-a-

Not single use. You are allowed two re-torques after the first install.

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3 minutes ago, LANCECASPER said:

Not single use. You are allowed two re-torques after the first install.


Thanks Lance!

Went to check details on the V-bands… you filled them in faster than I could look them up.

They are also common devices for TC’d engines, not so Bravo specific…

:)
 

Go MS!

Best regards,

-a-

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1 minute ago, carusoam said:


Thanks Lance!

Went to check details on the V-bands… you filled them in faster than I could look them up.

They are also common devices for TC’d engines, not so Bravo specific…

:)
 

Go MS!

Best regards,

-a-

It’s quite an accomplishment to know that somehow I’ve typed something faster than @carusoam

I may retire from Mooneyspace while I’m ahead.

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Some next steps that usually come along…

Finding the source of the CO leak…

The nice thing about having a portable CO monitor…

You can have somebody help you collect data from various different probable areas / causes… moving the sensor to various locations around the cabin while flying can really work…

1) Common deadly area… is the heat muff allowing CO into the cabin… put the monitor in the airstream entering the cabin…

2) Leaking exhaust pipes might expose air leaks entering the cabin around rudder pedals or other holes near the firewall…

3) Door seals have also been a place where CO and cold air and noise may show up… oddly, because the cabin is under vacuum during flight…

4) Most surprising… the area where cables pass from the cabin to the tail cone… provides a location where, when not sealed properly, CO enters the cabin…. Any new avionics lately, or antenna wires?

5) Outside air entering the cabin for modern Mooneys… comes from the tail root vent at the top of the cabin… so if you get CO entering from there…. It may be a big leak caught in the swirl of air around the fuselage…

 

Exhaust system leaks are also a serious fire hazard on the high pressure side of the hot turbine, not the cold side… this is the cutting torch effect that can cause a land now situation…

+1 For @mike_elliott’s knowledge and shared experience… and pictures…

Fortunately leaky exhaust tubes leave plenty of stains… and hints near the leak…

PP guesses only, not a mechanic…

Best regards,

-a-

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1 hour ago, carusoam said:

Exhaust system leaks are also a serious fire hazard on the high pressure side of the hot turbo… this is the cutting torch effect that can cause a land now situation…

The high pressure side is the induction air?

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15 minutes ago, Fly Boomer said:

The high pressure side is the induction air?

Thanks!
 

Note the second part of the description… ‘hot turbo’   I updated the description to be more specific to the hot turbine…

Leaking compressed air won’t be a CO issue…. But,

The high pressure exhaust feeding the hot turbine… is the cutting torch side of things…


In our normally aspirated engines… our exhaust systems don’t contain the hot gasses….   Sooooo… they are allowed to expand rapidly and cool because of the expansion….

 

Keep in mind, I struggle to write with accuracy… I keep working on it. :)
 

Thanks for pointing out where I can improve what I wrote… other people may be thinking the same way…

Best regards,

-a-

 

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6 hours ago, hais said:

Great outcome! 

Question: I recall reading that one shouldn't open the windows because that creates low pressure in the cabin, which forces more CO into the cabin.

What is the best strategy - open, or close?

Keep the knob on the center console cabin air closed. And keep the overhead vents and the knee vents open

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6 minutes ago, carusoam said:

The high pressure exhaust feeding the hot turbine… is the cutting torch side of things…

So the high pressure is caused by the engine relentlessly pumping exhaust gasses into a "blockage" in the exhaust system (the turbo)?

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Just now, Fly Boomer said:

So the high pressure is caused by the engine relentlessly pumping exhaust gasses into a "blockage" in the exhaust system?

Two things that cause pressure in a tube… (chem eng 101)

1) Flow rate

2) Constriction

The exhaust gasses leaving the engine are already hot, compressed, and flowing….

The restriction caused by the turbo keeps the exhaust gasses compressed and hot until they get out of the turbine….

If you have ever seen the pipes glowing red… that is an indication they are not seeing the drop in pressure of the open ended pipe…

 

Most exhaust tubes start life smooth and shiny….

When they see long periods of time being red, the metal slowly flows, their outer surface doesn’t look like the pipe mandrel that bent it any longer…

Erosion on the inside of the hot tubes causes thinning of the tube…

Somebody posted a nice pic of a Bravo exhaust that was due for replacement… they poked a hole through the tube wall to demonstrate how thin it had become…

Old fuzzy memories… primarily for discussion…

:)

Best regards,

-a-

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23 hours ago, ilovecornfields said:

That’s what I get for working instead of browsing Mooneyspace all day. 

I sent you a PM with my number and texted my mechanic to see if he’s able to take it on. If not, it might be worth calling ACI Jet or Sunwest Aviation. 

Thank you for looking, mechanics are in high demand/ short supply at SBP so I have learned!  Have one looking into it, nothing jumping out at the mechanic yet. And nice speaking with you today! Thanks!

On 7/17/2022 at 6:01 PM, carusoam said:

Some next steps that usually come along…

Finding the source of the CO leak…

The nice thing about having a portable CO monitor…

You can have somebody help you collect data from various different probable areas / causes… moving the sensor to various locations around the cabin while flying can really work…

1) Common deadly area… is the heat muff allowing CO into the cabin… put the monitor in the airstream entering the cabin…

2) Leaking exhaust pipes might expose air leaks entering the cabin around rudder pedals or other holes near the firewall…

3) Door seals have also been a place where CO and cold air and noise may show up… oddly, because the cabin is under vacuum during flight…

4) Most surprising… the area where cables pass from the cabin to the tail cone… provides a location where, when not sealed properly, CO enters the cabin…. Any new avionics lately, or antenna wires?

5) Outside air entering the cabin for modern Mooneys… comes from the tail root vent at the top of the cabin… so if you get CO entering from there…. It may be a big leak caught in the swirl of air around the fuselage…

 

This is a tough one, would love it if this were at my home base where I could fly it around and put my monitors all over the plane, but its a 3-4 hour drive to SLO for me. No new cone wires, exhaust pipes new. Very interesting theory including door seals which I didn't specifically check, but whatever it is, is got a pretty high 137ppm CO level.  Hoping he finds something that can drop the level a bit so I can at least hobble home and do the rest of the searching later.

 

Thanks everyone!

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  • JohnB changed the title to Carbon Monoxide incident - Mooney No longer Stranded

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