CO in the cockpit

Thomas Arsenault · Post by **Thomas Arsenault** » Wed Oct 23, 2002 12:02 pm

Because it is getting cold up here (Minnesota) I hooked up my heater to the muffler tube. I also tried my new AIM CO monitor. During taxi out I had all the alarms going off. During my short flight to pick up my instructor the monitor went to HI which is over 150 ppm. I opened the window and it went down to about 100.
My instructor did not want to fly in my plane.
My mechanic said that this is the same problem as before and many of the old planes have high CO. His solution "get rid of the monitor".

I removed the tube to the heater control valve on the firewall and duct taped up the intake opening. I flew the plane with low values of CO on the monitor ( 7 at cruise). I did see higher values during taxi (20) and takeoff (40) but they came down soon. My plane must be well sealed from the cold because the inside temp was at 58 while sitting in the sun.
(outside air was 27) In 3/4 hour of flying and testing it dropped only 5 degrees.

I took the plane to another FBO on the field I now hanger at. We took off the muffler from the left side (side for the heater) and found some leaks. They are sending it in for repair ($225 maybe) plus labor.

This time I should get the problem fixed for good.

Note to the group.
The spot CO monitor has never changed color. They are not good enough for checking for CO. Get an AIM monitor.

Tom Arsenault
N4163V

Dave Clark · Post by **Dave Clark** » Wed Oct 23, 2002 1:40 pm

I think I'll keep my leaky airplane. I like the fresh air of Washington state in the summer and AZ in the winter anyway. Seriously, report back what readings you get after the repair.

flyer170 · Post by **flyer170** » Wed Oct 23, 2002 3:33 pm

Tom..... Checking for muffler leaks into the heater shroud is part of every annual on my 170. We remove the shroud, use a vacumn cleaner to blow air into the tail pipe and use soap and water to check for leaks.
I hope others check in on this post with how they deal with this issue.
With Winter coming on it is pretty important.
I wonder if they have Winter in Texas.

Bob

Post by **GAHorn** » Wed Oct 23, 2002 5:00 pm

flyer170 wrote:Tom..... Checking for muffler leaks into the heater shroud is part of every annual on my 170. We remove the shroud, use a vacumn cleaner to blow air into the tail pipe and use soap and water to check for leaks.
I hope others check in on this post with how they deal with this issue.
With Winter coming on it is pretty important.
I wonder if they have Winter in Texas.
Bob

We have a phrase in Texas that goes: "The only thing between Amarillo and the Arctic is a barbed-wire fence!" There are days that is certainly true.

zero.one.victor · Post by **zero.one.victor** » Wed Oct 23, 2002 11:59 pm

Tom,you mentioned that the "spot" detector never changed color. Did you know they have a service life of 90 days. They seem to work OK when they're fresh--I have had them turn color on me due to an exhaust leak. I usually buy 2 to get me thru the cabin-heat season (October > April).

Eric

43a72v · Post by **43a72v** » Thu Oct 24, 2002 12:07 am

When taxiing, I usually get a strong smell of exhaust in the cabin. In flight, I do not smell it. I can see on the cowl where the exhaust follows the lower cowl lip around to the area where the gear legs enter the fuselage. I suspect this is where it is entering and will seal that better during the annual next week. Anyone have any other thoughts? I don't get the smell when using cabin heat (which is good because the entire exhaust system has about 60 hours on it).

CAS · Post by **CAS** » Thu Oct 24, 2002 2:37 am

Tom,

Which model CO monitor do you have?
Is it hand held or mounted on the panel?

I recently had a CO 'encounter' flying (taxiing actually) a Grumman Tiger AA5 (yes, I will fly anything I can get my hand on). On closing the sliding canopy there was a strong exhaust smell. The 'yellow spot' CO monitor had gone black. Needless to say I taxied back to the hangar to have it looked at. Subsequent inspection found a large crack in the exhaust mainfold. Cabin heat was not in use but a lot of exhaust gas found its way into the cockpit.

David.

flyguy · Post by **flyguy** » Thu Oct 24, 2002 11:10 am

[quote="flyer170"]Tom..... Checking for muffler leaks into the heater shroud is part of every annual on my 170. We remove the shroud, use a vacumn cleaner to blow air into the tail pipe and use soap and water to check for leaks.
I hope others check in on this post with how they deal with this issue.
With Winter coming on it is pretty important.
I wonder if they have Winter in Texas.

Bob[/quote]

I don't know about anything west of Crockett, TX but we don't allow winter here in Lousiana!

Leaks in any part of the exhaust system can be fatal on long flights. Carbon monoxide is called the silent killer! Very small quantities in the cabin air is capable of impairing abilities required for management of inflight situations.

Another thing to remember, CARBON MONOXIDE CAN BE ODORLESS! - - FIND IT OUT AND THEN GET IT OUT!

Thomas Arsenault · Post by **Thomas Arsenault** » Sun Oct 27, 2002 12:09 pm

Here is some more info on the subject. I had the muffler removed and sent in for repair. Welding is going to cost $375 plus shipping. I think the total cost is going to be around $700.
The muffler looks good. Mostly replacement. Here are some figures from my AIM monitor which is a hand held that I tie to the ash tray.

Before fix Cruise with heat on Over 150 ppm (highest reading)
After fix Cruise with heat on 8 to 10 ppm
This is about the same as with the heater hose off and the firewall intake taped up. (5 to 7 ppm)

Other figures about the same before (heat off) and after the fix.
Taxi 8 to 17 ppm
Runup 44 to 51 ppm
T/O 55 down to 47 ppm
Climb 34 ppm
Cruise 10 down to 8 ppm
Landing 16 ppm
Taxi in 25 ppm

I would like to reduce the remaining amounts but do not have to.

Tom Arsenault
N4163V

Thomas Arsenault · Post by **Thomas Arsenault** » Sun Oct 27, 2002 12:52 pm

Here is some more info that I have found.

How much is dangerous?

High concentrations of carbon monoxide kill in less than five minutes. At low concentrations it will require a longer period of time to affect the body. Exceeding the EPA concentration of 9 ppm for more than 8 hours is suspected to produce adverse health affects in persons at risk. The U.S. Occupational Health and Safety limit for healthy workers is 50 ppm. Carbon monoxide detectors, which are designed to protect against high concentration of carbon monoxide are required to sound an alarm when concentrations are greater than 100 ppm. Continued exposure to carbon monoxide can cause permanent brain, nerve, or heart damage. Some people require years to recover while others might never fully recover.

Tom Arsenault
N4163V

N1478D · Post by **N1478D** » Sun Oct 27, 2002 2:32 pm

That might be a good thing to add to 170 fly-ins. Someone who has the equipment and knowledge to use it could test other 170's and educate the rest of us.

zero.one.victor · Post by **zero.one.victor** » Sun Oct 27, 2002 3:56 pm

Tom,does your ragwing still have the pancake mufflers? "The muffler looks good.mostly replacement." Could you elaborate a little? Who did the repair work? Most exhaust outfits just about hang up on you when you mention pancake mufflers,or else try to sell you a set of Hanlon-Wilson's for $1500. My pancakes are airworthy,now,but have had a lot of weld repairs thru the years. It'd be nice to have them rejuvenated,next time they spring a leak.

Eric

Dave Clark · Post by **Dave Clark** » Mon Oct 28, 2002 12:49 am

Where does one buy an AIM CO monitor, handheld like yours, and how much does should one expect to pay?

Thomas Arsenault · Post by **Thomas Arsenault** » Mon Oct 28, 2002 12:16 pm

Answers to some of the questions.

I have an O 300 A engine that has Hanlon-Wilson mufflers. I only had the muffler for the heater (sans baffle) sent in for repair. The repair shop is in Burnsville MN (suburb of MPS). I will have an exact address after I pay the bill (today) and have my log books updated.

The meter is an AIM model 935 and I think the cost is about $70 plus shipping. It is a self contained an should run for 3 years and then tossed. The company is
IST Aim Corporation
1624 Headway Circle
Austin Tx 78754

Tech Support
1 888 391 7258

More on CO
http://www.carbonmonoxide.org

Thomas Arsenault · Post by **Thomas Arsenault** » Mon Oct 28, 2002 12:43 pm

Another item from Tom Arsenault

I still wonder if this (CO in the cabin even with the heater shut) and high altitude for 2 days did not have some bearing on my going off the runway at Durango. I had some feeling that when I started to leave the runway that I did nothing. It wasn't until I saw the fence coming close that I decided that I had to get out of there. I should have stopped the plane in the brush rather than try to get back on the runway with that big drop from the runway.

Read about the "incident/accident" at:
http://www.winternet.com/~taa/TomsTripToAccidentP1.html

Tom Arsenault
N4163V

The International Cessna 170 Association

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